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Topic Review (Newest First)
01-16-2013 03:06 PM
89Sierra
Questions about my 89' 350 TBI

You guys have already posted tons of good information in this thread and others. Thanks for taking the time to explain everything so clearly.

I have an 89' 3/4 4WD Truck with 3.73 gears and an NV4500 transmission. I want to help out my engine a bit without tearing into it too deep. It only has 50,000 miles on it since the new GM longblock in 97'.

I am thinking, based on all the info you have posted that I may go ahead and install the 670 Holley two barrel TBI, continue to use the stock heads and cam but install the 1.6 ratio rockers and add dual exhaust. Do I need headers for this pretty basic engine and will I need a performance chip? The Camshaft change is rather tempting as it sounds like you get alot for a little there. I don't really have the budget to teardown and replace heads right now. Going for better fuel economy, and hopefully better torque on the low end. I would like to eventually do the 383 stroker rebuild and want to be able to reuse the TBI stuff I buy now when I get there.
10-15-2012 01:08 PM
oldbogie
Quote:
Originally Posted by Jaykobo View Post
Thanks guys for the the sufficent and quick answer

I belive now that I was trying to build the engine with a blind eyes and tight brain....I think I was easy.

I already check the heads and the #14102193 which have a high comperssion and 64cc head chomber.

I read the instruction of the -14 cc and it required 2-4 dgreeing less timing.

I now make a mistake and want to correct the stuation now.want your help guys.

the most important and hard quiestion to me.......will the engine run with this piston or not......need more dgreeing for less compession ratio?I just read on the net pages that.


I will try to buy the 2inches intake and I read on google that you can bore the stuck monifold and just buy a 454 thottle body for more breathing...is it ok?


the chip....I know about it but like to hear which is recommended for the use?

with intake I think I need headrs exhust.

and I,m a little shy about asking....I think I asking much...be pationt with me

the engine is now for racing use??can't be used on high ways?the normal octan here in my country is 95 will it work well or need to increase it?

I won't run a high RPM......mixmum 4000

please recommend the parts needed to correct my mistake.....and would like to thank you guys for all answers
Don't be afraid to ask what you think are dumb questions, they aren't. We've all come this road; it's just that some of us have been on it for 5 or 6 decades so it makes us look smarter than we are. We at least have a sense of history and in that thought is understanding that what you first proposed would make a decent engine under a carburetor, it would even work pretty well with a port injection system like TPI using a mass air sensor (MAF) to measure intake air flow. But your combination just would be difficult to master with TBI and its inclusive way of indirectly (mathematically) calculating air flow from referencing manifold vacuum what they call Manifold Absolute Pressure (MAP). MAP can be found not only on TBI but also TPI as over the years all the OEMs using port injection have varied their systems between MAF and MAP sensing and back again several times, so when buying these things at the wrecking yard you have to be knowledgeable as to what system was used on which engines and models for what years. There are books out there that will help an easy way is to Google fuel injection and a ton of stuff will dump into your browser.

The down side of TBI, as has been pointed out, is fuel capacity rather than air. Even the 500 CFMish unit stock to 305s and 350s has more air capacity than it can fuel. This can be changed with larger injectors but this quickly gets into playing with the system pressure and that heads you at a new chip. Jacking up the system pressure is a quick and dirty method of delivering more fuel but it is indiscriminate to the engine's needs, rather than correct mixtures you get rich mixtures whether the engine needs them or not. Rich mixtures not only cost you at the pump because of burning thus buying more fuel but they are hard on the upper end of the cylinders, pistons and rings as the extra and unburnt fuel washes the already thin upper cylinder lube away leaving metal to run against metal. Moly rings will hide this awhile as they run well with very little lube, chrome rings will do OK as well since their hardness will slow the rate of micro welding to the cylinder wall. Simple cast rings will quickly self destruct in this situation as they have neither the self lubricating quality of moly nor the hardness of chrome. So these bare iron rings will quickly weld and tear at the cylinder wall destroying both in short order.

The MAP sensed systems also suffer from needing a large signal to be able to differentiate small differences in power requirements. As the manifold vacuum comes down with a large cam the engine gets into a situation where small changes in the relationship of manifold vacuum to throttle position and RPM make large differences in fuel requirements. The TBI's sensors just don't have the needed selectivity under these circumstances to provide the computer with discrete enough information that it can calculate the proper control number for the fuel and ignition map. The map has a bunch or numbers each of which tells the computer to switch on the injector for a select time period. (I know when you look at the injector it looks like it’s on all the time but it isn't; it's being quickly switched on, off and on again to deliver a certain weight of fuel in a time period. The pressure in the system does not vary therefore the proper weight of fuel is determined by the on-off-on timing. These Electronic Fuel Injection systems are not continuous flow systems like the old Rochester unit of the late 1950s early 60s nor like the Hilborn racing system.) So to keep the data selectivity band wide enough to provide good mixture management you want to keep the cam around 200 degrees on the intake and about 215 on the exhaust measured at .050 inch lift. Keeping the lift around .45 inch. The Lobe Separation Angle (LSA) is also very important as this tends to affect the overlap, for TBI you want very little if any overlap where the exhaust and intake are open together between the end of the exhaust stroke and beginning of the intake. So the cam choice will have a lot of LSA somewhere in the range of 112 to 116 degrees.

As I said in my previous post a good approach for more power from a TBI engine is bigger since you're cam limited a small engine would up to 6000 plus RPM to get plenty of top end horsepower is a quirky and difficult exercise. The related Holley TBI systems tended to be aimed at race applications having decent idle and top end but hunting anywhere in-between, the GM unit would do the same with a cam that gets the idle vacuum under about 15 inches. So less cam and more displacement makes a simpler solution and get the performance off the greater torque that comes with a larger displacement.

The problem of getting sufficient fuel remains this is why Holley went to 4 barrel injectors with the 700 and 950 cfm units not so much for air flow especially the 700 cfm 4 barrel compared to the 670 cfm 2 barrel but rather for the need to mount 4, 80 to 90 pounds/minute injectors to get the needed gasoline to feed above 330 horses without running the working pressures up to where the injector life is shortened. Still with a 670 CFM unit having 90 pound injectors, tweaking the system pressure up a bit and running a custom chip that retimes the injectors so the lower RPMS aren't awash in excess gasoline is a damn decent way to go. 670's as pull offs from 454 pickup motors or new/used Holley’s are all over E-Bay. These are physically a bolt on/plug in to your current intake, sensors and computer. In unmolested form they will support 280-290 horsepower, with a little tweaking of pressures and chip mods this is an easy 330-350. The Edlebrock 3207 cam characteristics are nearly the same as the old 300 horse 327 cam which in a 383 with 1.6 rockers will produce about 325 horses.

The Swirl Port heads can be ported to remove the vane, with a little care and time they can actually produce some excellent results. They are not going to exactly duplicate power and efficiency of more modern heads same similar to the Vortec, but they can be made to produce very credible results when cost is a big issue. The 193 is the head to start from if you go down this road as it has a smaller more efficient combustion chamber than the 191 version. Another little known and low cost solution is the 14101083 head this is a cast iron version of the Aluminum L98 Corvette head that is also used on the ZZ series crate engines. These use the 72 degree center intake bolt angle, therefore, will accept your intake. This is a 64 cc chamber head so you'll need dished pistons to control compression. You have to watch heads and manifolds especially on a tight budget as many heads such as the original L31 Vortec get you into an expensive intake for TBI or a carburetor intake with an adapter which while working well can get you into hood clearance problems.

The pistons will need a D shaped dish this is highly efficient as it keeps the dish all under the valve pocket and presents a flat surface to the squish/quench deck of the head, this maximizes efficiency and lowers the octane requirements of the compression ratio by 4 to 6 octanes. In otherwords whatever fuel you use it looks and reacts within the engine as if it had more octane so a 91 acts like a 95 to 97 octane fuel. Long story behind this for another day.

I think in my previous I talked about crank and rods so you can refer back to that. My always preference is for 4340 rods bushed for floating pins. Pistons need to also be for floating pins as many pistons made for pressed pins do not include the pin boss grooves for pin retainers.

Big thing to know is your budget; this can get out of hand quite quickly if you don't ride heard on your bank account. So knowing what you want to achieve and how much the budget is lets us match parts to dollars for the most effective bang for your buck. Sometimes you’re quite a ways ahead to start with a crate engine and modify it as or if required. The big OEMs making new engines and the recon guys that do this on massive volumes can often provide a lot of bang for the buck the your local shop just can't cost match. Kind of like Wal-Mart coming to town.

Bogie
10-13-2012 10:24 AM
Jaykobo
Quote:
Originally Posted by oldbogie View Post
For a TBI engine not much of what you bought is a very good solution. Let's start with the cam, TBI doesn't like and will not work with much cam timing. The one you bought is more for a Tuned Port Injection (TPI) at that a TPI with a Mass Air Flow (MAF) sensing rather than Manifold Absolute Pressure (MAP) sensing which is what your TBI also uses to determine fueling requirements. MAP sensed systems need a lot of manifold vacuum which gets smaller as the duration and lift at the valve get bigger. The Edlebrock 3702 cam with durations/lift for the intake of 194/.398" and exhaust 214/.442 at the valve is about all TBI will tolerate without needing special, and often quirky, custom chip burning. Lookie here <<< TBI CHIPS >>> the other problem with TBI is that it cannot inject enough fuel to sustain more than about 290 horses. This would be with the larger 670 CFM throttle body with the largest injectors that will fit which are rated to 88-90 pounds of fuel per hour. Your stock 305/350 TBI ain't even close to that they will do about 220 horses before they are out of injector capacity.

Compression, you didn't sight what head you've got if original the 1993 TBI engines use the Swirl Port head, these are not very high RPM heads as the vane that creates the swirl obstructs the port preventing revs over 4500 RPM regardless of the cam used. The Swirl Port head comes in two casting with different size chambers the 14102191 has a low compression 74cc chamber while 14102193 has the high compression 64cc chamber. So before you bought pistons you needed to pull a rocker cover to find the casting number of the heads on your engine. A 12cc domed piston is likely to cause compression ratio problems with a super tight tune and iron heads with 91 octane fuel about 9.5 to 1 Static Compression Ratio (SCR) with a mild cam is about as far as you can go without encountering detonation. Go here when you know what head you've got <<< United Engine & Machine Co. Incorporated >>>.

Pushrod length is determined by how the roller on the rocker tip traverses the valve stem tip; you can't determine this till the engine is assembled up to the and including the heads. Then with an adjustable pushrod you place a mark on the stem tip and turn the engine over by hand to get a witness mark of the roller on the stem tip, using this technique the proper mark will determine the pushrod length. Changes in build up from block decking, head milling, head gasket, stack-up changes of the type and manufacturer of heads and certainly changes to roller rockers will affect the needed pushrod length. Follow the instructions found here >>> COMP Cams® - Sorry... >>>

The SCAT stuff is cast or forged in China and finish machined in the USA and is priced likewise. Most of the high priced brands are also made in China and finished here but are sold at made in America prices. The SCAT stuff is damn good stuff we use a lot of it from street rods to full up race engines. I happen to like and use the SCAT 2-ICR5700 for 5.7 inch rods and really make use of the 2-ICT6000 6 inch rod, these are made from forged 4340 and use capscrews rather than bolts. They are plenty good for hot street engines and Claimer race motors. Capscrews make for a stronger rod as the compromises made in the shape of the shank to allow a headed bolt are avoided. The capscrew rod also gets around the issues of clearancing for a stroker which compromises the bolt head. These rods use a capscrew that passes through an alignment dowel that insures the cap and shank make properly, they also provide an extra step outside the fine-line of the cap and shank interface which is a great help in reacting the tension loads put on the cap when the rod assembly is jerked down on the intake stroke. This is a movement that wants to egg shape the cap which pinches it in at the interface line with the shank. This movement pinches the bearing taking the oil wedge off the rod journal, spinning the bearing and finally failing the rod. the design that SCAT uses along with the capscrew mounting hardware goes a long, long way toward eliminating this most common of rod failures. A bushed rod with floating pins is the only way to go. This eliminates making mistakes disassembling and reassembling pressed pins that can bend and twist the rod and in the case of alloy steels like 3140, 5140, or 4340 unlike the factory mild steel of 1046 or 1053 the alloy steels do not like to be heated and many shops heat the pin end because this is fairly safe to do with mild steel, but with alloy steel it's a disaster in the making as it modifies the molecular structure and destroys the heat treatment of these materials. Stay away from 5140 rods, this stuff is advertised as having the same tensile strength as 4340 at a lower price. While this is true there’s more to the performance of a chunk of metal than its tensile strength. In the case of 5140 it is brittle compared to 4340, refer to the Izod Impact Test numbers for these metals, For a connecting rod where the load constantly changes from compression to bending to tensile and repeat again a more brittle material is asking for trouble. 5140 is OK for a crankshaft when running an automatic on one end with an expensive/effective damper on the other. Unfortunately, you've made some really big decisions before coming here first and you have stuff like the pistons that in the first place aren't a good street piston and secondly have defined the rods and crankshaft for you.

Actually the best way to get power out of a TBI engine is to make it bigger a 383 being the way to go, use less cam, use a 670 CFM TBI from an older mid 80's to mid 90's 454 or get a new one from Holley and use a custom chip with the higher manifold vacuum that comes from the milder cam. This makes a much more stable and predictable engine. For about the same cost as what you've sunk this would have been a lot less painful. Now you've got these pistons which have you locked into the 5.7 inch rod. Short of sending this stuff back I don't know what you're going to do about compression especially if you've got 193 heads.

The other way to get more power out of the TBI engine is to replace the heads. The Vortec is always a good choice for these. This type head gets much better power by improving the burn rather than using more fuel and air to burn. This again lets you get away with a milder cam and fewer, if any, changes to the injection programming. Against the very mild OEM cam that the TBI engines use the Vortec head will pick up an easy 20 horses. Given the Edlebrock 3702 cam that will go to 30-40 horses with a like amount of torque increase in both cases. These do get you into some plumbing headaches with the EGR which are not too difficult to solve or with a custom chip the EGR can be eliminated. Don’t just disconnect it as this will cause the mixture to go lean more than the LEARN function in the computer can compensate for and you may just toast the engine as a result. There are aftermarket Vortec type heads from many sources in iron and aluminum. For a mild 350 these from Skip White are pretty decent and let you use your current intake <<< White Performance Detail Description >>>.

Frankly, I’d send everything back and completely rethink this project and certainly come here for advice.

Bogie
Thanks guys for the the sufficent and quick answer

I belive now that I was trying to build the engine with a blind eyes and tight brain....I think I was easy.

I already check the heads and the #14102193 which have a high comperssion and 64cc head chomber.

I read the instruction of the -14 cc and it required 2-4 dgreeing less timing.

I now make a mistake and want to correct the stuation now.want your help guys.

the most important and hard quiestion to me.......will the engine run with this piston or not......need more dgreeing for less compession ratio?I just read on the net pages that.


I will try to buy the 2inches intake and I read on google that you can bore the stuck monifold and just buy a 454 thottle body for more breathing...is it ok?


the chip....I know about it but like to hear which is recommended for the use?

with intake I think I need headrs exhust.

and I,m a little shy about asking....I think I asking much...be pationt with me

the engine is now for racing use??can't be used on high ways?the normal octan here in my country is 95 will it work well or need to increase it?

I won't run a high RPM......mixmum 4000

please recommend the parts needed to correct my mistake.....and would like to thank you guys for all answers
10-12-2012 03:42 PM
dromero5 I just ran this cam in my last 383 TBI. Let me give you some quick specs of what i did. I ran 454 injectors around 16psi, 50mm TBI, and a matched Edlebrock 3704 50mm intake. I ran the same cam with Trick flow 1.6:1 narrow body rockers. I had KB 135 pistons i believe with a Trickflow 23 degree 195 cc runner heads with 64cc combustion chambers. Was a 383 scat setup. I had Brian custom tune me a chip took about 3-4 tries to get it dialed in via datalogging. Engine ran really strong did start losing power past 5000 but the bottleneck was in the 2bbl TBI setup so a standard 4bbl intake with a TBI adapter would have been an upgrade with the EGR tuned out of chip. Unfortunately after 2 oil changes i went to synthetic and the cam went flat really quick so now i sold the shortblock and have the heads and TBI stuff in garage collecting dust. So word of advice the cam can be run but with the appropriate heads and valvesprings and break in is crucial and always run with zinc additive. I would really recommend you look at the 8-304-8 roller cam and stay away from flat tappet cams. I was running 9.6 compression with the pistons in the hole .006 and a .039 gasket. Hope this helps some.
10-12-2012 02:44 PM
AutoGear Listen to Bogie; print that post out and keep it, ask questions untill you UNDERSTAND it. Don't be the guy who comes here with his Killer Engine Of Death; and when we give him sound advice about problems he WILL have; because he doesn't have the experience needed for the performance he thinks he wants, he gets all internet-mad and argues with us because WE are wrong. Usually that guy just wants us to pat him on the head and say 'nice job sport!' regardless of how much of a Mongolian Cluster-eff this will be. These are the people who got trophies in youth league for showing up with their jockstrap in the proper place, and have never learned to overcome having a setback or being told 'No.'

You made a mistake; and the guys on the techline didn't do you any favors. We've all made mistakes, its okay. You're better off taking a week to rethink this.

Comp is a joke when it comes to customer service. They tell you how to properly measure for pushrods and tell you how critical it is; but the drooling meth head on the phone, sells an uninformed guy pushrods, with a NON- OE rocker ratio. That ones not your fault. I see it too at my job. Guy calls up, orders an overhaul kit. Easy sale is to just punch the ticket and make money; but no, I take 20 minutes trying to figure out what he wants, what hes doing and if he can afford it. If he tears his muncie apart when he gets the overhaul kit, and he finds he needs 2 forks, all the reverse parts and his case has a bore that wont hold the countershaft without silicone; he's usually over his budget and now he's got an overhaul kit he can't use. I'll take it back, but hes gotta ship it and lose 10% for me to put it on the shelf, assuming he didn't lose all the little springs, etc. Its better to EDUCATE my customer, have him disassemble and inspect before ordering.

Start a new thread: Tell us where you want to go; what your starting block is, dont even bother with the parts you bought at this point. Give us a reasonable budget for the motor, and what you want to do with it. You'll get a much better picture with a clean sheet rather than trying to erase all this stuff
10-12-2012 02:21 PM
oldbogie
Quote:
Originally Posted by Jaykobo View Post
Hi

How you doing guys?

I decide to rebuild my 350 TBI engine for 1993

In real... I jut need your help friends
I took a stuck engine and want to turn it to performance engine
I over size the engine 4.030
I boght my comp cam kit


COMP Cams K12-365-4 - COMP Cams Xtreme Fuel Injection Cam and Lifter Kits - Overview - SummitRacing.com


Rockers 1.6 ratio and pushrods
Magnum Pushrods: 5/16" Diameter, 7.800" Length

COMP Cams 1416-16 - COMP Cams Magnum Steel Roller Tip Rocker Arms - Overview - SummitRacing.com

COMP Cams 7372-16 - COMP Cams Magnum Pushrods - Overview - SummitRacing.com
Vlave from summit racing :

Intake :Summit Racing SUM-V8000-8 - Summit Racing® Race Valves for Chevrolet - Overview - SummitRacing.com

Exhust:Summit Racing SUM-V8008-8 - Summit Racing® Race Valves for Chevrolet - Overview - SummitRacing.com

Piston and ringes:

KB piston
Keith Black/KB Pistons 9903HC-030 - Keith Black KB Performance Claimer Pistons - Overview - SummitRacing.com

summit rings:
Summit Racing SUM-133-M139-30 - Summit Racing® Piston Rings - Overview - SummitRacing.com

summit racing Connecting rods:
Summit Racing SME-3-48-05B100 - Summit Racing® Stage I Connecting Rods - Overview - SummitRacing.com


I get summit racing rods and it's written on it"scat"

I want to know is it a china product or not??cos in google search all write it's china.


And the piston dome -14 cc....should I keep the recommend GM timing or need to dgree the cam?

Also does any thing wrong with my parts....all are fine and fit the engine?

and approxmately how many the hp for this engine?


the KB recommend the gap for the piston ring 0.026 for the steet normal aspirator and 0.032 for the street tow.

I use the car for loading stuff so will make the gap 0.030....is it ok??and should I make the first and second gap the same or only the first ring?

the gap now is 0.013 and I thin it's too tight ..what you recommend guys....filing the both rings to 0.030 or just the first?
For a TBI engine not much of what you bought is a very good solution. Let's start with the cam, TBI doesn't like and will not work with much cam timing. The one you bought is more for a Tuned Port Injection (TPI) at that a TPI with a Mass Air Flow (MAF) sensing rather than Manifold Absolute Pressure (MAP) sensing which is what your TBI also uses to determine fueling requirements. MAP sensed systems need a lot of manifold vacuum which gets smaller as the duration and lift at the valve get bigger. The Edlebrock 3702 cam with durations/lift for the intake of 194/.398" and exhaust 214/.442 at the valve is about all TBI will tolerate without needing special, and often quirky, custom chip burning. Lookie here <<< TBI CHIPS >>> the other problem with TBI is that it cannot inject enough fuel to sustain more than about 290 horses. This would be with the larger 670 CFM throttle body with the largest injectors that will fit which are rated to 88-90 pounds of fuel per hour. Your stock 305/350 TBI ain't even close to that they will do about 220 horses before they are out of injector capacity.

Compression, you didn't sight what head you've got if original the 1993 TBI engines use the Swirl Port head, these are not very high RPM heads as the vane that creates the swirl obstructs the port preventing revs over 4500 RPM regardless of the cam used. The Swirl Port head comes in two casting with different size chambers the 14102191 has a low compression 74cc chamber while 14102193 has the high compression 64cc chamber. So before you bought pistons you needed to pull a rocker cover to find the casting number of the heads on your engine. A 12cc domed piston is likely to cause compression ratio problems with a super tight tune and iron heads with 91 octane fuel about 9.5 to 1 Static Compression Ratio (SCR) with a mild cam is about as far as you can go without encountering detonation. Go here when you know what head you've got <<< United Engine & Machine Co. Incorporated >>>.

Pushrod length is determined by how the roller on the rocker tip traverses the valve stem tip; you can't determine this till the engine is assembled up to the and including the heads. Then with an adjustable pushrod you place a mark on the stem tip and turn the engine over by hand to get a witness mark of the roller on the stem tip, using this technique the proper mark will determine the pushrod length. Changes in build up from block decking, head milling, head gasket, stack-up changes of the type and manufacturer of heads and certainly changes to roller rockers will affect the needed pushrod length. Follow the instructions found here >>> COMP Cams® - Sorry... >>>

The SCAT stuff is cast or forged in China and finish machined in the USA and is priced likewise. Most of the high priced brands are also made in China and finished here but are sold at made in America prices. The SCAT stuff is damn good stuff we use a lot of it from street rods to full up race engines. I happen to like and use the SCAT 2-ICR5700 for 5.7 inch rods and really make use of the 2-ICT6000 6 inch rod, these are made from forged 4340 and use capscrews rather than bolts. They are plenty good for hot street engines and Claimer race motors. Capscrews make for a stronger rod as the compromises made in the shape of the shank to allow a headed bolt are avoided. The capscrew rod also gets around the issues of clearancing for a stroker which compromises the bolt head. These rods use a capscrew that passes through an alignment dowel that insures the cap and shank make properly, they also provide an extra step outside the fine-line of the cap and shank interface which is a great help in reacting the tension loads put on the cap when the rod assembly is jerked down on the intake stroke. This is a movement that wants to egg shape the cap which pinches it in at the interface line with the shank. This movement pinches the bearing taking the oil wedge off the rod journal, spinning the bearing and finally failing the rod. the design that SCAT uses along with the capscrew mounting hardware goes a long, long way toward eliminating this most common of rod failures. A bushed rod with floating pins is the only way to go. This eliminates making mistakes disassembling and reassembling pressed pins that can bend and twist the rod and in the case of alloy steels like 3140, 5140, or 4340 unlike the factory mild steel of 1046 or 1053 the alloy steels do not like to be heated and many shops heat the pin end because this is fairly safe to do with mild steel, but with alloy steel it's a disaster in the making as it modifies the molecular structure and destroys the heat treatment of these materials. Stay away from 5140 rods, this stuff is advertised as having the same tensile strength as 4340 at a lower price. While this is true there’s more to the performance of a chunk of metal than its tensile strength. In the case of 5140 it is brittle compared to 4340, refer to the Izod Impact Test numbers for these metals, For a connecting rod where the load constantly changes from compression to bending to tensile and repeat again a more brittle material is asking for trouble. 5140 is OK for a crankshaft when running an automatic on one end with an expensive/effective damper on the other. Unfortunately, you've made some really big decisions before coming here first and you have stuff like the pistons that in the first place aren't a good street piston and secondly have defined the rods and crankshaft for you.

Actually the best way to get power out of a TBI engine is to make it bigger a 383 being the way to go, use less cam, use a 670 CFM TBI from an older mid 80's to mid 90's 454 or get a new one from Holley and use a custom chip with the higher manifold vacuum that comes from the milder cam. This makes a much more stable and predictable engine. For about the same cost as what you've sunk this would have been a lot less painful. Now you've got these pistons which have you locked into the 5.7 inch rod. Short of sending this stuff back I don't know what you're going to do about compression especially if you've got 193 heads.

The other way to get more power out of the TBI engine is to replace the heads. The Vortec is always a good choice for these. This type head gets much better power by improving the burn rather than using more fuel and air to burn. This again lets you get away with a milder cam and fewer, if any, changes to the injection programming. Against the very mild OEM cam that the TBI engines use the Vortec head will pick up an easy 20 horses. Given the Edlebrock 3702 cam that will go to 30-40 horses with a like amount of torque increase in both cases. These do get you into some plumbing headaches with the EGR which are not too difficult to solve or with a custom chip the EGR can be eliminated. Don’t just disconnect it as this will cause the mixture to go lean more than the LEARN function in the computer can compensate for and you may just toast the engine as a result. There are aftermarket Vortec type heads from many sources in iron and aluminum. For a mild 350 these from Skip White are pretty decent and let you use your current intake <<< White Performance Detail Description >>>.

Frankly, I’d send everything back and completely rethink this project and certainly come here for advice.

Bogie
10-12-2012 01:09 PM
cdminter59
350 TBI first time rebuilding engine...question

Looked on Summit Racing at the head gaskets for a 93 350. The compressed thickness is .041. This would give you a Static Compression Ratio of 10.562 and a DYNAMIC EFFECTIVE COMPRESSION RATIO of 8.790 which cannot run on 93 octane gas with a set of iron heads without detenation. You have a TBI system which is computer controlled. I can see the computer trying to reduce the timing because of the knock sensors. Getting somewhere around 6 miles to the gallon of gas because the timing is retarded so much. I would try and clean the pistons up with some degreaser (Simple Green). Mix some Simple Green with hot water to clean them and dry them immediately to prevent spotting or turning white. If not maybe you can sell them later. But you definetely need the 9902HC pistons if you want to use this motor for the street. Maybe someone else can come along and give you some better advice. Good luck.
10-12-2012 10:25 AM
Jaykobo
Quote:
Originally Posted by cdminter59 View Post
Did you buy the pistons from Summit Racing and are they still in the box? Summit Racing will swap the pistons as long as they have not been installed on the rods. These are the pistons that are needed Keith Black/KB Pistons 9902HCKTM030 - Keith Black KB Performance Claimer Piston and Ring Kits - Overview - SummitRacing.com There is no way to use the pistons that you have. They have hollow domes that cannot be machined down. I feel bad for you being in this situation but you should have came here before you ordered any parts. You are saying they recommended that camshaft K12-365-4 and the 1.6 rockers. With the pistons you have the compression is so high you would have to use reace gas (110 octane).
I Calculate the engine ratio and it's appeare 10.52:1

I use a head a thick gaskit 0.045in

do you think this will help??it's diffecult to return the piston cos I already open it and it get some dirt
10-12-2012 10:22 AM
Jaykobo
Quote:
Originally Posted by AutoGear View Post
How did you calculate your pushrod length?
I massage comp cam and asked them what's recommended or my cam....they sent the linke and the recommended parts
10-12-2012 09:29 AM
AutoGear How did you calculate your pushrod length?
10-12-2012 09:15 AM
cdminter59
350 TBI first time rebuilding engine...question

Did you buy the pistons from Summit Racing and are they still in the box? Summit Racing will swap the pistons as long as they have not been installed on the rods. These are the pistons that are needed Keith Black/KB Pistons 9902HCKTM030 - Keith Black KB Performance Claimer Piston and Ring Kits - Overview - SummitRacing.com There is no way to use the pistons that you have. They have hollow domes that cannot be machined down. I feel bad for you being in this situation but you should have came here before you ordered any parts. You are saying they recommended that camshaft K12-365-4 and the 1.6 rockers. With the pistons you have the compression is so high you would have to use reace gas (110 octane).
10-12-2012 07:35 AM
Jaykobo
Quote:
Originally Posted by cdminter59 View Post
Let's start out asking if this is going to be a daily driver? Have you had the block, crank, and heads to the machine shop yet? Are you using the heads that is on your motor? Using your 1993 GM heads will need some work, mild porting to get them to breathe better. The pistons you list with the 76cc heads will have a compression ratio of 11.3:1. Too much to run off pump gas. You need this set of pistons if using your 76 cc GM heads. Keith Black/KB Pistons KB106KTD-030 - Keith Black KB Performance Piston and Ring Kits - Overview - SummitRacing.com or these Keith Black/KB Pistons 9902HCKTM030 - Keith Black KB Performance Claimer Piston and Ring Kits - Overview - SummitRacing.com Use a Fel-Pro 1094 .015 steel shim head gaskets (4.100 x .015) if your block has not been decked. This will give you a quench of .040 which is good for using pump gas. Your compression ratio will be around 9.1:1. The Scat rods are from China but are good rods. The top ring gap for the top and second ring should be .026. Unless you are doing a lot of heavy towing I would file them to .026. If you do decide to open the gap just do the top ring gap. I would also call Comp Cams to see what they suggest for your camshaft. I don't like the exhaust lift lower than the intake lift. Most stock heads need higher exhaust lift. I would suggest the Comp Cams K12-262-4, 218/224 duration, and 0.464/0.470 lift. I would call Comp Cams to get their opinion.
Hi


thanks for man...yes I plan to use the car for daily use...spically high ways driving.....the heads are stock and not decked...but the piston !!I already bought it and bored the block on it.......I didn't want that in in the beginning but some tells it will burn much fuel.....so is there any suggest without replacing the piston?
10-12-2012 07:27 AM
Jaykobo I asked comp cams and it it's answer to use this rockers...And I boght it
10-12-2012 07:01 AM
E.Furgal the 1.6 rockers might be to TRICK the factory ecu..
10-12-2012 06:58 AM
cdminter59
350 TBI first time rebuilding engine... question

Let's start out asking if this is going to be a daily driver? Have you had the block, crank, and heads to the machine shop yet? Are you using the heads that is on your motor? Using your 1993 GM heads will need some work, mild porting to get them to breathe better. The pistons you list with the 76cc heads will have a compression ratio of 11.3:1. Too much to run off pump gas. You need this set of pistons if using your 76 cc GM heads. Keith Black/KB Pistons KB106KTD-030 - Keith Black KB Performance Piston and Ring Kits - Overview - SummitRacing.com or these http://www.summitracing.com/parts/UEM-9902HCKTM030/ Use a Fel-Pro 1094 .015 steel shim head gaskets (4.100 x .015) if your block has not been decked. This will give you a quench of .040 which is good for using pump gas. Your compression ratio will be around 9.1:1. The Scat rods are from China but are good rods. The top ring gap for the top and second ring should be .026. Unless you are doing a lot of heavy towing I would file them to .026. If you do decide to open the gap just do the top ring gap. I would also call Comp Cams to see what they suggest for your camshaft. I don't like the exhaust lift lower than the intake lift. Most stock heads need higher exhaust lift. I would suggest the Comp Cams K12-262-4, 218/224 duration, and 0.464/0.470 lift. I would call Comp Cams to get their opinion.
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