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Old 10-15-2012, 12:08 PM
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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.


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The Following 2 Users Say Thank You to BogiesAnnex1 For This Useful Post:
89Sierra (01-16-2013), Jaykobo (10-15-2012)
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  #17 (permalink)  
Old 01-16-2013, 02:06 PM
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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.
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