[slammedchevy1500]

hey hot rodders, im doing a lt1 cam with 1.6 rollers in a 1989 350 tbi truck motor. do i have to modify the heads at all?
what parts will i need to complete the swap i just have the cam right now, thanks

[curtis73]

The cam snouts are totally different since the LT1 drives both the distributor and water pump off the FRONT of the cam. The LT1 is also a roller cam. There is a chance that your TBI engine is not a roller block so you would need retrofit lifters.

If its a stock LT1 cam, its also not much bigger than the TBI cam.

This might end up costing a whole buttload of money for not much cam. Why not just buy a $30 blue racer or melling cam from a machine shop?

[GMC boogie]

The LT1 hydraulic roller cam has a longer dowel pin which can either be cut off to the proper length or driven in.

I doubt your '89 truck block is factory hydraulic roller ready so it is unlikely you would be able to use it.

I would pass on using that cam even if you could....been there done that.


As the other poster mentioned, get a good ole Melling MTC-1 cam or equivilant flat tappet.

[slammedchevy1500]

wow im in shock, whats the biggest cam i can use with stock tbi heads

[Scotto]

I'm sure you will find that the heads are the biggest problem with the motor. I've been reading into this for a month or so to do with my Ford 302, and it wouldn't do much throwing in a new cam and using the bad flowing heads and probably factory exhaust. Work on those things first, and then pick up a cam.

[slammedchevy1500]

Originally Posted by Scotto

I'm sure you will find that the heads are the biggest problem with the motor. I've been reading into this for a month or so to do with my Ford 302, and it wouldn't do much throwing in a new cam and using the bad flowing heads and probably factory exhaust. Work on those things first, and then pick up a cam.

yeah scotto you are 100% right i've heard i can gain 40hp with deleting the y pipe and adding true duals. long tubes are at least 15hp more. heads are also 40hp gain

[scott29]

I had a buddy w/ a 89 caprice x-copcar that came with the lt1 motor 350, he did a cam swap. It came with a roller cam/ roller lifters. he wanted more power, and did it by using a regular hydrolic cam & lifters. he had to replace the pushrods because the rollers are shorter. I believe it works the opposite way also. In 87 & newer blocks the lifter bores are taller so lhe lifters are set in deeper on hydrolic., but overall dimentions are the same. The LT1 heads stock are decent to a point. Great low end torque, but won't really flow good at 5000+ rpm. Need to up runner cc for top end. I wouldn't go with a 275 lift or bigger without taking that into consideration. You will just spend more in gas.

[scott29]

By the way if doing a cam swap it is a good idea to replace the old valve springs w/ new ones. they are only good to a certain lift before they bind and break.

[slammedchevy1500]

Originally Posted by scott29

I had a buddy w/ a 89 caprice x-copcar that came with the lt1 motor 350, he did a cam swap. It came with a roller cam/ roller lifters. he wanted more power, and did it by using a regular hydrolic cam & lifters. he had to replace the pushrods because the rollers are shorter. I believe it works the opposite way also. In 87 & newer blocks the lifter bores are taller so lhe lifters are set in deeper on hydrolic., but overall dimentions are the same. The LT1 heads stock are decent to a point. Great low end torque, but won't really flow good at 5000+ rpm. Need to up runner cc for top end. I wouldn't go with a 275 lift or bigger without taking that into consideration. You will just spend more in gas.

tbi heads flow worse than lt1 heads thats why i wanted to change from tbi to vortec heads its a soild 40hp gain

[Jim Rockford]

Originally Posted by scott29

I had a buddy w/ a 89 caprice x-copcar that came with the lt1 motor 350, he did a cam swap. It came with a roller cam/ roller lifters. he wanted more power, and did it by using a regular hydrolic cam & lifters. he had to replace the pushrods because the rollers are shorter. I believe it works the opposite way also. In 87 & newer blocks the lifter bores are taller so lhe lifters are set in deeper on hydrolic., but overall dimentions are the same. The LT1 heads stock are decent to a point. Great low end torque, but won't really flow good at 5000+ rpm. Need to up runner cc for top end. I wouldn't go with a 275 lift or bigger without taking that into consideration. You will just spend more in gas.

9C1 cop cars didn't get the LT1 until 94, your buddy had a LO5, basicly a truck 350 tbi ,only they got the L98 tpi cam and roller lifters larger injectors and flat top pistons for a little higher commpression, good engines , but once again the heads where the choking point, the ramp in the intake side really cuts the flow . upgradeing to a earlier set of tpi heads , or a set of carbed 305 big valve heads off a 4brl 305 really helps out. all lo5 truck engine i have seen are cast with the bosses (Though most are not tapped)for the lifter spider , and the front of the cam area is set up for the roller cam, they just got flat tappets stuck in em.

[oldbogie]

Originally Posted by slammedchevy1500

hey hot rodders, im doing a lt1 cam with 1.6 rollers in a 1989 350 tbi truck motor. do i have to modify the heads at all?
what parts will i need to complete the swap i just have the cam right now, thanks

This is a good cam for what you want to do. It is a lot more cam than what comes in a truck TBI, roughly 205 degrees of duration versus the TBI's 167 degrees.

But your under-estimating the problems.

1) Block may, or not, be a roller

2) TBI's use Swirl Port heads, not good for performance.

3) Existing TBI doesn't flow enough air

4) The LT1 cam changes the relationships of throttle opening and manifold pressure (vacuum) to the fuel and ignition maps.

Taking this apart:

1) Prior to the Vortec in mid 95, truck engines may or may not be provisioned for a roller cam. Hardly any truck engines, if any, got roller cams though many blocks have the provisions to use them. Check the casting number to see if the block is at least provisioned for a roller cam.
For unprovisioned 350 flat tappet blocks, look for casting number 10054727, 14079287, 14088548, and 14101148. For provisioned 350 roller tappet blocks look for casting numbers 10243880, 14011148, 14088526, and 14093638. However, the 880 block is the Vortec block it appears in late 1995 production without Vortec heads but with Swirl Port heads and TBI. Certainly your 89 won't have an 880 block. If your block is provisioned for a roller then conversion is simply getting the GM kit that has the spider, guide bars for lifter retention, and the cam thrust retention plate. The roller cam requires a roller timing set. This uses a narrower gear and chain to accommodate the space the thrust plate occupies, thru which the longer nose of the cam projects to provide an attachment for the timing gear. It isn't uncommon to have clearance problems with the timing cover with this set up. I find a two piece cover that is made to provide for cam and timing case changes without having to drop the pan will often provide the forward clearance needed plus making maintenance of the timing set a lot easier. This does demand a long water pump which you've got.

The solution for a non roller block conversion is to use 4.3 V6 hydraulic lifters which are shorter than V8 lifters as the non roller provisioned blocks do not have the raised lifter blocks. The spider is bolted thru the main oil galley’s flow is maintained by increasing the i.d. of the galley and reducing the diameter of the bolt (remove the threads in the middle area) where its shank is inside the galley. Cam thrust is taken using the typical thrust bumper since there isn't any provision to mount the thrust plate. The roller cam needs the thrust space filled with something. The simplest something is to buy a thrust plate and cut the ears off, smooth edges, etc.

2) The TBI truck engines use the 14102191 or 193 Swirl Port head. This heads' port flow cuts off around 4500 RPM. This is a constraint inconsistent with the performance available from the LT-1 cam you're proposing to use. So the heads need to be changed to match the cam, otherwise the performance available from this cam can't be achieved by the engine. Certainly Vortecs would be the first choice that comes to mind, however the older L98 type head in cast iron casting number 10125377 is the simplest choice as it bolts on and accepts your TBI intake with no modifications to the bolt patterns or to the EGR system where the Vortec requires a unique and expensive intake for TBI and extensive modification for an externally plumbed EGR. As usual, you need to check clearances when using a higher lift cam and especially with 1.6 rockers. Look at retainer to guide clearance, spring coil to coil, rocker to stud, pushrod to its guide and hole clearance, and valve to piston clearance.

The other important thing with the heads is combustion chamber volume. Ideal compression with an iron head is about 9 to 9.5, with aluminum heads this can be pushed a ratio and still run gas station fuels. A vital consideration is the development of high amounts of squish and quench within the combustion chamber. These two events occur from the very close closing of the piston to the step on the side of the combustion chamber opposite the valves and spark plug. Squish is the ejection of mixture from the far side of the chamber toward the spark plug. This stirs the fuel and air one last time before ignition and increases the density of mixture around the plug giving a stable and reliable ignition, with a fast burning flame front thru a thoroughly mixed thus efficient burning A/F mixture. The result is optimized power and efficiency. The quench function is next from the same components in the same position. The difference is the accelerating flame front increases in pressure and temperature and if left uncontrolled will explode ahead of the flame front. The quench function presents the far side of the combustion chamber as an area of low volume to high surface area. It acts as a heat sink removing the excess temperature thus lowering pressure just enough to suppress the desire of the mixture to explode, what we call detonation or pre-ignition. You want this side of the piston and head’s step to close at TDC to within .045 to .060 inch. Factory or replacement pistons with circular dishes greatly limit the area closing together and reduce the squish/quench function which then requires a higher octane fuel for the compression ratio used. By using a flat top piston this zone is maximized for function but risks to much compression ratio for available octane fuels when combined with a tight chamber. The solution is found in the D cup piston which controls compression by increasing necessary chamber volume while maximizing squish/quench thru keeping the maximum amount of flat surface of the piston opposite the step of the combustion chamber. This adds what’s referred to as mechanical octane to the engine. Now it’s easy to think a solution is a large chamber head with a flat top and this is used with considerable success. But, the ideal configuration for developing a strong swirl of the incoming charge is a tight chamber around the valves. Modern Gen 1 SBC design for all out competition takes this idea to extremes with the likes of the SB 2.2 heads developed for NASCAR where the chamber is only about 40ccs. For the street, it isn’t necessary to go this crazy; I point it out only to show the modern power trend is away from open chamber heads and has been for many years.

3) The stock TBI only flows about 440 CFM this is minimally adequate for what you propose, there is a 670 CFM option with a 2 inch bore available with a 454 TBI, or the Holley 502 series, or your existing unit can be bored out and rebuilt by Turbo City, they’re on the web. This and the cam change will drive a new computer chip.

4) The changes you’re proposing upset the computer’s view of the world. TBI and other EFI systems that use Manifold Absolute Pressure (MAP) sensing do not measure air flow into the engine like Mass Air Flow (MAF) systems do. MAP systems, which your truck uses, compute air flow into the engine by calculation of sensor inputs. Three of the most important that it uses are throttle position, manifold vacuum, and RPM. Other sensors for atmospheric pressure and temperature, engine temperature, and oxygen content of the exhaust stream are used to fine tune the mixture ratio. But the first three I mentioned are the heavy hitters in determining how much fuel and what timing curve to use is determined by the computer. The changes you’re suggesting from the existing cam and valve train, plus the necessary changes to the throttle body will upset the relationships of throttle angle to manifold vacuum to RPMs. The sensors will send data to the computer that is erroneous to that which the computer is programmed to expect. Therefore, the mixture and timing will be incorrect for the engine load and RPMs. The only solution is a new computer chip that understands the changes and realigns sensor data correctly with new fuel and timing maps. Several top notch places make new chips see them at:

http://www.fastchip.com/

http://www.tbichips.com/

http://www.hypertech-inc.com/

http://www.superchips.com/

http://www.tpis.com/


Hopefully this is interesting material if not down right useful to you. The engine you’re proposing with the changes I’m detailing for you will dyno from 300 to 330 hp no problem.


Bogie

[slammedchevy1500]

Originally Posted by oldbogie

This is a good cam for what you want to do. It is a lot more cam than what comes in a truck TBI, roughly 205 degrees of duration versus the TBI's 167 degrees.

But your under-estimating the problems.

1) Block may, or not, be a roller

2) TBI's use Swirl Port heads, not good for performance.

3) Existing TBI doesn't flow enough air

4) The LT1 cam changes the relationships of throttle opening and manifold pressure (vacuum) to the fuel and ignition maps.

Taking this apart:

1) Prior to the Vortec in mid 95, truck engines may or may not be provisioned for a roller cam. Hardly any truck engines, if any, got roller cams though many blocks have the provisions to use them. Check the casting number to see if the block is at least provisioned for a roller cam.
For unprovisioned 350 flat tappet blocks, look for casting number 10054727, 14079287, 14088548, and 14101148. For provisioned 350 roller tappet blocks look for casting numbers 10243880, 14011148, 14088526, and 14093638. However, the 880 block is the Vortec block it appears in late 1995 production without Vortec heads but with Swirl Port heads and TBI. Certainly your 89 won't have an 880 block. If your block is provisioned for a roller then conversion is simply getting the GM kit that has the spider, guide bars for lifter retention, and the cam thrust retention plate. The roller cam requires a roller timing set. This uses a narrower gear and chain to accommodate the space the thrust plate occupies, thru which the longer nose of the cam projects to provide an attachment for the timing gear. It isn't uncommon to have clearance problems with the timing cover with this set up. I find a two piece cover that is made to provide for cam and timing case changes without having to drop the pan will often provide the forward clearance needed plus making maintenance of the timing set a lot easier. This does demand a long water pump which you've got.

The solution for a non roller block conversion is to use 4.3 V6 hydraulic lifters which are shorter than V8 lifters as the non roller provisioned blocks do not have the raised lifter blocks. The spider is bolted thru the main oil galley’s flow is maintained by increasing the i.d. of the galley and reducing the diameter of the bolt (remove the threads in the middle area) where its shank is inside the galley. Cam thrust is taken using the typical thrust bumper since there isn't any provision to mount the thrust plate. The roller cam needs the thrust space filled with something. The simplest something is to buy a thrust plate and cut the ears off, smooth edges, etc.

2) The TBI truck engines use the 14102191 or 193 Swirl Port head. This heads' port flow cuts off around 4500 RPM. This is a constraint inconsistent with the performance available from the LT-1 cam you're proposing to use. So the heads need to be changed to match the cam, otherwise the performance available from this cam can't be achieved by the engine. Certainly Vortecs would be the first choice that comes to mind, however the older L98 type head in cast iron casting number 10125377 is the simplest choice as it bolts on and accepts your TBI intake with no modifications to the bolt patterns or to the EGR system where the Vortec requires a unique and expensive intake for TBI and extensive modification for an externally plumbed EGR. As usual, you need to check clearances when using a higher lift cam and especially with 1.6 rockers. Look at retainer to guide clearance, spring coil to coil, rocker to stud, pushrod to its guide and hole clearance, and valve to piston clearance.

The other important thing with the heads is combustion chamber volume. Ideal compression with an iron head is about 9 to 9.5, with aluminum heads this can be pushed a ratio and still run gas station fuels. A vital consideration is the development of high amounts of squish and quench within the combustion chamber. These two events occur from the very close closing of the piston to the step on the side of the combustion chamber opposite the valves and spark plug. Squish is the ejection of mixture from the far side of the chamber toward the spark plug. This stirs the fuel and air one last time before ignition and increases the density of mixture around the plug giving a stable and reliable ignition, with a fast burning flame front thru a thoroughly mixed thus efficient burning A/F mixture. The result is optimized power and efficiency. The quench function is next from the same components in the same position. The difference is the accelerating flame front increases in pressure and temperature and if left uncontrolled will explode ahead of the flame front. The quench function presents the far side of the combustion chamber as an area of low volume to high surface area. It acts as a heat sink removing the excess temperature thus lowering pressure just enough to suppress the desire of the mixture to explode, what we call detonation or pre-ignition. You want this side of the piston and head’s step to close at TDC to within .045 to .060 inch. Factory or replacement pistons with circular dishes greatly limit the area closing together and reduce the squish/quench function which then requires a higher octane fuel for the compression ratio used. By using a flat top piston this zone is maximized for function but risks to much compression ratio for available octane fuels when combined with a tight chamber. The solution is found in the D cup piston which controls compression by increasing necessary chamber volume while maximizing squish/quench thru keeping the maximum amount of flat surface of the piston opposite the step of the combustion chamber. This adds what’s referred to as mechanical octane to the engine. Now it’s easy to think a solution is a large chamber head with a flat top and this is used with considerable success. But, the ideal configuration for developing a strong swirl of the incoming charge is a tight chamber around the valves. Modern Gen 1 SBC design for all out competition takes this idea to extremes with the likes of the SB 2.2 heads developed for NASCAR where the chamber is only about 40ccs. For the street, it isn’t necessary to go this crazy; I point it out only to show the modern power trend is away from open chamber heads and has been for many years.

3) The stock TBI only flows about 440 CFM this is minimally adequate for what you propose, there is a 670 CFM option with a 2 inch bore available with a 454 TBI, or the Holley 502 series, or your existing unit can be bored out and rebuilt by Turbo City, they’re on the web. This and the cam change will drive a new computer chip.

4) The changes you’re proposing upset the computer’s view of the world. TBI and other EFI systems that use Manifold Absolute Pressure (MAP) sensing do not measure air flow into the engine like Mass Air Flow (MAF) systems do. MAP systems, which your truck uses, compute air flow into the engine by calculation of sensor inputs. Three of the most important that it uses are throttle position, manifold vacuum, and RPM. Other sensors for atmospheric pressure and temperature, engine temperature, and oxygen content of the exhaust stream are used to fine tune the mixture ratio. But the first three I mentioned are the heavy hitters in determining how much fuel and what timing curve to use is determined by the computer. The changes you’re suggesting from the existing cam and valve train, plus the necessary changes to the throttle body will upset the relationships of throttle angle to manifold vacuum to RPMs. The sensors will send data to the computer that is erroneous to that which the computer is programmed to expect. Therefore, the mixture and timing will be incorrect for the engine load and RPMs. The only solution is a new computer chip that understands the changes and realigns sensor data correctly with new fuel and timing maps. Several top notch places make new chips see them at:

http://www.fastchip.com/

http://www.tbichips.com/

http://www.hypertech-inc.com/

http://www.superchips.com/

http://www.tpis.com/


Hopefully this is interesting material if not down right useful to you. The engine you’re proposing with the changes I’m detailing for you will dyno from 300 to 330 hp no problem.


Bogie

thanks for the info. but now im curious to know if my 700r4 in stock form will hold the abuse of 330hp

[Jim Rockford]

Originally Posted by slammedchevy1500

thanks for the info. but now im curious to know if my 700r4 in stock form will hold the abuse of 330hp

No need to be curious, just know it won't..lol TCI makes a good rebuild kit. done sevral with it and a new beast sun shell and there almost bulletproof.

[oldbogie]

Originally Posted by slammedchevy1500

thanks for the info. but now im curious to know if my 700r4 in stock form will hold the abuse of 330hp

Probably not well without a rebuild. I won't even go on one of these adventures unless the customer belly's up to the bar for a transmission replacement. I know people who have done this and it seems the auto trans is good for not much more than a month behind the new motor.


Bogie