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[knightowl73]

Ok so me n a buddy have been contemplating this engine build for about a month now, after finding out about a L99 motor in a caprice we have that was bought as a parts car. thought we had a lt1 and i quickly was interested in the donor motor to swap into our 77 stepper project. its kinda the shop's budget build.

anyway, we found this out thru some research:

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You can build a 1 piece seal 302 out of that by using the crank which as stated specs out at a 3 inch stroke, and you also use the rods from the engine which I believe they are 5.940 long, and then you use standard 5.7 rod length pistons from a 350 chevy, and assemble it all into a 350 block. The rods and crank are worth the money you paid for it. The block could also be used to make a 305 by putting a 1 piece seal 305 assembly into the block. That 4.3 V8 used the same pistons as a vortec 305.


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and i have a 87 305 tbi motor on a stand with 57k and a set of 062 vortec heads, thinkin of putting the lil 302 together to see what it does. this would still be a 302 right?
problem is choosing to stay fi or go carb, and trying to find options as we both know we must use a cam that will suit fi if we go that route.
Not too worried about having the chip retuned, no biggie. But if we kept the tbi what are our options for cam,pushrods,lifters. we have allthe roller stuff available inn the caprice motor, so will we be able to use the lt1 cam,lifters, and pushrods with the vortec heads.
the truck wil most likely end up with manual trans (recomendations would be cool too- we both are leaning toward the older 4-speed saginaw or muncies) and the 3.73 rear we got laying around here already.

if we choose to carb it, i dont think we would roller cam it unless we could still use the same stock lt1 cam, otherwise was pondering a comp 262-268 grind. the only benefit we see to going carb is to get the lumpy idle that goes aloong with the look we are after on the truck, dont think you could get that lump from and tbi motor or could you? also, can we use the felpro shim head gaskets on this motor or do we have to stick with 305 specific gaskets? anything else we might run into on this? Ive been looking into valve springs for the vortec heads, ive seen a few guys say ls springs work with the right retainers and wont need head machining, is this true?

[old Rusty C10]

moved this to the engine forum for better responses

[knightowl73]

wow i figured someone woulda jumped all over this, at least just to bash. but i figured more responses would have came bu now. maybe i shoulda put the tile as "87-up one piece rear main seal 302 torquer" prolly would get more attention lol. (nope not kiddin bob)

[Captainfab]

Yes you can build a lete model 302 using the crank and rods from a L99 4.3 V8. In fact I have been casually looking for a L99 to do just that, but haven't found one around here yet.

I would think that you could use the 305 TBI without much tuning required if any. Of course that depends on which cam you use. Whether you can use the L99 cam, lifters, pushrods and all depends on what block you are planning to use. If it has been machined for the factory roller cam, then you should be able to use all of those components. I would suggest staying with a roller cam one way or the other.

The Vortec heads will be just fine for a little 302. They are both a 4" bore so no issues with valve to cylinder clearances that can happen on a 3-3/4" bore of a 305 block.

I would imagine a steel shim head gasket will work fine as well, as long as you aren't going to run a domed piston.

The 302 isn't going to be the best choice for an engine in a truck since they really don't put out the low to mid range torque you need in a truck.

[knightowl73]

thats why we are trying to stick with a manual trans and 3.73 gears out back. itll be something to play in and maybe a partsrunner or somethin. think it would be a fun truck to drive with the right gears/trans. by the way the block is a 87 305 block from a tbi truck so i think i should be ready for the roller hardware i think. im wondering if the stock lt1 and lt4 cams would work and what all pushrod/lifter/rockers would i be using. are vortec pushrods the same length as lt1 motors since they are roller too? are there factory roller rocker arms also?
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[Captainfab]

You will not have a 302 cu in engine if you use a 305 block. The bore on a 305 block is only 3-3/4" You have to use a 350 block which has a 4" bore. With the 305 block, you'll still have a 262 V8.

The LT1/LT4 cams will work in the Gen I blocks. You will have to shorten the dowel pin in the front of the cam. As far as I know all the valvetrain of the LT1/LT4's are the same as the Gen I roller cam engines. The LT4's came with roller rockers from the factory. Although I don't remember if they were all 1.6's or if there were 1.5's also.

Originally Posted by knightowl73

thats why we are trying to stick with a manual trans and 3.73 gears out back. itll be something to play in and maybe a partsrunner or somethin. think it would be a fun truck to drive with the right gears/trans. by the way the block is a 87 305 block from a tbi truck so i think i should be ready for the roller hardware i think. im wondering if the stock lt1 and lt4 cams would work and what all pushrod/lifter/rockers would i be using. are vortec pushrods the same length as lt1 motors since they are roller too? are there factory roller rocker arms also?
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[knightowl73]

ah, thanks for the info. no wonder the lil l99's get such great gas milage, i was wondering how they were talkin making it a 302. so that would mean id have to use a 350 block and 350 VORTEC pistons also? also is it true that lt1 and 350 vortec pistons are the same? does anyone know? i know the vortec pistons would be easier for me to grab.

[rfmaster]

That's a very interesting combination of parts. Let see if I got this right. To built an LT1 based 302 you need to have LT1 block with its 4.0 inch bore. From L99 (baby LT1) engine you need to source the crank for its 3.0 stroke. Use standard 5.7" rods from LT1 or aftermarket. Standard 302 chevy pistons (TRW, KB, SP + others) should work - I did a quick look through and there are few low cost piston options. Perhaps some one can chime in. Also keep in mind that cast iron LT1 heads measure between 53 to 55 cc (give or take). I would spend some time with a compression calculator figuring my build options first.

The 302 should be a high RPM screamer - little shy on low end torque, but with a nice roller cam and heads should scream all the way to 7000 RPM.


//RF

[knightowl73]

thats what i was thinking, just didnt want the hassle of lt1 ignition and water pump issues. Just wanted a simple new-age one-piece rear main 302 with tbi and vortec heads or a good carb. im kinda scared of the lt1 and wated to keep it simple , and all factory if i could for the cool factor. i reallt think gm could have built one. woulda been a 4.8 vortec or somethin.
ill have to do alot more research,i thought i had to use the 6" rods from the l99, ill also look into the pistons aftermarket, just thought i was going to be able to use the whole rotating assembly from the l99 first in the wrong block. are there any factory pistons that i might could find in the boneyards to not have to buy any aftermarket?

[rfmaster]

Originally Posted by knightowl73

thats what i was thinking, just didnt want the hassle of lt1 ignition and water pump issues. Just wanted a simple new-age one-piece rear main 302 with tbi and vortec heads or a good carb. im kinda scared of the lt1 and wated to keep it simple , and all factory if i could for the cool factor. i reallt think gm could have built one. woulda been a 4.8 vortec or somethin.
ill have to do alot more research,i thought i had to use the 6" rods from the l99, ill also look into the pistons aftermarket, just thought i was going to be able to use the whole rotating assembly from the l99 first in the wrong block. are there any factory pistons that i might could find in the boneyards to not have to buy any aftermarket?

The way I see this (without digging into this further) all you need L99 crank - 3" stroke. Then if you have any 1 - RMS 86+ 350 block - it should work. My choice would be pre LT-1 roller LO5 or 96+ vortec L31 block. The L31 will have a 4-bolt mains! The 302 chevy pistons are rare by definition - there were very few factory built 302 and used for class racing (TransAM rules in the 60's <305CID). The few that did make it into the street were of HP forged flavor.
Pistons are still available - 302 is very popular with retro crowd! You'll need a good set of high flowing heads to get this motor potential. Couple this motor with a 4-speed (or -5-6) and TBI - watch - this can be hot combo in a lightweight chassis!

From online sources it would appear that L99 lasted only two model years - 94 to 96 in a Caprice which makes it some what rare. I wonder how many taxi cabs were equipped with L99 vs LT1. L99 Engine can be id by its displacement cast on the bell housing flange.

//RF

[Captainfab]

That's not quite correct. To build a late model 302, you need the following.
A '86 and newer one piece RMS 350 block. Preferably a roller cam capable block. A L31 Vortec 350 would be ideal.....and no not all L31's are 4 bolt mains, typically the ones that were in C2500's and 3500's. Then you will need the crank and rods from the L99 4.3 V8. By using the 5.940" rods from the L99, you can use an off the shelf 350 piston. There is no need to buy the expensive aftermarket forged 302 pistons.

Originally Posted by rfmaster

The way I see this (without digging into this further) all you need L99 crank - 3" stroke. Then if you have any 1 - RMS 86+ 350 block - it should work. My choice would be pre LT-1 roller LO5 or 96+ vortec L31 block. The L31 will have a 4-bolt mains! The 302 chevy pistons are rare by definition - there were very few factory built 302 and used for class racing (TransAM rules in the 60's <305CID). The few that did make it into the street were of HP forged flavor.
Pistons are still available - 302 is very popular with retro crowd! You'll need a good set of high flowing heads to get this motor potential. Couple this motor with a 4-speed (or -5-6) and TBI - watch - this can be hot combo in a lightweight chassis!

From online sources it would appear that L99 lasted only two model years - 94 to 96 in a Caprice which makes it some what rare. I wonder how many taxi cabs were equipped with L99 vs LT1. L99 Engine can be id by its displacement cast on the bell housing flange.

//RF

[rfmaster]

Originally Posted by Captainfab

That's not quite correct. To build a late model 302, you need the following.
A '86 and newer one piece RMS 350 block. Preferably a roller cam capable block. A L31 Vortec 350 would be ideal.....and no not all L31's are 4 bolt mains, typically the ones that were in C2500's and 3500's. Then you will need the crank and rods from the L99 4.3 V8. By using the 5.940" rods from the L99, you can use an off the shelf 350 piston. There is no need to buy the expensive aftermarket forged 302 pistons.

The only reason why I would stay from 5.940" rods (for high RPM, HP application) these odd ball pieces were produced using powdered metal casting process. The process produces connecting rod in a permanent casting mold using metal powder under heat and high pressure. The rod and cap are formed as single piece and then machined. Cap is literally cracked away from the rod along predefined score marks on the rod surface. This method creates a unique interface on each connecting rod, which prevents the substitution of one cap to another rod. As a result resizing these rods or attempting replacing rod bolts should be avoided.

Any engine that is capable of spinning above 6000 RPM (and expected to live there) should have parts carefully selected. Just my 2 cents worth. If you are planning to keep it under 5k stock rods should be just fine.

//RF

[Captainfab]

Everything I've heard about the PM rods, is that they are as good if not better than the old 'pink' rods. I've had a set of the PM rods resized with no issues.

Originally Posted by rfmaster

The only reason why I would stay from 5.940" rods (for high RPM, HP application) these odd ball pieces were produced using powdered metal casting process. The process produces connecting rod in a permanent casting mold using metal powder under heat and high pressure. The rod and cap are formed as single piece and then machined. Cap is literally cracked away from the rod along predefined score marks on the rod surface. This method creates a unique interface on each connecting rod, which prevents the substitution of one cap to another rod. As a result resizing these rods or attempting replacing rod bolts should be avoided.

Any engine that is capable of spinning above 6000 RPM (and expected to live there) should have parts carefully selected. Just my 2 cents worth. If you are planning to keep it under 5k stock rods should be just fine.

//RF

[knightowl73]

so right now all i need to find is a good 86-up block. wish i had swapped the motor in my truck already, it would be a nice core to start with. would the 305 vortec heads i have hurt me really bad without any valve changes? i was thinking new springs and maybe a mild port job but nothing more. would this be ok for this motor? i figured these heads were a better choice than the other 305 swirlports that i have available, but im sure i could get ahold of a set of 305 ho heads for pretty cheap, but again i think theyd need more work definately to compare to what the stock lil vortec head would do. id rather keep the vortec heads anyway.

[Captainfab]

I really don't know if the Vortec 305 heads would work on a 302 or not. I don't know how well they would flow in the rpm range in which you will likely be running that 302. If you're going to all the work of building this 302, why not get a set of Vortec 350 heads?

[knightowl73]

Originally Posted by Captainfab

I really don't know if the Vortec 305 heads would work on a 302 or not. I don't know how well they would flow in the rpm range in which you will likely be running that 302. If you're going to all the work of building this 302, why not get a set of Vortec 350 heads?

i already have the 305 vortec heads was going to use on my 283 which was originally the motor i was putting in this truck since i knew it was getting a sstickshift tranny. I opted for the 302 thinking i had the parts already and probably wouldnt need too much more to do it.

now it seems like id prolly just be better using my 283 as a vortec for now with a carb on itunless this ends up another long-long-term project, then im not sure. thought this would be the only way id ever get to experience any old high revving "legendary motor, and it might be one of the few i could afford to drive every once in awhile. like i said, this is going into a shop truck, but the truck is mine, so ill most likely wanna drive the rat piss outta it as im sure my buddy will too.

with me not being that big of a speed nut, i just like the loo,k im 0-85mph usually, im not sure if the powdered metal rods would ever come to fail me. im confused now, i really could pull off building this 302 motor, but if i have to opt for another set of heads, well right now that isnt thesable since im mostly tryna use what we got on hand and of course keep the build to a minimum. and if the heads i have wont really flow as good then for now ill take the easier way out im sure and just use the 283 as a lil vortec motor at least for a short while.

[Winola73]

I looked into this a couple years ago but never came across a decent L99 for the crank and rods cheap enough. I ran it through DD200 with 8.9 to 1 compression, L-31 Vortec heads and the '395 Ramjet roller cam. It showed an estimated 360 FWHP @ 5500 with peak TQ 370 from 4000 through 4500. It shows 335 FtLbs @ 2000 and is still making 340 FtLbs @ 5500.

[Captainfab]

Wow, that's a little more torque than I would have guessed. Thanks for the info.

I haven't found a crank and rods, or a whole engine yet either. I'll still be looking. Heck I have most of the parts to put one of these together.....except for the crank and rods.

Originally Posted by Winola73

I looked into this a couple years ago but never came across a decent L99 for the crank and rods cheap enough. I ran it through DD200 with 8.9 to 1 compression, L-31 Vortec heads and the '395 Ramjet roller cam. It showed an estimated 360 FWHP @ 5500 with peak TQ 370 from 4000 through 4500. It shows 335 FtLbs @ 2000 and is still making 340 FtLbs @ 5500.