Engine SwapEverything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.
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I have a 1990 RS with a 305 tbi in it and im gonna swap it for a 350, ive decided to go with one of theese 2 engines, both vortecs, so i will be able to use that GM tbi vortec intake. i want to get to about 300 HP and want to redo my 700R4 as well, ive already got the headers and the magnaflow exhaust, and upgraded to 3.73 richmond gears and posi traction. i was wondering if i could get some feedback on which way to go, and what motor.
and if i buy the L31 New i would be putting a new LT4 cam in it like the sticky tbi buildup article suggests. any feed back from anyone?
which one should i go with
that l31 is an obd2 engine, i would think itd be easiest to go with a gen1 sbc
please don't post about things that you aren't sure about. They're both gen1 motors. Regardless of the L31 engine being in an obd2 car doesn't mean he can't bolt on whatever intake for vortec heads and run that motor.
Have you already purchased the Vortec TBI intake? If not you don't need Vortec cylinder heads to get 300 horsepower but it would make it easier to get there. If you go with the crate L31 you're going to have to partially disassemble the engine in order to install the cam you want. With the 350 HO it's already rated at over 300 horsepower so you don't have to disassemble anything. Or go with an L31 shortblock and then you pick the cam and heads you want. These are just suggestions. Personally I would do one of the latter two.
Have you already purchased the Vortec TBI intake? If not you don't need Vortec cylinder heads to get 300 horsepower but it would make it easier to get there. If you go with the crate L31 you're going to have to partially disassemble the engine in order to install the cam you want. With the 350 HO it's already rated at over 300 horsepower so you don't have to disassemble anything. Or go with an L31 shortblock and then you pick the cam and heads you want. These are just suggestions. Personally I would do one of the latter two.
I would personally buy the STOCK L31 crate for a 8,600+ GVW truck. You will get the stronger crank, 4 bolt mains, and all the factory roller hardware. The 330 HP crate engine cam is not the best and its a standard flat-tappet. The L31 could easily make 315+ gross FWHP when setup like the 330 HP HO 350 was when dynod. It makes 255 NET FWHP in fully OBDII compliant form with the factory restricted exhaust and intake.
if i go for the new L31, should i bother putting the LT4 Cam in it? if so do you have a link for the other springs and rockers i will need for it,
also i was told i will have to replace my throttle body, would the holley 670cfm be enough for that engine and will i have to go with bigger injectors?
please don't post about things that you aren't sure about. They're both gen1 motors. Regardless of the L31 engine being in an obd2 car doesn't mean he can't bolt on whatever intake for vortec heads and run that motor.
yeah in retrospect that doesnt make much sense, i realize its the same sort of block, and i guess the main difference is just the cam position sensor, which would just become redundant seeing as how the obd1 computer needs less to run.
what advantage would there be of buying a vortec block over the pre obd2 blocks, or is it just to get the vortec heads as part of a pre-built combo?
yeah in retrospect that doesnt make much sense, i realize its the same sort of block, and i guess the main difference is just the cam position sensor, which would just become redundant seeing as how the obd1 computer needs less to run.
what advantage would there be of buying a vortec block over the pre obd2 blocks, or is it just to get the vortec heads as part of a pre-built combo?
thats all well and good but whats the difference between getting an l31 and a standard gm crate motor with vortec heads on it, i just dont get why youd get an l31
edit : bah more reading, i just glanced at it cause im going to bed, i guess the l31 in longblock form just has better internals then a standard crate motor cause it was designed for a heavy truck, then the similarly priced standard gen1 longblock
thats all well and good but whats the difference between getting an l31 and a standard gm crate motor with vortec heads on it, i just dont get why youd get an l31
The L31 crate is LESS expensive than the GMPP 330 HP HO 350. The HD L31 comes with a factory roller cam, 4-bolt mains, forged crank (the ones I have had apart), stronger pistons, different piston rings.
Its setup for a crank sensor so you can convert to a single plain intake with MPFI, 0411 LS1 pcm, and vortec electronics if desired at a later date.
Either one would have valve lift issues if you want to upgrade the cam. Typically no more than .480" lift, although some have reported issues at .440" lift.
hey five 7 kid i was reading some of your other posts and you dont seem to be a big fan of vortec heads. if you were in my position and had between 2 to 3 grand to spend on a crate motor, whcih one would you go with?
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i just want a 350 that will haul ***, and i can hear that cam rumble when it idles.
Last edited by tilerob79; 08-11-2008 at 10:01 PM.
Reason: Automerged Doublepost
I'm not a big fan of off-the-shelf Vortec heads for the very reason above.
sdparts.com has modified Vortec heads and kits that are a great value.
Fast Burn heads are Vortec-based, and are killer for the price. Edelbrock, RHS, others have Vortec style heads as well that work well.
For $3k, you can get a Vortec-headed 350 300 to HP without breaking a sweat. The previously mentioned roller lifter HD L31 with an LT1 cam would probably get there (assuming decent exhaust, proper intake/carb, etc.). Not installed for $3k, but at least to your door with a little left over.
what do you think the difference would be with the horsepower of the L31 with or without the camswap, in other words how much more HP is the LT1 cam gonna give me, and is it worth it.
also is it the LT1 cam or Lt4 cam?
also if it were you, would you go with the L31 crate or the GM 350 330/HO?
