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Vortec 5.7L swap


dyermullet

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I have a good running Vortec 5.7L i pulled from a 1998 chevy suburban.  I know about the vortec specific intake, no mechanical fuel pump provision etc.

 

My question is about the oil pan. Does anyone know if this truck oil pan will fit my 1971 monte carlo?  If not does anyone know what oil pan I need for a 1 piece rear main seal block?

 

Thanks in advance.

 

I am getting close to finishing up this swap.  So I thought I would update the thread with some details for future search.  I will try to update with some pictures and part numbers, and put in better order.

 

I swapped a complete L31 from my 1998 chevy suburban (I need to upgrade to a 3/4 ton truck, so I decided why not), into my 1971 monte.  The car is a 350 2 barrel factory AC th350 trans.

 

My goal was to reuse as many pieces as I could (keep the cost down), and stay somewhat stock appearing.

 

I pulled the L31 from the suburban, cleaned, painted chevy orange, and installed it as it.

 

Intake:

I purchased an Edelbrock Performer Vortec intake thinking it would be the best choice because this is just a cruiser, and I wanted the most hood clearance. 

It turns out the Performer intake doesn't have any provision to use coolant to warm the manifold, while the Performer RPM and GM performance parts manifold both do.  So if I was to do it again I would purchase one of those. 

The performer intake doesn't have the correct bolt hole locations to mount the rear upper AC compressor bracket. 

I reused the stock thermostat housing, the mounting surface on the intake is taller which required me to modify the stock upper alternator bracket.

 

Timing cover: I keep the stock L31 plastic timing cover because I just used the engine as is, it didn't have any major leaks.  The plastic timing cover is too large and does not allow the power steering pump bracket to be installed. The solution is to install a traditional tin timing cover.  Right now I just want to drive the car, so I am going to try an allen grove PS bracket.  edit: Allen Grove PS bracket worked perfect.  It allows the factory AC bracket to work with no problem. Stock length PS and AC belts.  Only negative to using allen grove PS bracket and the factory AC bracket is can't check the PS fluid while engine is running.  Have to reach into the belts to reach dipstick.

 

Oil pan - Stock truck pan fits the car no problem.

 

Fuel pump - I installed an inline fuel pump I saw referenced online.  I also remember selling these at the auto parts store back in my college days.  I will post a part number but universal inline pump fits 70's datson and mazda pickups. 

 

Revised Coolant bypass - I used 3/8" heater hose from intake to a T on the return hose from the heater core.  Vortec 350 blocks are not drilled for the internal bypass directly to the water pump.

 

Valve Covers - I reused the truck valve covers.  I don't know the best combination yet.    The DS oil fill tube interferes with the factory AC compressor. I swapped them DS for PS but accidently broke off the extended length oil fill tube when installing the engine.  I might try to get a TBI truck valve cover because it doesn't have the extended oil fill. 

 

Exhaust manifolds - I used the 1971 manifolds, so I could bolt the existing exhaust back in. I couldn't install the spark plug boot heat shields because the mounting holes exist but were not tapped on my L31 block.  I might go back later and correct this, but didn't want to spend the time.  The manifolds fit, but the spark plug boots are very tight to the manifold, so I think the spark plug location may by slightly different than the old heads.  If this turns into a problem I may try to run the truck manifolds or rams horns or other.  (as of Feb 2017 has not been a problem).

 

Distributor - old worn out HEI distributor that was already on the car. (had to change distributor gear to match the factory roller cam)

 

Spark plug wires - used a mixed set of wires I already had.  Most are too long need a better set.  I used the vortec hold downs to keep the wires cleanly mounted.

 

Carb - I am giving the 625 cfm Street Demon carb a try, I like Q-jets but I wanted to give this carb a try after seeing at a vendor display this summer.  And it was half the price of a good Q-jet.  The Street Demon carb vacuum fittings is in the way of the threaded hole on the intake for vacuum.  So PB is on one 3/8" port, PCV on a second 3/8" port and all other are on the 3rd smaller carb port (vac advance, th350 modulator, HVAC).  Will have to see how that works.  edit: Carb works great. even the idle mixture screws were perfect.  Any change resulted in a drop in vacuum.  Only downside is the carb is blocking the rear vacuum port on the intake.  I had to plug that.  I have power brakes on one carb port, PCV on second carb port.  And that left all other accessories (hvac, trans, distributor vac advance) on third carb port.  If I ever have the intake off i might drill and tap another vacuum port.

 

Throttle linkage and kickdown linkage - I used the lokar carb bracket.  It fit perfect.  I used lokar trans kickdown cable (my original started leaking at trans) and lokar throttle cable. 

 

Trans -reused the TH350 no problems that I can find.

 

Starter - I used the factory 1998 vortec starter.

 

Battery Cables - I redid the battery cables reusing parts from the suburban, and my new positive is a cable I had.  Negative from battery to the block, added ground from battery to body, and going to add another braided ground from body to frame.  Used some factory 98 hold downs to keep the cables looking cleaner.

 

Added 2 relays for the fuel pump and the electric choke, ran power directly off the battery through a fuse.

 

Motor Mounts - reused 1971 style motor mounts. Replaced bad DS mount.

 

 

Future will be cam swap, new timing chain, tin/aluminum timing chain cover, and maybe manual trans.

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  • 4 weeks later...

I'm curious how the butt dyno rates this engine compared to your original. Keep us posted.

I'm planning vortex heads on my '72 350 to bump the compression and get better flow. Do you know if the Vortec Performer RPM has bolt holes for the stock a/c bracket?

Scott

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  • 1 month later...

I updated the original post.

 

I don't know if any other intakes have correct mounting holes.

 

I can't compare to the old engine because it had three dead cylinders due to bad plug wires.

 

I love the way it runs, now I need to get rid of the glass packs.

 

I would not hesitate the L31 swap.  Good compresson, vortec heads, and roller cam so no flat lobes.  The engine has 255,000 miles and still runs strong.  My plan is to run it 2-3 years by that time I will find something to swap it for.

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  • 1 year later...

I updated the original thread with some more details. 

 

If you are building a cruiser, for the price of these engines from a junk yard, and the ease of swapping I can't see spending the time doing an LS swap unless you really just wanted to.   The only "hassle" is loosing the mechanical fuel pump, but a cheap electric inline pump has resulted in a super easy starting car never have extended cranking to fill the float bowls back up.  

 

Even with 2.73 gears the car has more than enough power.  The stock cam is so mild the engine will idle no problem at 550 rpm with the AC compressor running.

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