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The 72 350/200 auto trans l’m working on has 100k miles. I’m not overjoyed with its performance. Sitting in the garage is a freshly built 350 L-31 roller motor with AFR heads, flat tops, LT4 Hot Cam, and AFR intake (not sure about the intake’s height under the stock hood).
Do I rebuild the 350, (.030, flat tops, Melling cam, headers, Holley 750) or stick the L-31 in and call it a day?
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
you may have to put a oil pan on the L31 that will fit the corvette and swap out the intake to a low profile intake or pray that a low profile drop air cleaner would fit..... But the engine is built, run it and if you are into engine rebuilding for its relaxing qualities, rebuild/ modify the original up to atleast 450 hp...thats where an engine starts to get fun
This combination may fit under the stock hood on a 72 350 Vette.
If not, let me know:
AFR intake # 4812 height 5.25”
Holley EFI # 550-869 height 3.5”
I prefer the L31 choice that you have on hand; but unsure which-what induction you'll run.
Base 1972 has a Low Hood.
More height considerations are at stake than a "combined" pad height.
The angle of pad affects how the air cleaner lid may contact hood.
The motor sets in chassis at an angle as well; typically about 3 to 4 degrees Up in front. Per AFR site for P/N 4812 intake: Carburetor pad height is 4.725” ( front 4.200”, back 5.250”)
Edelbrock EPS P/N 2716 to fit L31 Vortec heads
squarebore pad Per Edelbrock site Manifold ht: A-3.87", B-5.28; Carb pad height: 4.57"
You indicated you would run a 750 Holley; usually that means a square bore Carb
But you reference a Holley EFI P/N 550-869 (that's a Spreadbore Throttle Body (not an intake) ?
Most intake manufacturers state their intakes will not fit under a stock Corvette hood.
The manufacturers have to, for legal purposes add the oem air cleaner assemblies dimensions on top of an oem style carburetor.
There are many intakes that will fit under a stock hood, but you’ll need to do research here to find an intake, carburetor and air cleaner assembly combination that actually fits.
Some will some won’t.
Google search for forum threads on the subject and you’ll find the correct combination.
Leigh1322 has a good data base in one of his threads.
Let me start by saying, this is a good problem to have. I’m curious what caused you to build the small block that’s sitting in your garage now. You asked for opinions so here’s mine, order the correct oil pan and a low profile intake, pull the old motor, slide the new one in and see how you like it. You’ll learn what you like and perhaps don’t like about the new motor and can press that knowledge into service as you jump into rebuilding your original engine to achieve the performance combination you want.
This is certainly in the right place to glean the experiential knowledge of all the members here that have tread the same path you’re on dozens of times in the past. The path to success here is to feed the beast some pictures. You’ll get engagement in return. With that said, how about some pics of that 72 and the engine waiting on the stand?
Here is the latest and greatest hood clearance thread. You may or may not be able to get away with that intake with enough of a drop base air cleaner. Then again, if you’re going with EFI you can run a single plane without having to worry about losing low end torque.
L31s are great engines, yours sounds even better yet. I don’t see a reason not to put it in. And I agree with the above, post some pictures!
Your suggestion on installing the L-31 in the 72 is valid. It will give me an opportunity to sort it out plus some fun driving time. I can rebuild the original 350 this winter. If I decide to sell the car the OEM motor will be ready to go. Buyers seem to pay more for originality plus I’ll have a well sorted 350 roller motor ready for the next project.
Here’s a pic of the new bullet.
Your suggestion on installing the L-31 in the 72 is valid. It will give me an opportunity to sort it out plus some fun driving time. I can rebuild the original 350 this winter. If I decide to sell the car the OEM motor will be ready to go. Buyers seem to pay more for originality plus I’ll have a well sorted 350 roller motor ready for the next project.
Here’s a pic of the new bullet.
Photo resolution too low for me to resolve what I think may be piston part number stamped or etched into 4VR piston crown. What is it ?
May begin with H ? What is number ?
Have you measured quench distance ? Have you measured how far down in hole top of piston is from deck when piston at TDC ? What is it ?
*accuracy matters
I got an Edelbrock RPM air gap to fit under a 1970 flat hood by using the factory drop base air cleaner with a 3 inch filter and using a bolt instead of a wing nut to hold it down. I have a Holley HP carb without a choke and shorter vent tubes. It fits under the hood with about a 1/4 inch of clearance.
The number that starts with the letter H is:
H645DCP/H345DCP .030
As I suspected; very popular piece but not among my favorites. They're made of high-silicon Hypereutectic cast aluminum. Are among the least expensive.
has the old fashioned thick 5/64" x 5/64" x 3/16" tractor-style ringpak that makes beaucoup friction although doesn't seal as well as thin metric. They're a good quality "replacement" grade piston for OE rebuilds But not a "performance" piece. Fits both 4.3L V6 & 5.7L V8. Like OE, has a slight pin offset to aid skirt slap reduction.
also, it's a short rebuilder grade w/ only 1.548" compression distance (OE's about 1.560"). Depending if deck's been cut or not, you may have difficulty achieving any functional quench distance. Guessing, based on pic showing old gasket stain; guessing deck hasn't been cut. That's why to measure as I'd asked prior.
If decks are OE and have Not been cut; these pistons probably sit about 0.037" down in hole when at TDC. Then add thickness of whatever compressed gasket is to determine quench distance. The thinnest steel shim gasket is about 0.015" . Quench matters.
Also, the L-31 does not seem to have a boss on the drivers side of the block for a Z-bar pivot bolt.
Does anyone make a bracket to fit the z-bar on this block?
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1972 Base 350 Dilemma
