Looking for a corvette engine rebuild on my 71 LT1. MUST keep everything ncrs original, located in central Illinois! Prefer someone wiyh ecperience with older vets, Any suggestioms or recommendations, THANKS!!!!!!!

 

I live near Chicago. I use Corvette Sports in Sheboygan Falls, WI. Dick has restored several cars for customers to NCRS standards. He also has built road race cars for customers. Refer to the Corvette Sports website for details.

 

Have it built as a full roller setup, lifters and rockers. We do these numerous times and ALL make it through the "judged" shows.

If done correctly you cannot tell it's a roller setup. You also have the option of building it as a 383" stroker while still maintaining the 100% factory appearance.

The HP numbers should range between 375 and 450, depending on the size, and be very "comfortable" HP with respect to street manners. No problems with vacuum either with the correct cam.

At a minimum, and assuming either the 350" or the 383" platform, I would recommend some Ross lightweight pistons and a Speed-Pro ring pack.

Thanks, Gary in N.Y.

P.S. Here's a shot of an earlier, very conservative BB setup with the same components listed above, has seen many shows. This is a 100% rollerized build and has been out for years now. Even the V/C gaskets are "standard" thickness!

 

Are you currently active in NCRS and having your car judged? If not your Vette is worth quite a bit of money with all numbers matching components. In that respect I would bag the LT1 and get a GM replacement engine and use all the LT1 comments on it. IS having it judged worth the chance of blowing the original LT1 ?

You save the LT1 and rebuild it when you want to sell it as without the Lt1 engine it is not worth any more than any '71 Vette. You can really only rebuild it once (.030") over so you can buy a crate engine put all the external parts on it to make it look like an LT1. And as said above you can fool around with the internals like roller cam etc. and really make some power. Then when the time comes the only time it matters if it has the original LT1 is when you sell it.

 

Yes, I am an NCRS member and working towards Top Flight award.

This is a 5 year project with only the engine remaining. Would like to bore it out a little as possible to smooth out the cylinder walls; slightly larger cam, new valves, springs: could't I have the intake manifold and heads, etc ported and polished??

The engine just doesn't seem to have much power for a 350/330hp solid lifter vet with a 370 rear end. The compression was #2,4,8--190, #1,7--185, #3--180, #5,6--175.

Thanks for any input. Not much of an engine rebuild expert.

 

Keep that LT1 in its origonal configuration. If it dosen't have enough power for you, you have the wrong car or it needs a good tune up .

Bill

 

The '71 LT-1 that I had came from the factory with the 3.55 "economy" rear gear . I had the engine pretty much rebuilt to stock specs with some mild porting, and it dynoed at 386HP. With the M-21, though, it was kind of a dog down low. At the track, it was not good out of the hole, and was a mid-14 second car at 99 mph (crossing the line in 3rd gear). A couple of years later I swapped in a 4.11 rear, and I couldn't believe the difference! It was so much quicker and fun to drive! I never took it to the track after that, but I'm certain that I could have gotten it into the 13's with no trouble. The point is that the LT-1 cam likes a lot of gear. I don't think I would have gained much going to a 3.70 .

 

I agree that it should be kept in original/stock condition. I probably think it's alittle slow because I also have a 2002 Z06--wow it's like riding a rocket.

 

The 330 HP rating is Gross and really only about 275-280 ( at best) Net HP in today's ratings. Its not that great and is the reason for 14's in 1/4 mile times. I would keep it original as well and I am debating this whole issue currently with my L-82 which has a weak #6 cylinder-I want to keep it an L-82, not just a high HP 350. I have a 2010 Z06 for real speed.

 

Does polishing and porting the engine change it from original? Is it worth the time and expense?

Would you use a hydraulic roller cam over a roller cam--no lash adjustment but you loose the solid lifter sound?

Thanks Wallifishrmn

 

O.P., has your car been properly tuned? Has the timimg been adjusted/modified per Lars' timing papers?

I'm an NCRS member as well (70 L-46), if you are not going to race this car, a stock rebuild is all you really need. Porting and polishing the manifold/heads will gain you a few HP at top end, but how much time will you be spending at 6500+ rpm?

No matter what you do to this engine (unless you go to a 383), if you use the original carb/heads/manifolds/etc. for NCRS purposes, you will end up with 375hp +/- when finished.

Again, if you are not going to race this car, a good valve job, new OEM cam, pistons & rings is all that you really need.

When I had my L-46 rebuilt, my goal was to keep it "all original" for NCRS judging. I had the heads ported (the 70 head is 63cc and doesn't flow all that well), used a slightly bigger cam (about 0.010 over stock) and 10.4cr so I could use pump gas. The results, 341hp/387tq. I'm happy with it. It makes more power than stock L-46's I've run against, but it's never going to be a rocket ship using OEM parts.

 

Compression makes power. LT1 has a "personality". The 71 cam is the same as the 70 minus 2 full points of compression, not good for making power. If you are asking what I would do I would retain the personality, retain absolute stock outside look and make only non visible changes. You could stroke it to 383, I wouldn't.

Heads

3 angle valve job
Pocket port, clean up casting flash and open up short turn radius and pinch point on heads. (minor porting)
Mill face to clean up
Open up spring pockets to accept new 1.460 springs.

Head gasket

http://www.summitracing.com/parts/fel-1094/overview/

Block.

Complete rebuild with stock crank and rods, reconditioned. This is still fully forged.
These Pistons (assuming it will clean up @ .020 overbore)
http://www.summitracing.com/parts/sr...make/chevrolet


Cam Kit

http://www.compperformancegroupstore...Code=K12-770-8

Rockers and polylocks.

http://www.summitracing.com/parts/cc...make/chevrolet

http://www.summitracing.com/parts/cr...s-16/overview/

The main problems with making power with your build is the factory heads, Above addresses that as good as you can and the exhaust manifolds with 2" outlets and pipes flaring to 2 1/2. Remedy is headers or 2 1/2 ramhorns into 2 1/2 pipes. This is counter to NCRS so I somewhat addressed this by increasing exhaust duration and lift as much as possible without big overlap changing the idle. This combo is 9.79 to 1 compression, 8.01 to 1 DCR, .040 quench and will run with full performance timing curve on premium fuel. It will pull way better at lower RPM and midrange up to 6000 RPM. It will still pull to 6500 redline, It will still have solid lifter sound and similar idle tone but the solid roller is a tight lash cam with the roller rockers and polylocks should maintain good stable valvetrain adjustment with yearly or 5000 mile checks. This should be 400 + HP, retain all NCRS and drive much better with more power everywhere. It will sound totally stock to 99% of everyone. You might have to grind the valve cover drippers and modify the baffle to clear the polylocks, worst case use the thick Mr Gasket valve cover gasket.
http://www.summitracing.com/parts/mr...make/chevrolet

You can build this in 1000 different ways. This is what I would do.

 

has anybody noticed the thread is from April 2013?

 

OP posted yesterday.

 

[63mako:

Thanks for your input--I really appreciate it. My builder was pushing for hydraulic roller lifters and I didn't really like them. I understand the shortcomings of the flat tappet lifter so he roller lifter sounds like a great choice.

Question: Most of what I reads says stay away from the roller lifters with needle bearings and stay with roller lifters with bushings. Too many failures with the needle bearings. Any thoughts on this.

Again Thank You!!!

 

Thread was started several years ago because that was when I planned on getting the engine rebuild. It has taken a lot of research to find someone to who I would trust this job to. Then my daughter decided it was time to get married. The wedding went great and I have a fantastic son-in-law but it dented my budget. Now I am trying to get the project moving again. Such is life.

 

In a big block, high lift, strong spring pressure, high rpm, high intensity ramp, big lash, drag race any combination or all of the above I agree, go bushed. Don't apply here. This is a small, tight lash street roller in a small block. It is a compromise with the reliability of a roller with the characteristics of a solid, It will still have the LT1 personality. I do agree with your builder a hydraulic roller would work great for your application but it won't have the solid lifter sound or lope. The K-kit is designed to work as a unit in a stock type build. $800 bushed lifters is overkill for the use and much better spent elsewhere.

 

One of the things that can wake an old motor up is something as simple as changing timing chain (preferably with degreeing in of the cam). With a high mileage motor it sometimes quiets down the internal rattles. Hard to say what a compression test with a 310 duration cam + low compression looks like. 190 might be OK.

If all compression is within 10% of each other (20psi from highest to lowest) and the engine has good oil pressure and no weird leaks, consider leaving it alone (timing chain and camshaft only). Its only original once.

As for 383 type rebuilds - one issue with non-stock cranks is the harmonic balancer. A dead giveaway. You can use stock balancer if you are careful in part selection.

Finally, personally I don't like the 70s era performance camshafts. I don't know the LT1 spec, but typically the cams had a wide lobe center separation. It smooths the idle but IMHO makes the cam a bit lazy (makes it want lots of gear - like 4.11:1). Companies like comp cams - at least their non-EFI cams - go with something close to 109 degrees. The tighter lobe separation makes for a loppy idle, but the engine will seem a bit snappier.
A modern 310-320 duration cam is pretty much a race only cam. A Comp Cams 270ish split duration cam would be the way to go (and probably sound better too). With 68cc heads 192/160 valves (~9.6:1), the comp cams 270 magnum cam is good for 330hp... and a decent _truck_ motor with plenty of torque. That makes for a fun daily driver. Put a cam in that you can't leave a traffic light under 2500-3000 rpm and you will grow tired of it. Add to it the lack of power brakes and your car will become un-fun.

Light, nimble, flexible power train == fun to drive.

 

Mark Jones of vortecpro just posted some specs on a 327 rebuild on the c2 forum. The engine hasn't dyno'd yet but it should be around 375hp and uses all original parts. A similar build for your engine might be a good option. He is one of the few guys who love to port old cast iron heads and is a great engine builder.

It would be interesting to see what he could do with an LT1. He would probably be willing to port the exhaust manifolds since you cant run headers. A ported intake would also be interesting to see how much hp can be had. My guess is 400hp+ and still be 100% original.

 

Hey Mako,

Will those rockers and polylocks fit under the stock valve covers w/ the stock valve cover gasket?