GrandSportC3

I'm thinking about installing my old 600+ HP 406 in my Vette (dyno tested at 590 HP without any tuning on race gas and will certainly be well above 600 HP on E85 with some tuning) and I'm not sure if that would require upgrading any of the drivetrain, including the M20 transmission.
Planning on running E85 as the engine has 13.5:1 compression. I have no intention of installing sticky tires or ever taking the car to the track. I'd think that the tires would spin before any damage is caused by the engine's power. I also have 3.08 gears which reduces stress on the half shafts.. However, I'm not sure. Does anyone have any experience with this kind of power on a otherwise stock drivetrain?

keithinspace

Probably not particularly helpful to you, but I'm running something in the 500 HP range from my 350 through my M20.

I regularly launch pretty hard, but not abusively. I'm running 3.23 gears and painfully tall 325/70/15 rear tires.

I would certainly put some time and attention into your universals and make sure the rest of your stuff is fairly fresh. You can get a bunch of 'clunks' really fast with old rubber.

I would politely offer that the 3.08 gears would probably put MORE stress on the transmission, not LESS. Another rear ratio like 3.23, 3.55, or even 3.73 would give you more mechanical advantage against the tire, pulling stress out of the transmission and putting it into the rear half of your drivetrain. This strategy would work better if you don't have sticky tires. And it would make 1st gear increasingly worthless, especially at that power level.

If you are kind to your equipment and don't go nuts with tires (stick to fairly ordinary BFG's), I don't see why you wouldn't expect a certain amount of durability from the combination. If you were itching to rebuild your rear end, I'd personally investigate 3.55 gears over the 3.08.

Pop Chevy

Only if you baby it, and that's no fun !

GrandSportC3

I won't change rear gears as I do lots of Highway driving and unless I would change to a overdrive transmission, I would turn too high RPM's.. Right now, I can drive 80 mph at about 3050 RPM or so..

GrandSportC3

That's what I'm afraid of.. If I upgrade the drivetrain, I'm looking at several thousands of dollars in drivetrain upgrades instead of just dropping in a engine that I already have..
When I had my racecar, I spent almost $10k in drivetrain upgrades.

keithinspace

I hear you.

I believe, rightly or wrongly, that 95% of the failures you would/could experience would be the result of off-the-line shock loading.

If you are respectful off the line and don't speed shift, I don't see why the equipment wouldn't stay together.

I wouldn't classify this as boring. I have some 50 foot long burnouts in my driveway and can say with supreme confidence that I don't "beat" on my car.

What are your choices, really? Drop the engine in and see what happens. If the stuff is in decent condition, you should be able to get some real mileage out of it.

TimAT

The Muncie in my 69 has stood up to the original L-89, an L-88, and an LS-7. All with the same 4.11 rear. IT's been apart exactly ONCE. I pulled it down last fall because the midplate had a minor annoying drip. All the gears and synchro rings were like new. A gasket set, and put it back together. It's never been subjected to a hard launch or a really hard power shift, but it has been used, autocross and a bunch of redlight playing.

Bad Bird

Sorry to go off topic, but do you have any photos of your rear tire fitment?

GrandSportC3

The transmission is the matching numbers transmission.. Maybe I could get a used TH400 with a 3500 converter and save the M20.. I can keep the matching numbers stuff stored.. A automatic would be less violent on the rear end and shafts..

GrandSportC3

Cooling might be another issue.. Not sure if stock style radiator would be sufficient to keep the monster cool..

fishslayer143

Tire spin is natures way of saving your expensive parts... If you put on some real sticky tires and launch real hard....well .......a broom and dustpan may be needed for your differential ... drive it sensibly, probably hold up... but wheres the fun in that???

diehrd

So you plan on doing everything with that motor that the motor was not built for ?


Why ?

ddawson

I was asking different shops about rebuilding my M20 to go with the 496 I was having built.

They all said it wouldn't hold even in just street use. Even a 4th gear flog could break it.

I now have it stored and went for a M22W to match what the M20 gears were.

GrandSportC3

No intention of using sticky tires. Rears are 275/40R18 street tires.

GrandSportC3

I want more power. The engine is a built drag engine, capable of high 9's in a 3000 lbs car.. I used to run that engine with 11.6:1 compression in the low 10's (best was 10.35 in the 1/4 mile. Then I rebuilt the engine with shaved and fully ported heads, bringing the compression to 13.5:1 and much better flowing heads (fully race ported RHS 235cc heads). Engine has been sitting in my garage since 8 years... Need to go through it to make sure that it has not suffered any major issues from sitting.
I did drive the engine on the street before but it ran kinda hot and I was running the best Griffin Radiator and triple electric fans.. The engine is a monster with a huge solid roller cam..

Here's the best run with that engine when it had worse heads and less compression in my old 68 drag car..

71454Chevelle

X2

fishslayer143

sooooo, you're only gonna drive stoplight to stoplight? I m all in favor of big power in street cars , I have 525HP in mine but, I can still run the A/C and drive to Florida if I feel like it.. Theres a point when a race motor belongs on a race track.. It seems to me, and this is just my opinion, if it overheats with alum radiator and 3 fans, it will be miserable to drive anywhere.

71454Chevelle

Depending on the specs of that "Huge solid roller cam", street driving with a large overlap cam, a manual transmission and 3.08 gears will make for a not very pleasant driving street car at lower speeds.

gkull

M's cases are weak. at the shop I used to work for always changed them to texracing I always saw cracked casings from M's These were trans am 302 -310 5 liter cars with less TQ motors like the the GT350 and Chevies

GrandSportC3

But less stress on half shafts.. The question is on what would be the weamest link..