What will 880 HP break first??? (Non-Mopar)

I'll start by apologizing for dragging a Chevrolet question into our forum, but I respect the opinion of many racers and fabricators here, so I'm soliciting good opinions:

I have a buddy that bought a really nice 66 Chevelle last year. It's a solid Street/strip ride with an iron-headed 468" big block / TH400 with a brake / 9". Car runs 10.70's. Rear suspension is stock geometry, but has been upgraded with amuminum trailing arms, aftermarket upper control arms and all Urethane bushings, along with a 9" running a moser spool and 30-spline axles, and 28x10.5 tires. It has a bar only, and is only legal to go down to 10.0.

He ran across a deal on a 565" big block that was dyno'd at 885 hp., and he couldn't help himself. He wants me to help him swap it in, which I'm happy to do.

Here's my question: what issues is he going to run into with that much power on tap? We know the obvious issue that the car is not legal for what this thing will likely be capable of, but I have concerns about the whole back half of the car, which is essentially "stock". Any car I've ever seen tapping this much HP is at least on ladder-bars, if not a full back-half with 4-link. His idea is to let go of the brake and send nearly 900 horses head on into a stock 9" case & housing on a stock suspension setup.

What do you guys think he'll run into?

I'd bet the stock 9" centersection will break first if it hooks. It'll rip the pinion clean out of it. He needs at least a nodular iron center w/ a good pinion support.

A couple of things come to mind.. axles will
twist IF it hooks.. U-joint might be on the
top of the list.. axle hop might be a issue
and he will need good shocks to control most
of the issues

A smile?

The wall if he's not careful.

There are plenty of Mustangs, Camaros, and other stuff out there with a lot more power than that, hooked up and going fast on stock type suspension and small tires. It takes some work and the right parts, but those coil spring cars can be made to hook. If he manages to do that, I expect the rear will be the weak link with that heavy thing. My dream wheel says 885 HP, 3400#, 9 flat at 150...best case scenario.

Upgrade to 35 spline Axles, 5/8"wheel studs.

I have a good friend who ran a all steel 69 Chevelle @ 3500 lbs+
All Motor 572 BB, 900 hp, turbo 400, 9" with 35 Spline Axles, all Strange parts it ran high 8.90s-9.00s on a 10.5 tire.
Neat car it looked like a street car you could cruse around in, the cage
was tucked up nice and tight with a full interior.

I would find out for sure what converter is in it. Converters tend to swell with that kind of smoke and only bad things happen after that.....

I know the converter is a Continental, that's about all I know. I'll find out more today.

Sounds like most of you think the car will handle it okay, but the rear end and axles will have to be upgraded. I'll suggest that to him, then watch him break parts.... haha. This should be fun.

Thanks guys.

That's a pretty anemic 565" engine for sure..a 4.600 bore BBC with a decent set of heads should be pushing 4 digits pretty easy, and most do

Stock 9" stuff if not particularly strong as pointed out. Also 30 spline stuff is not the strongest either. And while a turbo 400 can be a good piece it depends on whats in it.

The instant I read this, I figured everything behind the trans was at risk, and the whole car if something breaks down track.

A-body GM cars are body-on-frame. Decades ago it was trick to swap in a convertible frame, because it was boxed, while the sedan or coupe frame was a C-channel. This was like the early '70s.

Even though the body won't wrinkle like a Mopar, it will still have quite a bit of twist from being tied to a twisting frame. I'd say some chassis work, like a roll cage, would be a good investment.

The rear end WILL bend, that's why most all 9" rears have braces welded in. The axles are suspect, as is the differential housing. 35 spline axles and a way stiffer and stronger case should be on the menu. Looking around, I see that Yukon makes both a nodular iron and a bolt-through aluminum case, also an aluminum Dayton pinion support.

As mentioned above, all this strength will be needed if you get the car to hook.

R.

New center section and 35 spline - sell the one you have before you break it.

Break the linkage for the secondarys.

They way it looks , the engine deal is going to cost a lot more money. Buying a bullet proof rear, shocks , springs and what ever traction devices probably will cost him as much as the motor did.

Money is not a problem for this guy. He's got more than he knows what to do with. He's just not sure what to spend it on.
We got the 468 out tonight. Converter is actually a brand new 8" Hughes (I forgot he had replaced the continental when he had a brand new transmission installed last year).. He's going to call tomorrow and ask their opinion, if they suggest replacing it, he will. I also suggested he look into a complete aftermarket 9" chunk. He's gonna look into that also.

IMO he needs to spend it on the engine..Then worry about upgrading the car.

Not sure if you're joking, or really how to read this, Al; so I guess I'll just chuckle and wrench along.

Well, it broke something..... itself!

At the First TNT night, it spun off the line twice, until we got the right tire pressure and leave RPM. Then it hooked, bounced on the rev limiter at the top end. He just stayed in it on the limiter for a few hundred ft and it went 10.16 at like 128 or something around there. Last run he pulled limiter chip out, it hooked and was trucking but the belt came off the vacuum pump and it pushed oil out the reservoir (we think). It ran 10.04 at 132 on that run limping to the finish. Night over. (And there might have been more to that incident than he thought).

Last weekend he took it back out with the vacuum pump pulley situation re-addressed. It made a pretty good pass in Q1 and went 9.89 at 135. He was all smiles. 2nd run it nosed over when he hit drive, and spewed oil all over the engine compartment. From what I saw and he described, I feared something bad... it had actually split open a valve cover !?!? We pulled the cover and to my surprise, all the valves seemed to move correctly when he cranked it over. So he loaded it up and took off as I stuck around. He called tonight and said he had taken the intake off and immediately saw that the block is cracked and there's metal shavings everywhere in the valley, which has screen epoxied in.

All in all, he spent 8 grand and got 6 passes, only one clean. Reaffirming my feeling that I don't like engines of unknown origin, no matter how many receipts they come with.

Many people will sell a good running part JUST before they think it will break based on past experiences, DANG THEM A HOLES anyways

Dang that sux. But it's part of what we do! He still have the 468? Put it in and run it. But put the chip back in it! 😁

Tough car for the motor to go first. A car is engineered as a system, change one part and everything is affected. 750fwhp is as high as I got in a GM and I replaced all the major components 3 times.

Put the BIG motor in, it will be fun they said. If I ever find the "they guy" we are going to sit down and have a long talk. Sorry to hear about your friends issues. At least it sounds like he has money so that takes some of the sting away.