So i'm finishing up my 412, based on a 400 production block, 2 bolt main, 1976. Put arp studs in the mains. Didn't spay them though..

Got talking to my machinest yesterday, cuz I was thinking of running a turbo blower. He told me if I push that motor much over 500hp the crank is going to be on the ground... Little anoyed I am, because had he mentioned that before I put everything together, I'd have him put splayed mains on it and align bore it.. Don't want to take it all apart again now.


He mentioned I could try a main girdle, which are cheap at around $100.. How effective would that be?? I need this thing to stand up to 650 or so horsepower, and around 6200 rpm..

-- Joe

 

Any engine with a power adder should have 4 bolt mains or splayed caps. Even with a girdle, the webbing around the mains is still weak in an OEM casting. It may offer some strength but it's no guarantee it still won't fail.

 

Correct

The crank webbing in those blocks marginal anyway.
Spent many hours per block deburring and smoothing the web areas,
(Stress cracks under flex.)
At the power levels your trying to achieve with it are definately headed
to possible (Crank on the ground.)

Did you tell him it would be boosted when he did the machining?

Built many 400sb over the years so have some experience with them.
All OEM 400s/ 2 bolt and 4-bolt.
Actually the 2 bolts better candidates for splayed 4 bolt conversions.



Later

 

No, when I bought everything and dropped it off for machining, I said I was gonna run around 500 flywheel horsepower.. I went out, and bought a car.. (79 Z).. Machine work all done, steel crank, eagle rods, forged reverse dome pistons, deck mods, boring, honing, balancing, decking, etc.. Assembled everything, put it on a stand. Got a cam, some other stuff.

Then I found out how much my 2nd gen weighed, fell over.. Woke back up, and started doing the math. My thirdgen with me in it, weighed 3650 and did the quarter mile at 119-120mph.. We figure, with traction problems, given the high ET (low 12s / high 11s) and high mph guess about 525hp, maybe upwards of 560, depending on if you think the mph would have gone down drastically if the ET dropped to a 11.30 or something.

The Z28, 2nd gen, in all of it's glory, weighs about 3800lbs WITHOUT ME IN IT, and I'm about 280. I figure, to break 120+ mph in the quarter, I need to be putting down over 600 at the flywheel. I can get a vortech s-trim for $900 today if I wanted to, however it's now seeming the block won't take it.

So I guess my other option, is spend $900+ on getting the car 500lbs lighter..


Machine shop bill was around $1300 for labor, and some misc parts (rings, plugs, cam bearings, spiral locks, rod bearings, main bearings)

Block cost me $180.
pistons + rods (forum deal) $350
Forged crank $400
Oil pump (10550) $80

Kind of a lot of money in a shortblock to just see it explode.

Guess I should have dropped $1400 on a dart block, huh?

-- Joe

 

Sounds like you have the motor set up for boost as in reverse dome.
Didn't give the expected comp? Head cc, ect.

I woundn't trust a OEM 400sb with any good amount of boost unless it was
fully prepped, splayed 4-bolt, o-ringed, copper head gaskets ect.
Specially making that kind of power. Also, lots of block prep.

I ran them for years in our stock cars but with all the prep and lite
cranks ,Carrillo rod, pistons, 13.1 + Comp.
Our motors were making 700+ above 7000rpm with an ocassional problem.
Blowing across top inner cyl walls even with o-rings and copper gasket.
Ours were destroked 400's/ 372-378.
By the time you get the OEM where it should be, think its still flawed
under boost at that HP level.

I'd go the Dart route.
Didn't realize the 2nd gens were that heavy and I had a 70 split bumper
back when?



Later

 

Reverse domes are great all around, perfect quench pistons. Anyhow, I can get it down to 9:1, or 11:1 depending on head chamber so I can go either way.

'70 should be light. By the time they got around to '79 it was a pig. Trying to figure out where all the weight is, but remember the rear and front is totally different. About the only thing that stayed the same are the doors.

-- Joe

 

Well,

Its time to put a 58cc head on it,
18 degree head might be good idea,Money, Manifold,Money, forget it.

And, start ripping out everything in and out of the car that does'nt
spell, Need to keep.

Lotsa fiberglass and lexan.

Keep posted as to direction.

Later