383 stroker - ex race car motor, will it blow on the street

[Neal Zimmerman]

OK, about 2010 I bought a 383 on Craigslist for 350 bucks. When I got there the guy told me more about the motor, that his dad had built for some kind of stock car or roundy- round class that he had in a 67 coronet. It was an old school offset ground steel crank stroker with Chevy rods and some wild pistons. It has a fluidampr balancer on the front. He said the thing was a holy terror on the track, and after his dad died he drove the car around on the streets a couple days , but the compression was so high (13.5 to 1) he was terrified he would blow it up he packed the whole thing away.. The heads were a seriously shaved set of closed chamber 915's. It came with a box full of tach drive distributors, with several of those old transignitor boxes.
Fast forward to now. I had almost forgot its been sleeping away under my bench , but lately I have been thinking about trying to get this relic going, with some modifications for use in a street car. Mainly getting the compression ratio down, maybe by putting some 906s on it and a thick gasket. I figure that will drop it down pretty good. I also figure I can find some more street worthy rings than what's on there now. They look pretty fancy. Its looks to be all in good shape, pistons are beautiful, cylinders have zero lip, cam looks good but I am sure I could find a more street-able cam. No rust as he greased it up pretty good. It's a mild stroker, I think he said its stroked to 426 inches which by my calculations would be a .37 stroking.
What do u guys think.? Will it just blow apart in a street application. I don't know. I figure if it blows, oh well, not like I have been doing anything with it for the last 15 years anyway.
Yeah I know, I know, 440 source, etc.etc. and I should build a 511 or whatever , but I don't have that kind of money and this things already paid for.

 

[33 IMP]

A really thick head gasket could help..... but the first thing I'd do is find out if the pistons are solid dome, or hollow.
IF they are solid dome, the answer is obvious. Whack the dome off, and rebalance.
(A standard bore 383, with a 440 crank is 426 cubes, plus whatever overbore.)

 

[Bighouse]

Give it a try!!! Get some race gas and go from there.

 

[PurpleBeeper]

Do some math. 906’s I think will drop you to 12.5:1 range. You’ll need about 10:1 or less to run pump gas. Thicke head gaskets will help too. I’m thinking a piston swap may be your best bet

 

[pnora]

Are the pistons flat top or domed? post some pics.

 

[HawkRod]

I'm not sure why you'd be concerned about it "blowing up". If it was built well, it should hold up well. I agree the 13.5 compression makes street driving a problem, and likely it has a racy cam that will make poor power at low RPM. So I could see that the engine wouldn't be very nice to drive on the street.

Putting lower compression pistons into it (or cutting down the existing pistons) gets into balancing the reciprocating assembly and a lot more work. I agree with @PurpleBeeper to do some math and see what the volume, and thus compression difference you'd get with changing the heads. That, coupled with thicker gaskets, may get you into a decent enough compression that the right cam might make this workable. If not, then you may have to change pistons, but I'd try not to first.

 

[MiradaMegaCab]

Bolt a ProCharger on and run it!!

E85

 

[4speed68rt]

I'd say run it! Show us some pictures of the beast.

 

[33 IMP]

I was thinking of race gas, way too expensive to run on the street, at 13.5. But E-85 is a viable alternative. Assuming a holley carb, it might be possible to modify for E85, but a dedicated e85 carb would be better.
But that's assuming e85 is available in your area.


But I'd still look at wacking the piston dome first. (There is no way a 440 stroke motor is 13.5 with flattops)
But as somebody above said.... time to do some volume checking first, to see what compression you REALLY have!

 

[PRHeads]

My .02 is……..you’d probably end up spending less in the end by selling that stroked 383 to someone who could use it as is……..and taking that money and buying a rebuildable 440.

 

[j-c-c-62]

Isn't also going with a more "streetable" cam worsen your existing CR concerns here?

 

[#41]

Well, the good news is that it held together on a circle track at 6000 rpm!

I would do exactly what you have already concluded. First, I would slide the cam out and get the part number off it. I'd also make sure swapping out the "seriously shaved" heads did not screw up the existing valve train.

I have actually been through the exact scenario with a 383 I got in a trade. Yea, it turned out to have domed pistons and a big duration cam (but not much lift)... but it was not as un-streetable as described. I put new head gaskets in it and ran it on premium.

 

[Kern Dog]

The main reason that we study history is so that we can learn from our mistakes and NOT repeat them.
In 2003, I built a 440 with a 4.15 stroke using a rotating assembly from Hensely Performance in Tennessee. This was before the 440 Source existed.
The man on the phone told me that with aluminum heads, the 10.8 to 1 compression would be fine.

Even with a MP 292/509 cam, it knocked when I went past 1/2 throttle. I tried distributor tuning, bigger jets in the carburetor, larger diameter exhaust, even bigger camshafts to tone it down. Two of those cams went flat (2006, just as the rash of cam and lifter failures were becoming common) I had the engine out to clean out cam and lifter debris and had to resurface the heads, making compression even worse/higher. I calculated that I was now over 11 to 1.
I am limited to 91 octane for readily available gasoline but I decided to try race gas so I bought 5 gallon cans of 100, 104 then 110 octane leaded. The 110 was the only fuel that stopped the detonation. I took the advice of a guy on FABO and went with a rowdy Lunati solid lifter cam that would supposedly bleed off cylinder pressure at low rpms. I've learned since then that this tactic might work for some but it was a failure for me.
Whatever cylinder pressure it "lost" at low rpms was multiplied as RPMs grew, making the engine knock worse.
I tried using thicker head gaskets and yeah, it worked. I went with Cometic .075 thickness. They were not cheap but I was thick headed and unwilling to pull the engine to change the pistons. The gaskets lowered the CR to 10.17 and it ran fine on 91 octane. I had no quench but it wasn't knocking.
I did pull the engine again in 2022 and swapped in flat tops with a dish. I'm at 9.8 to 1 now with a quench distance of .043. Zero knocking even in 110 degree heat.
Learn from the mistakes that others have made.