I have a line on a lowish mile 5.7 L31 engine to swap in my ‘88 T5 TBI IROC.
It will be carb’d with the Chevy 12677151 hyd roller cam.

I have a fresh set of .500” lift prepped 58 cc Vortec casting heads for temporary use until I can get the #906 64cc heads done.

Do you think there would be any detonation problems with a reasonable advance curve in a non-HEI distributor, 93 octane, the 7151 cam, stock dished pistons, Hooker 2055 headers and exhaust?

The #520 heads are identical factory replacements for ‘96-‘02 #059 Vortec 58cc heads.
Thank you

 

I think they'll give you 10:1 compression if you have flat top pistons. If they are aluminum you'll be fine. If they're cast then IDK.

 

I had 58cc heads on a 400 sbc with dished pistons and it ran like a raped ape. It would detonate once in a while first kicking it down while cruising, had to back off on timing a little when hot out but I had a pretty aggressive advance curve. If using stock style distributor you should be fine, worst case just back off on the timing a little.

 

I have an LT1 with just under 53cc chambers and run pump gas on it always. The raw numbers make for a static CR of 10.8:1. You could run FelPro 1034 head gaskets and drop that closer to 9.5:1.

Stock L31 pistons reportedly have 12cc worth of relief, and with a gasket at 0.039" thick, you should net a static CR around 10.07:1. A stock 305 TPI is around 9.5:1 and L98 is around 9.6:1. Just make sure the fuel feeding device doesn't go too lean, and consider a functioning EGR if the cam overlap doesn't have some of that ground in.

Of course, the LT1 with little wedgies is SFI with better fuel control than a ThirdGen batch-fire TPI, and MUCH better than a carburetor, with a more active knock sensor approach than on our ThirdGens. I definitely notice the retarded timing when fuel less than 93 octane is used, but it will run, idle, and drive just fine with lower octane (in a pinch).

 

Have you measured the piston below deck? Have you confirmed the piston dish volume?
What you're trying to dial in is the SCR and then work through the dynamic compression based on the cam and the IVC it's installed at.

Now before the crowd gets their underwear in bunch, there are fairly established guidelines for what's successful with a pump gas Vortec headed SBC. It's not a universal answer for all makes and models or applications for that matter. But these iron headed examples have plenty of data to draw from.
I for one have buckets of info on what worked well and what was marginal. But you have to have the numbers verified before an educated answer can be offered.

The operating conditions make a huge difference as well. Driving cross the Nevada desert in the dead of summer or cruising in the fall in the northeast will dictate what's tolerable and what isn't.
That said, timing curves vary too. Problems with detonation can be snuffed out by pulling some advance but that's at the expense of performance and economy.

I've run 10.4:1 SCR with a short cam that gave 8.4 DCR. It was a handful with a carb and old school mechanical distributor. But a few tenths less compression made a significant driving difference from my experiences.
FWIW, I'm working through which way to go with a new 357 right now. If I'm drag racing and have finite scope of engine operating conditions, I can be more aggressive. If I'm after the same old, which is an all round cruiser and part time racer, I'll back way from the higher compression a little. Of course the choice of fuel also weighs in here.

These are some of the points Vader has covered above.
If you can provide the details, the answer can be more exacting.

If it's a temporary deal, pull 10 degrees of spark timing out of it and keep it safe even if it comes at the expense of some of the performance metrics.

 

THANK YOU everyone for the replies.
The carb will be a list #4776 600 mech sec Holley, AND I mispoke at the top, it will be a non-computer H.E.I. distributor.

2knight's 400 with 58cc heads! That had to be something. There was a guy on here, SR-71, I think that did that also.

With a 160* t'stat & a lower temp fan switch, hopefully this won't turn out to be a big deal. Maybe I'll just leave the heads on.
Some people here swear by those little 059/520 heads.

 

It depends entirely on your objective. The small intake valve and reduced CFM than a conventional Vortec limits their potential.

 

Dad ran 059s on a 350 in a TBI pickup for years. It had the stock L05 flat tappet cam and it ran good on 87 octane. Ran pretty strong too,