383 10:1 with 516 heads in california?

Posted By: 71Chip

383 10:1 with 516 heads in california? - 07/09/09 11:58 PM

A while back I made a thread about helping my friend on his 383. We are using machine tech in oceanside...

They have all the machine work done and all the parts except the 9:1 pistons they were going to use from keith black have been on back order for over a month.

The car is sitting in a borrowed lift stall so we need to get it out of there.

They have the block measured and the factory closed-chambered heads CCed. They said there is a similar price piston in stock (not sure of manufacturer...I can ask) that they know they can get that will put the motor at 10:1.

I went with the reccomendation of one of the guys at IMM and got the comp 265DEH. Car has highway gears and a 2200 stall...will 10:1 work on california 91 octane?

Posted By: RapidRobert

Re: 383 10:1 with 516 heads in california? - 07/10/09 12:35 AM

With actual measured .035"-.040" quench (piston to head clearance) in each hole, yes

Posted By: rexus31

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:16 AM

With the crappy gas we get here I would not run a motor at 10:1. What happens if it rattles on 91 octane? Then what? I would go with 9:1 or lower if I was your friend. Before I rebuilt my 383 (with 516's) it was 10:1 with the piston .035 in the hole and it pinged. When I rebiult it I put a set of 452's on which dropped the compression to 8.8:1 which is fine for a street motor. It's got a ton of low end torque and is fun to drive. For me, it's better to be safe than sorry.

Posted By: johnnyrotten

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:31 AM

Why not just go to another piston manufacturer? Or just get thicker head gaskets. You can get cometics in many thicknesses.

Posted By: 1_WILD_RT

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:35 AM

Rexus31 & JohnnyRotten should both read this...

http://www.kb-silvolite.com/article.php?action=read&A_id=39

Posted By: Rug_Trucker

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:40 AM

If it rattles? Water injection!

Posted By: Quicksilver440

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:49 AM

Quote:

If it rattles? Water injection!

It would work...but they are better off buying the right pistons.

Posted By: 383man

Re: 383 10:1 with 516 heads in california? - 07/10/09 07:21 AM

I run 10.0 comp in my iron headed 440. It has 906 heads with KB quench pad pistons for about .042 quench. Runs on 92 with no ping and 38 total timing. Ron

Posted By: patrick

Re: 383 10:1 with 516 heads in california? - 07/10/09 11:20 AM

Quote:

With the crappy gas we get here I would not run a motor at 10:1. What happens if it rattles on 91 octane? Then what? I would go with 9:1 or lower if I was your friend. Before I rebuilt my 383 (with 516's) it was 10:1 with the piston .035 in the hole and it pinged. When I rebiult it I put a set of 452's on which dropped the compression to 8.8:1 which is fine for a street motor. It's got a ton of low end torque and is fun to drive. For me, it's better to be safe than sorry.

1) unless it had a pretty decent sized dome or the 516's had a significant amount milled out of them, there's no way you were at an actual 10:1 with the pistons .035" in the hole on a 383.

2) quench plays a very important factor in detonation resistance. with the pistons down that far, even with a steel shim gasktet quench effect is going to be minimal. anecdotally, I have a friend with a 396" stroker SBC, flat tops .014 in the hole or so, right around 11:1 compression with the .050" or so head gasket he was running. had to be VERY selective on gas (could only use shell 93 octane, and even then, the EFI would occasionally pull out timing due to detonation on warm days). he switched to a .028" or so head gasket, his compression actually went up about .2-.3 points, but now he can premium from any gas station around here without detonation....

summitracing has .030 over KB162's in stock to ship today. $323/set.

what's the CC of the heads? assuming 80cc,

KB162's (1.908 CH, 5cc valve reliefs), 6.358" rods, 9.98" deck height, and the Mr. gasket steel shim head gaskets (.020" thick compressed, 4.45" bore) will net you 9.3:1 actual compression ratio, and .044" quench. should work on pump 91. one thought would be you could retard the cam 2-4 degrees. that'll delay the intake closing point, and reduce cyl pressure, and will shift the powerband up slightly.

another piston, speed pro ZL2315F forged are 1.92" CH no valve reliefs, would end up .012" in the hole. I'd probably deck the block that .012", and use .040" gaskets. using the MP composition gasket (.40" thick, 4.38" bore), it still only nets you 9.86:1 compression...not decking, leaving them in the hole gets you 9.6:1 compression, but I think it'll be less prone to detonation with the higher compression/tighter quench

Posted By: rexus31

Re: 383 10:1 with 516 heads in california? - 07/10/09 03:05 PM

I hear what you guys are saying and you are correct. The reason I like to err on the safe side is I live in CA, a state that probably has the tighest emmissions standars in the country. I woke up one day and premium dropped from 93 to 91 octane. What happens if we wake up on day and they change it again from 91 to 90 or 89? That 9.6:1 motor is going to rattle.

Posted By: 64Post

Re: 383 10:1 with 516 heads in california? - 07/10/09 04:05 PM

Quote:

I hear what you guys are saying and you are correct. The reason I like to err on the safe side is I live in CA, a state that probably has the tighest emmissions standars in the country. I woke up one day and premium dropped from 93 to 91 octane. What happens if we wake up on day and they change it again from 91 to 90 or 89? That 9.6:1 motor is going to rattle.

Then you retard the cam or change it altogether. It's much easier than a piston change.

These calculators are a nice pre-planning tool as long as you input your correct/actual values... http://www.wallaceracing.com/dynamic-cr.php Changing the intake closing point changes the results.

I'd shoot for 160-165 cranking pressure and perhaps 7.5 Dynamic with tight quench and iron heads.

Posted By: Real-Fury

Re: 383 10:1 with 516 heads in california? - 07/10/09 04:56 PM

I don't mean to HiJack the thread but I have a stock 1964 383 4bbl that's supposed to be 330HP and 10:1 compression. It doesn't "rattle" on 91 octane. Is this really a 10:1 compression engine or is that just the mfg's advertised ratio? What is the real or more likely compression ratio of a stock 383?

Thanks,

Butch

Posted By: patrick

Re: 383 10:1 with 516 heads in california? - 07/10/09 05:41 PM

no, it's not 10:1....I'd be suprised if it's a true 9:1....

Posted By: stubbs300

Re: 383 10:1 with 516 heads in california? - 07/10/09 06:07 PM

Well FWIW, my 66-300 w/516's is advertized as a 10:1 motor that's still original except for a Hughes 2330 cam and I have some mild ping with 89 octane. Call me a cheap skate, but I dialed back the timing a couple degrees and run 87 with no problems. I do live on the left coast! Ya know as gas becomes cheaper in quality, your either going to have to de-tune or suffer the consequences with pinging because I can see that super will go by the wayside in due time. Sooner than later! Everybody talks about this and that with pinging, but yet they are so pigheaded that they refuse to de-tune to prevent the complaints that arise here and on other boards. As the old saying goes, "You can't have your cake, and eat it too", something has got to give!

Posted By: Real-Fury

Re: 383 10:1 with 516 heads in california? - 07/10/09 06:34 PM

That's kinda what I figured.

thanks!

Butch

Posted By: JohnRR

Re: 383 10:1 with 516 heads in california? - 07/12/09 04:56 PM

Quote:

I run 10.0 comp in my iron headed 440. It has 906 heads with KB quench pad pistons for about .042 quench. Runs on 92 with no ping and 38 total timing. Ron

But you are in Maryland and they don't try to pass off goat urine as gasoline.

Posted By: JohnRR

Re: 383 10:1 with 516 heads in california? - 07/12/09 04:59 PM

Quote:

no, it's not 10:1....I'd be suprised if it's a true 9:1....

ding ding ding ... WINNER ,

Advertised 10.1 383's are more like 9.2 ACTUAL , you need to have small chambers and pistons that are zero deck ... which requires a sub 79.5 cc chamber ... OR .020 positive deck height, open chamber heads at 79.5 cc AND a steel shim gasket.

DO NOT BELIEVE published chrysler specs

Posted By: 383man

Re: 383 10:1 with 516 heads in california? - 07/15/09 08:03 AM

Quote:

Quote:

I run 10.0 comp in my iron headed 440. It has 906 heads with KB quench pad pistons for about .042 quench. Runs on 92 with no ping and 38 total timing. Ron

But you are in Maryland and they don't try to pass off goat urine as gasoline.

I thought it was Moose urine ?

Ron