Help with 360, too much comp?

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1972orangebeast

1972orangebeast

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Ok long story but I had a 360, .060 built with x heads, KB pistons kb190, comp 20-671-4 (.484/.484, 284/.291 duration), airgap intake, stock crank, everything has been balanced.

Now I came across some Edelrbrock 6077 360 heads I want to put on it, I am worried that It will be too high of compression. From the numbers I have ran for possible compression ratios, it looks like ill be close to 11.5:1, how streetable is that? Motor is going in a street car, I run 93/94 octane all the time anyway and know the aluminum heads will hold little more comp. Cars going to be taking a long 6 hr drive plus a ton of other drving this year. Also Im in ohio if that matters at all.

Also I bolted the eddie heads down without a head gasket and pistons hit, put a .038 head gasket on and they dont. I dont have the correct tools right now to measure how far piston pops out exactly. I am getting edelbrock head gaskets that are .050 compressed to help a little too. Please any advice would be great, I dont want to buy new pistons and I want to use the eddie heads.
 
You can have your pistons shaved to lower compression, also I think there is a 60s thousand gasket out there. Do it now before its too late.
 
If you have an already-compressed gasket you can use clay to get the piston to head clearance. Just check it at three spots: the outside edge, the pin axis, and the inside edge using clay like piston to valve.
You can mill the domes and make them into KB-107s... Or you could have the chambers cut a little bigger. I'm not a fan of losing compression via the gasket but do what you have to do.
 
Do with the others have said above, you also can go with a bigger cam to bring down psi.
 
they also make what they call a "head saver" it is a thin steel shim. It comes with 2 headgaskets to sandwich the shim. Talk to your machinist he should know about them. I had to use them once when my heads got shaved too much -- worked fine
 
The rebuild gasket kits from Mancini Racing have .055" head gaskets at 12.4 cc
 
Ok great info, I'll talk to my machinist about those couple options. Now anyone have any thoughts on running street motor with 11.5:1 comp? And would a different can help streetability?
 
I am running a 11.2:1 340 in my Duster. Runs just fine on 93. Has a solid roller cam with a lot of duration. Cylinder pressure is only 160psi.
 
OK, going by the premise you want to use Eddie heads, 93 octane and the pistons. With the combination you described you should not have any real issues. You can help with the thicker head gaskets to lower it a bit.

Just a note, I used 191 pistons with about 11.8 compression and had no issues with a .528 purple cam and generally the same setup you described. You could call Hughes and have them help you find a better selection in cams.
 
I will be very surprised if you don't have detonation problems, Shave the pistons. You don't need anywhere near that kind of compression for a street machine.
 
Ok I really was trying to avoid messing with the pistons at all but looks like thats the safe bet anyway. My dad will be at indy show this weekend, I may have him look for different pistons also.
 
I currently run a 11-1 360 without issue BUT my cam is a bit larger than yours @ 250 @ .050. It runs on 93 octane just fine.
 
1972orangebeast said:
Ok great info, I'll talk to my machinist about those couple options. Now anyone have any thoughts on running street motor with 11.5:1 comp? And would a different can help streetability?
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You certainly could run it that high - but you still have to look at the piston to head clearance and make sure that is kosher. Then you need to re-evaluate the camshaft - and it will need to be radical enough to need some spring updates, and probably a new convertor, maybe gears. You're talking pretty radical to let it live on pump fuel. At leas tthe stuff around here, which is 93 with 10% ethanol.
 
1972orangebeast said:
Ok great info, I'll talk to my machinist about those couple options. Now anyone have any thoughts on running street motor with 11.5:1 comp? And would a different can help streetability?
Click to expand...

My 416 with the Edelbrock heads was 11.9 to 1 i ran it on 93 pump gas no problem..
 
The 108* LSA is going to give you a higher cylinder pressure. Swap it to something with a lot of duration on a 110* LSA and I think you'd be fine with the eddy heads. Just make sure your PTV clearance is good. You'll probably want to degree the cam too while you've got the chance.
 
I say screw lowering compression and try it. It'll probably be fine with aluminum heads. You're forgetting the quench it will have with the closed chambers. That will also help.
 
If you go to a wilder cam to bleed off SCR: (1) it might not bleed off enough (A guy on Moparts had a nightmare with this) (2) a wilder cam than what you are comfortable with will make you unhappy very soon. If you are happy with your current cam keep it. You have a balanced short block in the vehicle all hooked up ex for the heads/intake etc. My 2 cents: Come up with a CONSERVATIVE SCR number to shoot for then buy a thick head gasket or order a cometic special thick ones to get the SCR reasonable. As you know gas is crap (& varies from state to state) & you're a traveler & you'd rather have the SCR on the conservative side for that reason & so that you can max out the dist subsystem settings: initial/total/springs/vac adv which will give you a much more powerful/efficient eng than one that has a too high of SCR and the timing is bandaided (retarded) to compensate. As said alumheads wick away heat & reduce pinging. #1 #1 find a conservative SCR number. measure your cyl vol etc & figure your current SCR for a baseline. However if I was to allow my OCD to kick in I would (1) order a Cometic gasket set that would give me a (measured) .035" quench and quench give you an efficient long block no matter what else you do (2) mill the piston decks (not the plateau-you need that for quench-maybe) and open the head chambers ALL to achieve the SCR you are after (3) weigh the pistons before/after to see if there will be a balancing issue & if so buy some heavier pins to restore those grams & reportedly 273 pins are very heavy (thick wall) on purpose & you can drill the ID to get em where you want for weight. this will give you/end results (1) cam manners you are OK with (2) able to run on your octane (3) efficient long block from achieving quench (4) conservative SCR so you can run a good ign curve
 
Lets get this terminology right. A camshaft with a later intake closing event does not "bleed off" anything. Bleeding off gives the impression that too much compression is built and the camshaft somehow magically makes it disappear. Ain't how it works.

Closing the intake valve later in the compression stroke means that the cylinders begin to build compression later in the compression stoke. That means the compression stroke is shorter than a camshaft with an earlier intake closing event. In short, you cannot "bleed off" compression that is not there. That is just incorrect.

All that said, IMO, if deck height is zero or close, then the OP will probably be ok, because he will have the aluminum heads AND some quench on his side. True that a domed piston is not the best for quench, but he WILL still have that effect. I think it's worth a shot.
 
:violent1::violent1::violent1:
:banghead::banghead::banghead:
:violent2::vom::tongue9:
:coffee:
 
swinger340 said:
I am running a 11.2:1 340 in my Duster. Runs just fine on 92. Has a solid roller cam with a lot of duration. Cylinder pressure is only 160psi.
Click to expand...

Winner winner, chicken dinner. CR alone is NOT the determination on octane. Also important is timing, QUENCH, air inlet temp and fuel temp.
 
RustyRatRod said:
Lets get this terminology right. A camshaft with a later intake closing event does not "bleed off" anything. Bleeding off gives the impression that too much compression is built and the camshaft somehow magically makes it disappear. Ain't how it works.

Closing the intake valve later in the compression stroke means that the cylinders begin to build compression later in the compression stoke. That means the compression stroke is shorter than a camshaft with an earlier intake closing event. In short, you cannot "bleed off" compression that is not there. That is just incorrect.

All that said, IMO, if deck height is zero or close, then the OP will probably be ok, because he will have the aluminum heads AND some quench on his side. True that a domed piston is not the best for quench, but he WILL still have that effect. I think it's worth a shot.
Click to expand...

BINGO..... Thank you..... I have run lots of high compression small blocks on the street. NO problems at all. People don't understand static compression don't mean much. It is the dynamic compression you need to worry about.
 
dusterdoug said:
Winner winner, chicken dinner. CR alone is NOT the determination on octane. Also important is timing, QUENCH, air inlet temp and fuel temp.
Click to expand...

In California, on 91 octane pee wang gas, this is a necessity....( We don't have 93 octane, we have 91(?) octane winter & summer formulas)
You tune , with that.
 
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