just given ya a hard time

remember folks, on the internet, everybodys a mechanic

 

I hear that!!

You should be fine w/ the 10.9:1 static ratio. I didn't run the numbers but it should be OK. Thats only like 10:1 w/ iron heads. Heck some engines come w/ that from the factory w/ iron heads. Good luck w/ the build.

Kyle

 

Hey another thing....how are you figuring these ratio's? You want a squish around .040-.050 so check the gasket size, and find out whether your block is zero decked or not. That stuff will greatly affect the static ratio.

 

General Rule of thumb is 3-4 percent power increase/decrease with every point of compression added/subtracted. What is the duration on ur cam (even if you dont know what it is abdc). Advertised and at .050lift.

 

If ur cam is decently sized and you can get 93 pump gas (unlike us in cali with only 91 ) i think youd be fine with 10.9:1. But once again do all the little calculations just dont think you have 10.9:1 because the piston says so. And you want a quench of .039"-.041" being optimum quench. So if you have a 0 decked block get a head gasket in the size of .039-.041 compressed thickness. If you have a standard deck height of 9.025 which you most likely will have. You will want a head gasket size of .015" compressed thickness. Now that is just a rule of thumb, like myself with my 412 build im using a 3.8" stroke crank instead of a 3.75" stroke crank because with my pistons (having a compression height of 1.125") it zero decks my block with out me having to really get my block zero decked. Lost me yet , motor building takes into account a lot of math. If your blocks stock and you can find me out the compression height of the pistons you will be using i can teach ya how to do the math urself.

 

wow... lol yeah you lost me, i'm sorry.... keep in mind i'm only in highschool and haven't had much experience with motors yet so i don't even know what zero decked means... sorry! i just know i bought the motor 2 years ago and it had decent hp, i looked up the heads number and the motor is a 72 block so i don't konw if that'll help you figure out all the numbers you wanted or not. sorry... but i'm pretty good at math so if you teach me how to do it i'm sure i'd be plenty willing to learn. but you think with a stock block, besides the .030 bore, and the 64cc heads i'll be ok if the pistons are rated to produce "10.9:1" compression on the premium 93 octane? i ended up getting a few tickets the other day and now the heads are gonna be put on hold for a few weeks, i'm also graduating in a month so its an expensive time period for me already. but when the money comes i want to get the edelbrock aluminum performer rpm heads since i can just bolt em right on without doing more work...

 

On my new 383 I was ideally looking to get around 10.5:1, but I would have had to order custom ($700+) pistons to get that with my combo....I searched and searched and found a stock JE/SRP forged piston that gave me 10.1:1 and I'm happy with the number on my engine.
I've heard you can safely go up to 11.0:1 on an aluminum headed engine and still run pump gas....but anything more and you're pushing it.

- Joel

 

.040 - .050 of quench?

That doesn't seem a tad high to you?



Also, I forgot who mentioned it, but a longer rod is actually going to make it easier for the mix to self-ignite. It does let the piston "hang out" at the top of the bore longer, giving the mix more time to do something wrong. A shorter rod will pull the piston away from the head faster, reducing the opportunity for detonation.

I think that there are some very good reasons to run a long rod, not the least of which is that Smokey said to; but increased detonation resistance isn't one of them.

 

It is .039-.041 optimal quench

 

Do me a favor and link me to rotating assembly and cam that you bought. Maybe i can find some stuff out.

 

I know what optimal quench is but as long as he is somewhere in that range he should be fine. Most engines come w/ more than that from the factory. Personally I would have it alittle higher since he has no idea whether the block has been decked or not, rather than have too little and have piston to valve clearance issues.

 

well i'm lookin through my summit magazine right now and the part number for the rotating assembly is ESP-B13005E30 and the cam part number i believe is SUM-1107 so you could probley go to the site and search for those part numbers... the cam is 234*/244* with .488/.510. hope that helps some...

also just for thought, the heads that i'm looking at are part number EDL-60899 or EDL-60999 but i'm not sure if i need angled or straight plugs, since that is the only difference between the two heads.

 

Doesnt tell the compression height on the pistons. Do you know which ones they use? Could always call summit and ask them.

 

need to know gasket thickness and gasket bore size

For right now im going to use a 4.100" Gasket Bore and a .040" Thickness.

That puts you at a 10.23 compression ratio. Now your quench is going to be messed up with the .040" gasket thickness and if i were you id go to ur local auto parts store and get a gasket with a thickness of .015". That would put you at a .040" quench (.025" deck height + .015" gasket thickness = .040" quench). Now with the same gasket bore but a thickness of .015" that will bump ur static compression from 10.23 to 10.86, which i would say you'll be fine on 93 octane with aluminum heads. Keep me posted.

Thats with a 64cc head btw.

 

awesome, thanks a ton devils. well for the time being i used the thick head gasket since i had to put the original heads back on the motor for a month or so. as soon as june comes around and i'm done with graduation junk and working 50+ hours a week i'm gonna get new heads, i originally planned on getting them now but its gonna have to wait,(in the past two weeks i've already spent $2500 so i'm officially FLAT BROKE!) so i just threw on the old heads(shˇtty and stock) and the thick head gasket. but now i know when summer comes around and i get those heads i'll get the thinner .015" head gasket and i should be good to go! i know you can't make any extremely close estimates but just with ur knowledge of motors what do you think this combo would produce for hp roughly? with my cam, rotating assembly, and the edelbrock heads at 10.86:1 compression? i also have an edelbrock 750 on top of an edelbrock performer rpm air gap intake. i'm just kinda curious as to what i'm gonna get out of this and how bad its gonna thrash the frame of my z28. thanks a ton for everything so far though guys!!!!!