? for engine guru's
Thread Starter
Drifting
Joined: Jun 2000
Posts: 1,476
Likes: 1
From: Mt Juliet TN
? for engine guru's
I bought a set of used edelbrock performer rpm heads from a friend of mine.
They need a valve job but otherwise look pretty good. I was going to replace
my stock heads with them but I wanted to run it passed you guys to see what
you think about the combo. They are 64cc with 170cc chambers. My jasper engine has flat top pistons and 76cc heads. I think that will bring me to 10:1 from 8.5:1 Is that right? Also my engine has a dual pattern cam here are the specs
050 214 224
dur 280 290
Lift 443 465
Lobe Center Intake 107
Lobe Center exhaust 117
I have a ZZ4 intake and a holley 650 to go with the combo.
Does this sound good?
They need a valve job but otherwise look pretty good. I was going to replace
my stock heads with them but I wanted to run it passed you guys to see what
you think about the combo. They are 64cc with 170cc chambers. My jasper engine has flat top pistons and 76cc heads. I think that will bring me to 10:1 from 8.5:1 Is that right? Also my engine has a dual pattern cam here are the specs
050 214 224
dur 280 290
Lift 443 465
Lobe Center Intake 107
Lobe Center exhaust 117
I have a ZZ4 intake and a holley 650 to go with the combo.
Does this sound good?
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: ? for engine guru's (TTop Tony)
they are 64cc chambers w/ 170cc intake runners. So, the chamber is smaller by 12cc from what you have now. Your compression will go up even more, around 11:1 or even higher (I'm lazy, don't feel like calculating :) )
That cam you have is more of a torque cam, with that high compression you can run a much longer cam without loosing too much low rpm torque.
Somewhere around 220 @.050 or even a bit longer would be nice, stick around what you now have for seat durations.
The seperation angle is (LCA or LSA) 112 { (107 +117)/2 } the overlap is 61 degrees.
Your cam has 5 degrees of advance groud into it.
Marck
That cam you have is more of a torque cam, with that high compression you can run a much longer cam without loosing too much low rpm torque.
Somewhere around 220 @.050 or even a bit longer would be nice, stick around what you now have for seat durations.
The seperation angle is (LCA or LSA) 112 { (107 +117)/2 } the overlap is 61 degrees.
Your cam has 5 degrees of advance groud into it.
Marck
Thread Starter
Drifting
Joined: Jun 2000
Posts: 1,476
Likes: 1
From: Mt Juliet TN
Re: ? for engine guru's (Twin_Turbo)
I was hoping not to have replace the cam. Oh well I can save the heads for another project or even sell them. What aftermarket heads would work better with this combo?
Intermediate
Joined: Aug 2001
Posts: 31
Likes: 0
From: Houston TX
Re: ? for engine guru's (TTop Tony)
10:1 sounds about right, but it depends on your deck height and gasket thickness also. There's a formula to calculate static CR that I've seen in several places but can't think where right now. Anyway, it sounds like a pretty good combo.
Good luck, Phil
[Modified by 90 KOTH, 9:48 PM 5/15/2003]
Good luck, Phil
[Modified by 90 KOTH, 9:48 PM 5/15/2003]
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: ? for engine guru's (TTop Tony)
The tricky thing is that with a short cam the cranking pressure and cylinder pressures at low RPM might be very high (needing a start retard to be able to start it)
Are you sure about the 10:1 with 76cc and flat tops? Sounds a bit high for 76cc heads. Was it spec'ed like that or is this a guess? I would guess it'd be closer to 8 or 8,5. Is the block decked (height?) what thickness gasket, how large (cc) are the valve reliefs ? do you have all the specs for your engine?
EDIT!!
Oh wait, it's 8.5 now.. I completely misread that. Yes, then it will be around 10:1 and you will be fine. i thought it was 10:1 now.. geez, I should read better. You will be fine with 10:1 and that cam.
Marck
[Modified by Twin_Turbo, 3:51 PM 5/15/2003]
Are you sure about the 10:1 with 76cc and flat tops? Sounds a bit high for 76cc heads. Was it spec'ed like that or is this a guess? I would guess it'd be closer to 8 or 8,5. Is the block decked (height?) what thickness gasket, how large (cc) are the valve reliefs ? do you have all the specs for your engine?
EDIT!!
Oh wait, it's 8.5 now.. I completely misread that. Yes, then it will be around 10:1 and you will be fine. i thought it was 10:1 now.. geez, I should read better. You will be fine with 10:1 and that cam.
Marck
[Modified by Twin_Turbo, 3:51 PM 5/15/2003]
Thread Starter
Drifting
Joined: Jun 2000
Posts: 1,476
Likes: 1
From: Mt Juliet TN
Re: ? for engine guru's (Twin_Turbo)
The engine specs from Jasper say flat top pistons with approx 8.7:1 . I'm assuming the 0.2:1 comes from decking the block. No I don't have all the specs for my engine one drawback to buying a crate motor.
Nevermind just saw your edit!
[Modified by TTop Tony, 3:54 PM 5/15/2003]
Nevermind just saw your edit!
[Modified by TTop Tony, 3:54 PM 5/15/2003]
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: ? for engine guru's (TTop Tony)
static compression ratio is just a calculation. It's the compression factor when you take into account a 100% filled cylinder volume with the piston down the bore:
The volume w/ piston at bottom dead center is:
4" wide (for stock bore) cylinder with a height of: 3,48 (stroke) + deck height (around 0,025 for stock) + head gasket compressed thickness (usually around 0,036 or so for common fel-pro) + valve relief volume + head volume ( minus spark plug volume if you are really thorough)
Then this set against the volume at the top dead center which is again a 4" wide cylinder with a height of deck height + compressed gasket thickness + valve relief volume + chamber size ( - spark plug size)
It's just a number to give an idea.
Dynamic compression takes into account the valve events, intake and exhaust efficiency and so on. DCR is related to cranking pressure. SCR not.
[Modified by Twin_Turbo, 4:04 PM 5/15/2003]
The volume w/ piston at bottom dead center is:
4" wide (for stock bore) cylinder with a height of: 3,48 (stroke) + deck height (around 0,025 for stock) + head gasket compressed thickness (usually around 0,036 or so for common fel-pro) + valve relief volume + head volume ( minus spark plug volume if you are really thorough)
Then this set against the volume at the top dead center which is again a 4" wide cylinder with a height of deck height + compressed gasket thickness + valve relief volume + chamber size ( - spark plug size)
It's just a number to give an idea.
Dynamic compression takes into account the valve events, intake and exhaust efficiency and so on. DCR is related to cranking pressure. SCR not.
[Modified by Twin_Turbo, 4:04 PM 5/15/2003]
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Advanced
Joined: May 2003
Posts: 54
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From: ewa beach HI
Re: ? for engine guru's (TTop Tony)
Tony...get the heads redone and put them on your engine...your compression should be right around 9.8 with the 64cc chambers, very tolerable with the alum. heads..you won't believe the difference! :yesnod:
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Re: ? for engine guru's (TTop Tony)
I bought a set of used edelbrock performer rpm heads from a friend of mine.
They need a valve job but otherwise look pretty good. I was going to replace
my stock heads with them but I wanted to run it passed you guys to see what
you think about the combo. They are 64cc with 170cc chambers. My jasper engine has flat top pistons and 76cc heads. I think that will bring me to 10:1 from 8.5:1 Is that right? Also my engine has a dual pattern cam here are the specs
050 214 224
dur 280 290
Lift 443 465
Lobe Center Intake 107
Lobe Center exhaust 117
I have a ZZ4 intake and a holley 650 to go with the combo.
Does this sound good?
They need a valve job but otherwise look pretty good. I was going to replace
my stock heads with them but I wanted to run it passed you guys to see what
you think about the combo. They are 64cc with 170cc chambers. My jasper engine has flat top pistons and 76cc heads. I think that will bring me to 10:1 from 8.5:1 Is that right? Also my engine has a dual pattern cam here are the specs
050 214 224
dur 280 290
Lift 443 465
Lobe Center Intake 107
Lobe Center exhaust 117
I have a ZZ4 intake and a holley 650 to go with the combo.
Does this sound good?
Thread Starter
Drifting
Joined: Jun 2000
Posts: 1,476
Likes: 1
From: Mt Juliet TN
Re: ? for engine guru's (cardo0)
Sorry Frosty but it sounds like the heads are a decent match for my combo after all. Thanks guys now all I need to do is save up some $$ for the valve job. :thumbs:
hey stalker those blacked out rims really look sharp on that car
[Modified by TTop Tony, 7:18 AM 5/16/2003]
hey stalker those blacked out rims really look sharp on that car
[Modified by TTop Tony, 7:18 AM 5/16/2003]
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: ? for engine guru's (TTop Tony)
Yea get the heads redone you will reaaly notice a difference, well worth it. If you can swing a cam upgrade a CC 270H or similar is a good match if you have opened up exhaust.
I agree that black car with the black rims looks :cool:
I agree that black car with the black rims looks :cool:
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: ? for engine guru's (TTop Tony)
nah, the weight savings are just a nice bonus. What really is neat about them is the much better chamber design than what you have now (assuming they're 76cc smog heads) and with the alu you can run about a point higher compression without problems. The heads will make much more power.
Marck
Marck
Thread Starter
Drifting
Joined: Jun 2000
Posts: 1,476
Likes: 1
From: Mt Juliet TN
Re: ? for engine guru's (Twin_Turbo)
Well the 75's were pretty heavy so every ounce counts. Reckon it would be worth the money to have them professionally ported along with the valve job or are the Edelbrock heads pretty good as is?
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Re: ? for engine guru's (TTop Tony)
porting will always give good gains if it's fone right but it's expensive. If you are not trying to squeeze every last but of performance out of the engine and sticking with something like under 350Hp or I'd just slap them on as they are. Check the intake and exhaust for casting flash and maybe some restrivtions in the bowl.If you want to those can be cleaned up pretty easily. Just taking the die grinder in there and altering the runner shape will probably do more bad than good. Porting is not exact science and only someone w/ a lot of experience and a flow bench can do a top job.