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Cilinderhead question for almost stock L81..

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Hello,

I just had my engine rebuild so I'm not in a hurry with this! This year and next year all the money goes to the painter and the custom interior builder so time is on my side to find a good deal (ebay or not). Important to know is that I wanted my engine to appear original from the outside, not NCRS original but normal original ;)
As I'm not looking for a big torque and hp engine the components don't need to be top of the shelf but good quality for a good price. Optimizing the engine and still having its "original" appearance is my goal.
My engine setup right now is:
Stock Qjet carb (750 cfm)
Stock Alu intake
Stock heads (far as I know: 76cc)
Stock short headers (not the ram horns)
Hypereutectic pistons.
Comp Cam X256.
2.5" dual exhaust with Dynomax Ultra Flow.
Updated ecm with knock sensor and esc.

The only thing I maybe want to change, (one day) are the heads (no alu!) and rocker arms. I think some nice heads for this combo are the Dart Iron Eagles, but there are several available...
Intake port 165cc with 72cc chamber.
Intake port 180cc with 64cc chamber or 72cc chamber.
Would a 180cc port be to big?

I don't want to change the intake so the vortec heads are a no go I think, so are there other heads to give me just that little more?
With my mild cam I think 1.6 rocker arms are overkill and 1.5 would do just fine or am I wrong?
I looked up several tests at the hotrodding page and superchevy but I didn't find what I was looking for.
Thanks,

Groeten Peter.
 

Crimson Thunder

Well-known member
Joined
Dec 16, 2001
Messages
814
Location
Orange Park FL USA
Corvette
1970 Marboro Maroon Convertible
Too bad you said no aluminum because the Edelbrock Performer head would be perfect.(170-64cc chambers)Do you know your compression ratio with your new pistons and the stock 76cc heads?If it is below 9.0:1 go with the 64 cc Iron Eagles.You have to be careful not to go to high with the compression with an iron head and your short duation camshaft.Then again,I dont know what kind of quality gas you have access to over in the Netherlands.I would go with the 180 port(but nothing larger).
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Thanks for the link Gerry!

I've looked at that page before but never came across this one :)

@Sharkcar, sorry I don't know my current compression ratio and the vette is at the painter but I'll have it back and Black :D by July.
Why would you go for the 180cc and not for the 165? In another chevyhighper.. article I read that if the ports are to big that would also be no good. When I look at the specs of the 165cc and 180cc heads. The intake flows are about the same (165cc even 1 point higher) but the exhaust for the 165cc is 72% and for the 180cc is 79%.
If somebody could help me out with this, that would be very nice :)

Groeten Peter.
 

Crimson Thunder

Well-known member
Joined
Dec 16, 2001
Messages
814
Location
Orange Park FL USA
Corvette
1970 Marboro Maroon Convertible
180 heads are generally as large as you want to go on a street car.Im acually more concerned with getting the compression ratio where it needs to be.(between 9.0 and 9.5 with an iron head)Im not sure what the stock L81 ratio is(8.5?)but since you changed pistons it could have changed.I went to Amsterdam in 2002 and remember traveling at very high speeds on the highway to get there from Germany so i was thinking at the time the 180 head might be better.The 165 would be better(not as lazy on the low end) if you do a lot of"around the town"type of driving but i would be concerned with the 72cc chambers and having the compession too low.
 

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