Opel GT Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter · #1 ·
Hi, I'm new to the forum. My father is an engine rebuilder and is currently working on a 1.9L cylinder head. The customer has upgraded to .080 pistons and a better cam. My question is about the exhaust springs. The cam is .430 lift, and at that, the stock spring is .008" from coilbind with the rotator under it. The valve stems are set to spec also. The parts warehouse we used is in California, and they said the stock springs would work with the cam for street use, but as an experienced engine builder, my dad is skeptical. Can anyone tell me about this issue? :confused:
 

·
Banned
Joined
·
3,842 Posts
If the valves are done correctly going to .435 is about the max you can do. Several here are running that and I've done it and revved the living daylights out of that motor with no problems. HTH
 

·
OPEL-LESS!!!
Joined
·
2,116 Posts
everything in my head is origonal, except a new camshaft and hydraulic lifters. i am using one of the .435 lift cams nobody mentioned, i've wound it over redline, no problems, even on this daily driver. i'm sure dave has wound a opel motor witha .435 lift cam more than 6,500 RPM on many occasions.
 

·
Member
Joined
·
583 Posts
Valve springs and retainers

You can also try Norris Performance Products. They sell a set of performance springs, retainers and shims to replace the rotators for $94 delivered. Search this website for Norris and you'll find the thread.

Good luck,
 

·
Old Opeler
Joined
·
5,564 Posts
Trick!

ricebasher302 said:
My question is about the exhaust springs. The cam is .430 lift, and at that, the stock spring is .008" from coilbind with the rotator under it. Can anyone tell me about this issue? :confused:
The Exhaust springs can be replaced with Intake springs (plus Intake spring retainers too) and the rotator removed and replaced with a thinner spring shim to get the spring installed heights the same on both valves.

This gives you the same gap between the spring coils as the Intake already has. However if the rotators are "solexed" (One of Nobody's wonderful terms for throwing something of little use away! :cool: ) then the exhaust valve seats need to have inserts fitted instead to control valve seat recession.

This "improvement" is possible because the CIH Opel motor has quite different springs on the Intake and exhaust to allow the rotator to fit under the shorter Exhaust spring.

Here is apic showing the difference between the exhaust and intake spring lenghts - ex on left; in at centre. The RH spring is a Pontiac 400 V8 spring that can be used with Chevy valves... but that is another story! ;)
 

Attachments

·
Super Moderator
Joined
·
5,922 Posts
When I had my GT head rebuilt last month for the OGTS Combination Cam (0.430" lift), the machinist determined that the intake springs were almost at bind at the full cam lift. This was a head abandoned at his shop by the PO and I bought it to replace the GT's cracked head. But he also found that the PO had installed hardened valve inserts on the intake valves, such that the valve was installed with too low a height. So he had to cut the seat down to get the height back on spec, and then the .430 cam worked fine. Perhaps this is the case with your head, or the valve springs have been excessively shimmed.
 
1 - 7 of 7 Posts
Top