Idle Vaccum, Copper head gasket leack?
Idle Vaccum, Copper head gasket leack?
(OP)
Hello,
I have a strange situation after I installed the engine and got it started,
first, the engine idles at about 5 in-Hg but when I press the throttle the Vaccum increases, I thought it should go down?
Second, It seems that water and Oil are mixing again (the reason for the rebuild in the first place) but this time I O-Ringed the head and using Copper head gasket but unfortunatley I did not know at the time that you have to aneal it (heat treat it) and use copper spray and use silicone around the water and oil holes, and now I am told that copper head gaskets leak if they are not treated right. I tried pressure test the cooolant system (w/o water) at 10 psig and it held without any leak. Could the head be cracked or is it just the head gasket not being seated good? (Any Ideas?)
I would appreciate suggestions.
Thank you,
Mike
I have a strange situation after I installed the engine and got it started,
first, the engine idles at about 5 in-Hg but when I press the throttle the Vaccum increases, I thought it should go down?
Second, It seems that water and Oil are mixing again (the reason for the rebuild in the first place) but this time I O-Ringed the head and using Copper head gasket but unfortunatley I did not know at the time that you have to aneal it (heat treat it) and use copper spray and use silicone around the water and oil holes, and now I am told that copper head gaskets leak if they are not treated right. I tried pressure test the cooolant system (w/o water) at 10 psig and it held without any leak. Could the head be cracked or is it just the head gasket not being seated good? (Any Ideas?)
I would appreciate suggestions.
Thank you,
Mike





RE: Idle Vaccum, Copper head gasket leack?
RE: Idle Vaccum, Copper head gasket leack?
We seal the water and oil passages with for copper gaskets with good old fashioned GM sealant. It works every time. We use "O" rings and reciever grobes. We always aneal the gasket.
I would pressure test the head and the block with a proper test rig.
Regards
pat
RE: Idle Vaccum, Copper head gasket leack?
A proper pressure test of block and head for cracks is indicated by your condition. Not all cracks will show unless you add in the heat factor, particularly in and aluminium engine.
To cover all the bases, is it possible an error of assembly has 'crept' into the equation?
Good luck
Rod
RE: Idle Vaccum, Copper head gasket leack?
I pulled the Head yesterday and removed the gasket. It looks like it sealed pretty good on the block where you can see uniform impressions on the the gasket. However, on the head side the impressions are not uniform and are in few areas here and there (warped Head?! it was machined before I installed it!! but who knows).
The O-Rings left a good impression on the gasket. The machinest who I saw after my first post is going to pressure test the head and inspect it but he thinks the gasket did not seal right.
As for the Idle vaccum, He says that this is normal and Vaccum always increases when you tap trhe throttle (I have to verify that by myself may be I forgot how it should act).
FYI
Thanks for the responses
RE: Idle Vaccum, Copper head gasket leack?
RE: Idle Vaccum, Copper head gasket leack?
Judging by the impressions on the head gasket, I think it did not seal right the first time and it was too hard for the O-rings to dig deep enough to allow the rest of the flat surfaces to mate.
I am going to anneal it and follow all the preperations this time (that I know of) and I have hope that it will work this time.
RE: Idle Vaccum, Copper head gasket leack?
If you have further problems, check the finish on the head. The first BBC I had with Copper head gaskets drove me nuts, it would show good compression, run fantastic until about 2nd gear, then develop a dead miss on 2 cylinders. By the time you got it back to the pits, it would be running on all 8 again. Pulling the heads showed compression leaks, but no one seemed to be able to figure it out. I finally went to a builder that surfaced the heads with a far finer finish, and the problem went away.
RE: Idle Vaccum, Copper head gasket leack?
At idle a normal engine will have around 17 / 21 inches of vacuum.
A low steady reading suggests a manifold leak.
Blipping the throttle will spin the gauge to about 25 then a fall to around 5 or perhaps even 0 as the throttle is closed and the engine returns to idle.
At idle the vacuum returns to 17 / 21 or whatever it was.
Cheers, Pete.
RE: Idle Vaccum, Copper head gasket leack?
Shaun TiedeULTRADYNE Arl,TX(stiede@ev1.net)