I have a new GM crate Gen I SBC. I put an aftermarket intake manifold on it; this manifold was on my previous SBC with no problems. But this time water leaks into the oil and there is no manifold vacuum. I suspect a sealing problem between the heads and the manifold. The gaskets are new and look OK.
Two questions: 1) are all Gen I SBC's the same, or could there be variations such that the heads and manifold don't match, and 2) how can I check the match on my motor?
I'd say that all GEN I SBC are engineered the same, however the machined surfaces could be different. The only way to know for sure is to tear it down and measure it. The questions I'd be asking are; Is the deck height the same on both sides? Is the deck square to the crank? Are the heads machined identical? Is the Intake even on both sides? Time to get out the measurement tools and mic it.
I have a new GM crate Gen I SBC. I put an aftermarket intake manifold on it; this manifold was on my previous SBC with no problems. But this time water leaks into the oil and there is no manifold vacuum. I suspect a sealing problem between the heads and the manifold. The gaskets are new and look OK.
Two questions: 1) are all Gen I SBC's the same, or could there be variations such that the heads and manifold don't match, and 2) how can I check the match on my motor?
I reckon 1/ is answered already. What I do is, I never use the cork gaskets that go on the flat valley ends. Glue your gaskets of choice onto the manifold. When they are securely held, carefully lower the manifold and gaskets into position. You should have a gap both ends at the valley ends. Some manifolds you can see down and check port alignment, if I can't do this I use bearing blue on the head surface, this will tell me if I have contact all over. Different intake gaskets are different thickness, and in some cases you may need to use a couple of gaskets glued together to get the height so as the ports align. When everything lines up, put a bead of silicon down each valley end, a smear around the water passage part of the gaskets, and torque her down. A wet finger will neaten up the silicon beads sealing the valley ends, you'll need to let this cure before running, of course. JM2CW, I am sure there are other ways and I will be interested to hear about them.
If the new engine is a gen1 ,2 pc. RMS block & heads ,it should be the same as every other Gen 1 -2pc. RMS block & heads. There are measuring fixtures that check angle & distance [of the head intake surface]. Also there are both .060 & .125 thickness intake gskts. available [Fel-pro 1206 &1266 are examples]. There's also charts that show how much to mill an intake vs. how much a block has been decked or heads shaved. There's a good how- to by tech-inspector over on "hotrodder's" about how to measure your setup "at home" hope this helps .....dave
All 1st Gen.'s should be the same, there are instances of experimentation from the factory in various areas.... someone somewhere could have cut a surface and gave you a bad seal problem.
When everyone buys a new intake,.... with compressed old gaskets on the head to intake surfaces, always, always look at your seal on the lifter valley area for a slight gap.
As Mango said, there are diff. thickness gaskets for correcting this. I have noticed on some aluminum heads that the intake decks are sometimes high or low....because I mic from the main bore to the deck and record these numbers during my rebuilds. The 'Hi-deck' blocks are a good bit over, so I don't think this applies here. Now, if it were a custom motor, anythings possible.
I've milled the block decks and the head decks to get the compression, I engrave the dimensions on the blocks and heads but I also note it in the paperwork for the owners that way their crewchief knows what they have to get for a rebuild....
Sorry PG , my knowledge stops w/ the 2-peice seal blocks. I know there were changes made w/ the newer engines but can't offer any insight into what exactly was changed...??
dave
Let me just add something here. While all 1st Gens are 'Suppossed' to be the same, there are mfg'ing tolerances that come into play here. Someone setting up the CNC machining center and they don't watch, mistakes can be made, deck low, valley area high. its on the high side of tolerance, and then you throw in the mix a thin gasket set, then the intake is cnc machined also, it could be low....
YES, you could have a bad mismatch.
There is the LS-1, it has some differences in the heads and intake. Other than that, the 60's models SBC all the way up thru the 80's ought to be the same. Later versions are different. They messed with head angles, all kinds of stuff for emissions, cost, etc. Like the GM Goodwrench crate motors at mostly done in their Mexico Plant.
This is a Mexican crate motor. I got a little irritated when I stripped a head/manifold thread just with a wrench while fitting the manifold. I've never heard of cast iron stripping like that. Had to Helicoil the thread.
Excellent stuff, guys. I will put on the manifold and check for any obvious mismatch. Then bolt it down and pressurize the water system. Leave off the pan and see if any water drips thru the valley and crankcase. Then maybe try a thick gasket or double gasket. Stay tuned.
If it is a HO Gen 1 engine the heads and and intake manifold are different if I remember right.
"HO" - High Output. Check and see if there is three triangles in the front of the head casting.
Here's what happened today: Checked the fit for any obvious mismatch; it all looked good. I swapped the generic gaskets for a set of Jegs Poziseal 210004. Smeared silicon around the water ports on both sides of gaskets. Then used my new Eastwood digital torque wrench 13630 to cinch the bolts to 30 ft-lbs. Hooked up hoses and a Schrader valve to pressurize water system to 20 psi. Had the pan off to see if any water came through. And...drum roll..no leaks! What did I learn? Two things: 1) use quality gaskets. I can't be sure the cheap ones were part of the problem, but quality ones aren't very expensive and could save a lot of grief and money. 2) use a torque wrench. Up to now I have tightened most bolts by feel, and that is asking for trouble. With a 6" ratchet I would have a hard time pulling 30 ft-lbs. That Eastwood wrench is really something. You can set the number you want and the wrench will beep and flash to tell you how you're doing. Damn near foolproof and I'm the proof of that.
Thanks for all the good info. Hope this little drama has had something for us all.
Great to hear things worked out for you PG! In the background I'm hearing the 'Mexican Radio' song the used to come on MTV back when it was good....Hahaha....
Good gaskets will cure a lot of ills in a motor....
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