The teething pains continue but I think I have found the cause of a few tuning issues...low vacuum, idle speeds up when hot and idle AFR I can't be leaned out. I came to the conclusion that I might have an internal intake leak after not finding anything externally. I couldn't find too many other signs other than one porcelain that was fairly white compared to the others. I thought it idled a little rough too. I remembered that the new Eddy intake was too narrow so I had to double gasket it. I didn't have the heads machined on that side and the bolts went in ok so who knows why. Rather than buying a smoke machine I thought I would just change them out since I found out that Cometic makes 0.120" thick intake gaskets. Here are a few pics. I'm not sure how oil could end up inside the intake runner (just) other than a leak. Thoughts?
Intake gasket leak?
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Its all new, no smoke or anything. I'm going to clean it up and have a better look. After that I will fit the manifold with some shims and inspect it further.
middleagecrisis
Well-Known Member
Any evidence of oil underneath the intake gasket on the head side? I always put a very thin bead of rtv (black or red) between the head and intake gasket along the bottom face of the intake ports just for this reason. Same reason I put a thin film of blue rtv completely around the water ports on the head. It keeps fluids where they belong and out of where they don’t.
The gaskets seemed fairly well stuck to the head. I'm going to fit the Felpro 1213 s3 pintoseal gaskets and see what I got.
Inertia
Well-Known Member
Please don't put any rtv anywhere except a pea sized dab where the gaskets meet.
Those 1213 S-3s have raised seals around each port, don't mess it up with rtv.
The end-gaskets for the China wall are thinner, and fit better than other sets.
I've been using them since they came out, - for use with aluminum manifolds to get away from chugging a bead of jelly rtv on the China wall.
Glue the gasket to the China wall with a good adhesive like 3M weather strip adhesive, or similar contact cement.
4 dabs of "Right Stuff" at the joints, (I threw all jelly rtv in the garbage).
All surfaces clean, - Good luck
PS, I think if you check, it is not recommended to use rtv in contact with anything fuel related. Please Google it, it does cause issues/dissolves.
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Cal Tonsley
Well-Known Member
I’d think that you’ve probably had a less than perfect seal and have been drawing oil into the bottom of the ports from the valley area.
FWIW, I’ve used Felpro 1213 S3 in the past and probably placed too much faith in the PrintoSeal beads doing their job on my application. While the 1213 S3 gaskets are a little thicker than the regular (non steel shim) 1213 I still needed something thicker. I’m currently using .090” Cometic intake gaskets on my 410 and have had good success with some blue Hylomar (it’s fuel resistant) around the intake ports and grey Permatex around the water ports and on the China walls.
FWIW, I’ve used Felpro 1213 S3 in the past and probably placed too much faith in the PrintoSeal beads doing their job on my application. While the 1213 S3 gaskets are a little thicker than the regular (non steel shim) 1213 I still needed something thicker. I’m currently using .090” Cometic intake gaskets on my 410 and have had good success with some blue Hylomar (it’s fuel resistant) around the intake ports and grey Permatex around the water ports and on the China walls.
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I've never had one leak before but then I have never double gasketed before. I just fit the manifold without gaskets and it looked pretty good. I have no idea why I thought I needed to double gasket it but that was a few years ago. Usually I make very light use of RTV on the sides around the ports and run a thin bead front and back on top of the China wall gaskets and heavier in the corners. I believe I Gasgacinch'd the China wall gaskets to the block last time. I just picked up a fresh tube of Permatex Right Stuff black gasket maker this morning.
That is what I am suspecting based on finding some oil near the manifold ports on some cylinders. I'm sure hoping it resolves a few issues. I haven't used the Printoseal gaskets before but with the beads I agree that extra sealant might not be a good idea.
If you set the intake on the heads without a gasket the bolt holes in the manifold should be 1/2 a hole lower than the bolt holes in the head.
If the holes line up you need to mill the face of the intake manifold the thickness of the gasket plus a clean up cut to start.
I'll have another look but I think the holes line up with no gasket. I don't believe the shop milled the heads much but they may have been cut before.
B3422w5
Well-Known Member
Just fire it up and spray brake clean around the intake, if it’s leaking the idle will take a dive when you hit a leak. Won’t take 3 minutes
I think we are fighting the same battle. Mine has an airgap intake and I'm getting oil in the cylinders. The joy of hotrodding! Good luck, watching.
Slick idea to check clearance.
pntastar69
Well-Known Member
My new air gap had to be cut .050 on one side plus both sides were not true. Went thru several sets of gaskets.
I think most guys would be appalled if they knew how shitty these intake flanges are out of the box.
It’s horrible. I’m surprised more Gus aren’t having sealing issues.
Maybe the fancy gaskets will help
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