[Lthompson]

I have a 95 chevy 350 in my 84 shortwide and ive developed a bad oil leak. Its got an edelbrock performer intake on it. A while ago i had to take the heads off and such and when i put the intake back on, i used on of those rubber seals along with the silicone. I think the seal has gone bad on me. This oil leak is like about a quart every 50 miles, It runs down the back sides of the block, dripping off the started on one side and the filter on the other. Does enough oil get into the lifter valley under the intake to cause such a bad oil leak? at first i thought it was the head gaskets but it seems like there would be more problems if they werent sealing. im not sure now after i cleaned it all and then tried to pinpoint the leak, i just cant really see far enough behind the intake to see if this is for sure where it is leaking. I dont want to do more work than i have to. could such a bad leak be caused from a bad seal between the rear of the intake and the block?? Thanks for any suggestions and opinions.

Lance

[jmhollis]

It sure can - there is a lot of oil flying around above the lifters. The best bet is to remove the intake, clean all the old gasket material from all surfaces, and replace with a good set. I don't use the rubber front and back pieces, I just lay a thick bead of black RTV and reassemble. The only time I have had leaks was when I used the cork or rubber front and rear gaskets!

[56Maynard]

^Yup me too

[Ratchet]

Are you sure the oil pressure/idiot light sender that screws into the block next to the distributor isn't leaking. I had one crack on me and it sent oil all over the back of the block.

[sbchevfreak]

Ditto on all the above. The rubber end seals are never used with aluminium intakes. It has to do with the expansion/contraction rate differences between cast iron & aluminium. Make sure everything is squeaky clean, and apply about a 1/4" bead on the block surface, and torque it down. I reccomend some stuff called "The Right Stuff". It is made by Permatex, and is the best sealant I have ever used. It is a little pricey, but a can lasts a long time, and the seal is unbelievable.

[oldchevy1956]

I agree with using the good Permatex 1/4 bead. That will 9 times out of 10 seal very good, but in some cases when you put on an aftermarket intake the permatex will 'blow' or slip out after a few thousand miles, so I have used the cork front and rear gaskets and glued them in place with the permatex #1 or #2 black gunk. The trick is you need to let it set good on all surfaces before attaching together and even then when placing the intake on, let it set for a while before tightening down. Another trick is you may need to trim the cork front and rear gasket to not be to long because when you tighten down the cork will swell and push out of place. I have been so frustrated with oil leaks in the rear of the intake I have been tempted to weld it on. I would not suggest it but I have thought about it.

[ernkazern]

As someone already mentioned be sure to check the oil pressure sender first.

[red65mustang]

have you retorqued the intake since you put it on?....pretty normal for 2-3 heat cycles and re-torques before the gaskets are fully compressed....

to find the leak: clean it (409 works) then sprinkle flour/baby powder/baking soda/what ever ya got that's fine white powder on the motor...the leak will show up nice and clear

I use a piece of a rough cut file to put some scratches into the block manifold ends for new clean metal exposed and to give the silicone something to bite and grab...use 36 grit sandpaper on the bottem of the new manifold to expose new rough clean aluminum

I wipe the surfaces with brake cleaner on a paper towel then again and again with lacquer thinner on a paper towel to "know" the surface is contaminent free

[Holder350]

Originally Posted by jmhollis

It sure can - there is a lot of oil flying around above the lifters. The best bet is to remove the intake, clean all the old gasket material from all surfaces, and replace with a good set. I don't use the rubber front and back pieces, I just lay a thick bead of black RTV and reassemble. The only time I have had leaks was when I used the cork or rubber front and rear gaskets!

yep I always throw those stupid little gaskets as far as I can when I open a new pack of intake gaskets.