Just want to hear some ideas on why my intake seal might be blowing so much. I have a '68 307 engine with an edlebrock performer intake and 600 cfm carb. This was a throw together motor so not sure on all the little details. I have had the intake for maybe 8 years or so? Started on the stock 305, then went to a 350, and now to the 307. The engine was running pretty crappy a couple months back so I tore it apart a little bit and addressed a few issues. One of them being a blown intake seal front and rear. Got it back together and it was running like a champ. Now it is running crappy again and I can see the rubber seal coming out from between the RTV so same thing again. But why? Too much pressure in the intake? Should I have not put the rubber seals in? I've heard guys just leave those out and use RTV but if I do that then how well will the RTV hold? Would adding a breather on the valve covers help alliviate the problem? Let me know what you think, I really hate having to pull the intake off all the time. Thanks

 

You should have a PCV system, or at least a breather to allow the blowby to escape the crankcase. Not having a PCV system will cause sludging.

The rubber china wall seals do come out from time to time. I used them in the past, and sometimes they work, sometimes they dont. If you dont have a breather, then they will blow out in short order. As for sealing, RTV is teh best method. Make sure its good RTV and not the cheap colored silicone crap.

 

Yeah I have a PCV on the one valve cover that goes back up to the carb. The other valve cover has a breather on it but it is only looks(I found this out when I tore the top end apart last time) Just need to get a different rubber grommet so it will be functional. Oh, my cam is a comp cam with .470/.470 lift, would that make a difference with the intake pressure? When I put the Intake on last time I used permatex high temp RTV, the red stuff. It had always worked good for me before but now.....yeah. Do I need to get a different RTV? What kind would you reccommend? Thanks for the help.