Thread: Quadra Jet, ign timing and Pontiac 400

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Here is what I got going on. It's my 77 T/A of course ( turns out it's not a 78 ) . It's been too long to remember what I did to the inside of this engine but I do know I put in higher compression pistons to increase the factory 8.5 and I did install a healthier cam. I do not remember the details of either which will make this a bit of a guessing game but the rest is stock. Seems like I can't get enough vacuum, a shaky 15 at best and I also can's seem to get my Idle low enough after it's warmed up, it stays at about 1000.When the A/C kicks on it about kills it then comes back and generally everything is just a bit erratic and doesn't react to adjustments and the motor doesn't seem to pull like it used to ( not 100% sure about that though). The base timing is at about 10 deg and hooked to manifold vacuum, total advance seems a bit high at 38 deg. A lot of this points to a vacuum leak but I can't find anything. I screwed around a lot with this engine when I was younger and I think now I'm paying the price.

YES I'd start looking for a vacuum leak may be carb gasket or more work the intake gasket How about your PCV valve?

I ran some butane around the intake and carb and found the back of the carb was leaking. We had it mostly off and Christian noted that the brake booster line was finger tight. We took it off the rest of the way and also found that there was silicone used instead of a gasket under the tin plate that Pontiac uses on top of the intake before the main gasket. I don't remember doing that but it could have been a " if this works for now, great and I'll fix it right later " . So for today we took a Wheaties box and I made a gasket out of that and if it works for now, great and I'll fix it right later We'll it did help quite a bit, still have a low shaky vacuum but it could maybe be cam related? It does have a thumpity- thump- potato- potato sounding idle but still is lacking the pull I thought it had in 3rd and 4th gear. I'll get a carb kit coming for it, and maybe my exhaust is choking it out as well. I should order some Ram Air IV manifolds and larger exhaust but sometimes I get tired of spending money.