Hello All, been having issues with my 68 - 400 engine. Running rough, running hot, occasional popping in exhaust. vacuum gauge shows low and erratic vacuum. Compression test hits pretty consistent 125 / 130 on all cylinders. No noticeable coolant leak. Been thru this thing many times trying to find the issue. So decided to pull intake and heads. Valves look good (at least on one, only pulled one side for now. Did notice on issue on the head (well I don't know if it is an issue.) Were the intake meets the head, the wall between chambers has a depression, kind of looks like a casting issue rather than broken away. No way the valley pan can seal this. Could this be causing an issue, vacuum loss? Shared some photos on my google account, let me know what you think. https://photos.app.goo.gl/Y2K3C5hguWVPEi426 Thanks
We've got the same thing on our 67 heads. It has to be a factory casting deal. how's your ignition system doing? what are you running? stock or aftermarket? Did you know what your timing is set at?
I'd try a .032 composite gasket from TA. Cut up your original metal gasket to fashion a valley/splash pan. http://www.taperformance.com/PDF/Intake_Instructions.pdf
Did you pull the timing cover? My stock gs400 cam gear looked like this when we pulled it apart. Any idea if yours is original or not? 20180520_184721 by Grandpas67 posted Jun 7, 2018 at 7:35 PM
Cam and Timing Gear where replaced with a comp cam setup. stock grind, nothing crazy. I replaced these 5 or so years ago but never ran the engine. Life happens and couldn't get back to it until now and are having these issues. Tomorrow will pull the other head and inspect. Can pull timing chain cover and take a look. I also put an edelbrock 1406 carb with the spreadbore adapter a few months ago. Could not get anywhere with the old quadrajet. Larry, Thanks for the info for the intake gasket modification, did check TA's website but did not see that.
Our 68 gs was pulled from the scrap yard in Kansas for 400 bucks, fully numbers matching orignal 400, th400 and factory rear end, with protect o plate and orginal owners info.........found out their son junked the car when he was in college there cause he thought the motor locked up. Car lived it's whole life in texas. Found when pulling apart our timing set looked very much the same. Put a new chain and pulled the pan and put it all back together just to see, and sure enough it purred like a kitten and still does 15 years later.......a true living breathing 100% orginal minus timing chain, tune up parts, and new gaskets built by 68 Buick gs 400. Crazy to think a car was junked for a less than 50 dollar part
