Vacuum Leak (insulation spacer, under the carb)

[BQS4]

Ok All;
I'm at a lost as to where to go. I recently develpoed an exhaust leak. I thought I had it pin-pointed to the dreaded headpipe-to-exhaust manifold leak. Come to find out, after breaking off two of the 6 bolts, that it wasn't there, it was where the intake manifold and exhaust bolt together. Well, I had a decent replacement exhaust manifoldand made all the correct repairs. When I went to fire it up, it runs rough. I have checked, plugs, points, condensor, wires, cap, rotor button, no difference. I have checked the timing to the point of manually setting up the timing mark on the flywheel, the crank pulley keyway is pointing up, and the rotor button is straight up. The cam marks are lined up. The motor will run if you hold it above 2500rpm, but, you can still feel it missing. It won't idle. Any ideas, help?

[Old Hippie]

BQS4, Sounds like you have a vacume leak in the intake manifold or the carb base gasket. If it ran good before the change, that's where I'd be looking. Make sure your In-manifold dosen't have a crack or a open port.
My 2c's for ya.

[RallyBob]

Is the vacuum fitting at the valve-cover side of the intake hooked up? Easy to miss that one, it's caught me out a few times before.

[ging]

"Mr. Ging" had an idea for you. A quick check for the intake manifold leak/carb base leak - spray some starter fluid around the intake manifold/carburetor base (when engine is cold) and if you get a jump in rpm's you'll know if that's the case.
Sorry to hear about the trouble,

[opelwasp]

on a more catosrophic note it may also be a cracked exhaust valve. had this a couple years ago. i couldnt get the engine to run smooth. valve had a 1/2" crack in it. so after i sucked another exhaust valve into piston #2 i had to get a new piston and head done. come to find out i also almost lost a second valve. seemed valves from pistons #2 & #3 were destined to go. definatly a good idea to drill the holes between 2 and 3 on the head gasket.

[Gordy]

Wasp, You stated drilling the hole in the head gasket...I've got mine apart for a valve job, and on the old head gasket it looked like there were water ports with no matching holes in the gasket...Why is that?? And why don't they make the replacement head gaskets with the holes? Before I put the new gastet on should I open up the holes?? Thanks, Gordy

[soybean]

Gordy, Check out this thread. I did the conversion a couple of weeks ago. HTH, Jarrell (It was in Tips and Tricks)
http://www.opelgt.com/forums/opel-tips-tricks/3296-improved-coolant-flow-cyl-2-3-exhaust-valves.html

[BQS4]

Ok, this is one where sheer dumb luck happened my way. I fixed my problem and thought I'd share it with everyone. It seems that the insulation spacer, under the carb, was the culprit. As you can see in the attached pic, the spacer has cut-outs for the 4 screws that hold the intake to the exhaust manifold. Well, as I was going back into all the work I did to fix the broken exhaust manifold, I noticed the sealing pattern the carb made on the gasket and when the indentations went across the notches, there was a fine dusting of dirt and grit that shouldn't have been there. So I decided to replace the notched spacer with an un-notched spacer and cut new gaskets. That did the trick. I used a divider from my desk drawer (these are hardwood plates designed to allow you to make compartment in your desk drawer) I used the notched spacer as a template, but, leaving out the notches. I hope this helps someone else in the future.
Gene