69monzaredbigblock

I've got a relatively stock 69 L-36 with an Edelbrock 1901 tuned by Lars. The cam is a mild Lunati 302A4LUN. Compression ratio is about 9.2/1 with a stock points type ignition. I'm using the stock 69 aluminum intake with the three piece gasket and I have it installed correctly. My idle rpm changes +-50 rpm and my manifold vacuum moves from 14-17 in. The idle mixture screws don't make much change even when both are screwed all the way in. Idle is set at 700 rpm. I had the manifold checked for cracks and straightness and both are OK. The intake gaskets look like they were both sealing well. I have true dual exhaust and hear a slight sputter at both tail pipes. I see a light coating of soot at the tail pipes and the plugs are white, almost new looking after 1000 miles. Looking for help here.
Warren

knbwag73

What condition is the distributor in? Is there allot of free-play in the shaft? Does it have allot of miles on it? Connect a dwell meter and see if the distributor will hold a steady dwell reading or if the dwell is fluctuating up and down a few degrees. I had a similar issue, my distributor shaft bushings were worn out. Replaced the bushings and now enjoy rock solid 600 RPM at idle with 18 inches of manifold vacuum.

69monzaredbigblock

My distributor was rebuilt by Lars when I had the carb done, 1000 miles ago. With a dwell meter hooked up I get no more than one degree of change in dwell at 700-4500 rpm. Thanks for the response, got any more ideas?

...Roger...

If that 14-17 is a gentle fluctuation thats usually idle mixture.Is your intake suppose to have that stainless baffle plate under carb?If it does do you have it on right.The gasket goes against manifold and then the plate,then carb--no gasket between carb and plate.Also I think you can get it flipped and then it will upset idle.If its not there it will upset idle.If your intake has a groove cut across under the carb with holes going down to the exhaust crossover then you should have it.That groove heats the bottom of carb with exhaust forced across by the heat riser.You could have some valve issues like valve guides but I dont know what you have done to the heads.Usually the vacumn flucuations are more eratic with valve problems.

oregonsharkman

Lope...Lope...Lope....My goal in life

Perfomer

Are you running a lead additive ? I also have a stock l-36 when I runn93 oct after awhile I get a flapping in the exhaust . I run some 100 oct avgas with lead and the noise goes away and engine smooths out . Might some Max-Lead 2000 I use this also

Muddywaters

Hammer Head Fred sent me this link on vacume...troubleshooting http://www.secondchancegarage.com/public/186.cfm

73, Dark Blue 454

A possibilty,..If you're running manifold vacuum and a stock vacuum advance can, and you have 12-14 inches of vacuum at idle or less, that's probably your problem. The stock VA can isn't fully "in" until 15 hg of vacuum (typically) and your VA can is in no-man's land,..not fully in, not fully out causing inconsistent idle speeds. You can switch to ported vacuum which means there's no vacuum signal sent to the VA during idle or you can get another VA that's fully actuated below your idle vacuum (a better solution than the ported idea).

69monzaredbigblock

Thanks for the responses. I'm using a three piece carb gasket set (correctly installed) and don't think I have a vacuum leak. I'm using manifold vacuum for the vacuum advance and I can see it slam all the way home at idle. I looked at the website recommended by Hammer Head Fred and will explore the idle mixture screw adjustment option. Thanks again.

...Roger...

When you said Lars tuned the carb did he install it or adjust it on the car?

69monzaredbigblock

I sent the carb and the distributor to Lars, he tweaked them and ran them on his test car. I am now trying to dial in the carb to my car. Lars has been very helpful and has responded to every question I have put his way. I just can't get it to idle smoothly. Maybe a road trip from Connecticut to Colorado is in order? Lars?

...Roger...

Are you sure you have the gaskets right?that plate goes against bottom of carb