ive got the 'wildcat 355' in my 65 lesabre. it started dieseling a bit out of the blue so i started poking around and found there is a small leak on the carb gasket. i was told by a buddy of mine that it should be a metal crush type gasket but im not sure as i dont have much experience with the 300's. its still got the factory rochester qjet...all original engine. so is it a specialized gasket or is it just a generic qjet gasket? o No:
First off, that car cant have a qjet on it. should be either a carter afb or a rochester 4gc. If I am remembering right. the qjet is a spreadbore carb and there are no intake manifolds for that carb and engine. Now for the gasket ; It should be a sandwich of stainless steel in the center, with black heat resistant material on each side. you are right, any kind of vac leak will throw every thing off. Use a 180 deg thermostat with a fan shroud to keep the heat down and run real good gas in it. The comp. can be as high as 11 to 1 on these engines so it is easy for them to diesel. Keep the idle low, [550] and set the timing at 2 1/2 deg with the vac line disconnected.
Doc is correct that it would be Carter in 65 but I think possibly the 64 300 that used the aluminum intake and Carb may have used the rochester though,I am not 100% sure on that.On my 65 I just went and got a base gasket from the local store and never reused the stainless center at all and just put a single MODERN gasket in there and have never had a problem with it..........Maybe for some reason I am in error for doing so but have seen no ill effects from doing it this way and eliminating the stainless one..........
The exhaust gasses will corrode the aluminum of the carb, which will eventually cause vacuum leaks. More often than not, those exhaust passages in the intake are clogged, in which case there won't be a problem with omitting the stainless shield. Those shields are repo'd... Sold by Russ Martin who goes by 'buickrodder' on e-bay. Lots of other good Nailhead stuff too!:TU:
I still have the shield Walt,are you reccomending I put it back in?If so I will do so asap........Thanks
i knew it was a high comp motor so we have always run 91+ octane in it. the timing has always been 2 1/2* with vacuum disconnected but ive been running 750rpm idle because my wife hates low idle cars. carb has been adjusted recently as well. dwell is at 30* i keep on top if this car as its my wifes daily driver although its 100% all original and it being a 42 year old car, things are bound to break! i changed the thermostat last week because it was stuck open and it was an original style trap door one. i havent seen one of these in ages!! i thought for sure the carb was a qjet but i guess i just saw the rochester and the size of the thing and assumed ou: i run NGK v-power plugs. its got new plugs, wires, cap, rotor, 180* thermostat, points/condenser. here was the old thermostat. broken in a couple pieces (the spring was) and stuck open)
Yes, you don't want exhaust gases flowing against an alum carb. And exhaust gases may burn thru a standard carb gasket as well....causing a vacuum leak, and even an exhaust leak! Byron, if it is an old Rochester 4jet, they have iron bases, so don't worry about a stainless shield. They didn't use them.
so i guess the question now is im assuming there is a shield and i can reuse that shield when replacing the carb gasket with another square bore one? or is it a special gasket all together? the thing is we are currently depending on the car so i gotta make it right in one shot, no margin for errors, you know? here is my carb guys. i dunno why i thought it was a rochester. maybe ive dealt with my other buick stuff too often lately. not bad for an original '65, huh?
First of all...I am assuming the 300 is like the 401/425 and has the metal shield on the intake, then a carb gasket on top of that... You can reuse the metal shield if it is in good condition. Dieseling/running on is usually caused by carbon deposits in the combustion chamber, carb throttle plates that don't close all the way, too-hi idle speed, and I believe (wrong)timing too. (too much advance?) I suppose a vac leak could contribute to the problem. Hopefully, 'the wizard' (Larry70gs) will see this post and add his thoughts....
You could try running some Sea Foam cleaner thru the engine, its supposed to do wonders in removing any carbon build up. Also reduce your idle speed to factory specs at 750rpm the butterflies are being held open slightly which contributes to the dieseling.
That is a good old Carter afb. [aluminum four barrell] That is a good carb. the present day edelbrocks should bolt on, if you want to go bigger. i helped my 300 by milling the front barrels of the intake out to match the secondarys size and making up a cold air pkg. On those years of cars you will have to have a carb shield under the carb or the exhaust gas will eat up the bottom of the carb base plate. I usually fab my own out of ss. In a way Walt is right if the carb has a cast iron base you can get away with not using the shield but ,long term even those will erode. Better to just use the shield.
