better carb and intake for 401-425 Nail head

**gforcecuda** · 12-14-2010, 09:41 AM

I have posted on here about my 64 Riviera with a 425 in it...I also have a 401 punched to 413 in my 58 Buick Caballero wagon...The carbs are boiling down the gas when I stop for awhile...I was looking for a carb like an AFB or a Holley but on't seem to find one that will bolt on...Also I would like to buy a phenolic spacer of something to insulate the carb from the intake heat to stop the boiling of this alcohol infused junk gas which boils at low temps..Does anyone make an after market intake for these 2 engines? Anyone know of a spacer? Anyone know of a carb that will adapt? any other ideas??

**telriv** · 12-14-2010, 06:41 PM

One very IMPORTANT & overlooked part is the metal gasket under the carbs. With it the carbs. run hot. Without it the carbs. get eaten up & run hot. I've used a Holley 750 dbl. pumper with an adapter plate on my '64 Riv. for about 40 yrs. now. At the time they only came with manual chokes, but I made my own automatic choke using parts from old Holley carbs. I believe today you can get one with an automatic electric choke. You will need an adapter plate which will also serve as a spacer plate. You NEED to block the exhaust holes under the carb. in the manifold. NOT block off the heat riser passages in the heads. You will be astounded at the performance improvement. You will want to change to 35cc accelerator pumps front & rear if the Holley comes with 50cc pumps. From there it's just getting the jetting correct. I believe I went down 2-3 sizes front & rear.

**gforcecuda** · 12-15-2010, 07:23 AM

so you found an adapter plate that made the Holley fit the stock intake? where did you find that...i haven't seen one..you think you need a double pumper to enrichen it off the line? did yours ever tremble like mine does? it just does it until it builds a few RPM and then smoothes out...i saw the article in Street Rodder i think it was that went into recurving your distributor, the initial, vacuum and centrifugal advances for this new bull **** gas..Also rejetting the carb for this alcohol infused gas is supposed to come out in a future issue..anyone on here played with recurving the whole set-up of a stock distributor to get it to run good on this new gas...my motor runs great, but you can tell it isn't completely happy at part throttle..needs some fine tuning from stock...I would like to put a Holley on it if I can find that adapter plate you are referring to...

**telriv** · 12-16-2010, 04:56 PM

Your distributor question was answered in another thread. The adapter plate can be found at Jegs/Summit or most any Hot Rod/Speed shop. I like the dbl. pumper for a variety of reasons. One being that when I'm at WOT I KNOW the secondaries are OPEN. Second being that when I take my foot out of it, it immediately starts to slow down. Unlike a vacuum secondary carb. where you have to play with the diaphragm spring to make it open where you want. And the lighter the spring to get them to open faster is an even BIGGER lag, that momentary feeling the car is still accelerating when you have released your foot.
Just my opinion.

**BigRivy** · 12-17-2010, 03:58 AM

Is your heat riser valve in the exhaust manifold operating like it is supposed to? I ran alcohol gas for years in my '65 Riviera for the octane and used the stock Rochester 4G and stock distributor and never had a problem. If I was gonna go through all the monkey motion to swap a carb on this thing I'd get a spread bore adapter and put a Quadra Jet on it. They make electric chokes for them too.

**gforcecuda** · 12-19-2010, 02:04 PM

Originally Posted by BigRivy

Is your heat riser valve in the exhaust manifold operating like it is supposed to? I ran alcohol gas for years in my '65 Riviera for the octane and used the stock Rochester 4G and stock distributor and never had a problem. If I was gonna go through all the monkey motion to swap a carb on this thing I'd get a spread bore adapter and put a Quadra Jet on it. They make electric chokes for them too.

the Caballero has a set of one off headers on it..no heat riser valve on them...there are a set of machined risers on ebay now that space the intake up and block off the heat to the intake...any comment on those?