Hey there fellas , I have a 54 cadillac with a freshly rebuilt 331 motor and trans. This thing runs like a dream, don't think I've owned a better running engine ever. I noticed I was getting some heat soak/ fuel boiling issues after driving it for a while then letting it set. So I ordered a phenolic carb insulator for Dashmans hot rod parts. The spacer is only 1/4 thick plus a gasket on top and bottom. It's also the thickest one I could find for the factory intake and carb. After I installed it and did a test run I let it set for a about 15 minutes. Still boiling fuel! Is there anything else I could do to aid this problem?? Engine has a good running temp at about 190 degrees in traffic and on the hwy. thanks Posted using the Full Custom H.A.M.B. App!
Might try using a different brand of fuel. Does this engine have an exhaust heated cross-over in the intake manifold? Is there a heat riser valve in one of the exhaust manifolds, and is it working properly? Is the valve possibly stuck in the closed position?
Does the intake have exhaust open to the bottom of the carb like the early chevys? If so did you install the stainless plate between the carb and intake.
The intake does have two dime sized ports for the exhaust to heat carb . Those are covered(plugged) by the new phenolic spacer, would another thin stainless plate help rather then just relying in the spacer to block it (saltflats)? Good thinking on the heat riser valve ClayMart , I'll check that for sure
Also, the temp down here in south texas hasn't been too bad at all lately . Maybe low to mid 80's . When the 100's come back next summer this is gonna be no good.
You will want the plate on there to keep from burning out your spacer or the bottom of the carb if you don't have a spacer.
Or you can switch to a throttle body fuel injection like I did on my Buick. Not H.A.M.B. correct, but modern gas friendly. Ben
In that climate, I would pull the intake manifold off to block the heat passages right at the intake manifold side gaskets. Right now you still are heating the manifold itself. Also, I don't know if Cad is like Olds, but Olds has a wind deflector at the front of the intake manifold to prevent fan air flow from cooling the underside of the intake manifold (underside) heat passage area. On the Olds, it is just a bent-up lip on the tin valley pan, and can be trimmed off.
Electric fuel pump will fix it. When the cars were just "used cars" you'd carry a couple gallons of water to pour over the fuel pump when it vapor locked. The hotter the weather, the more water you pack ...
I have two Cadillacs and don't have that problem on either one. I haven't blocked off my exhaust crossover either. I intend to but just haven't yet. Does your fuel pump have the glass sediment bowl on the carb side?
i just blocked off the heat passage at the head to manifold joint with a thin piece if tin. loosen the bolts a bit, pry the manifold up and slip in the shim. no need to completely remove the intake.
I think in gonna try that ,F & J and john walker. I have noticed some discoloration in the fresh engine paint on the intake on either side. I guess some very thin sheet metal would work ok? Txturbo, my fuel pump does not have the glass bowl, but I do have a clear filter in between the carb and pump.
Here's some pics of the intake. you can see the brownish discoloration of the fresh blue paint near the middle of the intake mounting bolts. I guess I should block this port on both sides? Posted using the Full Custom H.A.M.B. App!
mine eventually burned off all the paint at that center section. it might help to build a bracket and get the line and filter up off the intake, then insulate the line.
I'd plug that heat riser passage on both ends. You can also make a heat deflector that goes under the carb. It's like the stainless plate, but larger, & sticks a few inches beyond the carb all around. Stainless will work but they're usually made from about 20 Ga. aluminum.
Matthew, I would suggest that you rid yourself of the "rubber fuel lines" going into and out of the fuel filter. Having a PAST Midas Motor Home franchise under the same roof as a Chevrolet Service Dept., I cannot tell you how many times those hoses ruptured, split, or fell off ...... causing a ball of fire within the engine compartment of those motor homes. Amazing damage ! Solid fuel lines, along with proper couplings, going in and out of the filter assembly. That is what is needed. Use this type of glass bowl filter, as shown in the link below, with a replaceable element. This AC filter mounts directly to the carb inlet, via a fitting, followed by a solid fuel line going into other end of filter. Filter is solidly mounted to carb, with permanent fittings and hardly a chance of an underhood"fireball". https://www.chevsofthe40s.com/detail/13666/Chevrolet_Gas_Filter_Assembly_With_Glass_Bowl_Fuel_.html If I cannot convince you to remove those rubber lines and THAT filter, raise the present filter away from the intake manifold. A filter, with rubber hoses holding it in place, WILL vibrate and WILL move around at highway speeds, touching or bouncing against whatever it can. So very common on so many motorhomes that we rebuilt .... after the "fireball" under the hood. You've done a lot of work, now protect it as best you can. See the TWO filters in my avatar ? One AC glass bowl filter for each carb.
You've got a good eye there! Anything to get the fuel line and filter away from some engine heat and maybe up into a bit of air flow is bound to help. If you want to get creative you might take a piece of thin aluminum, maybe 1/16" or so, and make your own heat dissipator. Cut an opening in the middle that's just large enough to clear the throttle bores and drill holes for the mounting studs. Trim the outer part of it so it's maybe an inch or two larger than the base gasket, provided you've got clearance around the base of the installed carb. Then sandwich the plate between two base gaskets and make sure that it doesn't interfere with your throttle linkage or anything else on the intake. It will act like a heat sink and help pull some heat away from the base of the carburetor. Oops... I gotta type faster if Ulu's on the board!
Thanks for the info! Those glass filters are pretty sweet , I may order two just to have another around at all times. I'm a big fan of hard lines for fuel. Mainly this setup was just to get it running and getting everything broke in. But you are right about the rubber junk, not good for long term. Posted using the Full Custom H.A.M.B. App!
So I could use this plate/heat shield directly on the intake side and with another gasket ? Or just metal to metal on the intake? Posted using the Full Custom H.A.M.B. App!
Greetings! Friend had a nice '67 Chevelle until it caught fire and burned to the ground on a country road. When the fire truck finally got there the first thing the Fire Chief asked was "Did it have one of those cheap plastic fuel filters?". Apparently when they get heat soaked a few times they split and spew raw fuel everywhere.
the reason I asked about the glass filter on the output of the fuel pump is it was installed from the factory upside down......previous years it was right side up but caused vapor lock issues. Turning it upside down fixed the problem.
I'm from Texas like you and have had the same problem . In W. Texas you an only get the10% gas , and the boiling point of the ethanol gas is 172 deg. F. I went to elec.pump ,insulated line with regulator that has return, cools gas , and a spacer under carb . Problem solved . Can you get non e gas in Beaumont ? Good luck . By the way I was in Lubbock last week and one gas station I went to had done away with regular and replaced the pump with e85 .
This is the spacer both of mine have and I don't think the carbs with the cast iron base had a stainless steel shim.... Just the later ones with the aluminum base carbs. This particular one is off a 1961 cad 390.
Yes, with gaskets (!) but always respecting any vacuum passages (if any) which communicate through the gasket or spacer. Sometimes the gasket must seal these, but sometimes they go through. What was common on the factory carbs with metal heat shields was that the shield was actually the carb-to-manifold gasket too, and it was a stamped out waffle-sandwich construction of metal foil and probably asbestos paper or some other gasket paper that is heat resistant. Similar in construction to common head gaskets. I recall seeing this on various trucks and industrial engines over the years, as well as on foreign cars. It was often combined with an additional non-metalic carb insulator or spacer. Anyhow, this "gasket/shield" stuck out, but not always all the way around, and not always the same amount all around. Mainly it shielded the underside of the float bowl and fuel inlets. Not so much reason to shield under the linkage side, and the shield would interfere in many cases. All the ones I've seen that were solid metal were ones people hand made. I like the setup on my old Autolite carb, where the filter was metal and screwed right into the carb. Of course not being glass you couldn't see the fuel flow. I agree most heartily with the fire hazard of rubber fuel hose & plastic in the wrong place. Those things always eventually swell/crack/leak from heat and the solvent properties of fuel. Steel-to-steel was always used from the factory, from carb to pump, with but one short steel-braided flex hose from fuel pump to frame. On well designed cars it was placed well below and forward of the manifolds & pipes to avoid heat.
GM GM used a solid metal stainless steel one along with a phenolic spacer under Q-jets in the mid 60s.
Not surprising. It's a great balancing act on some cars: keeping the carb hot for good fuel economy & power, but not so hot it cooks whenever you drive on a hot day. One of the major reasons to leave the hood at home.
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