Jerry ran the top ones and they were in the car when I got it and ran great with it, but I just tried running without them per some comments in the thread. I will make an extra set and try with some smaller holes in them. I wanna squeeze every .001 out of that Nailhead. It turned quite some heads that a Nailhead ran those numbers.
Has anyone tried Docs dual plane mod with a matching carb spacer (4 hole into oval 2 hole like the mod intake)? Does anyone have any power numbers to see what power gains would be had with a matching carb spacer?
I recently tried to do the dual plane mod on my nailhead. Now it seems to run rough in the idle and low rpm range. I have a edelbrock 750 cfm carburetor. The motor even sounds different too. Does anyone have an idea of what i might need to change or what i could have done wrong? Thanks
Did you install the metal plate between the carb. & gasket??? If not your sucking in exhaust. ALSO, are the intake gaskets installed correctly???
I used a gasket under the carb. What metal plate are you talking about? What is the proper way for the intake gaskets. I believe they are correct but please refresh my memory. Thanks alot for the response.
The "Smile" (exhaust channel) that is used to heat the carb has to have a metal shim (gasket) to block that channel from the bottom of the carb base, with a fiber gasket. That metal shim prevents the gases from eroding the base of the carb. Unless you live in very cold environment, it is best to drill and tap with NPT plug (hex head) and block the holes in the (smile) . It might take a few minute more to warm up, but it will also prevent vapor lock and other heat issues, especially with the crappy gas these days. https://jcaparts.com/collections/bu...take-manifold-exhaust-crossover-port-plug-kit The intake casket, when correctly installed will have the "pointed" corner of the gasket facing the center of the valley, and hanging over the intake mating surface at the corner. You can hook your finger on it. (and the metal one will slice your finger when your polishing the valley cover, ask me how I know...) If you put them on "backwards" they look like they are correct, but they almost always will leak as they do not set centered and the side of the narrow sides of the gasket to surface is very thin and in some cases will not even seal at all. The steels are more prone to leak due to incorrect installation, but the composites will leak as well. (just random stuff...) Pure speculation on my part, but from knowledge of stamp and die cutting of metal, I think that design drawings got flipped, (there are typically several drawings done for process steps) and the stamp and die drawings got 180 (mirrored) so they have always been "wrong", since they "mask" correctly when set on the mating surface incorrectly.
Recently discovering and reading this thread, it seems to me that Doc definitely recommended leaving the heat riser setup intact. He specifically stated that due to the divorced intake design the Nailheads need the heat riser to work well for everything but a straight up race car. Is your suggestion above to plug the smile ports contradicting this?
I'm pretty certain Doc was talking about the exhaust crossover that heats the intake. (it's been years since I read that information) But it is separate issue from the carb heat I am talking about. And as I mentioned, in places where cold weather driving is not encountered, the few minutes of warm up is not a real problem for most. Almost all people are driving "fair weather" cars for giggles and grins, not slogging through snow every day through winter to make Mr. Scrooge rich. And, the plugs can be removed and steel plate put in place in about 15 minutes, if one is not happy with the way the car runs. The only thing that is permanent is the threads cut in the holes and they affect nothing. FWIW, I had mine blocked on my 2x4 with oem manifold and drove it year round. It was no more trouble to start and drive in 30-40 degree weather than 90-100 in the summer. (I did change to an EELCO intake and 2x4 EFI the past year, as well as electric fans, for the record) There are a lot of variables affecting the fuel/air flowing through the intake, and what effect(s) the crossover heat blocked or not has on wetting, flashing volumetric efficiency, signal and such would need to be a focused study. It would best be assessed by proper dyno and incremental testing to see how it affects overall performance, power and fuel economy, since anything else is simply guessing.
The 2x4 intake has the 'smile' channel in it, but it is not drilled through to the exhaust passage. No need to use the metal heat shield on those. The main purpose of the metal shield is to prevent the exhaust gasses from burning through the gasket, creating a leak.
(I hate getting old, and posting when I should be in bed, but pain keeps me up, so...) Yeah, I said that about the shield. Just got mental mazed on the rest. The intake I drilled and plugged was the Quadrajet intake, not the 2x4. I meant that the 2x4 ran well without a choke (the external tube removed, riser blocked, adjustment knob/cap "open/lean") and that the Q-jet also ran fine with the passage blocked. Background. I ran the Q-jet for a while as I thought I was chasing a vacuum leak that caused some fluttering and lower than expected vacuum. It turned out that it behaves the same way with 2x4 OEM intake and correct carbs in great shape, as well as with the Q-jet manifold and rebuilt carb by Mark @ QuadrajetPower, and with the EELCO and FiTech, so I figure the cam is the issue, since compression and leak down are all good, and no intake leaks. Car runs great, just the idle is a bit unsteady below 600 RPM (manual). The lower it goes below 600, the more obvious the flutter and hunting, but I can get it all the way down to 450 and it will idle, but is "happy" at 650. I just had a desire to have it at 550. Put the EFI on so see if it would behave better (it does, very much so). Anyway. I hope I did not confuse the important points.
None of the 2x4 stock manifolds have the heat passages drilled out from the factory, although the "smile" channel is there. IF the factory didn't feel/think it was nec. do you think they would have deleted it??? I haven't had ANY problems with my 1x4 Riv. since I blocked the heat crossover on my Riv. some 40-45 years ago & I used to drive the car as a daily driver in Ct. in ALL kinds of weather. NEVER gave me a problem with NO heat riser or those holes under the carb. blocked. Tom T.
Doing the mod on a ‘55 322, question, do I leave the carb to manifold gasket with the four holes or should I trim it to match the new opening? It’s got the old WCFB, don’t want to mess anything up.
