Operation "Buzzin' Half-Dozen" Underway

[DWright]

Finally got my intake and carb today and quickly got to work. will keep you posted.

[DWright]

more....
this was accomplished in less than 45 minutes! i love these motors! i'm gonna try to get back to it tomorrow and post more pics. next is gonna be engine bay clean up and paint.

[Captainfab]

What size Holley is that?

[DWright]

i was told its a 390cfm, but i haven't run the numbers yet.

[Captainfab]

Yeah a 390 ought to be about right for that 6. I would definitely look up the numbers and make sure.

[Corts60]

Sweet! That engine oughta breather better with that set-up. Any plans for headers?

[slepysal]

nice !! Looking good. One thing you may want to consider is a set of headers it will let your motor breath better

[DWright]

i definitely want headers but my intake isnt water heated which means i need a water-plate. anyone know where i can find one? i hope it wakes this old engine up. i rebuilt the original 1bbl 3 months ago and then the sock on the sending unit disintegrated and somehow made it way past the cheap napa filter and now the truck runs like crap. i do have plans for headers though. i've already bought a 3-speed floor shifter in preparation for 'em.

[ol Curt]

I had a Holley 390 on mine shortly after this setup. I'll see if I can find some pics of it with the Holley. The 390 was perfect.

[ol Curt]

WHY YOU NEED HEAT TO YOUR INLET MANIFOLD - by Tom Langdon



The most frequent complaint I have is from members who complain that since they’ve installed their multiple carbs, the engine hesitates and stumbles at low speed on initial normal acceleration even after warm-up. The most blamed culprit is the darn Rochester Carburetor. Usually it is falsely accused!

Usually when installing dual exhaust manifolds or headers, the production exhaust heat supply to the inlet manifold is eliminated because (except Edmunds and most recently Clifford) there’s no provision or instructions to provide heat…Why?? I don’t know and could only guess. In any event heat will be required to achieve good driving response and reasonable fuel economy. Here’s why:

As liquid fuel enters the manifold from the carburetor, the vacuum vaporizes the fuel and causes a chilling effect on the walls of the manifold much like the chilling effect of spraying an aerosol on your skin. Now you have a cold manifold. If you do not supply a continuous supply of heat the manifold will remain cold and even build frost in some conditions. At this point, if acceleration is attempted, the vacuum will drop, fuel will no longer vaporize, and will condense on the cold manifold walls until they are fully saturated with wet fuel – this takes about three seconds, during which time no fuel is going into the engine ( and thus no power or a "sag") After the walls are fully saturated with fuel the air flow finally picks up and floods some of the cylinders but not all of them because liquid fuel is notoriously bad for equal distribution.

More fuel (bigger jets) will only slightly help this problem and actually worsens the over-rich condition and spark plug fouling and fuel economy.

The solution: Moderate, and continuous heat supply to keep the walls of the inlet manifold warm and fuel in vapor form. Exhaust heat is fast but requires a butterfly valve in one manifold to force the exhaust flow. Water heat is slower but very clean and not corrosive to aluminum manifolds. This method utilizes the water pump to continously supply warm water to a passage underneath the manifold. It is sometimes necessary to weld a tube to the manifold but be sure to obtain intimate contact between the coolant and the manifold wall and floor. Simply tack welding a closed wall pipe to the bottom of the manifold will not result in sufficient heat transfer.


Tom was an engineer at GM who played a big role in the development of the inline 6. I have used him before. You could probably call him and get some info.

You can contact him here, and here is a link to his heat plate for $30. I found he answers email but is slow....best to call.

http://www.stoveboltengineco.com/aca...?productid=109

[DWright]

thanks for the info Bob. i know that the rochester sometimes gets falsely accused sometime, but this time its definitely the culprit. after i rebuilt the carb the first time the truck ran as smooth as my '06 ranger. then one day the electric fuel pump stopped pumping; it also was only 3 months old. i replaced the pump but the trash had already made its way to the carb. now the choke has to be 1/4 to 1/2 way out for the truck to run ok. like i said, thats what i get for using cheap fuel filters. but i am looking forward to the new setup. i was thinking of either using a water plate and headers or trying to find a good split manifold.

[ol Curt]

I would consider the headers. Hardly anybody(nobody that i know of) makes a good split manifold for the 250. Most, say they can't because of the metal used in the originals not being so friendly to the welding process.

[DWright]

i'll probably get headers. i passed up a near perfect split manifold on ebay for only $100 and now everyone i see on there looks like crap. oh well.

[DWright]

soooo... how do these motors run witha 600cfm 4bbl w/ vacuum secondaries? cause after running the numbers on my new mystery carb it appears that it' what i have; a 4010 series Holley. i beleive leo's book says that combo is acceptable for street.

[DWright]

i take that back. leo's book says that a 500 cfm carb is good for a 292. any input or experience with is would be helpful.

[ol Curt]

I personally think it might be a bit much, but if you run into a good carb man on here or elsewhere, he might be able to jet it down and make it work. The vacuum secondaries are nice so you are only running on two barrels until you get heavy on the throttle. I ended up going with a two barrel on mine and it ran great, but I'm becoming an original freak. I have put the original 250 back in and will be getting rid of the Holley Weber 2 bbl and going back to a 1bbl Rochester. I think you just have to try it and see how it runs with it.

[DWright]

yeah, i guess i will have to try and see what happens; i dont have the green to get another carb at the moment. i wonder if i could get away with leaning it out just a little bit.

[DWright]

would some of you nice gentlemen post some pics of your 4bbl setups? i especially would like to see what some of you have done with linkage.

[ol Curt]

I turned my carb 90 degrees and used the factory linkage. Some say this is bad to have it this way, but unless you are doing some high speed cornering(unlikely in these trucks) I don't think it would make any differrence. I'll try to find a photo from the other side.

[DWright]

yeah, pics from the other-side would be very helpful and greatly appreciated.

[DWright]

just bead-blasted the exhaust manifold and sprayed with "as-cast" coating, also blasted intake; looks alot better.

[DWright]

got the truck running tonite! runs rough with alot of black smoke, but i'll chock that up to the carb needing to be tuned. dosent idle smoothly but its very responsive. now i just have to figure out the linkage; anyone wanna post some pics of there setups? i'll post new pics tomorrow.

[protrash64]

Congrats on the firing.....always a nice sound after the work.

[DWright]

yeah; i was trying to take my time and do things right but at the end of tonite i wanted to hear the truck so bad i rigged up some fuel line just so i could start it! i'll have to fix that tomorrow. i was surprised at how much louder the exhaust note was. (no leaks anywhere by the way)

[Joey~AP]

Lookin good!