The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Using an early to mid 70's carb..?

Hey guys,, Had a thread going on another part of the form.. But then I saw this 60-66 form.. Must be pretty new..? Don't remember seeing it before..
Anyway, I have a 62 c-10 short bed fleetside..
235 with the call out 1 barrel carb and the stock sm420.. I swapped the rear end out for a one legger 12 bolt 3:07 R&P.. Took it off a 69.. Bolted right up pretty much.. Replaced the points with an electronic ignition and running 235/75 R15's.. Pretty much runs like a top but the fuel economy is poor.. Already replaced the carb with a new call out for that year.. But those things are leaky and barbaric even when they are new.
I found a 4 year single barrel carb they made with the same bolt pattern as these single barrel rochesters from the early 60's.. you can get them with the manual or auto choke and they are what they call mono jet carbs made by rochester.. Point being is you can adjust the jet as oppose to having the fixed jets they have in the early 60's models.. Also, the carb seems to be made with better tolorences.. I'm guessing that an additional 12-14 years of carb improvement made these early to mid 70's carbs less leaky and efficient.. I'm sure it will bolt right up to my current mounting.. Already bought the gasket to see if it would match..
Plugging the additional vacuum hoses and maybe having to replace the linkage with a cable should be the only mods..
I was wondering if anyone has ever done this..?

Do you have a make model number for this new and improved carb?

What is your timing set at?

Are you getting a little ping when you put foot down on the accelerator?

The problem may not be the carb at all. The 3.07 sounds pretty tall for a 235. What RPM are you cruising at?

Larry

LGriffin,
Timing is set exactly at factory specs according to my 1960 shop manual..
The part number for the carb is 33385,, you can find it on RockAuto.com.. This particular one goes all the way up to 1978.. There is another one that is very similar and is from 69 or 70 all the way up to 74.. Both have the same bolt patterns as the call out for the 60-66..
My motor does not ping at all.. My rpm cruising speed at 65 mph is 2300 rpm's..
Originally i had a 2wd 10 bolt rear axle that was running a 4:10 r&p.. My gas mileage didn't improve that much when I made the rear end switch.. I picked up a couple mpg but the improvement was small considering the expense of the rear end swap.. Which surprises me because it certainly dropped my rpm's considerably at the same cruising speeds..
The only thing I can think of is that perhaps my motor is just worn out? I did put a new head on it when I bought the truck.. I inspected the lower end of the motor and it looked like it was in really good shape and no signs of ware.. Plus the fact that is runs with no noise out of the ordinary and it runs very good.. My plugs are always clean and my fuel/air mixture is on the lean side if anything..
But I am more inclined to think that it just may be the inefficient one barrel rochester carburetor from 1962.. As I said, these things are leaky right out of the box.. It seems to me they were just made with poor tolerances and a bit crude compared to the later model carbs.. Technology and machining for carburetors advanced a lot by the mid 70's.. Just when they were starting to perfect carburetors everything starting switching to fuel injection.. At least that's my take on it.. The reason I haven't gone ahead and bought the carb to try my experiment is because I have never heard of anyone else doing it.. So I figured I would try the StoveBolt.. These guys have done everything you can imagine on this site..
Anyway, The bolt patterns match and the theory seems to make sense to me.. And so far I haven't heard any objections from anyone,, So I guess I'm going to be the ginny pig..

sounds like you've covered all the bases. I would like to hear a little ping out of it, but I wouldn't go there with out first doing a compression check. The reason being - Oops I haven't run a 235 in 45 years, that said - the tired 292s I was running wouldn't ping either. The rebuilt 292 I have now does ping, with 10:1 compression it better. The RPMs sound right, if anything a little high in the torque curve, but I wouldn't bother with it. The distributor is in good shape and the vacuum advance is working.

The carb you are looking at is Rochester Monojet. I replaced the Mod. B on my 292 with a Monojet, I like the carb. The Mod B design is probably 8o years old or better. The Monojet will let you do some tuning the Mod B won't. When you get the Monojet get a carb kit with it so you have some spare gaskets and the diagram on how the carb goes together. re-manufactured are generic rebuilds they work on everything, but don't work great on anything. If you take the carb apart write down the jet size and the power needle number, I think they put one on the needle, mine are down stairs. Any ways after you get it setup and running you can play with how much gas the engine is getting by adjusting the power needle up or down.

Then another option would be to get Landons Holly/Weber. Tom has been selling them long enough that they should be pretty well dialed in for a 235. If you keep your foot off the secondary the bets on getting better mpg should be better. I don't remember if the $80 includes the 2bbl adapter or not. The have been a lot of post on how well it has worked.

Larry

I'm all ears on this one, cause I am also unhappy with my "leak-chester" carb, and would love an alternative for my 292.

Kerry3, IMO the Monojet is a good upgrade. The Monojet was used on 68 and up 250/292, till GM introduced the integral head. The latter versions have added solenoids for emissions. There is one on that auction site now, but it closes in about and hour.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260470684468&viewitem=&sspagename=STRK%3AMEWAX%3AIT

The Holley/Weber is not option on the 292 from the reports I've read, too small.
Larry

LGriffin and kerry3,,, you guys are funny.. Thanks for the input.. I am going to track one down and toss it in.. See what happens.. I can spend $200 on the carb experiment or $2000-3000 on a new motor and tranny.. Gonna do the carb first.. Let you guys know..

my 65 has a motor from a 75-79 car i believe (integeral manifold). its a 250 I6. the throttle linkage is mickey moused together... the previous owner did it. the carb works good, electic choke is very nice as well.

I'm not sure on the integral head 250, but the integral head 292 used a Quadrajet2. The Quadrajet2 is essentially 1/2 a Quadrajet. Same idea as a Holly/Weber (progressive 2bbl.), but larger.

Larry

ive picked up an nos 2jet rochester. wondering if anybody has experience on these/advice. i want to install it on my 95 mexican spec inline 6 - 250, came with throttle-body injection, but not ready to wire all that into my 62, maybe someday, but not for now. anyways its a 2 barrel,(of course) with both butterflies on the same shaft & the manifold on the 250 is made for 2 barrel efi....also need a carb spacer/adapter for it. anybody with ideas as to where to find this would also be appreciated