1966 C20 new owner
July 16th, 2021, 7:21 PM
#11
CF Monarch
[QUOTE=kevinkpk;467925]
Yeah, if the Chevy C-20 327 pickup has a good compression ratio, the 650 CFM would be a good choice. I've always liked Holley's with Carter/ Edlebrock's in second place except for the Carter Thermo-quad, which is still not as bad as the Rochester Quadrajet is. The 2-Barell Rochester's are okay carbs.Yeah, the OP's pickup was designed to haul loads, thus the 4-Speed with a granny gear, not a true first gear like my K-1500 has with the NV3500 OD transmission. Saginaw's are great transmissions, so I agree with you.
The 2-barrel Rochester carburetor is well, built, unlike the four barrel carb, the Rochester Quadrajet, which is a nightmare to repair and jet properly. Trust me, I have rebuilt lots of carburetors. If you wish to switch to a 4 barrel. I'd go with a 450 CFM Holley carb.They also make a two-barrel carb. You might increase your gas mileage and HP, but the cost isn't cheap, and you may have to put a new intake manifold on it, if it didn't come with an adapter plate for the two barrel carb Rochester carb.
I'd suggest a 650 cfm, oilcanhenry may have a typo. If you want to do doughnuts etc, you will have to replace the granny tranny with a saginaw or something higher geared. As far as a gas drinker, I enclosed a rochester 2 bbl carb. spec pdf.
I'd suggest a 650 cfm, oilcanhenry may have a typo. If you want to do doughnuts etc, you will have to replace the granny tranny with a saginaw or something higher geared. As far as a gas drinker, I enclosed a rochester 2 bbl carb. spec pdf.
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CaliC20 (July 20th, 2021)
July 16th, 2021, 11:29 PM
#12
Administrator
Not sure why you dislike the Q-jet but I'd much rather rebuild one than a Holley and I've done both. It's also very easy to tune and modify. The good news about a Holley is it has lots of adjustments. It's also the bad news.
Never worked on or saw a Carter Thermo-quad but read back in the day that it was a poor clone of the Q-jet. I know Holley made a spreadbore carb and although not sure maybe Edelbrock did too.
July 18th, 2021, 10:26 PM
#13
CF Monarch
But isn't the bore and stroke the same? Not sure.
Not sure why you dislike the Q-jet but I'd much rather rebuild one than a Holley and I've done both. It's also very easy to tune and modify. The good news about a Holley is it has lots of adjustments. It's also the bad news.
Never worked on or saw a Carter Thermo-quad but read back in the day that it was a poor clone of the Q-jet. I know Holley made a spreadbore carb and although not sure maybe Edelbrock did too.
Not sure why you dislike the Q-jet but I'd much rather rebuild one than a Holley and I've done both. It's also very easy to tune and modify. The good news about a Holley is it has lots of adjustments. It's also the bad news.
Never worked on or saw a Carter Thermo-quad but read back in the day that it was a poor clone of the Q-jet. I know Holley made a spreadbore carb and although not sure maybe Edelbrock did too.
I show a slight difference in the old 327 and the 5.3 liter but still both basically a 327 cubic inch motor:
1962 327 cubic inch V8 motor:
Bore 4.1/25 inches
Stroke:3.25/100 inches
------------------------------------------------
2003 5.3 liter V8 motor:
Bore: 3.780 inches
Stroke:3.622 inches.
What blew me away is that according to Rockauto.com, the 366 V8 engine was available in a 1966 C-20 pickup. That was a big-block engine that I only thought was used in the Chevy medium-duty trucks and buses. My father had one in his C-60 medium-duty truck. It was a tall deck block engine, and the C-60's came with the hollow sodium liquid-cooled valves and stellite valve seats. It had tons of torque, but not like the 427 in horsepower Once I tore off the governored carb off for a Holley 650 cfm carb; got rid of the smog pump, which was a POS, installed a vacuum-advanced distributor, that motor increased HP and higher gasoline mileage than before, stock.
July 20th, 2021, 8:58 AM
#14
CF Beginner
Thread Starter
The 2-barrel Rochester carburetor is well, built, unlike the four barrel carb, the Rochester Quadrajet, which is a nightmare to repair and jet properly. Trust me, I have rebuilt lots of carburetors. If you wish to switch to a 4 barrel. I'd go with a 450 CFM Holley carb.They also make a two-barrel carb. You might increase your gas mileage and HP, but the cost isn't cheap, and you may have to put a new intake manifold on it, if it didn't come with an adapter plate for the two barrel carb Rochester carb.
I don't know what your axle ratio is but if it's likely a 4.10 ratio on a C-20. Switching up to a 3.42/3.55 ratio might save you on gasoline. There might be a motel tag on the rear axle, but you can figure it out by jacking up a rear tire and marking the tire and axle with chalk or something like it. Make sure you block the front tires, so it won't roll away. then spin the tire and see how many rotations makes. the driveline moves.
Likely has a Dana 60 rear differential Have you calculated your gas mileage by filling the tank, and reading the odometer after filling up again? Make sure your vacuum advance canister on the distributor is not blow out as that will decrease gas mileage. it's a cheap and easy repair to do.You just suck up the vacuum hose to the carb. If air comes though, the diapram is blown out and needs to be replaced. The cost is dirt cheap for a new one and easy to fix. Make sure the hose is soft. If not I's get a new hose too. Just have them cut it off to the length you need and replace it.
You might increase you shifting by switching to a 75-80w gear oil. Lots of pickups back the used 140 weight which is too thick unless you a driving in high heat under a load of stuff in the pickup.
I don't know what your axle ratio is but if it's likely a 4.10 ratio on a C-20. Switching up to a 3.42/3.55 ratio might save you on gasoline. There might be a motel tag on the rear axle, but you can figure it out by jacking up a rear tire and marking the tire and axle with chalk or something like it. Make sure you block the front tires, so it won't roll away. then spin the tire and see how many rotations makes. the driveline moves.
Likely has a Dana 60 rear differential Have you calculated your gas mileage by filling the tank, and reading the odometer after filling up again? Make sure your vacuum advance canister on the distributor is not blow out as that will decrease gas mileage. it's a cheap and easy repair to do.You just suck up the vacuum hose to the carb. If air comes though, the diapram is blown out and needs to be replaced. The cost is dirt cheap for a new one and easy to fix. Make sure the hose is soft. If not I's get a new hose too. Just have them cut it off to the length you need and replace it.
You might increase you shifting by switching to a 75-80w gear oil. Lots of pickups back the used 140 weight which is too thick unless you a driving in high heat under a load of stuff in the pickup.
great information I will check the rear differential to see what I have
the 2 barrel is working good so far I was able to adjust it and truck runs better
I will change the gear oil on the manual transmission since I used 85/140 by mistake
I have not keep track of the gas usage since si been driving around the house not long drives yet is been too hot here in Los Angeles and I just got the rims and wheels replaced with 16” steel rims and tires since it had the old tires on the 16.5” rims
Truck is running better now not 100% but way better than when I got it running
thank you for the information