Advise on carb selection.

[dude69300]

Hi Thank you. The base was cracked when they dropped the carb. The owner said it was overtightened either way it broke . They used a direct replacement from quikfuel.When I got it out of the shopit was very unpredictable it would run well then next minute it ran terrible.I ket getting the small backfires in the mufflers. The body shop took the car for there supposed 6 month job which turned out to be over 3 years. They said they started it at least once a week. I doubt it I went down drained the fuel and put new in. It ran but not well. About two weeks time they were moving it back and forth and they said they had to adjust carb it was running terrible. I picked it up it did not drive bad at first but then stated pulsingand popping in the mufflers. when the car is shut off over night it drain all the gas out and floods the engine. I backed off the screws and put them back to factory settings but it still runs like hell.

Well schitt happens like that, it being over tightened. Switched from a 625cfm 4160 to a dual feed 750. A buddy stopped over and was helping me. We got it on, tuned it in the drive , then took it for a ride for 3-4 mi.came back and was letting it cool. I went and was messing with something else in the garage and when came out he popped off the air cleaner and was checking to see if it was tight enough after the cooling off. As I walked up he was checking them and I heard a little "click" when he was on the nut . He snapped the freakin mounting ear of the carb! So I just pushed the car into the garage and left it sit. So I've got a 750 sitting in the box in the garage with just a couple miles on it. I'll have to get a new base for it or JB weld it. I got another new 4160 and put it on, been running fine ever since

 

[Dana]

Those mounting flange bolts/nuts are just there to keep the carb from falling off in event of a rollover. As long as your base gasket isn't hard as a wedding prick, engine vacuum will seal it to the manifold. But seriously, barely snug is more than enough on a fresh gasket. Then just give it a little check once in a while. There are some super stock guys out there that use a fresh soft gasket or even a thin piece of rubber and leave the bolts loose. They say it takes some of the resonant harmonics off the needle and seat.

 

[bajajoaquin]

I have a 68 440 hp motor which I had redone. It has 10.1 compression, A lunati voodoo cam Adv duration int/exh 270/280. Duration @.050 int/exh .515/.530. It is a roller cam. There are Edelbrock rpm heads with full int porting,full exh porting (stock gaskets) no chamber work. It has a edelbrock CH4B intake ported The intake was gasket matched. Port plenum, drop divider. The motor has 458 horse at the crank and 500 ft pounds torque. It was done 3 years ago and basically went into the body shop. It had a quick fuel 780 on it. The car is running terrible, flooding,surging and popping. It will not improve with any adjustments I wanted to go with an edelbrock 750 or 800 electric choke vacuum secondaries. There are several models. I was looking for someone who has similar set up for advice. The quick fuel carbs people swear by but I would prefer to go back to single feed and a stock appearance. I am not going to race or beat on car just looking for reliability. The motor is in my 1968 Plymouth sport fury convertible. Thank You sorry for long post.

I don’t have a carb answer for you, but could you tell us what exhaust you have on the car? Also, what rpm did the hp and torque peaks occur at? Any chance you could share the whole dyno sheet?

 

[CBODY67]

IF you can snap a mounting ear off of a carb, than means you don't have the correct OEM-spec carb base gasket under it! Reason I know? Back when I was driving my '70 DH43 "N" all the time, it seemed to get a bit harder to start after a hot soak period. I toyed with getting one of the Holley/GM heat shield base gaskets, but opted for a Mr. Gasket "stack" of gasket and aluminum plates. I figured that'd work better . . . but as I was gently torqueing the nuts on it, side to side and all of that, the compressibility of the gasket stack was more than the OEM gasket AND lacked the metal bushings in the stud holes, SO . . . I cracked the baseplate on the OEM AVS with just a 1/16 turn final tightening. Right in the area of the vac advance port for the distributor. So I bought a 4734S (replaced the 4732S OEM) and put the factory-spec base gasket with the metal bushing (to prevent such cracking upon torqueing-down) and called it "as good as it can be". End of story.

If the crack is not too bad, then some "sealer/putty" might work. Just be sure that you make sure the result is flat with a straight-edge when done.

CBODY67

 

[440sportfury]

IF you can snap a mounting ear off of a carb, than means you don't have the correct OEM-spec carb base gasket under it! Reason I know? Back when I was driving my '70 DH43 "N" all the time, it seemed to get a bit harder to start after a hot soak period. I toyed with getting one of the Holley/GM heat shield base gaskets, but opted for a Mr. Gasket "stack" of gasket and aluminum plates. I figured that'd work better . . . but as I was gently torqueing the nuts on it, side to side and all of that, the compressibility of the gasket stack was more than the OEM gasket AND lacked the metal bushings in the stud holes, SO . . . I cracked the baseplate on the OEM AVS with just a 1/16 turn final tightening. Right in the area of the vac advance port for the distributor. So I bought a 4734S (replaced the 4732S OEM) and put the factory-spec base gasket with the metal bushing (to prevent such cracking upon torqueing-down) and called it "as good as it can be". End of story.

If the crack is not too bad, then some "sealer/putty" might work. Just be sure that you make sure the result is flat with a straight-edge when done.

CBODY67

Hi I have had that happen before . It does not take much. Luckily I was able to use a little jb weld. I remember one of my friends using one of those Mr Gasket stacks cracking his years ago. This carb that the shop broke was definitely dropped. It was scratched up and the base crack was huge. Thank you for help

 

[440sportfury]

IF you can snap a mounting ear off of a carb, than means you don't have the correct OEM-spec carb base gasket under it! Reason I know? Back when I was driving my '70 DH43 "N" all the time, it seemed to get a bit harder to start after a hot soak period. I toyed with getting one of the Holley/GM heat shield base gaskets, but opted for a Mr. Gasket "stack" of gasket and aluminum plates. I figured that'd work better . . . but as I was gently torqueing the nuts on it, side to side and all of that, the compressibility of the gasket stack was more than the OEM gasket AND lacked the metal bushings in the stud holes, SO . . . I cracked the baseplate on the OEM AVS with just a 1/16 turn final tightening. Right in the area of the vac advance port for the distributor. So I bought a 4734S (replaced the 4732S OEM) and put the factory-spec base gasket with the metal bushing (to prevent such cracking upon torqueing-down) and called it "as good as it can be". End of story.

If the crack is not too bad, then some "sealer/putty" might work. Just be sure that you make sure the result is flat with a straight-edge when done.

CBODY67

Hi the crack was huge. They had to of dropped it on the floor I'm sure. The base was replaced by them

I don’t have a carb answer for you, but could you tell us what exhaust you have on the car? Also, what rpm did the hp and torque peaks occur at? Any chance you could share the whole dyno sheet?[/QUO

 

[440sportfury]

I just want to thank everyone for their help.

 

[bajajoaquin]

You quoted me, and got my hopes up!

 

[440sportfury]

You quoted me, and got my hopes up!

Hello I do not know what happened. Sorry. I only have one page of my dyno results handy but honestly each one is basically the same. The highest hp reading is 458.4 at 4900 rpm. highest torque is 500.0 at 4500 rpm. I am using stock 68 hp manifolds with tti exhaust with crossover. I do not have the reciepts handy for exact model #, All the other specs are listed in opening post.

 

[bajajoaquin]

Thanks. That’s exactly what I was hoping you’d have. A mild engine rebuild is next for me and I’m trying to see where power peaks are with various cams.

Good luck with the carb!