I ran the good old 750 for a few years. I read that this may be too much carb for my setup so I have been running a 670 Street Avenger for the last couple years. I did put my old 750 on for the last race last season and my numbers were noticeably better.
My setup is 350 small block bored .060 over 10-to-1 flat top pistons Summit cast iron heads 2.02 1.60 that have been worked Edelbrock Performer RPM AirGap Mallory Unilite
This is my daily driver that I race quite a bit in the summer. All I do at the race track is uncork the exhaust cut-outs just behind the headers and put on the slicks. I have to rebuild one of the carbs so need to decide which one? The 670 does have electric choke which I do like being I am in Minnesota!
Bowtieman427 said
Mar 4, 2012
If you run faster with the 750 (assuming when you were collecting data and supporting your statement " the last race last season and my numbers were noticeably better. " they were both equally tunned and tweaked for best performance) and you are ok with its street and MPG performance of the 750 then run that. What people say and what the car wants could be 2 different things. You have the data go with it. Is the 750 chokeless ?
Chris R said
Mar 4, 2012
Thats a difference of 80CFM. I would try that 670 CFM carb and the next time at the track, make a few runs with it and see if there are any improvments. You might notice a big difference in improvments with less CFM since you are running warmed over 350. My expierence has been that when you get closer to 400 cubic inches, a 750 is about where its at.
Bungy L-76 said
Mar 4, 2012
I'd go with the 670 as this is primarily your DD. After a rebuild, it may even perform as good or better then the 750 at the track. You can always just swap on the 750 at the track too.
4-door Chevelle said
Mar 4, 2012
The rebuild kits are only $35 and they both should be gone through. The 750 does not have a choke and being I will be driving her in a few weeks the idea of an electric choke is a big deal for a daily driver in Minnesota. If I do setup the 670 I may bring the 750 to test day like you suggested and with any luck catch the elusive 12.99!!!
Lost in the 60s said
Mar 4, 2012
Bungy L-76 wrote:
I'd go with the 670 as this is primarily your DD. After a rebuild, it may even perform as good or better then the 750 at the track. You can always just swap on the 750 at the track too.
My thoughts are along the same line, Darren. You're asking one carb to play 2 roles. The 670 should deliver better street manners and mileage as a DD but the 750 will outperform it on the track. The first generation Z28's came from Chevrolet with a 750 Holley and they were only 302 cubic inches. The heads and cam you are running are better than what was on the 302's, so the 750 should be a good choice at the track where the engine is run primarily in the upper rpm range. That's where the extra cfm and fuel delivery is going to allow the engine to breath better. If you are OK with the mileage and finicky behaviour of the 750 as a DD, then leave it on all the time.
Dave Seitz said
Mar 8, 2012
Years ago I think it was a Ford 351 that made more power with a 750 but ran faster at the track with a 650. If it runs faster at the track with the 750 then run that over the 670, do a back to back test at the track.
I ran the good old 750 for a few years. I read that this may be too much carb for my setup so I have been running a 670 Street Avenger for the last couple years. I did put my old 750 on for the last race last season and my numbers were noticeably better.
My setup is 350 small block bored .060 over
10-to-1 flat top pistons
Summit cast iron heads 2.02 1.60 that have been worked
Edelbrock Performer RPM AirGap
Mallory Unilite
This is my daily driver that I race quite a bit in the summer. All I do at the race track is uncork the exhaust cut-outs just behind the headers and put on the slicks. I have to rebuild one of the carbs so need to decide which one? The 670 does have electric choke which I do like being I am in Minnesota!
Thats a difference of 80CFM. I would try that 670 CFM carb and the next time at the track, make a few runs with it and see if there are any improvments. You might notice a big difference in improvments with less CFM since you are running warmed over 350. My expierence has been that when you get closer to 400 cubic inches, a 750 is about where its at.
I'd go with the 670 as this is primarily your DD. After a rebuild, it may even perform as good or better then the 750 at the track. You can always just swap on the 750 at the track too.
The rebuild kits are only $35 and they both should be gone through. The 750 does not have a choke and being I will be driving her in a few weeks the idea of an electric choke is a big deal for a daily driver in Minnesota. If I do setup the 670 I may bring the 750 to test day like you suggested and with any luck catch the elusive 12.99!!!
