NEVER put a 750 on a 318........

-
LocuMob said:
I couldn't tune my Holley 750 DP worth a piss after some engine work, I lost track of what I did and slapped an Edelbrock on so I could drive the thing. I still haven't taken the time to learn, but I may down the road. I can always bring it to my buddy who just retired, he knows what he's doing, and I just have to bring some beer!
Click to expand...

I have a 750 Street Demon on the "medium" build 360 in my Duster currently but I plan to swap that over to the 440 I'm building for my truck once that's done. And then I'll be looking at a Holley DP-type (Quick Fuel, Brawler etc.) 750 to replace it with on the Duster because I want better fine-tuning and response; Street Demons are rather limited in what you can do tuning-wise and like the name implies they're really designed for street use whereas my Duster is becoming more of a weekend warrior amateur race car. I still don't yet have a lot of experience tuning Holleys but something that has been a Godsend to me is my wideband O2 sensor and AFR readout gauge. I'm pretty confident that between having real-time AFR readings and that Vizard book on how to tune Holleys I'll be able to get it dialed in nicely. I'm sure it'll take time and patience but that's expected for tuning in general really, doesn't matter if it's different types of carbs or EFI tuning with a laptop.

I really like the design and features of the ThermoQuad but a big show-stopper for me is simply the fact that very few performance intake manifolds exist with spread-bore flanges anymore. It's also tricky living at high altitude the factory jetting is always too rich on stock or OOTB carbs and it's not easy to find TQ tuning parts. Plus the fact they're all old used cores so you have to buy 3-4 cores just to make one good one and then you run into the issue of all the different years and configurations based on the engines and vehicles they were originally spec'd for and sometimes you can't just swap parts between them if the OE applications vary.
 
Mopar put 800cfm carbs on 150hp smogger 318s. GM put 750cfm carbs on 4.3 and 4.1 litre V6 engines, in heavy cars with tall gears!

I drove a truck with a 750cfm carb on a 370ci engine that never topped 3500RPM.
 
Jarlaxle said:
Mopar put 800cfm carbs on 150hp smogger 318s. GM put 750cfm carbs on 4.3 and 4.1 litre V6 engines, in heavy cars with tall gears!

I drove a truck with a 750cfm carb on a 370ci engine that never topped 3500RPM.
Click to expand...
Exactly. What people simple cannot get through their heads is, carburetors like the Thermoquad and Quadrajet are unusual carburetors, even though millions of each were used. They are a mechanical/vacuum hybrid. I can close the secondaries on either one COMPLETELTY OFF and run only on the primaries. What size is the carburetor then? 280 CFM? Maybe? That's why they are so forgiving. You can run one on a slant 6 and tune it to run well, pull it right off, put it in a 440 and re-tune it for the 440. Some people just cannot get their heads around that.
 
LocuMob said:
I put 750's on all my engines.
Click to expand...
Same here. I like em so much, sometimes I put 2 on there....:lol:
Boss Mag Pic.jpg
 
Jarlaxle said:
Mopar put 800cfm carbs on 150hp smogger 318s. GM put 750cfm carbs on 4.3 and 4.1 litre V6 engines, in heavy cars with tall gears!

I drove a truck with a 750cfm carb on a 370ci engine that never topped 3500RPM.
Click to expand...
What RRR said is what I was about to say.
The QJ & TQ having a small primary is very helpful on any engine, smogger or HP engine. The engine will just swallow what ever it needs going slow or @ W.O.T.
 
That and the side rod to the vacuum pod.
 
Jarlaxle said:
Mopar put 800cfm carbs on 150hp smogger 318s. GM put 750cfm carbs on 4.3 and 4.1 litre V6 engines, in heavy cars with tall gears!

I drove a truck with a 750cfm carb on a 370ci engine that never topped 3500RPM.
Click to expand...

RustyRatRod said:
Exactly. What people simple cannot get through their heads is, carburetors like the Thermoquad and Quadrajet are unusual carburetors, even though millions of each were used. They are a mechanical/vacuum hybrid. I can close the secondaries on either one COMPLETELTY OFF and run only on the primaries. What size is the carburetor then? 280 CFM? Maybe? That's why they are so forgiving. You can run one on a slant 6 and tune it to run well, pull it right off, put it in a 440 and re-tune it for the 440. Some people just cannot get their heads around that.
Click to expand...
And the other thing people forget (or are unaware) is the fact that as soon as you put a 750 cfm carb or whatever on a 318, it becomes the cfm carb the engine will pull because it will only flow what the engine will pull.
 
Slap Stick said:
Ha ha! Cough n Spit carbs!
Every one we ever bought wouldn't run right. They either had missing parts or were assembled incorrectly. I drive past their little place regularly.
Click to expand...
I must have been lucky then. Not only was it complete & properly assembled, but it has a much crisper response than my old 4777.
 
On the subject of carbs how the hell does one read the stamping on the metering rods? I play hell reading numbers with my old *** eyesight. And that’s with a magnifying glass.
 
I have a magnifying glass. (It’s actually called a “Loop” designed for checking small details on various printing apparatuses.)
Some stallings are bigger than others depending on manufacturing or manufacturer, when made and of course, over the years of fuel passing over the numbers…. Fade…

Meep a log book on what you start with and what changes you have made and when with a space large enough for notes. Runs rich, rum lean, doesn’t run, burned my eyes out! LMAO….
 
You must log in or register to reply here.
-

Back
Top