On the two stroker motors I dynoed that had Indy heads and a x-ram intake with edelbrock 750 carbs, when jetting for best power, I ended up with jetting quite a bit richer than the as delivered edelbrock jetting.
One was 675hp, the other was 745hp.

One of those came to me with torched head gaskets from being run too lean.....and those carbs were richer than stock as well.

i hear of people going to very large jets in big cube n/ss engines using afb/edelbrock type carbs. i've always wondered about that and my thoughts were; has anyone ever taken the plugs out of the fuel passages and checked them for restriction/flaws/size? after all the jet is just a restriction device and when that gets reduced big time wouldn't that indicate a possible problem somewhere else? are the cams so large that they can't create a good pressure differential? is plenum volumes excessive?

Although the ede 750's and the last of the carter 750's were both made by weber, and both came with the same jets and rods, they did not provide the same a/f ratio when run on the same motor back to back.
Subsequent disassembly and inspection showed definite differences in the calibration with the air bleeds and clusters.

No way would I assume that the jets for an OE MW carb would be optimum for an aftermarket similar version of that model carb just because the throttle bores and venturii are the same size.
In the same way not all 750 Holleys are supplied with the same jets, or would require the same jets, to achieve equivalent a/f ratios on a given engine combo.

[quote=fast68plymouth]On the two stroker motors I dynoed that had Indy heads and a x-ram intake with edelbrock 750 carbs, when jetting for best power, I ended up with jetting quite a bit richer than the as delivered edelbrock jetting.
One was 675hp, the other was 745hp.

One of those came to me with torched head gaskets from being run too lean.....and those carbs were richer than stock as well. [/quote
Were they the stock mani or aftermarket, my jetting comment was based on the stock mani. Some of the NHRA Maxie stockers are near the 650 HP range and not varying far from the factory jetting that was right for the maybe 400 they made stock. I'm guessing cam design, aftermarket head and mani ports and large headers make this a different animal. I could be wrong but IMO that motor that burned the head gasket had some other issue if it required much larger than stock jetting.

The 750 Edelbrock carbs have been known to have AF problems. Tuner did a long (even for him) explanation a while back on the issue. It had to do with the size of the air bleed as well as a crimp in the emulsion tube.

I've run the 800 carbs on a number of stroker motors. They do tend to be lean and putting big jets in them sometimes doesn't help until the needle and seat are enlarged.

So I'll say the Edelbrock carbs can be made to work but sometimes you'll end up spending a full day chasing your tail when working with them.

I looked back in my notes and what it says on my 505 cross ram engine was that the 800 carbs worked fine out of the box. But when we switched over to the Indy ram the carbs needed to be jetted up significantly. So that is just due to the difference in the intake. Something was messing with the signal on the Indy ram and the carbs required a lot more jet to deliver the same amount of fuel.

the one 800 avs i've spent a lot of time with had .110 needle and seats ootb. for the application it was used in it was jetted stupid rich. the 800 had the large open emulsion tubes vs the 600's swagged down tubes. the 1407 750 edelbrock i have came with .093 needle and seats and after measuring all the air bleeds in the primary clusters they were near identical to the 4618s avs i use on my 69 r/t; big exception was idle jets.. the 750 i have uses a straight open emulsion tubes like the 800. there are some recommendations from mopar to solder up the small holes in the emulsion tubes. i think the performance community has had holley stuck so far up their rectums for decades and can't get their mind around something different. i guess tomorrow i get off the couch and star "drilling" one apart to learn more.

The car I mentioned with the old jetting had over 700 passes when it was sold, ran another 2 years with that setup. Car was sold again and I lost track of it. My current 572 with Indy X-ram Eddy 750's usually runs 113 pri/110 sec with stock rods. I did drill the secondary cluster feeds last fall to .120" as they were around .075" if I remember. That along with 116/113 seemed to help a little but the air was pretty good. As far as being lean it runs the same MPH (148) with the Eddys or a pair of Pro-Systems Holley 750's. I clean cut with the Holley's and the plugs looked perfect. 300 passes, rod bearings and rings looked excellent on tear down. If it's lean it sure hasn't showed it.
Doug

116/113 jets is way richer than some on this thread are recommending, but that's in line with where I ended up with the ones I had on the dyno.

On a 557 with the Indy intake I was at 119 on all 8 holes with the performance series Carter 750 carbs.
Again, I was jetting for power.

Honestly though, I'm all for people finding out what works best for them.
The main point of my initial post on this thread was to just encourage jetting on the rich side "just in case".
The ramifications of taking that approach is a little less costly that finding out you're way too lean.

The Edelbrock 750 has 1 major problem and that is the length of the primary booster is shorter than it should be. Any early pre Carter/FM 750 will have the correct longer booster if you want to compare.

From memory when i compared the both the longer booster activated the primary flow sooner.

Heres an Eddie 1407 thread at Speedtalk:
Edelbrock 1407

I would look to the NSS guys for guidance as thats their bread and butter.
Also heres a write up from Dan Dvorak on AFB's. Well worth the download price $1 for what he knows.

Carburetion: A maximum performance treatise
Hope this helps

Hysteric

Thanks for the link.....a lot of interesting info there.
Answers some questions as to perhaps why some of those carbs just can't seem to be sorted out with normal tuning methods.

When I get a chance I'll read through the stuff from Dvorak.

Great read! We need more posts like this on Carter/Eddy carbs.

As far as the boosters go I know some Demon carbs have that issue like the King Demon I just converted to a 2-circuit for a 1000+ hp BB Chevy. The booster is too high in the venturi making the depression point less than desireable and a weaker signal needing more fuel when the boosters are active and making it richer down low..............

Thanks for the links good info. I'm going to call Dvorak about his carb synchronizers and any other info I can get from him.

Are you stuck on AFB`s? Can you run Holleys?

I can run Holleys. The AFBs look more period correct. Not that most people would know. I have thought about holley might be easier.

I know some haul azz w/the AFB/E-brocs and agree they look more "correct" but I still love the easy tunability of the Holleys and they just look meaner to me...........

I agree with you! I have more experence with holleys but none with dual carbs. I have a little time yet to decide for sure. If I was smart I would put a single Dommy on it.

I think w/properly calibrated duals, the distribution would be better but a Dommy gets it done everyday for many...........

A single plane intake with a Dominator will make 100 hp more than a MW cross ram on a race type engine. When you think about it that means that the cross ram intake is destroying 100 hp of potential power but keeping the air and fuel from getting into the cylinders at the right time. I know that people love the look of the cross ram but sheesh, 100 hp is nothing to sneeze at. Plus the single 4bbl setup costs less and weighs less.

On a different note, a GOOD t-ram intake will make more power than a single in most applications.............NOT cross ram............