chiefbob

I've got a 383 Stroker crate engine in my '78 with a 750 Edelbrock carb.

It hasn't run right since the modification, only at times then rough.

I've been told by two different people that the 750 is too large and is probably dumping gas into the crankcase and that it should be replaced with a 650 Edel.

Two Questions:

1) Do you agree?

2) Will the 650 fit the intake manifold that the 750 currently uses?

Comments and suggestions are well appreciated.

694speed350

Go with a Q jet or a 650 Holley. The original Q jets were 750 from the factory.

Oldguard 7

[QUOTE=chiefbob;1589159720]I've got a 383 Stroker crate engine in my '78 with a 750 Edelbrock carb.

It hasn't run right since the modification, only at times then rough.

I've been told by two different people that the 750 is too large and is probably dumping gas into the crankcase and that it should be replaced with a 60 Edel.

Two Questions:

1) Do you agree?

2) Will the 650 fit the intake manifold that the 750 currently uses?

Comments and suggestions are well appreciated.[/QUOTE/]

Something else going on with that. 750cfm is not too big for a 383. It is said that Edel carbs don't perform as well as Holley, the Q-jet (a damn good but misunderstood carb) not sure why. Work with the carb instead of replacing it with another brand unless that is what you want to do.

vette_20

Hi I have a 600 edelbrock on mine I find I works great have not had on dyno yet but performs fantastic, did get a 750 because I was told the 600 to small but runs like a dog but does not seem to get a good squirt of fuel from accel pump so have taken of for now might try again when on dyno if they think it needs it
regards Ian from down under

chiefbob

G'Day, Ian

Do you also have a 383 stroker in your Vette, or a stock 350?

So, your Edel 600 works great. I wonder if that "someone" knows what they're talking about. I'm getting so many conflicting opinions on this issue that I'm ready to replace with fuel injection.

I'm taking mine to a performance shop that has a great reputation next month. They have been repairing other owners' cars that were modified by the one that did mine five years ago.

Switching to non-ethanol gas helped a lot, plus hotter, larger gap plugs also helped. My setup includes an MSD HEI.

If your 600 works as well as you said, I would put it back on.

Let me know how your carb fun turns out!


Bob

cagotzmann

I have a ZZ383 with a 770 street avenger installed. so a 750 as far a size should not be a problem.

I also have O2 sensors to measure AFR. I am running at 2200 ft evevation. I changed the primary and secondary jets to get a better running engine from the start. Original jets where 70 / 75. I am now running 67 / 70. This changed the AFR readings from a 11-12.5 at WOT to 13-14 at WOT.

Do you have overall poor running.

poor idle, poor WOT , hesitation on quick acceleration ?

What kind of timing are you running ?

7t9l82

before id change carbs i would make sure it isn't a tuning issue. a 750 is not too big.

74modified

No, I don't agree with the two people who don't know what they are talking about. What you have is a probably a tuning problem. Most all performance engines need to be tuned to match their individual needs.

lars

That's complete nonsense. A big carb will not "dump gas into the crankcase." In fact, a carb that's too big will have inadequate fuel metering signal, and the carb will run lean. Not rich. Your 383 will take a 750 to 850 cfm carb with no problem. I regularly test 1050 Dominator carbs for people on my 355: No problem.

You don't have a carb sizing problem. You have a setup and tuning problem. Find someone who knows what they're talking about. Or simply ship the car out to me and I'll set it up for you.

Lars

vette_20

I did put it back on and runs great could not get any joy out of the 750 have in a box in garage .I see all the reports about edelbrock as well and I have always bee a holley fan ,I put the edelbrock on to make it easier to pick up vac ports as the holley got in the way of the rear one on manifold and I have little clearance to raise carb.yes its 383 with all edelbrock gear heads cam manifold. I was going to get rid of the 600 but heh just runs to good so went back to that and will get rid of the 750 .
regards Ian

chiefbob

I think the problem stems from the original modifcation five years ago when everything under the hood was replaced with the 383 crate engine. The "performance" shop didn't do a good job as I had to take it back a number of times for various problems.

I am not a mechanic.

I've met two other people who had their cars modified there and were really pissed off with the work and expense. A mechanic who was honest enough to tell me he wasn't qualified to take the engine apart referred me to a shop that has a great rep (confirmed by people who had their cars fixed after the aforementioned shop screwed them up). I'll be taking it next month.

Here's the specs:

383 Crate Engine 420 HP Stroker
Ceramic Headers
MSD Distributor
MSD 6A1 Box
MSD Wires
Intake Manifold
Edelbrock 750 Carb
Air Cleaner
Trans Lines
Be Kool Radiator
Fan Sensor
Flex Plate
Fuel Pump
Starter
Balancer
Water Sensor
Exhaust System
AC Idle Boost
Spark Plug Wire Looms

All the pollution equipment has been removed as its exempt from NY requirements due to age.

One other thing I should mention is the fuel. The idiots who did the mod never told me I needed to run 93 and above octane fuel. I didn't think of it and I've since been running 93. Also told I should add an octane booster, so I've been adding Lucas super octane booster (or something like that) to each fill up. Also been using non-ethanol premium since it became available here. All that seemed to make a big difference.

On one of the threads here I was told I needed plugs that run hotter with a gap of 0.035. Seemed to help.

Bottom line: I'm not doing anything until I get an analysis by the shop next month.

I appreciate everyone's opinions, but as you can see, a lot of conflicting opinions are out there.

Thanks for the replies. I'll update next month FWIW.

And Lars, I'd love to have you take a look at it but it's a long way from upstate NY. LoL


Bob

74modified

I hope you find a good shop. The problem is that there are not as many "good" mechanics as there once were for old school (non fuel injected) engines. It used to be easier to read spark plugs, but today's fuels are less likely to leave deposits, so an O2 meter is the best way to read fuel mixtures. If it were me, I would ask how they are going to go about tuning your engine. If you educate yourself, you can tell if you are at the right shop. Getting the timing sorted out would be first thing. Then tuning the carb could take place. Check out the papers from Lars. Look at this Edelbrock tuning paper to get an idea how jets, rod, and springs can be changed, and adjustments made.
http://www.edelbrock.com/automotive/...ers-manual.pdf
Most people mis-understand fuel octane. In very simple terms, the higher the octane, the less easily the fuel "explodes". So a high compression engine can have low octane fuel explode from compression alone before the spark ignites, or when the spark is early it explodes too quickly. All you need to do is match octane to your compression and timing, any higher octane will not accomplish much.
Good luck

7t9l82

lars isn't any further than your mailbox.

lars

New York..? Heck, another guy from New York pulled his entire engine out, crated it up, and shipped it to me. I fixed all the setup errors, tested it, tuned it, and shipped it back. He bolted it back in the car, and it runs great..! I know shops that charge more to do a good setup than the round trip shipping costs were for the engine..!

Seriously - I hope you find someone competent out there to get you set up right. It's an unfortunate aspect of this hobby that the cars are becoming old enough that there are very few of the "old guys" left to assist in setting them up right. There's a lot of hack work going on out there, and a lot of really bad advice is being handed out to people who just want to enjoy their old cars. This was the motivation for me to do the "Tuning for Beer" seminars: To get the old, "secret" tuning info out to as many people as possible so it could be shared. I might have to start the Program back up again...

Lars

cv67

Call Summit spend $200 and get an AEM kit so you can see via 02 sensor and gauge what the car is doing and where. Use the "ideal A/F" as a guide only leave the car where it runs best youll know. Save you a lot of headache and expense fine tuning. Very few carbs are "right" from the box as every cars a little different