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Steve welder

Steve welder

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My 383 is freshly rebuilt, all good internal parts, mild comp cam, weiand manifold 1406 Edlebrock carb HP exhaust manifolds
Ive felt its not running right, ive thought a vacuum leak as it did have a vacuum leak on the intake manifold but its still running to rough, car has a shake to it and ive turned over every stone
Today I put vintage Snap On cylinder shorting meter I have and I found something interesting.
The car fires on all eight for sure, there is no hesitation but again idles to rough
1 3 5 7 when shorted one at a time gives a noticeable drop in RPM as I watch meter
2 4 6 8 also give a drop but not as much as the odd side, close but not as much
Now the meter also lets you short the 4 odd plugs and 4 even
When I short the even big drop in RPM but engine still runs
When short odd engine just about stalls out, barely runs
There is a very noticeable difference in the odd side head and even side head
Im thinking I have to do a complete compression test asap
What do you think? And off course thanks
 
Don't forget...and this may not have anything to do with it, but a LOT of guys don't realize this.....the 1406 is NOT the performance version 600. It is VERY lean. The 1405 is the performance version and the boosters are different. I like Eddy carburetors, but they are generally lean as a whole and the 1406 doubly so. On a 383, I would think it's not enough carburetor. Now whether that's your issue remains to be seen.
 
You probably have fuel problem. You have a dual plane manifold-right? They seperate right from left, odd/even.
 
RRR,
I think the boosters are the same, but the performance version has richer jetting.


Steve,
The 1405/6 are 625 cfm. If the 383 is just a mild perf engine, then it will work fine & a good choice. The factory fitted AVS was 625 cfm, & it was also used on std 440s.

Who built the engine? FT cam? Broken in correctly? What brand lifters? Cam specs?
 
Bewy said:
RRR,
I think the boosters are the same, but the performance version has richer jetting.


Steve,
The 1405/6 are 625 cfm. If the 383 is just a mild perf engine, then it will work fine & a good choice. The factory fitted AVS was 625 cfm, & it was also used on std 440s.

Who built the engine? FT cam? Broken in correctly? What brand lifters? Cam specs?
Click to expand...
No sir, they are different. I've seen it first hand, plus we have e member here who tore both apart and showed all the differences. They are different. Trust me.
 
Bewy said:
RRR,
I think the boosters are the same, but the performance version has richer jetting.


Steve,
The 1405/6 are 625 cfm. If the 383 is just a mild perf engine, then it will work fine & a good choice. The factory fitted AVS was 625 cfm, & it was also used on std 440s.

Who built the engine? FT cam? Broken in correctly? What brand lifters? Cam specs?
Click to expand...
Here you go, buddy. I found it. Read this. There are several differences between the two.

Another 1405 vs 1406 thread
 
On some of the carb forums I’ve read some pretty interesting things people have found “wrong”(not built with the correct parts) regarding the 600cfm Eddy carbs.
My first test would be to try a “known good” carb on the motor and see if it behaves any differently.
That might mean seeing about borrowing something from a friend, not necessarily getting a new(unknown) carb.

Another test would be to try an open spacer under the carb to see if it evens things out some(all cylinders accessing both sides of the carb).

I agree a compression test should be done, along with a leak down test if there are any anomalies found.
 
RRR,
Thanks for that, did not know. Very interesting. I have read that some sec boosters in the 750s had the bullet shaped emulsion tube end & that the metering hole was smaller than the jet!
 
Dartswinger70 said:
I'm thinking carb / fuel also is it a dual plane intake?
Click to expand...
Yes dual plane,,,,,Its hard for me to think after all the money I spent buying brand new, the car would idle like this
Off idle there is. no hesitation....Im pulling all the plugs and. checking compression as soon as time allows.
 
Steve welder said:
Yes dual plane,,,,,Its hard for me to think after all the money I spent buying brand new, the car would idle like this
Off idle there is. no hesitation....I'm pulling all the plugs and. checking compression as soon as time allows.
Click to expand...
Usually dual planes feed cylinders in a "Y" configuration looking down at the carb flange. For example one side of the carb would feed the two outer cylinders on one bank, and the two middle cylinders of the opposite in a dual plane intake. Its a balance issue with air fuel ratio I'm not saying this is your problem though.
 
Dartswinger70 said:
Usually dual planes feed cylinders in a "Y" configuration looking down at the carb flange. For example one side of the carb would feed the two outer cylinders on one bank, and the two middle cylinders of the opposite in a dual plane intake. Its a balance issue with air fuel ratio I'm not saying this is your problem though.
Click to expand...
Thanks, so reading this correctly the manifold and carb while might be not giving the performance should not be the problem
When I shorted out the entire passenger side bank leaving the car running on just 4 cylinders as compared to shorting out the drivers side there was a very noticeable difference, car would almost and would id say stall but keep running when I tried the other side
I read that as maybe whats going on with this engine.......Im busy today but I will do that compression check and a cylinder leak down if I find a low cylinder......Thanks again to you and everyone else
 
Steve welder said:
Thanks, so reading this correctly the manifold and carb while might be not giving the performance should not be the problem
When I shorted out the entire passenger side bank leaving the car running on just 4 cylinders as compared to shorting out the drivers side there was a very noticeable difference, car would almost and would id say stall but keep running when I tried the other side
I read that as maybe whats going on with this engine.......Im busy today but I will do that compression check and a cylinder leak down if I find a low cylinder......Thanks again to you and everyone else
Click to expand...
it a possible point of causing imbalance from one bank to the next, however like said the runners on a dual plane are in a "Y" configuration the intake runners on the manifold aren't truly split left and right. If you look at your intake you'll see what I mean. yull see two runners gong to the one side center ports, ant two outers going to the opposite side etc.
 
Your average 4 barrel has two idle mixture screws, if they aren't "balanced " correctly the engine will idle poorly etc. This is why they say "back each screw out 1 1/2 turns " etc. Then the dual plane intake splits the mixture up and distributes it from side to side. gain not saying this is the problem, but if the carb isnt set right at idle it may play into your symptoms.
 
Bewy said:
RRR,
Thanks for that, did not know. Very interesting. I have read that some sec boosters in the 750s had the bullet shaped emulsion tube end & that the metering hole was smaller than the jet!
Click to expand...
Hay it was news to me too when he did that! I have the 1405 equivalent of the AVS2 now, the 1905, that I'll be trying on Vixen soon just for kicks. It's the 650 AVS. Should run pretty good. This present engine may not need that much carburetor, but I have no doubt the current build will.
 
Steve welder said:
Thanks, so reading this correctly the manifold and carb while might be not giving the performance should not be the problem
When I shorted out the entire passenger side bank leaving the car running on just 4 cylinders as compared to shorting out the drivers side there was a very noticeable difference, car would almost and would id say stall but keep running when I tried the other side
I read that as maybe whats going on with this engine.......Im busy today but I will do that compression check and a cylinder leak down if I find a low cylinder......Thanks again to you and everyone else
Click to expand...
"Should not be" is correct. Even though small, the carburetor should run fine.....and from what you've said, IMO that's where the trouble lies. Not because it's a little small, but because there's an issue somewhere. Might have some trash in a jet or something.

Here's an old trick you can try. Get the engine up to temperature and with the choke open, run the engine up to about 3K and manually close the choke with your fingers a second or two, rinse and repeat. A lot of times that will suck some trash out of "wherever" it might be and clear it up. It doesn't work every time, but it's FREE and a lot of times it does work.
 
j par said:
What are the cam specs...
Click to expand...
Comp CAM PART # 21-223-4
27184DB0-F05E-463A-A997-FABE4492C454.jpeg
 
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