Completed my swap this weekend put a offy dp with efi exhaust with a eldabrock 600. Having an issue it seems like when I kick in the 4 barrel in forth gear it doesn't seem to have a lot of pull... second and third I'm pulling like no other its a whole new truck. But in fourth gear it doesn't have great pull. I'm tacking about 2 grand at 55 but when I kick it just doesn't have the umph. Does anyone have an idea or adjustments or things I should add. Overall I am very satisfied with the swap. Big sixs rock.

 

Could be a lot of things. Recurving the distributor might help. Stiffer step up springs might help. Try driving with a vacuum gauge attached and see what kind of readings you're getting in different gears at different RPM. Checking the AFR with a wideband O2 sensor would give you some good info too.

 

Is the Edelbrock 600 cfm 4v a mechanical or vacuum secondary carburetor?

If it's a mechanical secondary, you might just need to adjust the secondaries.

I'd also recommend a vacuum gauge to check your fuel mixture for the primaries and secondaries.

The other thing is regarding the DP intake.

The primaries BOTH have to be parallel with the valve cover, and the secondaries have to both be towards the firewall, like this:

S
E --> cyl #6 V
C P A
O R --> cyl#5 L
N I V
D M --> Cyl #4 E
A A
R R --> Cyl #3 Cover
I I
E E --> Cyl #2
S S
--> Cyl #1

I'd be willing to bet that that's your issue. The main reason I think that the carburetor is mounted wrong is because you say that this occurs at 2000 rpm. That tells me that when your getting on the throttle, that the secondaries aren't open yet and when they do open, the motor isn't breathing right.

If your intake manifold was a C-series, it wouldn't matter which way the carburetor is mounted because it's just an "open plenum" intake. That Dual-Plane intake has little dividing walls all in the runners.

At least, this is the information that I've "heard" from others on here regarding the DP intake.

On a side note, how is your throttle response now? The 300 should really grab you by your britches now that the motor can breath like 1000% (not a real numerical figure fwiw) better.


EDIT: I see Baron has posted. I agree 100%, the distributor might need to be re-curved because the motor doesn't have the total timing necessary to take advantage of the new setup.

 

I have adjusted the timing a few times doesn't seem to make much of a difference. As far as the carb goes I have the secondaries on the upper side and primaries on the lower side. I'm thinking maybe I might need to widen my gap on my spark pulgs or thicker wires to carry my upgraded coil power what do you think?

 

Upper side and lower side? The primaries should be on the engine side and secondaries on the fender side, although I don't think you could even mount the carb if it was off 90 degrees.

Recurving affects how soon and how much advance there is off idle. You need either a dial-back timing light or someone with a distributor machine to see how the spark curve is advancing at different rpm. It should start to advance just off idle and reach maximum mechanical advance ~3,000-3,500 rpm.

After I swapped on my C and Edelbrock the truck runs best at ~16 degrees BTDC static timing with the vacuum advance can hooked to manifold vacuum.

Edelbrocks are pretty forgiving out of the box. Get a set of step up springs (~$5) and swap to the stiffest ones and see if that helps before you start dicking with the jets or rods.

 

Yes i have it setup like that the Dp has the split runners im sure you know. my bad should have clarified that when i said that. my bad but on a lighter note 1st through 3 is awesome.