How critical is the use of Edelbrock's 4 hole square to spread bore adapter. I am using an open style adapter that was present when I removed an old Carter AFB. My intake is an older spread bore Performer. I am currently trying to tune my 1406. Hoping someone can explain why my Edelbrock says "you must use adapter #2696" and if it's absolutely necessary. I greatly appreciate all the advice I've gotten from the hotrodders community.
Due to budget constraints I used the open center adapter I had at the time. Now that my project is driveable I am trying to get my 1406 carb and Chev 327 burning cleaner. Smells gassy so I went down a size on the primary jets & rods and up to a orange spring. I wish I woulda just left the stock primary jet/rod combo and tried the blue springs. Oh, Well. Still learning. I was just wondering why Edelbrock took the time to explicitly say don't use an open center adapter. I did just drive to O'reilly's and see they carry the Edelbrock 4 hole adapter. Made in China though. If someone chimes in a says they know for a fact a 4 hole adapter will get my 1406 to perform better, I will start searching for a USA MADE one.
The 4 hole adapter is intended for use on just the factory Quadrajet manifold and factory Chrysler Thermoquad manifolds....it is used to get the fuel mix cleanly distributed in these large secondary barrel manifolds. Read what it says again and you will see what I'm saying.
It is not exactly needed in you case since you are using a Performer intake manifold, but using it will keep the right and left plenums on the manifold separate from each other just like a factory manifold does....it may work better for you if your 327 is really mild or you are searching for better low rpm response, better idle, and better mileage.
The only way to really tell if you need it is to try both the 4-hole divided and the spacer you already have(open type) and see which the engine prefers. No one, not even Edelbrock could tell you with 100% certainty which will work the best.
If you gave some info about the rest of the engine and car, trans, rear gear it is hooked to we might be able to give you a better idea of what would likely be best.
Thanks Ericnova72. You've helped me a bunch and I am greatful for your thoughtful responses. I am pretty sure my 327 was built in 1969 and is basically all stock with an RV cam. I dropped it in a 4x4 rig with a manual 4 speed tranny. It's low geared, I have an old blue Moroso HEI dizzy set at 6 degrees advance. Been running on ported vacuum, not sure if manifold vacuum would be better. Been thinking about trying 12ish degrees and turning down my idle screws. I have good throttle response in 1st. In 2nd gearthru 4th I have to gradually push the throttle to effectively gain power. A sudden pop of the throttle doesn't do much. I think I had more instant power in 2nd with the stock primary jets/rods. May go back to that when I get a new adapter plate. I'll do some searching, but do you know if any smaller companies offer a USA made 4 hole adapter that would work. I hate the thought of Chinese made stuff on this build.
Trying to get USA made stuff if pretty much a hard thing to get these days and times but I can tell you from experience of using spacers that the open spacer will take away signal to the bottom end of things and a four hole will give a better signal compared to the open one. I use a four hope spacer on my two builds and when I used a open spacer I lost quite a bit of signal.
As far as USA made it can be made here but it can be made with Chinese metal as I have gotten American stuff and it will state made with foreign materials. Bite the bullet and get what you need. Even having a GM block its not made here as its hecho en Mexico. Ericnova72 gave some good info and I would do as he suggests and try and see.
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