What Jets? 670 Holley

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demon700

demon700

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I have a mildly worked 318 with a holley 670. The engine is very lazy and I am wondering if it could be a jetting issue. Anybody know what jets I should be running? I believe the jets in it now are 68 front and 69 rear. Thanks
 
That seems about right. What is the rest of your combo? What kind of advance curve are you running? By lazy do you mean the engine is slow to rev?
 
My timing is out of whack as well for sure. At 10 base, i have 50 advanced. I bought the summit dizzy with the ecu as a kit and am trying to see now if i can adjust the dizzy at all. Setting my base at 0 puts my advance around 38. I realize this is also a problem, just the jet question popped up first. lol its been about a year and a half since this engine was put together, so my memory is a little foggy. I believe it was bored .040, comp XE256H cam, mild head work, I believe I had the larger valves 2.02 1.60 installed in the heads. Weiand stealth intake. Start at a stop, put the foot to the floor and it is lazy coming up to speed, no umph so to speak...anyone know if the summit dizzy can be adjusted with a heavier spring?
 
15-16 initial and limit the distributor. It may require taking the distributor apart to do it. How much mechanical advance in the distributor? Make sure you are setting initial with the vacuum advance disconnected and plugged off. See the instructions. If you reconnect the vacuum advance and the timing jumps up to some huge number at idle, something is wrong

If that thing has a vacuum advance, make sure it's on ported, not manifold vacuum.

Don't mess with the jetting at all until you have the timing and curve straightened out.
 
crackedback said:
15-16 initial and limit the distributor.

If that thing has a vacuum advance, make sure it's on ported, not manifold vacuum.

Don't mess with the jetting at all until you have the timing and curve straightened out.
Click to expand...


the vacuum advance is plugged into the vacuum port on the carb, the one next to the choke, not either of the two near the base, they are plugged. How do i limit the distributor?with the spring?
 
Won't do it with any spring.

I don't know how those advance mechanisms work. It may require taking it apart or you might be lucky and only requires loosening some torqueshead screws.
 
'S not clear to me whether you are talking about 50* timing WITH or WITHOUT the vacuum. You want to measure your high RPM advance with the vacuum DISconnected.

Set the timing, no vacuum, high RPM at 38-40 and see where the initial (base) falls.

Some of the factory mechanical advance curves were way too long for performance, but I find it hard to believe a "performance" dist. from Summit would be.
 
I had that dist from summit after I took it to a fellow he made a few changes 35 total 17 initial with a 600 holley it ran like a fuel injected car. Now Ihave the 770street avenger on all the little bugs are worked out but I think the boss is right get your dist working and set up dont touch thecarb 50 bucks a good guy will fix it for you.
 
Thanks folks, the timing was done with the vacuum connected. i will try again next time i am out with it unplugged and see where it falls. i will do a little more research and find out how to adjust the distributor
 
So i reset the timing on the car, base@17 as suggested, and unplugged the vacuum advance, and the advance fell at 35, which is right around where it should be. At idle with the vacuum plugged in, it runs 17. I took it up the road and it is certainly running better. Thanks again everyone.
 
it seems to. Still not where it should be maybe, but this was my first attempt at tuning a carb as well, so there probably is room for improvement. The engine is brand new too, so the more use it gets the better it will.
 
If your running vacume secondaries you can change the springs to open it up quicker, also try going up 5 on your squirter.
 
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