Explosive

No way I'm getting the Mach done in time for this season.

I wanted to get some stuff done on the fox and it's appearing the better choice right now as far as cash goes.

Anyways, it's always had this stumble, it's not as bad when the cars driving, just a slight stumble if you're cruising and lay into it, around 1800-2000 rpms it will hiccup and then take right off.

However as you can see in the video (sorry it's a cell phone vid) it's a bit worse at idle/off the line. I'm not really a fan of this carb (holley street avenger 670) I've tinkered with it, my dads tinkered with it and a local speed shop owner has as well and that stumble always returns. We had one of the steel braided steel lines collapse just before the carb and we got that fixed but the things never been the same since then. And we've rebuilt the carb since then thinking some of the line may have gotten into the carb. I'm to the point where I think I'm going to just buy a new carb and start over this spring. I don't need to do a ton to the car to have it track ready really. Just a handful of stuff. I want to race and I'd like to be running a bit quicker than the Mach was last season. Thoughts/opinions ?

Kinda hard to notice but if you look close in the vid you can see it's a pretty decent lag

Things going to fall on it's face if I try and launch it like it is.

http://www.youtube.com/watch?v=LsAX3...86AUAAAAAAAAAA

Tony71502

Looks like your choked for fuel to me. What are your engine mods? Might not have the proper fuel system.

Explosive

91 block, some machining. Nothing crazy still have factory rotating assembly. Edelbrock air gap intake, AFR 165's non emission heads. roller rockers, e-303.MSD ignition ect. H/C/I build no F/I or juice.

I've always thought it was running rich if anything. When that fuel line collapsed it would run up about half throttle and at like 3200 rpms it would just cut out as it wasnt getting any fuel.




It's got a fuel pressure gauge before the carb. IIRC it reads 5-6 lbs. I'd have to look sometime again.

mjr46

try advancing the base timing , what's it at currently?? also have you played with the cams on the accelerator pump circuit?? there are varying degrees of colors they come in, that change the ramp up of the delivery to accel pump circuit, stock is a slow ramp usually, sounds like you may need a more aggressive ramp up, go to holleys website and look at the assortment of cams for them, also may need to change the squirters in conjunction with a cam on the accel circuit.

Explosive

So you guys are thinking a lack of fuel ? I was always thinking the opposite

AdderMk2

since you think differently than we do, why dont you invest in a wideband O2, so you can actually tune the car and stop guessing.

Explosive

Eh, I know some guys that are in with a shop near me with a chassis dyno. I was going to do my best to get the carb dialed in then see about gettin it tossed on the dyno.

Tony71502

A small and semi-relevant piece of info, only because of my Chevelle.... people change from small blocks to big blocks in cars that are not worth keeping original number matching parts...

They upgrade the carbs and fuel pumps and die at the drag strip... cuz the stock Chevelle Malibu runs a tiny fuel line.... upon upgrading just the lines in between their "amazing" aftermarket fuel system parts... they can flow so much more fuel and drop 1.5-2 seconds in the quarter. Because they get the fuel they need.

Explosive

theres the fuel line, holley red fuel pump.