Engine won't run right with zoomie headers

[DiggerDon]

I have a 18 degree 428 engine in my fed 14 to1 comp ratio 950cfm gas carburetor that I had built for a dirt track car. Never used engine in dirt car, (sold dirt car with old engine) built my fed with the new engine. Made zoomie headers and ran rough would not idle right, I made collector headers and it runs great.
Would like to put zoomies on car to look original. Seems like I have vacuum problems .
What can I do to fix the problem. Thanks Don

[crider]

I just went thru this very same thing on my BBC, try making you zoomies longer. It took care of my idle issues. Engine was acting like it had a massive vacuum leak and wouldn't idle, added some length to the pipes and it cleared right up

[jspell]

I went through this last year with my 423" SBC with 18* heads etc...ran great on dyno...would not run with the zoomies...14:1 comp and big cam...I put collector headers back on it...runs great.

[Rusty Kramer]

I wanted to put Zoomies on a naturally aspirated   engine many years ago and I was advised not to because they do not make enough back pressure for an N/A application and you will lose a lot of low end power. 

[wideopen231]

Have run zoomies for years on NA motors with no real issue.As to power loss .I think its mostly bottomend power and I lleave at 5000 with 6600 stall converter so who cares about bottom end power.I run mostly in a 1500 to 1800 rpm range 6600 thru 8400 maybe cpl more in 1/4.

Zoomies seems to always be fine with injection and take some tunning if running one of those craparators.

[Roger]

Hey Digger

How much overlap does your cam have?

[retroboy]

I've run them with out a second thought on Ford Windsor and Cleveland engines. Funny thing is I'm having some trouble sorting out my small block Chrysler and I never gave my Zoomies a seconds thought ?

[DiggerDon]

Roger
The cam card is faded but it looks like 22 degrees

[Roger]

Sounds low for an overlap figure, do you have the # of the cam? Reason I ask about overlap is the more overlap in the cam the rougher the engine with collector headers runs at idle. Put zoomies on it and it runs even worse. Zoomies don’t scavenge exhaust like a tuned length collector header. Then use some short pipe zoomies and it could be that exhaust reversion is taking place; exhaust moving into the intake port before the intake charge starts following towards the cylinder. It’s to do with exhaust pulses and all that stuff. Just like Crider said you add some length to the pipe and you start to reach the tuned length part of this deal and makes the exhaust pulses work in your favor so the engine idles better. I’m dealing with this same situation now as I start to assemble my new gas burning zoomie equipped engine: trying to figure out what camshaft to run knowing that all the advantages of tuned collector headers and their camshaft designs are tossed out the garage door. I’ll take a leap of faith here cause this a slow evening and suggest that a cam with a minimum amount of overlap is used to minimize exhaust reversion that might be affecting idle quality. Maybe try the zoomies again and loosen the lash on the intakes and exhaust which will take out some of the overlap, to see if it idles any better. Just my 2 cents worth.

[Oldschool]

I run zoomies on my 434 SBC with a 1050 dominator and runs like a bat out of xxxx. The idle is great,but pipes not real short. Could not imagine not running them ,very cool ride.