Technical > Matt Shaff's Engine Shop

Zoomies vs collector headers

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janjon:
There's probably a bunch of factors that come into play here, but generally, how much more HP and torque might one expect to see from collector headers on a carbureted engine than one with zoomies? Any input appreciated.

JEFF/21C:
that's an open ended question have run everything from weed burners' to zoomies to stepped headers only did dyno test on 305 sbc we were running zoomies because there was no min weight to get as light as possible then a rule change they added min weight so we rented a dyno for a day ran test on tube size and lenght collector size and lenght the best results were with small long tubeand a small collector. we won the championship that year i haven't seen anyone running zoomies in that class but they are like sheep and do what the winner does. all this to say headers are better and bigger isn't always better.

tcoupekyle:
On a carbureted engine, hands down the collector header works better. The signal to the carb is much much better down low. I just had this conversation with Steve Taylor of PRC carbs. The zoomie gains in the upper rpm range are pretty small when compared to the sacrifices at the bottom of the rpm band.
I had a BBC n/a 2 dominators, 1000hp deal and it would barely run with zoomies put a collector header on it and boom it would come to life.
My 2 cents

Frontenginedragsters:
About 4-5 years ago we tested collector headers VS zoomies on our dyno.
540ci BB Chevy engine. Tunnel ram with 38sq inch Crower blower hat on alcohol.
The engine made just over 900 HP with the collector headers. No mufflers or extensions of exhaust pipe. Just like on the race car.
We made about 3 pulls and then swapped to the zoomies. These were long tube Gasser/Pro-Mod style zoomies. Same tube diameter.
Lost 40 HP.
The zoomies still went on the car because the cool factor out weighed the 40 HP.
The car sounds better and barely lost a 10th. For us it's all bracket racing anyway.

Matt

lake_harley:
I'll be going for the "traditional" look on my FED with a mild 283 Chevy so Zoomies it will be. HP might be less than I'd have with a collector header but to minimize the potential HP loss I'm using small 1 5/8" tubes to build my Zoomies, which might be a benefit. Most SBC Zoomies I've seen listed and/or for sale are a lot bigger tubes, like 2" or maybe even larger. The small tubes should at least help a little with low-end power. My FED will be for bracket racing too so consistency is really the name of the game.

Lynn

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