The difference between genius and stupidity...is that genius has its limits...
1989 Bezer Mango Maddness
1988 Hallett Vector
1975 Hallett Barron Sprint (sold)
2006 Corvette Z06 (sold)
This one ran fairly well for what it was. It would have been better with an optimized length (which it did not have). If they are tuned and sized properly they can run quite well. Now a properly sized and tuned header will always work better in this kind of application but then again most of us do not run proper headers anyway.
Last edited by fc-Pilot; 04-14-2012 at 02:22 PM.
Hallett 270T "Kahn Job"
Unless you are naturally aspirated with LOTS of compression, the Zoomies will be a pretty big power loser compared to properly-sized headers
Dang Mike, you beat me to it.
July 2009 269.jpg (96.8 KB)
Seems a little flatter on the top now than with the Bassetts before
Well you can take the following for what it is...
I have run Zoomies on unblown engines for years...And I have done it knowing just about exactly what it costs me.
Now granted some engines may need to be tuned different, some cams/heads may react different. But in drag racing as long as it ran the number, I liked them better...easier to work on, sound bitchin, look bitchin...AND I have never had a problem with losing the amount of horsepower claimed by some...FYI...(tube size has alot to do with it)
Unlike most others, I am able to dyno without mufflers...to run the exhaust exactly how it will be run in the boat.
I have been reluctant to post the following, but figured it was time to let those who have questions in on at least what I have learned...so like it or not...I think there will be some information learned...stuff here that even might make the "experts" go HMMMM!
Our example in this case is a pretty staightforward 500 inch BBC, aluminum heads, Roller cam(.785 lift), Nice topend pieces, 13.5 to 1, Hilborn stack injectors with a vertex mag...engine was built to go circle racing...
These first numbers show where we ended up with the stepped Leach headers that all the monkey see/monkey do boys run on the Sprint Boats these days...
So we have a maximum HP number of 794.6 at 6800 and the torque peaked at 687 at 5400.
I really like this format because you can see an average of what the numbers are from 4800 on up. Very handy especially in a sprint boat application.
Next up 2.25 Zoomies...
We see our maximum HP came in at 785, but we had to stretch it out to 7100, peak torque pretty close 684 at 5500...but look how the torque numbers change between the 2 on the way up...big advantage to the leach headers...16 ft+ pound of torque on the column average...IMHO Torque is what moves the boat...most would disagree. 14hp on the average...not a ton...
And just for fun...a 30 year old set of shortened bassetts...
This can't be! A worn out set of Bassets within 2 HP and under 5 Ft Pds of torque versus a 1500.00 header...HUH?
Well, if you look at all the numbers(and I hope you all do, cause you can come up with alot of interesting theories) the Leach's are better by a bit and probably worth running(but for the price diff?) versus the Bassetts, but it is interesting in what most people get their heads wrapped around in it terms of overall hp and torque like you would read in an advertisement or one of the Car Comic books, that they are pretty close!! Remember to that the engine was tuned for the Leach's...could there be more hp/torque coaxed out of the thing for the other headers with some tuning??? Maybe???? Love to show ya what a set of Lemons do...But, maybe another time!
If you think about it the modern unblown dragboat that runs no quicker than 9.00's spends it life with the new deadwater starts in the 6000-7500 range...Maybe more on the low end depending on prop burn, Are the zommies gonna kill that much HP/torque...ya probably couldn't feel it if you had the tune up right...so for a lake boat? I say Zoomie away!!!
Hope some of this was useful!!!
Last edited by DaveSammons; 04-16-2012 at 07:31 PM.
Dave, thanks for posting up numbers instead of some of the theories that have been thrown around (including myself in the throwing). Numbers produced in a careful dyno session always trump what I "wanted" the dyno to tell me. I will refrain from questioning the details as the trends there are close enough to answer my basic questions. Being that I can't shut my mouth I will reiterate what you said as the size of the pipes are important.
If you don't mind we asking, did you play with different diameters and lengths on the dyno?
Nice stuff guy's, and special thanks to Professor Sammons, that is a Great share on your part, keep them coming and I'll let you know what we find when we start comparing the old known performance numbers with the headers to the zoomies..... Thanks Scott