High horepower Twin-cams?

[1owner69Elan]

No question about being skeptical regarding engine output numbers. Some people buy and make modifications based upon claims that such a mod will add "x" horsepower. Then add these claims up to arrive at an assumed output number to be bragged about. Clearly, need to be looked at with some level of skepticism when not backed up by some evidence.

To defend the numbers for my car:

1. The numbers come from a series of engine dyno runs (posted). These are not even back calculated to the flywheel from a rolling road.
2. The dyno being used, in my case, is regularly used to test a variety of twin cams (and other engines) for historic racing. Dave Vegher's (engine builder) engines are widespread in historic racing, at least here in the US.
3. If Dave's dyno was "juiced" it would have been easily picked up in actual on-track performance. Moreover, his engines are regularly "re-dynoed" (on different equipment) as racers look to tune them for optimum performance. Any major disparity from Dave's dyno numbers would have been flagged. Dave's customers would hardly stand for inflated dyno numbers and he would not enjoy nor deserve the reputation that he has earned.
4. My numbers, while exemplary, are not unique. If you look at twin cam dyno sheets from Tony Ingram, John McCoy, and other premier engine builders, similar types of output are evidenced on their twin cam builds via dyno runs and real world performance.

I have encountered a lot of skepticism about my build. Generally quieted by chronicling the build attributes, showing the dyno runs, and the fact that the builder is Dave Vegher.

In any case, my 2 cents, for what it is worth.

[1owner69Elan]

One-owner ?

Would you please elaborate on the design of the high volume airbox that gained 7 bhp? Any pictures?

See:

post280883.html?hilit=%20airbox#p280883

[rgh0]

Every time I see threads like this I tend to smile and somewhat disregard the numbers being flung around unless said numbers are accompanied by a dyno printout - which dyno is known to be properly calibrated and operated.

This is the price I gladly pay for being a cynic.

Yes a lot a engines are more wishful thinking than dyno reality. However the Vegher engine build and dyno curve attached above I would believe..

Incidently when I tested a 150 hp engine with and without the air box many years ago I saw a 4 hp loss with the standard airbox . Like I said above you need to do a careful build paying attention to all the details to get the sort of outcomes being discussed

cheers
Rohan

[elancoupe]

John McCoy/Omintech tractable street motor, 1950 cc, 180 hp, 160 lb/ft. With dyno sheets.

[Slowtus]

John McCoy/Omintech tractable street motor, 1950 cc, 180 hp, 160 lb/ft. With dyno sheets.

THIS - I absolutely believe!!!

I know the man, know the company, know what they do and I have seen his craft (not work, craft) and would be happy to clean up his swarf.

[rgh0]

I have learnt my understanding of modified twinks initially from Dave Bean and his catalogue back in the 80's which was the only source of information in pre internet days. More lately I have learnt directly and indirectly via the internet from the work of McCoy, Vegher, Stagg and a few others. i have done enough of my own engine builds and race and dyno testing to learn a lot also of what works and does not work plus i have a racing friend who I taught how to build modified twinks who has pushed our level of knowledge even further as he is now building engines right on the ragged edge in his attempts to out race 3 litre Porches and 6 litre Corvettes in his 1600cc S4 Seven. I have also spent a lot of time building computer simulations of various types of twinks and calibrating the models against actual dyno data to explore build many more variations options than you can do in real life.

I now have enough data and experience to tell what is bulls**T and what is real in twink HP claims. In general I would trust what McCoy, Vegher and Stagg claim they can do as i have seen the data , others I would subject to more analysis.

cheers'
Rohan

" In God I trust .... all others please bring data"

[PaulFinch]

John McCoy/Omintech tractable street motor, 1950 cc, 180 hp, 160 lb/ft. With dyno sheets.

Sorry for the thread revival but I’m currently thinking seriously about a high capacity twin cam build, maybe even utilising a new alloy casting.

Does anyone have any info on how McCoy gets his 1950cc capacity? Is it a bespoke long stroke crank or an 89mm bore with a crossflow crank?

Cheers

[elancoupe]

I do believe he has a bespoke crank. If you do Facebook, he is very responsive, will answer any questions.

[PaulFinch]

I do believe he has a bespoke crank. If you do Facebook, he is very responsive, will answer any questions.

Thanks, I’ve just seen that he replied to my question on Facebook yesterday but I didn’t get a notification. It is indeed a custom 86mm crank and bespoke rod combination.