I took my Corvette to the local DynoJet chassis dyno yesterday and made a few runs. This is the first time I had a chance to check flywheel HP vs wheel HP directly.



The engine is a pump gas 565 (4.60 bore x 4.25 stroke) Dart Big M, with modified AFR 335 heads and ported Vic Jr intake. The cam is a custom solid roller with lift in the mid 0.7” range and .050 duration high 260 / low 270 range. The carburetor is a unique Twin Blade unit rated at 1220 CFM on a 4150 base.







First runs were pig rich, so we pulled some jet from the carb before making full pulls. Once we got A/F above 12.2, we made a full pull at ~ 36 deg total timing (~ 705 HP). Next bumped timing to 38 deg total and got the best run (715 HP). Nudging the timing up to 39 deg lost power. We were going to make another run at 38 deg timing and slightly less jet, but the bushing in the accelerator rod pulled out and was lost in the dyno pit so that put an end to the day. Its possible there is another 5 to 15 HP from further fuel curve trimming.



Comparing engine to chassis dyno results was interesting. The offset was perhaps less than expected, but not surprising given the stingy engine dyno at PK Machine (also built engine). Paul does great work, and his engines typically run better than raw numbers would suggest. In any event, the offset was as low as 5% at lower rpm, and about 11% at peak HP. Note the engine dyno runs were made using my full exhaust system.

All in all a good day – made decent power and nothing of consequence broke!

Mark

 

Beautiful '67, and nice dyno numbers!!

Very unique carb design!

 

Damn Mark, that is very impressive. Awesome car!


Bill

 

Thanks! Good news on the carb is its not just a pretty face - it works very well. Street manners are very good!

Thanks Bill, how's progress w/ yours? Had a chance to install the shifter?

Take care,

Mark

 

Would love to see a video and hear that motor sing

 

I have video...but not sure how to post...any help appreciated.

 

Impressive........love everything about it.
565's are my personal favorite Big Block.......they can take a lot of abuse......
But that is a hoot on the street!

Jebby

 

Big fan of those also, would love to hear it!
Cant imagine what having that kind of torque is like...thats a real sleeper you got there.
Driving impressions? Entertain us broke dreamers!

 

Put it on youtube and then you can post it on the forum as an embedded video using the "yt" tag.

 

 

Very impressive.
Nice build all around.

 

It is a lot of fun! Traction can be a challenge although drag radials help... a little...

It's fun - with decent street manners as well. Obviously a lot more power, but it still retains the essence of a period correct Corvette. Just more so!

I've never posted to YouTube before...may have to look into it

Thanks...tried to keep a reasonably stock appearance

 

I used to use Photobucket to host videos. I just tried postimage and it can't upload *.avi or *.mvi I can't imagine running a 565 through the gears!

 

Wow, am i lucky i stumbled onto this thread!

Those are some awesome results! You have got to be happy with the numbers even with the limited number of runs you made. That carburetor looks like a piece of art. I would have loved to see a comparison to a conventional high cfm 4150 style carb.

Any closer to getting it out to the track? Hey, I had to ask!

 

I tried posting video directly as well w/ same results...running it thru the gears definitely focuses your attention!

Hi Steve, nice to hear from you, hope you're well. I did test carbs on the engine dyno (well tuned HP 1000 vs Twin Blade 1200) and the TB was worth ~ 12 HP. No to track...still balking at installing a cage. One of these years...

I'm planning to send you an email me in the next day or so - will be good to catch up.

Take care

 

That is just badass!!! Congrats on having a monster. That carb is a work of art wow!

If you need help on the video, I'll be happy to host it on my YouTube page. You just need to figure out how to get it to me. My part would be quick & easy. Let me know.

 

Thanks! I've got videos of both engine and chassis dyno runs. What would be your preferred way to send them to you - email? The files are less than 6 MB ea. Much appreciated!

 

Killer build once again Mark!

Now...I've just gotta plan a trip to come out and flog on it!! Love that car!!


JIM

 

I'm far from being a techie but email should get it done. I'll PM you.