At this point I am more or less just updating this thread because I know how pissed I get when someone starts a thread but never posts resolution once they get it figure out...

So, I did finally get the car back, turns out the car was way over jetted on the primary side which was resulting in instant flooding. I don't know how it was engine dyno'd like that but what ever.... I have had the car on the road for about 200 miles now, have been adjusting the carb even more, squirter sizes, air bleeds, main jets and PV. Minor dial in adjustments. The car pulls strong and combined with my 0.82 5th gear ratio, no down shifting needed when passing. The thing launches like a rocket. Have not yet put it on a chassis dyno, going to get at least 1000 miles on the engine and a hot valve lash adjustment before I do that. I am very happy with the car. There will no doubt need to be some more secondary adjustments when she is on the dyno. The car is finished, just installed a new custom stainless 3" exhaust, Kooks 1-7/8 primary headers through super 40 flowmasters. I love the MSD programmable 6AL-2. I haven't even started to dial in my timing. Seems to like 21 initial. With that unit and a PC, you can adjust you timing curve real time. Anyway.... about the only thing I may change on the car is go to a hydroboost brake system that ties into the power steering pump. The brakes are a little weak. My vacuum at idle is around 8". After I get her on the dyno, I will post the numbers.

 

Glad to hear it was just a jetting issue, what did you end up having pri/sec for jets? I think your hp/tq numbers are impressive for the CI size. By the way, don't ever get caught out in the rain (unless you're a Rainx user of course).

 

Haha...I use RainX for sure. I have the canister but just didn't get it back on....

The jets: 79/85.

 

I did ALOT of research when I was considering building a near 700 hp sbc and what I found was that yes 700 hp was attainable BUT I would have to spin it up real high to get that number and to have a decent curve it would have to spin close to 8k. With the 245 heads you have, your dyno curve does not surprise me one bit. At 6k those heads are just getting started.
I decided to build a big block motor after the info I learned about the 434 and I ran into a similar issue with the heads. To make 850 hp I would have to use something like a Brodix Head hunter head and that would also have so spin real high to make that hp with a decent curve.
I had to bite the bullet and spring for 20 degree heads-it was the only option to make the power I wanted at a moderate rpm.
Your builder should have informed you of the limitations down low with that head.
It's still a killer motor but I think will always be lacking down low and on a street or street/strip motor its just not ideal as you are finding out.
Just build a valvetrain that can handle the higher rpms and let that motor live where it wants to be and drive the crap outta the thing.
You would make BETTER than 700 peak and the thing would be a beast with a killer curve.

 

i make around 650hp with my 427... and it pulls from 2K-6500... 1.5-2K may work if the car is rolling below 850-1.5k is good for idle and initial takeoff with a fathering of the clutch... But that being said, I also have a lightweight drivetrain which is not a big help with low RPM's... it is still very steerable..



O, I'm back by the way, if anyone missed me:-)




When you going to put that 81tch on the rollers???

 

Paul- I owe you that! Your build is what inspired mine. I am going to put another couple hundred miles on her, change the oil, adjust the valves and then head to the dyno. Unfortunately a friend of mine who happened to own the dyno shop where all my runs were done over the last 15 years passed away. Shop is gone now as well. I wanted to buy it as a business but for sound financial reasons his family felt it was worth more money to liquidate it. Now I am on the hunt for another shop in the area. There is a place have just contacted not far from my house.

Not looking good regarding finding a dyno. Unless it is an LS injected engine or one they built for you, no one wants your business.
Update: I found a place in Dallas GA about 1 hour from my house that will do it. It is called Mo's Speed Shop. I figure early September for my first pull.

 

Update- Dyno day still has not happened. Life keeps getting in the way....plus just not happy with the Carb. I decided to try putting the metering blocks and fuel bowls from the 950 onto my 830 cfm body which has annular boosters. My 427 combo put 450 to the wheels with it. It also has 50cc accelerator pump which works very well on these large displacement small blocks. Maybe increasing the size of the PVCR's would have eliminated the need for a larger pump. Also I found a dyno facility only about 7 miles from me which helps as the only other places I could find were an hour away. Going to try and schedule pull in March sometime. The carb tune is very close to what my 427 was with some larger primary and secondary jetting.

Throttle response down low has improved as well. I may also try swapping out the single plane AFR spider and replacing with their dual plane.

 

(I should have asked for all specs, I am surprised in hind sight that he never offered to provide compression and leak down numbers and obviously never bothered to tune the carb)

 

Finally have some numbers!! I ran her with the 830 cfm body instead of the 950. I limited the run to just over 6000 rpm but based on the curve my guess is she may still have another 20hp still in her. I have not yet review the data. I logged the O2, rpm, MAP and throttle position for all three runs. The numbers are:
Max RWHP Power: 559hp @ 6100rpm
Max RWTQ Torque: 503 ft-lbs @ 4800 rom

Engine Dyno w/950 cfm carb:
Max Power: 694 hp @ 6400rpm
Max Torque: 588 ft-lbs @ 6000 rom

 

That's +144hp/+50tq over my CNC 415ci (dynojet). Outstanding!

 

Great numbers! My new build is similar to yours, and I'm waiting for good weather to put in some break-in miles and get to the chassis dyno.

 

Thanks! I was looking at the data this morning and everything looked pretty good but I am not sure that was my best run. The last run we had it a near 6500 rpm. I need to call them tomorrow. Another thing I noticed is at WOT my manifold vacuum was about 3 to 4"hg of vacuum. I know when people talk about WOT it is always said one should be near 0" of vacuum. Maybe in a perfect world but I wonder what is typical with this engines. My vacuum climbed to near 5" on the 6500 rpm run. I am going to post this observation as a separate post to see what others may have seen. Not many C3s out there have MAP sensors.....

 

Don't worry about the chassis dyno......go to the drag strip, MPH over 1320 at a known verified weight will show the truth, pretty simple.

137 MPH @ 3500 pounds?=693 observed crankshaft HP


Alan Rothman's Corvette

460 RWHP
3720 Pounds
10.59
127.9 MPH
3.36 gears
Turning every piece of power robber you could turn

Now what does this mean-it means one thing.....chassis dyno's are good for one thing... tuning for a change, that's it.

 

wow.
144 hp with a 120 cfm increase?
guess that settles cfm needs
do you have any fuel / air ratios to go along with the carbs?

 

Agree however not everyone has a drag strip in their back yard or one that is easily accessible. My car is a convertible and most strips around here would require a roll bar. The dyno is a means for me to track progress and maximize the engines capabilities. Two years ago the engine was a 427 with different heads,valve train and intake. It put down 450 rwhp at 5500 rpm on a dynojet. The torque was 485 at 3600 rpm!

My new curve shows me at about 450 ftlbs at 3600 rpm.
At 3000 rpm I was at 450 ftlbs now I am at about 400ftlbs.

this new engine is not as responsive down low like it used to be and that is a trade off.

My original plan was to bring it to the strip but I really don't want to cut the car up and put a cage in it. There may be times that require a cage, last time I checked it was better than 12's required a cage but that was for coups. My guess is convertibles would require one regardless.

 

See attached PDF. Shows My AFRs and other logged data. I run around 13 to 13.5 on the primaries and when the secondaries tipped in it looks to have dropped to about 12.5.

 

Would it be possible to put the engine dyno test up, I couldn't see it any where.

 

 

I'am looking for the real dyno test, example below

 

So your are looking for the engine dyno or chassis dyno results?