BadDog

Thanks, I wonder why ithere are so many recommending the 741 for a 502? Is Desktop Dyno that far off? Seems most opinions say to run the 741 yet these numbers show the 731 to be best? It is only off by 7 or 8 hp and ft lbs. at the practical limit of 5500 and way better in the middle.

GO4BROKE

Desktop Dyno is very accurate IF all the data used was accurate. I.E. I would need the flow bench #'s for USA1's ported heads to accurately use the D.D.
I think that comparison between 2 cams is where DD is most accurate. The peak #'s aren't as important as seeing the difference in #'s between them.

US1 Fountain

Tim, like I mentioned before, if I had to replace the cam, I would have gone down to the 731. No facts to back it up, just a gut feeling. I originally ordered the 731 cam as it was a step up from the HP500 cam, yet not so radical. My 1st engine builder talked me into the 741 after he talked with the Crane rep. The rep said the 741 was more suited for higher rpms. I agree that the 731 appears to have more practicle power range use.
CheckmateF1 had his 400 hr stock hp500 rebuilt this past spring. Originaly outfitted with the 741, he had more power on his worn out motor before the rebuild. So his builder sent him the 731 to install. Said the difference was very very little, if any.
Confused even more now??????

Back4More

How about the 761? It's in between those 2.

BadDog

Yes, this is puzzling. Perhaps what is missing is that with a ported head the 741 may make more power in the middle than the 731? I wonder if it could be worked backwards in the absence of the flow data for US1Fountains flow numbers. In other words modify the flow numbers for the head until the peak numbers matched what was actually recorded and then compare the 741 to the 731. My main concern in using the 741 over the 731 would be carburetion changes. How would jetting between the two cams change if at all? I would be using the carb with the jetting Jerry had used with the 741, I would not want to have to start all over again if the 731 was used. This is getting weird!

I did not see a 761 listing for the Gen 6? What was the full Crande part number for the 761 for Gen 6?

Tim T.

Scott

I ran the numbers and came up with the same results with ported heads (I need to find my flow numbers) so I can get an accurate comparison.

I tried to start a new thread on this the other day I felt bad about taking away from this post. Dead Post

I did all this research last year about this time. Want to guess what cam I chose?

Bobby,
Thanks for the offers for help but I am not trying to make a choice I was trying to find out why? With the input of you and others plus answering some of my own questions I think I have a pretty good understanding.

US1 Fountain

OK guys, heres the flow numbers for my heads that I got from Bruce. Take that with a grain of salt as I wouldn't be at all surprised that he actually never flowed the heads and just made up some numbers. Don't ask me any flow questions other than what I post about how, what, where or when. I'm a head idiot. To bad I don't have a scanner, I would scan my dyno sheets at different timing for all the other numbers.

Lift@ Intake Exhaust

.200 134 150
.300 200 166
.400 267 195
.500 300 224
.600 332 236
.650 344 240

BadDog

It looks like the choice may come down to the 761. Looking at the numbers for the 761 on the a 454 with the 177 it seems it has as much peak as the 741 at 5500 and better down at 5000. I would only assume from looking at the 502 with 250 that the 761 would have similar traits. I asked Go4Broke to run the numbers for the 761 on a 502 with midrange and peak numbers. The 761 is not a catalogue cam, they have to make this one for you. Any opinions?

731
http://dab7.cranecams.com/SpecCard/D...1=Display+Card

761
http://dab7.cranecams.com/SpecCard/D...1=Display+Card

741
http://dab7.cranecams.com/SpecCard/D...1=Display+Card

GO4BROKE

OK, 761 cam, stock 502, b&m 250, 1050 dom, stock heads
Sorry Bad Dog, rpm's only come in increments of 500.

761

3000=339hp, 594tq
3500=402hp, 603tq
4000=463hp, 608 tq
5000=556hp, 584tq
5500=564hp, 539tq

GO4BROKE

plugged in the head flow #'s for US1, now the #'s are too high!
5500rpm's-655hp, 626 tq
there must be another piece of data scewed, probably the exhaust. In forced induction applications I can't select different exhaust. These #'s are for dry (auto style) headers.