you have a motor that would easily rev to 6000 rpms, and would live a long and happy life reving to 6000 rpms why would you want to take it upon yourself to never go past 4900 rpms. 6000 rpm motors live for ever. My car would go from 3000-6000 in the blink of an eye, especially in the first 3 gears. I think I read you have 4.10's so yours would be even quicker. 13.0-1 at 4900 rpms is crazy lean.. I thought you were 13.0 at 6000 rpms or so. I hope you have a msd with a rev chip of 46-4800 or so cause heaven help if you rev it to 6000 or mis a shift. you lost a half point of a/f in 240 rpms. That's not slowely creeping that's crashing. Not trying to bash but I can't believe anyone would let you walk out the door like that. There is no intercooler in the world gonna save that car on pump gas if rev it anymore rpms and probably would only take one time. with fuel dropping off like that it would likely be off the chart by the time you realized you screwed up. If you feel safe then again good luck with it but i'd address your fuel issues and pulley it down so you use a broader power range and make the same hp and keep the a/f fatter all the way through the power range. good luck.
FINALLY got the car dynoed!!!!
- Thread starter SmockDoiley
- Start date
I hope you know the 03 cobras come leaner than that. Read the results, I said 4900. I only take it to 4900 because the carb is too small to support more and that is where the power is maxed. Why would I take it to 6000 if its not making power then? Besides, that thing will last forever if I dont take it past that. My limiter is set at 5000k. Trust me, 14.7 to 1 is perfect A/F by theory, but performance dictating richer is safer. 11s and 12s is really rich, and I dont see new cobras getting into the 11s.
Just for a comparison. The Kenne-Bell '03 Cobra project in 5.0 Mustang ran the A/F ratio at 12.8. And they were pushing more boost than me. And thats fine if you can rev your engine out to 6k and make 460 horses, but if I can make 56 more horses with 1000 less rpms than it looks like I'm doing just fine.
I'm tempted to go with a larger carb and intake to get the A/F in the 12's at higher rpms but next thing you know I'm building lots of boost and power and I blow the engine. Pushing the engine to 6000 would net 13-15 lbs of boost and probably another 50 horses at least if I upgrade the carb and intake, but then I'm closing in on 700 flywheel horsepower. I plan to get a sportsman block, forged crank, do the carb and intake, and port the heads. This would net 6500 rpms, 15 lbs of boost, and about 800 flywheel horsepower.
SmockDoiley said:
03 cobra's come leaner than what 13-1. No they don't. unless you want to count at 3000 rpms where they aren't making any power. even with the i/c they go PIG rich and is the reason people can up the boost without a chip. Heck they are 11.3 at 4900 and go off the chart rich at 6300
here is the details of the dyno
http://dynoperformance.com/search_details.php?ID=561
here is the chart
You asked why you would take it to 6000 if it's not making power then.. precisely my point.. your induction is too small and your fuel is nowhere to be found hence not making power there and why it's dangerous. the x cam will easily support 6000 rpms. If you were to put a larger pulley and make the same boost at 6000 rpms then your power curve would be much larger and broader and would not sacrifice longevity. that's why I would make it safe until 6000 rpms.. each to their own but a 4900 rpm motor is too short IMO. As far as a/f ratio's being perfect at 14.7.
I guess some lessons are better learned the hard way.. esecially with boost. Again good luck. i'm not trying to bash you but you asked for opinions.SmockDoiley said:
which kenne bell 03. the one they are makeing a ton of boost and running race fuel. then yeah 12.8 wouldn't be all to bad.. 21 extra octane makes a huge difference. and take what you read in the mags with a grain of salt. they tune for max power not longevity, streetablity, and reliablity.. they look for huge numbers to sell mags.
Michael Yount
Mustang Master
Based on reading a bunch of posts over time, it seems to me that there's not just a single number where the stock block (or anyone else's) starts to be overwhelmed. Given quality control, and the nature of how the engine makes it's power (boost stresses differently than nitrous which is different from one that's set up to rev to 8000) it's more like a range of numbers. And I'd have to say that 600 is at the top end of that range. I wouldn't be comfortable consistently asking a stock block to handle that much. Stock blocks have been split at power levels well below that. I'd say that for reasonable reliability, if you stay below 500, you should be in good shape; if you're in the 500-600 range anything can happen at anytime, and if you're over 600 it's not if, but when you'll break the block.
SmockDoiley said:
Yes they claim fully race prepped and girdled stock blocks will support 600 hp.. but that depends on the builder. Not all will claim that although I will tell you I once called one of the companies you mentioned and asked them on their fully race prepped top of the line stock block if they would recommend running 600 fwhp and he flat out said that they rate them high but he WOULDN'T run that much out of it on stickies and expect it to last. Like Michael said 5-550+ fwhp stock block is a gamble.
The sportman is not much different than a stock block.. little extra material is all. I can't find the link that compared it to the real blocks (R302 and Dart) but there isn't a whole lot of difference in the B50 and stock and it's worlds apart from the Dart's and R's. I heard that FRPP has actually dropped the hp rating on them to 450 down from 600 due to failures.. I wouldn't waist my time on a B block, here are a couple of links on the subject. Do a search and you can see, the B block is the just like a stock block in it's a gamble. some guys last and some don't. I definetly wouldn't go past 600 fwhp with a B.
http://bbs.hardcore50.com/vbulletin/showthread.php?s=&threadid=11516&highlight=sportman
http://www.corral.net/forums/showthread.php?s=&threadid=429917&highlight=sportsman
88stangmangt
Active Member
A little off the subject. But I'm wondering something. If the 351 blocks are a lot stronger due to more material and bigger mains, why does DSS rate them at the same power level as the 302W. Also, since the 351 is stronger, and the motorsport 351 is suppose to be stronger than a 351, wouldnt the sportsman 351 be pretty friggin strong. I know it again wouldnt compare to the other blocks out there, but Im guessing it should hold a lot more power than a stock 302. Honestly, I'm just really screwed because I want to do a 408 with my blower, but Id have to get a dart block because a combo like that would easily without trying make 800 flywheel horsepower.
the FRPP 6010-A351 SPORTSMAN BLOCK 351w is a whole different story.. that block is actually a very good block for the money and will support upwards of 800-900 fwhp according to a couple of builders I have talked too. Still worlds apart from the 351 dart Iron eagle but it's a nice block. I'd probably keep it closer to 800. It's still 2 bolt mains but with a girdle I wouldn't be to worried with the correct fuel system,tune, and internals. Can't even compare that to a B50 302 sportman block. I almost went with the 351 sportman block in a 408 but opted for a Dart Iron Eagle 418 since the sportman 351 is currently unavailable and FRPP isn't supposed to make them for a few months. The sportman talked about in above post is the M-6010-B50 since you said you wanted to see the potential of the 347 in post #14 and they aren't worth much..
I say screw it, I ordered the proform main body and Torker II intake. If I'm going to break this engine, which I wont, then Im going to do it now before I go to the track. Besides this will help level off the A/F so it doesnt keep rising. Larger means more jetting. I figure I'll start out with 2 more jet sizes, and dyno from there. I have to do this, dyno, struts, C/C plates, and alignment by friday night. I'm nuts, but its all a learning curve. This block will hold damnit!!
HO93LX302
Founding Member
Hey nice numbers you got there Smock... Do you plan on running it at the track anytime soon?? I bet that you should get a mid to low 11 on slicks with a good launch
I have slicks and I plan on running it, but Im not sure how hard I want to try and get traction. The more traction I get, the better chance of it breaking. I think I'll use the slicks but not heat them up with a burn out. Itll be better than drag radials but still not totally hook. Trying to be a little cautious, plus I just got these gears installed. I feel bad because Im really pushing the car to get done. Its really crunch time for me.