The 4v head flow good numbers,.. they always have even back to the B heads. But they are still only run a 170cc intake runner. Ford used IMRC plates in order to compensate for the lack of low RPM velocity in early versions of these heads. FR500 heads are only 160cc heads. The latest heads IIRC are 177cc but they use 'VTEC' which helps give them a cam profile for low end torq and then another for high rshared_pm HP. I've yet to see a SBF cam that works well on both ends of the spectrum.

The lack of velocity using a larger head on a small engine will cause low end torq to suffer, but it will definitely make good numbers on the big end. The right cam choice will be cruicial for good street manners. I think he will have to give up some of the top end hp in order to maintain a good idle that doesnt sound like a machine gun.

Going with EFI should result in a smoother idle than with a carb application. The IAC is constantly trying to smooth out the idle and with the speed sensor working properly it should bump idle during coasting so there 'should' be less bucking and kicking with EFI.

I guess it have to come down to trial and error as far as cam choices go. I can provide a video of how a carb'd version with 185 heads and a NX274HR cam sound. I experienced low rshared_pm bucking with both EFI and carb with this particular cam.

Hurst

 

Look at the specs of some custom ground turbo cams....They tighten up the lobe seperation to keep up velocity, and not bleed it off in overlap.

 

Thats turbo though,.. apples and oranges compared to an NA motor. You can run big intake runners with power adders,.. they artificially inflate the velocity and will make big numbers with big runners. If I had ever sprayed the 150 shot I was going to on my motor it probably would have broke something. Wishing I kept that kit now but at the time it was smart to sell. Out of boredom I was tempted to spray my truck,.. LOL.

 

Not speaking turbo, was speaking about a cam profiles. Same way some people have 13.1 compression and run pump gas...its in the cam

 

Most turbo cams run a split duration,.. similar to the nitrous cam I ran. I dont see where that will help velocity on a small motor with big heads. The only thing I see working is big rpm's. 185 heads really arent that big,.. but with his intake choice a similar motor with 165 heads and a larger intake would probably beat him on the street and definitely get him off the line at the track. I had the same problem running Bitemark. I treed him but he pulled me hard off the line,.. I had to play catch up on the big end.

Also IMO it would be a little more than the cam to run 13:1cr with pump gas. Timing and A/F would be critical as well. I personally wouldnt do it... thats a fine line to walk.

Hurst

 

Yeah, the heads at .550 lift (what seems to be the sweet spot for power/manners based on the graphs on AFR's site) are flowing ~275cfm. That fucking intake, being ported, flows just about 320cfm. That doesn't even match up a little. One thing I'm confused about, though. Everyones always swapping out for larger throttle bodies, but the stock throttle body already flows a shitton. Those aftermarket TBs flow 800-900+cfm.

 

off topic here bas ass mo-fo, lol...are you still selling that block or are you using it?

 

I actually traded the whole thing for a different motor. No boss block, just a stock one, but still a forged rotating assembly, girdle, fresh(ish) rebuild, and the heads and intake on it.