Does anyone know which head would be a better performer for out-the-box performance between the Bowtie phase III with it's 184cc runners and World Sportsman II with it's 200cc port. I know bigger doesn't mean better, just take a look a AFR's 190/195. I got a Pro street 383 with a victor jr intake and a .630/.630, 288/296 ad., 252/258 @.050, with a 106 LSA. I would like to make my power by 6200-6500.

I got a chance to buy either for the same money. Any thoughts which would be better?

My Bro-in-law runs a box stock set of Phase II Bowtie heads on his mild, 9.6CR, XE268 cammed, 383 in his 3890 lb '69 Chevelle.
TH350, 3K stall and 3.73 gears...he runs 12.80s on ET Streets with 1.76 60fts. Good TQ!
I talked to Mike Stark at CFM in Indy about tweaking on these heads...he said with very little work, he could easily get another 25-35HP out of them.

Looking at your cam .630/.630, 288/296 ad., 252/258 @.050, with a 106 LSA I am assuming the only street duty you see will be driving to and from the track. With that consideration I would recommend that you use the World Sportsman II Iron over the 12480034 head.

Stan Weiss doesn't even list flow values for the Sportsman head for 0.10" and 0.20" valve lift. The Bowtie head's flow is centered around 0.40" which is were you would want it for the street. (@ 0.30" lift flow is 205/123 60.00% 422 hp, @ 0.40" lift flow is 225/123 54.67% 463 hp, @ 0.50" lift flow is 210/127 60.48% 432 hp-469 hp, @ 0.60" lift flow is 209/127 60.77% 466 hp).

The Sportsman is centered on 0.60" lift which is were your cam tops out (@ 0.50" lift flow is 240/164 68.33% 494 hp, @ 0.60" lift flow is 243/162 66.67% 500 hp 542 hp, @ 0.70" lift flow is 223.8/151.8) With these heads you may want to look at a 0.72" mechanical roller some time in the future.


Larger Dave

Dave, I drive this thing in town and where ever. It pulls enough vacuum, with a canister of course, to work my power brakes. I don't take no long, highway trips with it no, but it has decent street manners considering.... The heads on it now are Dart Iron Eagle 215cc. I need those for another project and I think they are too big anyway for the 383. It flattens out about 5600-5800 on the big end and I think it may be velocity/vacuum related. Like the runners are too large to keep up the velocity with low vacuum in third gear. Sound right?

Ray,
I ran Dart Pro 1 215cc heads on my 385 and even with a hyd flat tappet cam it would pull to 6500. I don;t think your lack of upper RPM pull is due to the heads, if anything they would start working even better in the upper RPM range. I also ran those same heads (215cc) on a 383 with a small solid roller (about the size of your cam) and it pulled to 7200 RPM no problem. I understand you need the heads for another project, I just wanted to give an aopinion of if the heads were too big or not. They are on the large side for a 383, but it depends on the engine.

I have never seen flow numbers for the Bow Tie heads but I did run Sportsman II's for a while. They make good power but you will need touch up the bowl on the exhaust side and a 30 degree back cut on the exhaust valve is highly recomended.

Sounds more like a valve float issue or and ignition issue. Those heads on a 383 should easily pull to 6500rpm or higher. Is your cam a solid flat tappet? Do you have enough spring pressure? I woul also use the World heads over the GMPP heads, but I'd use another set of PRO 1's or Trick Flow or Edelbrock Performer RPM's if I had the budget.My friends 406 that we built uses the Pro 1 215cc heads (with the springs that came on them) and a 245 @.050, .550" lift 108lsa hydraulic cam and that engine pulls to 7000rpm's no problems.As faras velocity, that's more important at lower rpm's.You may even need to change the cam to move your power range up in rpm's a little, either add duration at .050" or more than likely you'd need a cam with a slightly wider lsa. Tight lsa'a help torque by moving the torque into a more concentrated power range usually at a lower rpm. Although I still think it's another issue why your engine won't rev higher, this is definately a possibility that that cam in your engine is all done by 5800.

Thanks men, all good info and points. My Dart 215's came out the box set up for roller. I have 195lb seat pressure at an installed height of 1.9". This engine has done this from day one of building it and I have chased my tail the whole time. I change the ignition completely from a Mallory Hyfire to MSD 6 AL and billet distributor. Then I changed my mallory fuel pump to holley blue pump. I have tightened my valves from .026/.028 to .020/.022 and no difference. I changed from a 750 modified dp to a proform 850 dp and still no difference in nothing.

I got a 4.11 with 31X18.5X15 tires in the rear. I'm going to a 30X12.5X15 and try that. I went over my cam specs and checked my springs with cam motion and with my combo, I should pull to 7200 but they said I have too much tire and not enough gear for my HP. Dropping to that size tire is "supposed" to be like adding a 100hp to my engine. I guess I'll see.
Anymore possibilities is greatly appreciated.

What kind of compression are you running? Did you degree the cam? If so how did you set it?

What kind of compression are you running? Did you degree the cam? If so how did you set it?

I am running 10.5:1 CR and I degreed the cam the first time at 106 center line and ran it for a while. Then I advanced it four degrees without a degree wheel, just used the crank gear marks which were accurate at zero when I degreed it the first time. The only change it did was raise my cranking pressure from 180 psi to 200 psi. No change in 60ft, 1/8, 1/4, or MPH. I don't know why. Seems like it should've gained low, and maybe lost high, but nothing changed.

Ray, sorry about the race only comment I saw the advertised figures and my speed reading missed the 0.050" numbers lift seeing only at std lift. That coupled with your displacement makes for a great lumppy street cam. As to your 60' times I assume you are running slicks; if not, the lower torque you added may be slipping either tranny clutches (assumes automatic) or the tires.

Larger Dave

When you advanced the cam, Did that make any difference in your powerband? It should have brought it down, which would explain why it doesn't want to RPM. Maybe you just have a "bad" cam. I don't see any reason why a solid cam of that size would not want to rev, unless you are running into valve float.

Ray, sorry about the race only comment I saw the advertised figures and my speed reading missed the 0.050" numbers lift seeing only at std lift. That coupled with your displacement makes for a great lumppy street cam. As to your 60' times I assume you are running slicks; if not, the lower torque you added may be slipping either tranny clutches (assumes automatic) or the tires.

Larger Dave

Larger Dave, I run sportsman pros. They don't spin. We checked that first. The trans is pulling too. It's a th350 manual valve body and it's good. I ran it all last year doing different things to try to get it pulling on up in the RPM range. I don't know what else to check. I appreciate the thoughts. Sooner or later, something will come up that I haven't tried. Thanks for replying.

When you advanced the cam, Did that make any difference in your powerband? It should have brought it down, which would explain why it doesn't want to RPM. Maybe you just have a "bad" cam. I don't see any reason why a solid cam of that size would not want to rev, unless you are running into valve float.


When I advanced the cam, it made no difference in 60ft, 330, 1/8 or top end. It flattened out at 57-5800 before and after. The springs were checked ruled out. The pressures are in specs with the cam. The bad cam idea may be on to something. I may go next size up if nothing else works. The next one will be from Cam Motion. Thanks for the ideas and thoughts.

What about tire/gear ratio? I went over all the specs with cam motion and they said I'm trying to pull too much tire without enough gear/engine. The theory is when I lug the engine in 3rd, I have no vacuum coupled with large runners. That's a sticky theory, but I needed new tires so I have some 30X13.5X15 down from 31X18.5X15. I will see what it does with that. What do yall think about this theory? (Fishing in the sewage ditch--Maybe)

Well you can rule that out by just keepingit in 2nd gear, does it rev over 5700-5800 RPM? If so then maybe you don't have enough HP to pull 3rd gear. If it still won't rev above 5700-5800 in 1st or second then the issue is in the engine.

Are you running a gear drive by any chance?

First will run up quick, 2nd takes a while, and 3rd just lays down. No gear drive.

4.11's with a 31 inch tire seem kind of high, even with a 30 inch tire you're changeing to. Small blocks like to rev and like alot of gearing. With the 31inch tires I'd run 4.56's, maybe ever 4.88's.With the 30", I'd still run 4.56's. My Pontiac 400 runs out at 7000 in the traps and I run a 4500 convertor, 4.56's and a 28" tire @ 121 mph. It sounds like you need more gear, on shifts, your rpm's may be falling out of the engines power range and far away from torque peak. If you shift at 7200 in first gear, your engine is falling back to around 4400-4600 in second, and 4700-4900 on the third gear change.This dosen't sound too bad, but I think 4.56's would be better.

I have to agree it sounds like the combo wants more gear.

This is what I think the problem is coming come. I would like to cross the line 6500 or less. I got cast crank and really don't want to turn it much higher than that. But, on the other hand, I want the engine to pull from start to finish. If it ran 11.50 pulling, I would be happy. The difference in weight of the tires from 31X18.5 Sportsman Pro to the E.T. Street 30X13.5 is tremendous. One inch shorter and a lot less wide got to help something. I could have probably went to a 29" tire without running out my max rpm I want to turn, but was unsure. I thank you all for your post.