sbf heads
Posting Guru
Joined: Dec 2003
Posts: 1,483
Likes: 1
From: Northern California
Hey P51, yeah, the flow characteristics of the GT40x is pretty good and should be adequate for most truck applications, I agree. But the flow #'s are considerably less than all of the aformentioned aftermarket heads. These aftermarket heads with the higher flows are more of a nessisity when you stroke out a 351 to a 393-408 and then you need that additional CFM. 
Elder User
Joined: Mar 2004
Posts: 660
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I checked some dyno numbers and you are correct pertaining to the AFR and TFS heads. The TFS Twisted Wedge has the best numbers short of a race car head, with the AFR being with in about 1% of the TFS Twisted Wedge. Those two heads show an average of about 14% better flow numbers across the board, than the Ford GT40X. More so on the exaust side. However, I need to point out that the AFR and the TFS heads out flow the other after market street heads by about the same percentages. The GT40X gives virtually the same intake flow numbers as the Edelbrock, Holley System Max, and so... The GT40X actually outperforms the popular Windsor Jr and some other after market efforts, by about the same amount (14%) that the TFS out performs the GT40X. So really were additional CFM is concerned, it would be wise to step up to the AFR or TFS, but several of the other popular aftermarket heads are no better than the GT40X, and some are not as good.
Posting Guru
Joined: Dec 2003
Posts: 1,483
Likes: 1
From: Northern California
I'm pleased with the TFS heads on my 393, but your right, you have push rods, guide plates and special pistons to spend $$ on for these heads. Mine have a stage 3 full port on them and could support alot more than what I'm giving them, thats for sure. I was surprised on the low flow #s on the exhaust side of the GT40x heads myself when I was reading up on them, I'll bet with a little port work and some larger valves they could give most heads a run for their money! 
Elder User
Joined: Mar 2004
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I'm very pleased with my TFS heads that I'm using on 5.0 Mustang. The first time I didn't get the pushrod length right, so I had to get new valve guides. I havn't ported these, but I'm sure that 5 liters don't really take advantage of the TFS's potential. I really need a 351 under em. A friend went with the Gt40X heads on a 306 with a comp cam and it dynoed at about 340 HP with pretty strong low RPM response. The main attraction of the GT40X head, other than using stock valve train componants, is the better low RPM and low lift flow velocities on the smaller displacement motors, I believe. I'm getting about that 355HP out of the TFS heads, and the relatively mild E-303 Cam on only 5 liters, but it's it little softer on the very bottom end, even with the E cam.
Posting Guru
Joined: Dec 2003
Posts: 1,483
Likes: 1
From: Northern California
It sounds like you've definitly put your TFS heads to good use! I'm going to be putting a 200HP shot of juice on my 393 after its broken in well, mine are the o-ringed version so I think they should hold up fine to the additional pressure. The blower crowd has been pretty fond of these heads from what I understand. Do you know of anyone using a blower or NOS with these heads and are they happy with them?
Cargo Master
Joined: Dec 2003
Posts: 2,735
Likes: 38
From: Sunny Florida
I work with a guy that has the TFS heads. I already mention I have them and love them. He had his heads ported and has something like $5k in the heads now. I think he installed akk ti valve train? He has a blower and his car is one bad mother. He doesn't even waste his time with corvettes, he looks for vipers. This is a small block 302 and he has plans to upgrade the SC.
Cargo Master
Joined: Dec 2003
Posts: 2,735
Likes: 38
From: Sunny Florida
Originally Posted by 94F150-408
Sounds cool RTM, any idea what that akk ti valve train is? I havent heard of that before.
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Elder User
Joined: Apr 2003
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I put world products 180 cast heads on my 302 and have absolutely no low end power, I can't even keep up with traffic until the rpm slowly (very slowly) climbs to 2500+ I thought I'd see an improvement not a loss of power, at this point not a very good investment . I've tried 3 different carbs and I'm now playing with the dist. to try and get some power back. Any suggestions???
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
Originally Posted by daerhldgs2
I put world products 180 cast heads on my 302 and have absolutely no low end power, I can't even keep up with traffic until the rpm slowly (very slowly) climbs to 2500+ I thought I'd see an improvement not a loss of power, at this point not a very good investment . I've tried 3 different carbs and I'm now playing with the dist. to try and get some power back. Any suggestions???
Elder User
Joined: Apr 2003
Posts: 627
Likes: 1
this truck ran good until the valves burned in the original heads and I changed nothing else but the heads and now it's a slug , even though it starts and idles perfectly. So what I'm saying is performance shouldn't be worse than stock heads!!!
Posting Guru
Joined: Dec 2003
Posts: 1,483
Likes: 1
From: Northern California
Your right, the performance shouldn't be worse than stock heads, only better, so something else is going on, you probably should retrace your work that was done. I cant think of any one thing off hand that would have caused this.
Elder User
Joined: Mar 2004
Posts: 660
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If the valves burned in the original heads, then you may have a too lean condition at low RPM. A higher flowing head will need typically a richer jetting than before, so you may be super lean now. This would torpedo your low end tourqe big time. The Rousch heads are pretty mild, with still fairly small ports compared to AFR, or TFS, or even the GT40X..ect, so they should have good low speed port velocities, but this will require even more fuel. Just an idea.