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Guys the flow numbers from GPI aren’t promising….Tonys 243 heads flow more than the BTR rectangle ports do. This endeavor isn’t a whole lot different from a GM LT head. Me and Tony have been been discussing this….I’m not sure this is going to be everything we hoped for. Time will tell. Hopefully I’m terribly wrong here.
can you share the mamo 243 flow numbers? I dont think ive ever seen a 243 head flow much over 320cfms if at all. The cathedral canted valve heads flow over 350 at .650. I dont think a 243 head is capable of that.
Here are PRC ported 243s for reference. not doubting tonys skills, i just dont think 243s can be modified to get near 350cfm on the intake.
can you share the mamo 243 flow numbers? I dont think ive ever seen a 243 head flow much over 320cfms if at all. The cathedral canted valve heads flow over 350 at .650. I dont think a 243 head is capable of that.
Here are PRC ported 243s for reference. not doubting tonys skills, i just dont think 243s can be modified to get near 350cfm on the intake.
I've yet to see a pump 427 with 243 heads make anything close to 800 hp like the canted valves.
Last edited by 65LSXNOVA; Apr 19, 2026 at 04:39 PM.
Canted valve combustion chamber Canted valve exhaust port
I bought the btr heads after seeing the horrible port alignment the tfs 235 had on my single plane.
so far these look very promising and come standard with iron guides.
they call them powdered metal, which is also what is in GM OE heads. I think that's different than iron
they call them powdered metal, which is also what is in GM OE heads. I think that's different than iron
tomato TOMOTO.
Tooley says he got with the GM supplier for their "powder metal" guides and had his made by them but changed the material in the guides to make them stronger than GM guides.
I've been seeing around 360 cfm at .650 lift.
More and more I dont think flow bench numbers at the end of the day mean as much as what alot of people think.
Steve Morris has said the same recently and Tooley also.
I've been seeing around 360 cfm at .650 lift.
More and more I dont think flow bench numbers at the end of the day mean as much as what alot of people think.
Steve Morris has said the same recently and Tooley also.
Flow bench is just a tool to measure, but REALITY is a whole 'nother ball of wax. Head design trumps flow to a point. Some just "work" and other put up bench #'s. I've looked at all this so much for so long, I've seen dead 416 LS3's make 450whp with all the cam/750+pump gas 6.2 LS3's with ported stock heads, 6.0's make 600fwhp w/ ported 243's and small cam/600whp ported 243's on a 402. Tusky's Cookbook gives a good range, but needs an update. There are some outliers that are putting up the #'s that are not on here. I still rate my heads by smallest valve/highest flow. It just makes sense. It's why I'm keeping my Brodix BR1's out of all the heads I've owned. That being said, I'm eyeballing a set of TFS 260 heads and doing some light magic to them for my upcoming LSX 427 build for the AMX. Time will tell. If regards to the BTR heads, I'm happy he got them to market, but waiting for actual results. Edelbrock couldn't get traction on their canted LS3 head except for a few in the CTSV camp. I didnt' think it was a bad head, but flow was not fantastic, even with GPI fixing their port shape. I still apply to the 300cfm@.400 rule, which these heads might be able to do. It's a short list.
Edit: To give you guys food for thought, I really compare all the highend LS builds to SB2.2 builds. SB2.2''s make 2hp per cube on pump gas like a walk in the park. As advanced as we think we are, there is still better out there. Keep digging
Last edited by DualQuadDave; Apr 20, 2026 at 12:50 AM.
The heads are on the BTR website. The description says material needs to be removed, so I'm not sure if they will work (well) out of the box. i wonder if the larger valve clears a 3.9 bore.
The heads are on the BTR website. The description says material needs to be removed, so I'm not sure if they will work (well) out of the box. i wonder if the larger valve clears a 3.9 bore.
these are porters castings meaning they will not work out of the box. These will not only clear a 3.9" bore but they will also clear the bore for 5.3s. Maybe even 4.8s
The heads are on the BTR website. The description says material needs to be removed, so I'm not sure if they will work (well) out of the box. i wonder if the larger valve clears a 3.9 bore.
these are porters castings meaning they will not work out of the box. These will not only clear a 3.9" bore but they will also clear the bore for 5.3s. Maybe even 4.8s
The 5.3 and 4.8 have the same bore. The 4.8 just has a shorter stroke.
As far as I am aware, the valve sizes are the same for both heads, so off the shelf LT1 valves can be used. I'd be curious if the valve spacing was somewhat different for the rec port, and that's why the minimum bore has to be larger. I am sure for some max effort versions of the rec port heads, one would want to go bigger than a 2.125" intake valve and having a wider valve spacing would allow that.
Once they have the CNC program figured out (all the final tweak have been done - sounds like they have), it would be interesting to see a true just change the heads (an only the heads) dyno test.
can you share the mamo 243 flow numbers? I dont think ive ever seen a 243 head flow much over 320cfms if at all. The cathedral canted valve heads flow over 350 at .650. I dont think a 243 head is capable of that.
Here are PRC ported 243s for reference. not doubting tonys skills, i just dont think 243s can be modified to get near 350cfm on the intake.
I think he means 243CC intake runners, not a 243/799 casting head
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