Only if that's how the porter decides to port them.

Texas Speed's CNC ported heads are......260cc.

KW

 

Stock is 257cc, so they are not removing much, which will keep velocity up. Likely mostly a good bowl blend and cleanup.

 

I would actually consider a really efficient cathedral port head....this is going in an extremely heavy "hot rod" and I use that term loosely here as we are discussing a full size truck of sorts

An efficient cathedral head with a properly ported LSXRT that would fit under the hood would be an incredible combo in my opinion and make the 408 engine feel 50 cubes larger with so much more part throttle grunt and responsiveness.....and it would post some serious power and torque on the dyno as well (similar in fact to square port heads IMO with a stronger curve in the lower / middle RPM's very beneficial for an application like this).

And note I sell alot of Mamo Motorsports 260 cc LS3 heads (390+ CFM with a conservative runner volume) but if you called me up and we had a conversation based on some of the info you posted here I wouldn't recommend it. I would be all about my cathedral 235 head and we could easily make 625 HP with that set-up at the crank with 560 ish Ft/lbs of torque (also crank #s) . I'm not quoting rear wheel because a truck driveline has even more variables than a car when it comes to losses at the rear wheels.....throw it on the dyno before you mod it if you have the opportunity and you will see a number 50 RWHP lower than you might have thought but a proper baseline is the only way to appreciate what has been gained in an unorthodox build like this. Bottom line is 600 plus ponies in a cathedral head will hit hard and immediate at any RPM.

This is not a light sports car with a manual trans.....you cant approach the build like your dealing with that type of situation

If you had the opportunity to drive both you wouldn't hesitate to choose the highly efficient optimized cathedral set-up.....a good cathedral head makes more power than its flow numbers might lead you to speculate (and that's because its not just about flow numbers) while on the other hand I feel an LS3 combo tends to do slightly the opposite (make a little less than the much stronger flow numbers would lead you to speculate).

Again....not hating on LS3....I sell a bunch of them and in the right application they work very very well....I just dont feel like this is one of those applications

OP if you would like to discuss this and some of my other thoughts in more detail I would encourage you to PM or email me and we can arrange a time to get on the phone

Cheers,
Tony

 

Tony, I think you are unestimating your 235 heads and here is why i say that. Richard Holdener made 640hp/580tq with a fast 102mm intake and AFR 245 heads both right out the box. Cam was a basic 240/246.

 

OP, I think Tony raised an excellent point about a correctly ported LSXRT matched to a great set of heads. Definitely worth detailed discussion with him.

 

This exactly....I woulda tried to explain the same but it woulda took me 10 min to hunt and peck all that. I'm still old school I use No 2 pencil.

 

I appreciate that (and I certainly agree!) but the the numbers I quickly threw out there was more me factoring in a build more optimally designed for a heavy vehicle with a good bit less cam duration and more conservative compression (and aimed towards making more bottom and middle than larger numbers up top).

I have actually engine dynoed many MMS 235 combos on 402, 408 and 416's that usually fall in the 645 - 660 range with your pretty typical low mid 240's HR cam. I think the best one I tested hit 670 in a 416 I did years back.

I did have the opportunity to speak with the OP and it looks like we may be moving forward with this build and a set of my 235 heads coupled with that ported LSXRT manifold. We are working on the rotating assy first and it will likely take him a number of months to put aside all the pieces he needs for this build. As most of you know that have embarked on a stroker build previously, the costs add up quickly so he is kind of building this as the funds coming in allow. It should be an awesome build when its finished though and turn alot of heads with the performance this rather large vehicle will be capable of. He is going to hurt some feelings with this deal for sure....LOL

Catch you guys later

-Tony

 

Hello everyone here I am again ,so I was originally going to do the stroker route but I didn’t get to do it was too much money something came up was too much money for it. Anyways, what I did for now was get a 5.3 put a custom 233/239 cam was full bolt ons with 799 milled heads @.40 with the restalled circle d converter now to a 5C 4000-4200 I believe. Hit a beat of 13.47. I just recently swapped to a 2013 6.2 was going with the F-35 cam in it but decides to do a custom grind cam that required me to flycut pistons I milled the 823 heads @ .40 for more compression running stock L92 intake for now. Cam specs are 244/258 not sure on lift but they said it was dual springs. I’m curious as to how much power I’ll be at the wheels for now. What do you guys think? I’m on e85 50lb injectors for now. What do you think 1/4 mile wise? Should I install my 4.56 gears or stay with 4.11s? I have a nitrous kit as well but don’t know if this cam is good for spray.

 

I personally think the cam is too big for what you wanting to do.

 

Camshaft is too big for an ls3.

Its certainly not good for nitrous either.