No. The low profile actually loses power all over, and the high ram loses most low and mid range. Look up the manifold test done by Hot Rod a few years ago. It tells all on Cathedral manifolds.

 

Would ls2 heads work for the budget or would the AFR's be better

 

I'm truly not trying to push you in any given direction, but consider this in your thinking.

The 243 head was designed for a 5.7. It will do decent on your 451, but I think it will hold it back. If you are dead set on staying cathedral, then you should be looking at AFR or TFS or one of the other sellers who starts with their castings and makes great heads out of them. But beyond the heads, consider the intakes - unless you jump to something pricey, I think are going to further choke you back. THe LS6 intake is great on a 346. That 78mm throat is going to choke that 451 hard. There have been lots of dyno runs showing that larger engines like intakes with shorter runners - even for improved low end torque. The only short runner option cathedral is the MSD, which will run you >$1K without any port work.

The combustion chamber of the LS3 head is superior to the 243, The LS3 heads are cheap, the intake options are so much better and more plentifule. ****, a stock LS3 intake is the best factory intake you can get. Have it rod-modded a la Rick Crawford, and it picks up even more (radius rods at port entry) and performs almost on par with out of the box fast 102. Then, just run less cam to compensate for the larger heads. There is a valid argument on smaller engines to stay cathedral for improved low and midrange torque. On a 451, you don't have to worry about it unless you way overshoot the cam. Put a 5-cc valve relief / dish on the pistons, with 70cc chambers, you're at 12.1:1. Stock LS3 heads and intake will cost you so much less than any other option for the performance you'll get from them.

This will be a REALLY odd cam recommendation to match it, and it might start a interesting....disCUSSion, but 230/242-117+2. Not a typo. That'll put you at 8.7 DCR to go with the 12.1 SCR, IVC of 50, EVO of 60, overlap only 2 degrees. You'll have tremendous intake vacuum, it'll have great throttle response, and it will definitely get that truck moving. That cam in a 346 would be a high RPM cam. In your 451, it'll be a stump puller with those LS3 heads. Will run great on 93 octane.

Whatever you decide, best of luck with the build.

 

^^^^^ Wisdom from Darth! ^^^^^^^ Heed, understand, and apply….

 

Indeed Darth is right on the money.

The LS6 is an excellent intakes and works well with 346 5.7's and 383's with the 90mm snout and a fan of the LS6 intake
However, the LS6 or LS6 90 will limit any healthy 451 with a good set of heads and cam in my opinion.

The 451 would be a good candidate for a ported Fast LSXRT with the 102 NW TB if your staying with cathedral heads. I would want a set of ported Trick Flow or ported AFR's or similar.

The 451 is also a great candidate for rectangular port LS3 heads ideally with a little porting to clean up and a ported Fast LSXRT or LSXR.

 

Going by what is said above, a complete stock LS3 top end (heads and intake manifold) would put you ahead of any cathedral setup. A FAST intake would improve things a bit over that, but for more $$$$.

 

With the ls3 heads being about 1100 from summit assembled vs the AFR cathedral ports being around 2500 i could use the other part of that for the LSX intake Can i use truck style injectors or what would i have to do in that case also what size should i use 60 lbs injectors? its going in an 01 sierra 1500

 

Try it with the stock LS3 intake first. It might be enough for what you want. Then if more is needed/desired, get the LSXRT. Intakes are easy to switch, and you might save a bunch of green stuff.

 

Yes you can use truck style injectors. How I would do it is LS3 style on ls3 intake with ls3 rail. It'll look clean that way. If you do the lsxrt, which really is the best bet, then do a Holley fuel rail. 60's will be plenty. Do yourself a favor and get FIC instead of SD. Better data. Easier to tune.

 

If i dont want to have to change my accessors with the l96 intake work? and what oil pan do i use? Will the stroker clear the pan rails i know some of the old SBC's had a problem with needing an aftermarket stroker pan

 

 

Yeah especially since ill have to have it clear the differential up front as its a 4x4 are lunati rods any good?