408ci which cathedral would u choose?
Thread Starter
Joined: Dec 2009
Posts: 2,331
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From: Glennville, GA.
408ci which cathedral would u choose? Building a 408 and was gonna run some LS3 heads with a high ram 102. This is a gonna be a nice street combo for my 2000 Silverado reg cab. I know the LS3 will make some power but way out higher in power band. Trucks are heavy and I'm now leaning toward some nice cathedrals with a high ram. Which would you run? The 408 has a set of summit +8cc dish pistons so I'm wanting around 11.5:1 compression so I need something around 65cc heads with a .40 cometic gasket. This engine may see a lil nitrous in the future. Thoughts?
Thread Starter
Joined: Dec 2009
Posts: 2,331
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From: Glennville, GA.
I was checking them out. But I see they have a larger head as well. 235s I wanna say.
I've had some advanced inductions 236cc 243s on a stock bottom 6.0 in the past that done awesome as well. So I'm undecided at this point lol. But I would like to try an aftermarket cast head for sure.
I've had some advanced inductions 236cc 243s on a stock bottom 6.0 in the past that done awesome as well. So I'm undecided at this point lol. But I would like to try an aftermarket cast head for sure.
I actually have the 235 head on my 403. I felt the 225 head may fit your build better more because of it being a truck build and having the lower rpm and more torque needed was my thought on it.
The compression ratio is going to limit your choices, but I half way agree w/ the TFS 225. Get then from TEA and order the nitrous exhaust port option, totally worth it. If you can live with somewhat less compression, the Brodix BR1's are destroyers, but have a 70cc chamber. They are deckable, you just have to see who much room you need to cut. Look at a LME 243 head, it will surprise you how bad that head is.
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Last edited by stockA4; Jul 31, 2025 at 07:22 AM.
Thread Starter
Joined: Dec 2009
Posts: 2,331
Likes: 29
From: Glennville, GA.
Lol. I went dish Incase I decided to turbo it later. Easy enough to mill heads to the compression I want. I like nitrous tho. I already have a turbo new edge mustang lol
I run 235s on my 402 in a 4400lbs TBSS. With my cam it peaked at 6600 and makes a **** ton of torque down low and through the curve. I wouldn't be afraid of 235s on an engine that big.
I will say though putting a hiram on the cathedrals is going to do exactly what youre worried about the LS3s and hiram doing.
I will say though putting a hiram on the cathedrals is going to do exactly what youre worried about the LS3s and hiram doing.
Thread Starter
Joined: Dec 2009
Posts: 2,331
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From: Glennville, GA.
Yea I've seen the high ram push the power way out similar to what a LS3 will do. Im all over the place. I feel the LS3 heads will make the power but will be way out in the power band coupled with a high ram. Cathedrals with high ram shouldn't be terrible.
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From: Michigan
The intake manifold choice is going to have a much larger affect on the powerband than rec port vs cathedral port.
The 6.0 and 6.2 trucks ran rectangles from the factory and they had plenty of torque, I really don't think rec port heads are going to be an issue, especially being a 408.
With that said, I think the best setup for your truck would probably be some TFS 225 or 235s if you don't mind spending the money. Paired with a Holley high ram, Fast 102 or MSD Atomic. All of which can be ported too.
The 6.0 and 6.2 trucks ran rectangles from the factory and they had plenty of torque, I really don't think rec port heads are going to be an issue, especially being a 408.
With that said, I think the best setup for your truck would probably be some TFS 225 or 235s if you don't mind spending the money. Paired with a Holley high ram, Fast 102 or MSD Atomic. All of which can be ported too.