Hello All,

I'm new to engine building. So far I've done as much research as I've can, although I feel like before I get too far in to it, I better check. The goal is a boosted application, but I will be running the engine N/A for a while before going with FI. This will be a street car, it'll probably never see the strip. I'll be sticking with Cathedral heads. I understand that a 427 would see the best peek numbers with a rect. port heads, but I'm not worried about peek numbers.

M6 T56
427 Short block with -20cc dish
PRC 247's (cathedral heads. So far I've read up on plenty of articles. Seems rect port are better for more peek HP, while cath are better for torque every where else??)
.04" cometic gasket (If I'm not wrong, this combo will then be 10.1:1 cr)
102mm Fab'd intake mani (I understand these are better for mid to high end rpm ranges, I'm okay with that. I can't spend $1000 on a fast 102)
Stock LS1 Rockers with Trunion Upgrade kit (what is the stock ratio? 1.7:1? is that safe for PTV clearance?)
MS4 cam 239/242 .649"/.600" (since I'll be running n/A for a while....will this be enough cam for a 427? I'm wanting to stick to a fairly aggressive build without it becoming too much to handle with bucking)
1 7/8" headers
91 Octane

Again, this will be strictly a street car. Will probably never see the strip. Important take aways for me will be:
Cam choice, and why it's good or bad, and what would be the "prime" cam specs for an aggressive street build without too much bucking/idle issues
I know that with a CR of 10.1:1, I won't be putting down much power in N/A form. The goal is to be running an F/I setup (with a different boost cam later down the road).


Please give me your thoughts/criticisms, and advice.

Thanks,

Andy

Edit:

I'd be happy with as little as 490whp with this combo in its' N/A form. Any guesses on dyno numbers? feel free.

Including PRC 247cc heads flow data:
.100" 66 CFM 57 CFM
.200" 147 CFM 117 CFM
.300" 228 CFM 170 CFM
.400" 282 CFM 206 CFM
.500" 321 CFM 227 CFM
.600" 343 CFM 235 CFM
.650" 355 CFM 241 CFM
.700" 360 CFM 245 CFM

 

Okay let me ask a much quicker/more concentrated question:

For a 427 ci (4.125" x 4.00" stroke) + 68cc chambers on a cathedral port set of heads + 10.1:1 CR + Daily driven but still wanting an aggressive cam =

What custom ground specs for a CAM?
&
How do the MS4 specs (up above) compare?

New builder here. Please don't yell at me

Thanks,
Andy

 

I would hit up Pat G for a proper speced cam.

 

I'm struggling with why to put PRC 247 cathedral heads on a LS7. I can sort of understand not wanting to use LS7 heads if you're worried about the valve guide thing, but if nothing else, use LS3 heads. Your 427 will make torque on accident regardless of head selection. Your intake options are far better with LS3 heads than cathedral.

 

I'm sure someone has done 265+ cathedrals out there but they're not cheap!

 

Thanks for the feedback. Question for you:

Am I right to assume that with cathedral heads giving us more torque every where in the range (sacrificing peak hp), that I would be able to spin a turbine quicker and at lower rpm's? Thus decreasing lag, OR increasing the turbo's optimal RPM range? (As this will be a turbo build when it is finished that will be accompanied by a proper boost cam)

Thanks,
Andy

 

The only company that's known for this I believe *was* MAST, but they replaced their 265cc Cath's with 295cc caths, which are apparently about $2200 per head with all the hardware.
That's just too far beyond my budget.

 

I dont deal much with FI so I cannot really give you a good answer. I had always thought the rate of blower spooling had to do with how the blower is configured and not the head selection.

 

 

How much power is the plan when you have finished boosting the motor.

 

If you have the money buy these:
https://www.corvetteforum.com/forums...ti-valves.html

 

That's definitely a bad *** set of Larry Meaux ported heads. They would be fantastic on a 427 I bet.