Toque

NICE !

2" primaries huh ? That should allow that 434 to breath much better !

How about the top end... anything needed there to reduce all restrictions which was choking your motor ?

Toque

427ZM

Hope so! Looking forward to finding out!

Supercharged111

Sweet, but I must admit that I am curious as to why you knowingly undercammed the engine if your goal was 100hp/L?

427ZM

Ahhh, well, hindsight is 20/20. Here was the logic: In the C6Z section this cam has produced 570-590 with supporting mods and stock intake. My builder has had this cam w/ these heads in stock C6Z's produce 580-595. Logically, more cubes, more compression, same heads, same cam= similar results. So, what are the differences between the C6Z cars and mine? 1) Headers. All 1 7/8 or 2". 2) dry sump oiling 3) heavier forged rotating group. Heavier, and forged pistons; the C6Z pistons are interference fit, forged pistons, although tight, aren't that tight. This accompanied dry sump oiling in the C6z creates complete sealing along w/ zero windage.

Hence the 30 HP difference.

We'll see what it gains w/ the headers. From there, we'll about going to a big nasty bump stock. This one does drive fantastically though.

Supercharged111

How far you think the headers will get you? I've seen where going from 1 3/4 to 1 7/8 did virtually nothing. Is it you or the C6Z with the heavier internals? I'm assuming you.

427ZM

Yes, me w/ heavier internals. Cranks weight is the same, the rods and pistons are where the weight is added. The TI rods in a true LS7 weight 480g a piece! The callies compstar's I'm running weight over 600. There's a similar difference in the pistons as well. It's strong, and that's good, but that comes w/ a penalty.

The 2" headers my head porter thinks will gain big power. I think 15-20 throughout the curve, he things more. He built the heads for a minimum 1 7/8 header. Literally, he took the "D" shape out of the exhaust port. He's the reason I'm doing this first. After the dyno and final tuning was finished up, he said headers are holding you back. So, I'll be taking that out of the equation.

rjwz28

Let us know if it's noticeably tighter to fit those vs your 1.75s, please

427ZM

I will. I was under the car last week, and it looks like it's going to be tight right around the starter.

rjwz28

PRE-Z06

Notice ARH doesn't even sell 1.75" headers for a 427, a modded one needs to breathe even more...as far as the dry sump in the C6Z it actually has been shown to rob a little power as seen in the link below being it doesn't pull a vacuum like a race set-up yet you have two pumps as a parasitic loss:
http://www.hotrod.com/techarticles/e...mp_conversion/
Figure the bigger cam will be worth ~25hp, is that what you were told?

427ZM

Not sure. We'll see what the 2" headers do, and possibly a 247/260 on a 114+5

CTD

I hope & think the headers are a huge bottle neck. Not from the size, more the port mismatch the wrong way.

Smaller camshaft & let the heads work.....that is the way I like to get err done.

427ZM

Yep, these are LS7 flanged so they will align perfectly w/ the exhaust ports.

TXGS507

crank, wheels?

427ZM

Wheels. We'll see. I'm just going to take out all bottle necks before going up in cam size.

PRE-Z06

Sounds like a plan, I'll take good flowing heads over a bigger cam every day of the week My little 346 with ~13% bore area, a tiny 218* cam and heads that flow ~25% less than yours picked up 7rwhp from 1.75" to 1.875" headers...looking forward to see your gains going to 2"

Pumba

I haven't seen where you listed what correction factor your dyno shop used for your 554/490 pull.

• Did they correct to SAE?

I think testing will demonstrate that the restriction we face having to package our engines in Corvettes with low hoods is the intake system, not the exhaust. If you could use a high-rise single-plane intake manifold with a Holley fuel injection throttle body you would see 680+ RWHP, without changing your camshaft. An associate changed from an LS7 intake and 90 mm GM throttle body on his 442, to a Harrop ITB intake manifold and he picked up 41 HP and 54 lb-ft. of torque and his camshaft was very similar to yours.

Good luck with your project.

427ZM

Pumba thanks for the words. Yes, they are SAE numbers, and WOW! That's a serious gain from the Harrop! Those intakes look real cool. Also, I wish I had of reacted faster, your CF driveshaft would've been a addition!

The Highlander

Did you make that power with the 2" headers?

rjwz28

I'm curious what clutch you have backing this