[Motornoggin]

I'm thinking about what I want to do with the 428 I have for my 68' Lemans. It is a 69' XF 4bolt block. I really want to go EFI and a centrifical supercharger (Vortech, ATI, Paxton etc...). I would like to be able to run pump premium and still make 600hp or so. My thoughts are to use a set of #51 heads, have them decked to lower chamber size and port them to improve flow. I have read published chamber size for these heads at either 121cc's or 124cc's depending on the book (7.6:1 cr on a 455). If I can get the chambers down to 115-116cc's, use thin head gaskets and with an .030" overbore, I get right around 8:1 cr . Am I close? I'm thinking this would be great for pump gas and 10-12 psi boost (maybe a bit more, 15 psi... I don't know). This should make good power with the right cam and still be fairly easy on the bottom end. What are your thoughts? Suggestions? Ideas?

Never trust a fart. They sometimes suprise you.
http://community.webshots.com/user/motornoggin

[Motornoggin]

I'm thinking about what I want to do with the 428 I have for my 68' Lemans. It is a 69' XF 4bolt block. I really want to go EFI and a centrifical supercharger (Vortech, ATI, Paxton etc...). I would like to be able to run pump premium and still make 600hp or so. My thoughts are to use a set of #51 heads, have them decked to lower chamber size and port them to improve flow. I have read published chamber size for these heads at either 121cc's or 124cc's depending on the book (7.6:1 cr on a 455). If I can get the chambers down to 115-116cc's, use thin head gaskets and with an .030" overbore, I get right around 8:1 cr . Am I close? I'm thinking this would be great for pump gas and 10-12 psi boost (maybe a bit more, 15 psi... I don't know). This should make good power with the right cam and still be fairly easy on the bottom end. What are your thoughts? Suggestions? Ideas?

Never trust a fart. They sometimes suprise you.
http://community.webshots.com/user/motornoggin

[Tom Vaught]

You should be able to run 15 psi with race gas
and 8.75 to 1 compression ratio. The higher cr
will help when you are "off boost". The 8.75 to
1 ratio will also allow you to drive around on normal gas during the week.

The twin turbo car in my avitar used a dual fuel tank system and carried enough race gas for a
couple of good shots on the street. Most of the
time it could go from Detroit to Indianapolis on
any gas in the country.

It made 550 hp using a 327 engine (Chebby) in
1980 which was respectible then. Your goal of
600 hp should be no issue.

The Vortech superchargers "T" trim will easily
make 600 hp with EFI. John Mahovitz, the owner
of Accufab - a throttle body company, made 813 hp
with one on a Ford 4.6L Cobra engine.

Good luck. Tom V.

(ps a 4.6L engine is 281 cubic inches. You have
428 inches. The blower sets the power, not the engine).

[PONTIAC DUDE]

I like the 428 crank and.............


a 455 block .030 to create 440 cu.in's.

You can use the SRP 4.185 pistons and a good rod and let it eat.

I think this is a good forced induction combo and ran it myself.

My current Funny Car blown and injected set up is a 440 cu.in. deal.

As was my ATI Procharger set up that ran 10 flats with a P1000b unit in a Street car.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

[SupergasDil]

Hi Motornoggin,
You should be able to end up with a final comression ratio of 13 to 1 and run pump gas.So you'll have to figure out what your starting compression ratio is going to be and then you can figure out how much boost you can safely run to be able to run pump gas. The burn rate is different when you're packing air. I'm not framiliar with the Paxton style superchargers and it Sounds like Tom has had some experience with this type, but with the roots type, the closer you can get to 7 to 1 starting compression ratio, the more boost you can run and, the more effective your super charger will be. Since supercharger boost comes on instantly there is no lag like with a turbo, so your low end torque will be awesome and instant.

[SupergasDil]

P.S. Give Paxton a call and ask them what compression ratio they suggest. I think you'll find that your 124cc heads will be perfect. I'm using 6H's (124cc) for a starting compression ratio of 7.8 to 1

[fast1970transam]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PONTIAC DUDE:
I like the 428 crank and.............


a 455 block .030 to create 440 cu.in's.

You can use the SRP 4.185 pistons and a good rod and let it eat.

I think this is a good forced induction combo and ran it myself.

My current Funny Car blown and injected set up is a 440 cu.in. deal.

As was my ATI Procharger set up that ran 10 flats with a P1000b unit in a Street car.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc<HR></BLOCKQUOTE>

Is the p1000b one of the loudest unit' Ati sell's?

"Like a Midget using the unrinal,I'm gonna have to stay on my toes."

[SupergasDil]

I did the math on your set up. I know there are many ways to figure volume but they usually come out very close. 428 + .030 and if you're heads are 124cc's, you're right close to 7.28 to 1. I think you are perfect for a supercharger.

[SupergasDil]

Hey Fast70,
Do you know what your starting compression ratio is?

[fast1970transam]

I'm gonna have pontiac dude build mine.I kinda want 8.1 comp though.whatever it takes to run 10's.

"Like a Midget using the unrinal,I'm gonna have to stay on my toes."

[Motornoggin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by SupergasDil:
Hi Motornoggin,
You should be able to end up with a final comression ratio of 13 to 1 and run pump gas.So you'll have to figure out what your starting compression ratio is going to be and then you can figure out how much boost you can safely run to be able to run pump gas. The burn rate is different when you're packing air. I'm not framiliar with the Paxton style superchargers and it Sounds like Tom has had some experience with this type, but with the roots type, the closer you can get to 7 to 1 starting compression ratio, the more boost you can run and, the more effective your super charger will be. Since supercharger boost comes on instantly there is no lag like with a turbo, so your low end torque will be awesome and instant.<HR></BLOCKQUOTE>

Yup, if if I was running a big posotive displacement blower (6-71 or 8-71) I would use the heads as is for lower compression, but I don't think the centrifical superchargers don't hit quite as hard or quite as fast as a roots blower. I think I'm on the right track though. I sure appriciate all the responses. I'm just thinking right now, but this is the direction I'll try to go.

Never trust a fart. They sometimes suprise you.
http://community.webshots.com/user/motornoggin

[PONTIAC DUDE]

From my experience on the street. Centrifigul superchargers like between 9 and 9.5-1. It helps then spool up faster. So to speak.

I ran a 428 with 87 E-heads and had 9.5-1 with a P100B (15 lbs of boost) and weighing 3450 lbs. I ran 10 flats in the 1/4 and 6.30's in the 1/8th thru the mufflers and street legal. Even had it when I ran Rashie at Farmington.

Now strickly racing. Go to the 72 cc e-heads and 11-1

They no longer make the P100b unit. It was a modified impeller in a P600 case. Sorta like a turbo design and made more boost and flow upstairs as the rpms increased.

As ATI is currently fazing out the P600 engine oil feed units and going to internal supply, I'm currently re-designing the P1SC head unit and such to fit a Pontiac.

It's easy to make one fit. The hard part is designing it to take any pulley size and still use the same belt. And I deign it to use a commonly available 12 rib belt without going back to ATI for one of their $80.00 belts compared to a NAPA or dicount parts house $35.00 belt. And I strickly use a 12 rib design. Cost more as I also design for overkill and future power upgrades witout buying all the extra stuff your gonna need.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

[PONTIAC DUDE]

Hope to have a P1SC on Lady Dude's 79 daily driven T/A by Norwalk.

Build it fast, build it right, build a Pontiac.

http://PontiacDude.cc

[70L34]

Hey guys,

Sorry to hijack your post but I wondered where you thought the practical compression limit lies for a centrifugally supercharged 455. 10.2:1, FAST EFI, Edelbrock 87cc heads...want to run a Procharger but I'm afraid my static compression is too high. Thanks in advance!

[Injunjoe]

Yeah Dude if I remember right your Pro Charger setup had that wicked blower surge sound and you could never quite get it to hook, kept blowing the tires off of it. It was a sweet setup though and I loved to hear it run. That event at Farmington was really nice up to the point when they locked everyone in at night. Wish they would have another event up there .

[fast1970transam]

Man i love blowers, i want one the of the loudest ones.When i get the cash this year i want one p-dude!!!!

"Like a Midget using the unrinal,I'm gonna have to stay on my toes."

[SupergasDil]

Blowers are (BAAAAHD)

[GTOGEORGE]

DITTO on the blowers!!

Headed for the seven's!

[fast1970transam]

Every man loves a good blower.............in his car

"Like a Midget using the unrinal,I'm gonna have to stay on my toes."