ibd2328

iTrader: (2)

Torsion bar change is a pita plus they discontinued he good 7700 bars

fordmotorsport

When I installed my lift, I couldn't even get mine out, I had them cut out at the shop. Then I had 7700 put in too.

charliedyal

What year are the GM 2500 TB's your running? Same spec's as the f150's?

jferg92

Carcrazy is running the gm ones supposedly

BossRacing71

Hey Guys, hate to break the thread flow here, but I've got a engine mod question......I'm planning a PI swap on my 97 Scab 4X4 4.6L. I've done this swap on both my sn95 Mustangs, and it really woke them up with just the swap and a tune, even before adding any other mods. How many here have done this to a NPI truck, and what was your opinion? Any extra info on cams/TB/Intake/header combos you might recommend with this swap that you can include will be helpful.
My truck use is mostly light to medium loads, and trailer towing about 4-8 times per month. Also the occasional foray off-road in hilly terrain. Not the BAJA 1000.....lol. I'm also planning to up-size to 34"-35" tires along w/ a 4.10 gear change.
I'm a total gearhead, and former race engine builder, so none of the work is beyond my abilities. All inputs/opinions appreciated.
THX.

P.S. Plz leave turbo or SC combos at the door. Not interested in anything other than N/A setups.

charliedyal

You'll have a lot more compression. Combustion chamber is much smaller on the PI heads. I think [MENTION=99584]ibd2328[/MENTION] knows what the final numbers are. Probably wouldn't be able to run a charger on it anyways. Stock intake manifold & TB, stock cams, headers & good exhaust, GOTTS mod on your intake. You don't have to worry about port & polish because your not boosting. Then you just need a good tune. I've not done one of these swaps, but I'm sure the high CR would be a lot of fun to toy with.

ibd2328

iTrader: (2)

Not sure about all of them but most gm trannies are shorter than the 4r100. So some may not fit. My buddy had a 2013 2500 duramax he lifted and gave me the bars. Just needed keys and adapter for the control arm. They make some funky looking ones.

I had my factory ones in today to see if I could clear and the tcase wouldn't clear.

There are holes in all the 5.4 trucks to move the torsion bar member back 4.5" and To relocate the tranny support. The 7700 frame is no different than ours.

You could take six rivets out of the back of the frame. Right where the leafs bolt up and replace it with a 1ton without any issues. Frames on our models are the same dimensions, only the thickness differs on the 3/4 and 1 ton for 02-03.

BossRacing71

The new CR on a PI swap is roughly 10.2-10.4:1, depending on milling and/or head gasket choice. On one of my Stangs, I put in 96-98 MK VIII pistons, which are -3cc dish instead of the -10cc of a std NPI piston, and got about 11.3:1. Of course, that's a Stage 3 motor for my Sunday driver. You are right that a PI swap has too
much base compression to boost, unless u change to deeper dish pistons.
I'm just trying to find out if the swap is really any benefit in a truck. I would think there would be SOME advantages.

BTW Charlie, I really like the look of your truck. Pretty much how I'm picturing mine when my wish list of mods is complete. Oops, did I say "complete"? The wish list is NEVER complete. LOL.

ibd2328

iTrader: (2)

Just a few notes:
Piston dish
SOHC 4.6L, 5.4L,and 6.8L
1991 thru 1998 ------- 10.49cc dish
1999 thru 2000 ------- 18.10cc dish
2001 thru 2004 ------- 15.80cc dish
DOHC 4.6L
1993 thru 1998 ------- 2.66cc dish
1999 thru 2002 ------- 4.54cc dish
DOHC 5.4L
1998 thru 2004 ------ Flattop

If you do a straight swap, you are looking at 10.23 static with felpro mls gaskets .040.
If you decide to bore or hone: say .020 over you move to 10.32

If you bore .020 over and deck .001 you move to 10.35

If you deck only you move to 10.26


However, if you move up in gasket size to .060" then you are at 9.77

Moroever, if you want to go NA just change to PI heads.
If you want boost with new heads, use a thicker gasket.

ibd2328

iTrader: (2)

PI head chamber volume is 44cc
NPI head chamber volume is 52cc

Not to mention the 4.6 deck clearance is only .008" whereas the 5.4 is at .120"