congrats on the numbers! no doubt the mani's are holding you back a little, but it never ceases to astound me that you can get 450+ hp with little more than a cam swap.

that BOP rear will certainly hold... until you drop the clutch and hook at a good rpm. FWIW, the 8.5" 10 bolts would easily hold the power levels you're looking at, and they're much cheaper than the more popular rears (12 bolt, 9", etc.).

 

Well, I don't plan on running slicks or even drag radials at the track. So I guess on street tires the rear should be fine. If not though, I'll definitely look into an 8.5" 10-bolt. When did BOP start using (or in what vehicles did they use) the 8.5" rear over the 8.2"? Is there an easy way to identify them if you were junkyard digging?

Thanks,
Jeff

 

Great #'s I bet your happy!! Off the top of my head I thought a 71+ 10 bolt would be the 8.5" but don't quote me on that

 

I'd personally run the 8.2 until you grenade the thing, unless you're concerned w/ losing an axle on the highway or something.

Here's some info on the 8.5" rear (see post 12). They're pretty easy to spot. I hear the 71-72 Buick/Olds A body would be best, as they've got bolt in axles (i.e., no c-clip) and control arm bracketry. That style has cutouts at the 3 and 9 o'clock positions to easily identify it from other diffs.

 

What year are your manifolds? Using the edel mount and able to retain the z bar is awesome. Im running edel headers and with a lowered car I have 2.5" at lowest point to ground --thinking about going with a factory manifold.

 

Thanks for the info! I'm definitely going to run this one for now, until is explodes. The 8.5" BOP is a fantastic idea. I'd say that's my top choice if needed. Cheap and an easy bolt-in......I'm in!

-Jeff

 

The manifolds are 98-02 LS1 F-body manifolds. They fit like they were made for this car regarding flange/downpipe angle. I'm very happy with them. The passenger side manifold was a little tight to the frame.....I had to trim off one of the tips of the triangle on the downpipe flange, but there was plenty of extra material on the manifold to do so.

Like most, I'd guess there's the potential for 10-20 HP gain with long-tube headers, but it's a tough decision whether it's worth it for a car like mine that's mostly street driven and only taken to the track a couple times a year on "street nights". The fit, spark plug and starter acces, and zero maintenance (header bolts coming loose) of manifolds is very appealing to me. Then again, 10-20 HP is very appealing as well. The battle continues....

-Jeff

 

I know this is a old thread but how's this bad boy doing?? Have you changed anything up yet. Can you give some insight on what works or what you would recommend for a fellow 67 GTO/LeMans LS swap.. I'll be getting my 5.3/4L60E this weekend..

 

She's doing awesome! I drove it a ton last summer and fall. Went to NE dragway once and went 12.9 @ 113. I ran on my street tires, so traction in 2nd and 3rd wasn't very good. I actually hooked decent out of the hole, but 2nd gear spun really bad and even 3rd spun more than I would've guessed. I tried granny shifting instead of power-shifting, but it still spun bad.

The only thing I've changed so far this winter is the intake tubing. I fabbed up a cold air intake plate for the fender well, which came out decent. And I moved the MAF sensor closer to the air filter and out from behind the radiator so it doesn't read inaccurately hot. But I've got a hydraulic clutch kit from Keisler that I'm about ready to install. I'm hoping it'll help my clutch chatter. This car has been cursed with clutch chatter since I bought it 18 years ago......thru 2 different engines, 2 different transmissions, 2 bell housings, and who know's how many clutches! The only constant was the Z-bar, so I'm hoping the hydraulic clutch helps. There's other benefits too though if it doesn't.

Let's see....insight on what works? I was pretty happy with all my choices. I love the F-body manifolds, I'm very happy with the cam, and the wiring harness from PSI was awesome. If you need a harness, PSI is the way to go from my experience. Jon gets great reviews on here all the time from others as well.

If you have any specific questions that this thread doesn't answer, let me know.

Here's some pics of the cold air intake. Excuse the dust, she's been sitting in the garage all winter.









Thanks,
Jeff

 

looks great, I love this build.

 

Thanks! Your GN build is sick. Love those cars.

 

Where did you by the hydroboost?

 

The hydroboost is a Hydratech unit. I bought it from Mark at SC&C (Savitske Classic and Custom). scandc.com

Thanks,
Jeff

 

If you do not mind me asking what were your mods on the Pontiac 400? 5500rpm no problem with stock bottom end or did you modify that part?

 

The main mod was simply the cam. I used this one.
http://www.cranecams.com/product/car...detail&p=24170

Highlights are the 234/242 duration which made great power, but not the best for driveability, espeically on a flat tappet. (Hence the LS swap). It bucked pretty bad below 2,000 rpm.

Other than that, everything was mostly stock Pontiac. I ran the stock 670 heads with some DIY pocket porting and Harland Sharp 1.6 ratio roller rockers. And I sent the stock Q-jet to Jet Performance for a Stage II build. Oh, and electric fans, Pontiac "factory headers", and 2.5" exhaust.

Bottom end was stock. And I think it could handle 5500rpm no problem, but that's just my opinion. Who knows what the longevity would be. I only had maybe 10k miles on that setup.....tops.

 

Thanks. Dynos of a Pontiac 400 are very rare on the Pontiac forums. Instead gross flywheel numbers are posted without any proof. Never know what the peak or average numbers are for a given combo like here. Reminds me of the 1980s.

 

Yea, and even the stock HP numbers were inflated back then (by all manufacturers). The standard 4-barrel Pontiac 400 was advertised at 330hp. Sure, the one GM tested was probably 330 with open headers, perfectly tuned carb, etc. Shipped from the factory I'd guess they were much lower except for a maybe a few freaks here and there.

I think today it's the opposite. The LS motors are probably under-rated.

 

Put the car back on the dyno tonight. Decided to run 93 octane, plus I've done the cold air intake and put in a 180 thermostat......all things to help add timing. Final result.....an extra 30HP!

 

I have a 66 GTO to restore after I finish this 67 GT Mustang. I'm planning an LSX swap as well but will probably do an automatic in the GTO since it's an original column shift car. It looks like it's pretty painless, I can't wait!

Your car looks great, I'm in NH as well.

 

Cool! Where in NH? I'm in bow.