Ashyukun New Reader
Oct. 9, 2012 10:21 a.m.

Here's the deal. I'm working on a G-body for next year's Challenge (those who I talked with for longer periods of time at the Challenge this year may remember that I had intended to bring it THIS year, but other factors intervened and I came across the 500ci Fiero...). I snagged a posi rear end with a 3.41 gear (the one in mine is either 2.43 or 2.72) from a Monte Carlo for $300 for it.

But... if things go how I expect them to and with leaving a bit of leeway, when all is said and done if I keep and use the posi, I'm going to have around $300 so spend on making more power with the 350 SBC I've got for it.

So, my question is this: is it worth the $300 to keep the posi, or would that $300 be better spent on improving the engine's power (or possibly putting a bit more into suspension mods)? Were budget not an issue (or a lot less of one...) I'd of course be keeping it, but this IS the Challenge...

ransom SuperDork
Oct. 9, 2012 10:26 a.m.

I'm no expert on either that chassis or that engine, but I'd have assumed that most cars with a reasonably healthy 350 in them would be less limited by power than by the ability to use that power effectively...

Whether that means posi or suspension is a separate question, and I'm sure there are folks here who know a thing or two about G-bodies.

aussiesmg UltimaDork
Oct. 9, 2012 10:45 a.m.

Ford Explorer V8 8.8 has LSD, disc brakes and is stronger for less than $300.

oldtin SuperDork
Oct. 9, 2012 10:48 a.m.

GRM Posi = about $1 in welding wire.

although I'm not sure it's the best for autocross

Ashyukun New Reader
Oct. 9, 2012 10:55 a.m.
oldtin wrote: GRM Posi = about $1 in welding wire. although I'm not sure it's the best for autocross

I would imagine that wouldn't be very good for the AutoX, especially given this vehicle will be a boat anyway. I also intend to drive it down from here in Kentucky, so would prefer not just welding up the diff...

GameboyRMH PowerDork
Oct. 9, 2012 11:04 a.m.

There's a guy who runs a rally-oriented Datsun with a welded diff in autocross here, his runs are fun to watch but never among the fastest. I drove it once and it would make a good drift car.

Gasoline Dork
Oct. 9, 2012 11:07 a.m.

8.5"? or 7.5"? Pretty sure Monte Carlo SS's got both.

What type posi is it also? If it is a gov-lock I would not use it at all. I have blown them up on stock motors.

yamaha Dork
Oct. 9, 2012 11:14 a.m.

I'm going to second the explorer axle.......its surely been done before

ClemSparks PowerDork
Oct. 9, 2012 11:22 a.m.

I'm quite interested to see details about how (if) someone got an 8.8 into a G-body. I'm assuming it's a matter of welding on mounts and coming up with a compatible U-joint.

Hmmm....(that's the sound of a G-body owner pondering hopefully)

yamaha wrote: I'm going to second the explorer axle.......its surely been done before

And don't call me Shirley!

stan_d Dork
Oct. 9, 2012 12:07 p.m.

Making more power that can be used... Wait I added a turbo to v8 in a car that couldn't use any more.

Ok I am bring a g body to 2013 I'll just sit back and learn.

Ashyukun New Reader
Oct. 9, 2012 12:23 p.m.

It's the factory posi, and a 7.5" rear end. I don't think any of the Montes got the 8.5", but don't hold me to that though they've certainly been put into them over the years.

The Ford 8.8 might be an interesting project to try and undertake. The problem with the Explorer vs. the G-body is that the Explorers were leaf-spring rear ends vs. the G-body's control-arm/shock/spring setup, so the whole suspension system would have to be fabricated from scratch. There's also that the Ford used a 5x4.5 lug pattern and the G-bodies a 5x4.75, so to use the wheels I have I'd need an adapter or to change out the hubs. The rear disc brakes though would be nice...

It's an interesting option to explore (no pun intended) though- and I imagine doing so would garner a few more engineering points on the Concours if it were done well.

hrdlydangerous HalfDork
Oct. 9, 2012 12:36 p.m.

That center section is the same used on '89 (iirc) and up F-Body cars. Most of the guys racing those cars get rid of the 7.5" rear for something more robust. If you lurk on the F-Body forums I'm sure you can find a limited slip center section on the cheap or free. You don't need an entire rear end, and there's no way I'd spend $300 of the budget on it.

More motor is useless if you can't put it to the ground.

OH, and don't forget; GM made different carriers for 2 series ratios ie. 2.73/1 compared to 3 series ratios (3.42/1, 3.73/1).

Ranger50 UltraDork
Oct. 9, 2012 12:42 p.m.
ClemSparks wrote: I'm quite interested to see details about how (if) someone got an 8.8 into a G-body. I'm assuming it's a matter of welding on mounts and coming up with a compatible U-joint. Hmmm....(that's the sound of a G-body owner pondering hopefully)

I know it isn't very grassroots, but TRZ in Florida has the control arms and bushings to make an 8.8 from a Mustang fit up.

aussiesmg UltimaDork
Oct. 9, 2012 12:54 p.m.
Ashyukun wrote: It's the factory posi, and a 7.5" rear end. I don't think any of the Montes got the 8.5", but don't hold me to that though they've certainly been put into them over the years. The Ford 8.8 might be an interesting project to try and undertake. The problem with the Explorer vs. the G-body is that the Explorers were leaf-spring rear ends vs. the G-body's control-arm/shock/spring setup, suo the whole suspension system would have to be fabricated from scratch. There's also that the Ford used a 5x4.5 lug pattern and the G-bodies a 5x4.75, so to use the wheels I have I'd need an adapter or to change out the hubs. The rear disc brakes though would be nice... It's an interesting option to explore (no pun intended) though- and I imagine doing so would garner a few more engineering points on the Concours if it were done well.

Read up my S10 build, I made an 8.8 fit and used a homemade 4 link and panhard.

http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/1996-chevy-s10-challenger/52505/page1/

Ashyukun New Reader
Oct. 9, 2012 12:57 p.m.
hrdlydangerous wrote: OH, and don't forget; GM made different carriers for 2 series ratios ie. 2.73/1 compared to 3 series ratios (3.42/1, 3.73/1).

I got the whole rear end, drum-to-drum, for the $300, so I've got the carrier and this shouldn't be a problem. If I were to try the 8.8 rear end, if nothing else the stock (posi) rear end can be used as a template for fabbing the suspension mount points...

Sky_Render HalfDork
Oct. 9, 2012 3:03 p.m.

I'd rather have positraction than more power.

evildky Dork
Oct. 10, 2012 1:20 p.m.

I came in second with an open diff, but the mid engine helps a bit. Only 2 of the turns at the autocross were an issue, and mini me has proved that an open diff fwd car can run 11's years ago. Power without traction is frustrating, but traction without power is just a bad, you have to find your ballance, and perhaps a welded diff is the answer?

miatame HalfDork
Oct. 10, 2012 9:24 p.m.

A proper working LSD (posi) can make a huge difference putting the power down in a corner.

We picked up a nasty boat anchor Ford Explorer 8.8 LSD (3.73 gears and disk brakes) for $100 from a junk yard to stick under the XJ-R. It was very rusty and it needed a LSD rebuild (about $60) and new disks but works great now.

$300 is 15% of the total budget. It is going to improve the performance by 15%? Maybe, maybe not. If not, it is not worth the money. My suggestion, find a cheaper axle with posi.

Either way, the $300 you have for the engine can go a long way on a small block Chevy.

novaderrik UltraDork
Oct. 10, 2012 9:59 p.m.
Gasoline wrote: 8.5"? or 7.5"? Pretty sure Monte Carlo SS's got both. What type posi is it also? If it is a gov-lock I would not use it at all. I have blown them up on stock motors.

just for the record: the only G bodies that got the 8.5 were the 84-87 turbo Regals (GN, T Type) which had a 3.42 ratio and usually a posi (but not always), and the 84-88 Olds Cutlass 442/Hurst Olds which had a 3.73 ratio. no other G body had a factory installed 8.5.. the 87 and 88 Monte SS got the slightly beefier 7.625" ring gear with 3.73 gears.

Gearheadotaku SuperDork
Oct. 11, 2012 8:02 p.m.

posi is always worth it

curtis73 SuperDork
Oct. 11, 2012 9:00 p.m.
Ashyukun wrote: So, my question is this: is it worth the $300 to keep the posi, or would that $300 be better spent on improving the engine's power (or possibly putting a bit more into suspension mods)? Were budget not an issue (or a lot less of one...) I'd of course be keeping it, but this IS the Challenge...

My first question is... what 350? Spending $300 to upgrade a TBI engine is like polishing a turd. Spending $300 to upgrade a Vortec or a Smogger is money well spent. I used to build engines for a living. Just ask if you have questions.

The posi you have is probably a clutch-style (not the gov-lock). The springs are very light and they're designed to handle 140 hp from stock wheezer engines of the era. I would actually opt for the gov-lock from the S10. Gov-locks get a bad rap, but in anything less than high-hp drag racing they hold up VERY well. I have a gov-lock behind a 900 lb-ft Duramax that tows 12,000 lbs. The internet talks about gov-locks failing in massive-hp drag racing and all of a sudden it is a weakling that can't handle a 4-banger.

curtis73 SuperDork
Oct. 11, 2012 9:09 p.m.
Gasoline wrote: 8.5"? or 7.5"? Pretty sure Monte Carlo SS's got both.

Nope, Montes got the 7.5" The SS got 7.625 which is the same case with a bigger ring gear/carrier. Its no stronger since the main failure point is the bearing caps.

curtis73 SuperDork
Oct. 11, 2012 9:12 p.m.
novaderrik wrote: just for the record: the only G bodies that got the 8.5 were the 84-87 turbo Regals (GN, T Type) which had a 3.42 ratio and usually a posi (but not always), and the 84-88 Olds Cutlass 442/Hurst Olds which had a 3.73 ratio. no other G body had a factory installed 8.5.. the 87 and 88 Monte SS got the slightly beefier 7.625" ring gear with 3.73 gears.

Agreed. I didn't realize you had already addressed this

Ashyukun New Reader
Oct. 12, 2012 11:35 a.m.
curtis73 wrote: My first question is... what 350? Spending $300 to upgrade a TBI engine is like polishing a turd. Spending $300 to upgrade a Vortec or a Smogger is money well spent. I used to build engines for a living. Just ask if you have questions.

I have two 350s at my disposal, though for one 'disposal' is most likely the operative word.

The one that came with the car is a 350 that appears to be a crate motor, if not it's a '79. It had the 624 heads on it (I've got another thread just on heads...), and needed a new rear main due to the Edelbrock carb it came with dumping fuel down the intake. When torn down, I found that it had been bored 80 over and had definite pitting on several cylinders and as such the block itself (and the 80-over pistons; it may have longer connecting rods too) was largely unusable. Did come with an Edelbrock 2701 Performer EPS intake manifold that the 650cfm Edelbrock carb was sitting on.

The second is a '89 TBI 350 out of a K1500 truck. I picked the truck up dirt cheap because both the engine and transmission (a 700R4, mine came with a THM350 and since this will be driven on the highway I wanted the overdrive...) had been rebuilt only a few hundred miles before the truck was hit and salvaged. I've not pulled it out yet, but it appears to be a fairly stock '89 TBI.

I also have access to a '87 305 cheaply, which has 081 casting heads.

The plan at the moment is to build upon the base that this engine & the parts from the other provide- a new cam is pretty much a definite as the TBI trucks apparently had an absolutely worthless one power-wise, I'm looking for better heads (I'd like Vortec heads, but they may not be in the budget unless I come across some either really cheap or in a junkyard), am planning on doing all the mods to the TBI unit to improve it, and hope to get a better manifold. If I use pre-Vortec heads, I have the Edelbrock 2701 that came with the first 350.

The posi you have is probably a clutch-style (not the gov-lock). The springs are very light and they're designed to handle 140 hp from stock wheezer engines of the era. I would actually opt for the gov-lock from the S10. Gov-locks get a bad rap, but in anything less than high-hp drag racing they hold up VERY well. I have a gov-lock behind a 900 lb-ft Duramax that tows 12,000 lbs. The internet talks about gov-locks failing in massive-hp drag racing and all of a sudden it is a weakling that can't handle a 4-banger.

Correct, the posi I have is a clutch-style, a 3-series carrier 26-spline with 3.41 gears (my memory isn't perfect on the gears though). Don't the S-10's use 28 spline axles though? The G-bodies used 26-spline axles, so I'd need new axles as well...

I did some more checking and updated my build spreadsheet, and I was off by a bit in what I had and hadn't included. Assuming I'm able to sell the K1500 down to $0 or very close to it and taking out what I estimate I'll need for paint and incidentals, if I include and use the current posi rear end, I have $400 for enhancements to the engine.

If I don't use the posi rear end I have, I'd have about $675 for the engine and/or a different rear end approach (the posi rear was $300, but I'd have to FMV the rear sway bar it came with at around $25...).

Suggestions and input as to how to get the most bang for my buck with the engine would definitely be appreciated!

wae New Reader
Oct. 12, 2012 11:46 a.m.

Make 1,000 pounds' worth of El Camino disappear?

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