No other like it.

[8literbeater]

Can you feel the 1630 drop off - is it pretty big bog or hardly felt?

I think I am/was confused about the air/fuel number. I thought bigger was richer and you were leaving it a little rich to keep it running cooler. Why leave it lean?

I forgot the history on that engine - has it had a valve job? Do they make turbo cams for that engine?

$95 for 12 runs seems like a smokin' deal.

In second or third gear it's seamless. In fourth gear you can just feel it. If you were riding along, you probably wouldn't notice it unless I told you.

The air/fuel ratio is [parts air] to [parts fuel]. 15:1 is more air than 13:1, because the air number is bigger for 1 part fuel. The thing is, with propane you don't get any cooling by running rich. It's a dry fuel, so there's no wet "mist" to carry away heat. Anyway, the EGT didn't go over 1000°. Staying lean will hopefully err to the side of better economy.

All I know about this engine is that I had the head off, and everything looks good. The compression was normal, as I remember. I'm sort of winging it.

The only turbo cam I could find is an Iskenderian Turbocycle-A.

Application: Maximum economy/torque. Turbocharged. Up to 7 PSI Boost. Smooth idle. Stock converter. Std. axle ratio. Up to 650 CFM Carb.
http://iskycams.com/cart/index.php?main_page=product_info&products_id=1284

They sell it in a kit with lifters, springs, retainers, locks, valve seals, lock nuts, and a new cam gear.
It sounds like a good time to me.

I was on and off the dyno in under an hour. He said he could probably do your Chevy in less than two hours.

 

[CORPO]

i bet they never had anything that unique and awesome on their dyno before!

 

[DJ3100]

Thanks for explaining the air/fuel ratio. I'm not sure if I have always had it backwards or if that was just a senior glitch.

The part about the propane being dry makes sense, I know I didn't know that.

I'm really thinking about getting the Ranch Wagon dyno'd if I ever get past the paint. The '53 runs good enough for a 350 with 8:1 compression.

 

[8literbeater]

Speaking of running lean, I guess we didn't actually leave it lean. Here's a few runs to compare mixture to torque. Blue first, then red, then green, then yellow. It builds boost sooner and makes more power across the board at about 13.25 to 1.

As for low rpm, how's 150 ft lbs at 950 look? It's not as much as a 350 I guess.

 

[8literbeater]

i bet they never had anything that unique and awesome on their dyno before!

I bet he wishes they were all so easy! He didn't have to climb under anything to tie it down, didn't have to lean over a fender to hook anything up or to adjust the timing, and mixture adjustments took 3 seconds. He dropped the O2 sensor in the end of the exhaust and said "Well I've never done that before"!

 

[8literbeater]

I finally cut my back window last night. I traced the opening, then took 1/4 inch off all the way around for the rubber. It was still really tight. I was having a hard time getting it into the rubber, and I had more of my hands inside the cab than outside, and it slipped out and fell behind the cab on the driveshaft, frame, and concrete. I have just enough glass left to do the side windows, so instead of cutting one of those up, I just put the thing in anyway.

On the second try, I put the rubber bead in the gasket first, then put the glass in. It wasn't that hard, except for being pretty tight. I'll have to make the next one a bit smaller. I tore the gasket too.

 

[8literbeater]

So next, I had to test drive my new back window. Well, the back window works good. I was a little rough on her when pulling away from a traffic light, and got a loud pop sound, and I wasn't going anywhere. Dang it.

 

[soltz]

cracked glass adds character[cl looks good

 

[DJ3100]

I forgot, What differential did you used to have? Got a plan yet?

Good job on the glass - I have broken every piece I ever tried to install.

 

[DJ3100]

I have a GM 12 bolt with 6 lugs. Not sure of it's condition, but I am pretty sure it has fewer things laying in the bottom of the case than yours. It's yours if you want it.

 

[8literbeater]

I would like to have a 12 bolt, but this is a 5 lug axle. Switching axles would be a pretty big chore, but changing wheels would be even bigger. I'll have to remember your 12 bolt for my next project.

This axle is a 10 bolt out of a 2002? V8 Trans Am. I picked it for the disc brakes. I thought it should handle the power of a little old 250.

I think I can just replace the spider gears and the preload springs. I can't seem to find any diff carrier that looks like mine though. Plus, I'm now having visions of my axles breaking off at the wheels.

 

[CORPO]

there's some extra parts in your case there... thats a bummer...

 

[DJ3100]

Six lugs is why I still have it.

New spiders should do it, those axles have to be strong enough to handle the torque and weight you have. Probably the spiders already had some issue. That diff went in a lot heavier cars with a lot more torque.

Actually, the problem is the new sticky tires you got - should have kept the old worn out hard ones.

 

[8literbeater]

This thing is trying to be as expensive as all my other differentials.
$179 seems a little steep for spider gears.

http://www.ringpinion.com/b2c/Produ...oduct=YPKGM7.5-P-28&Brand=Yukon_Gear_and_Axle

 

[smallfoot]

8 liter, be careful that you have not come up with what they call an 8.6 rear assembly instead of a regular 8.5. I ran into the same problems on the rearend I picked up at a pick and pull for my rod. The upgraded 8.5 is called an 8.6. The changes involved the internal pieces like larger carrier bearings and other internal parts. That difference started happening about 2001, mine came out of that years Blazer. I have it sitting on the floor of my barn until I get time and inclination to figure out what I can do with it. I wound up replacing one axle due to a bent flange that resulted from the wreck that put this vehicle in the yard to start with . The new cost of an axle was about twice as much as the entire rear assembly cost from the yard. You can make searches and review the changes online with what was supposed to be an upgrade to 8.5 GM rear that supposed left you with an 8.5 that had nearly the strength of a 12 bolt. Your bolt pattern from the rear cover will be the same as the regular 8.5 10 bolt rear. If I remember correctly the difference internally were bigger bearings and other parts of the carrier. The looks of the carrier I have appear to be the same as yours. Mine is on for future investigation and I went back to my original to get mine back on the road with replacing bearings and seals. The newer style ones referred to as 8.6 rears will be mostly the same in appearance and bolt pattern sizes every where. It will have the more rounded cover like the 8.5, came with 5 lugs small pattern Chevy in 4.75x 5. the only differences will be internal and it may not be noticeable until closely measuring all parts after disassembly...just for your info. Check it out first for info before get parts only to find you might have one of the upgraded rears, it'll save you some grief!!!

 

[8literbeater]

Well Smallfoot, I don't know what I've got here. As far as I know, there's 4 or 5 different GM 10 bolt rears. There's an 8.2, 8.5, 8.6, and 7.5/7.6. The parts on the 7.5 and 7.6 are interchangeable, even the ring and pinion. I don't know why it has two different names.

Judging by the diff cover, mine is a 7.5/7.6. I pulled it out of a 2002 Firebird Tran Am.

Then the limited slip carrier came in Gov-lock design, Auburn, Eaton, or Torsen. It looks like mine is none of them. I am at my wit's end trying to find out what it is. I know it's not a Gov-lock or Torsen. Those are obvious.

This thing has the two spring plates between the side gears, and coil preload springs, not the S shaped spring. That's pretty typical. Here's the problem, it's a split case. The diff carrier splits down the middle at the cross pin. It also has only one window. It's completely closed on one side.

The only thing that I can find on it is a <C><S> logo on the ring gear side of the carrier. I can't even find a picture of anything with that logo online. (Those are letters inside diamonds.)

I don't even care about the limited slip capabilities that much, as I got it for the disc brakes. I just don't want to spend a bunch on putting in a new carrier. If I could just find spider gears that fit, I'd just slide them in without the preload springs and plates, and get back on the road. I doubt I'll find those springs and plates anywhere for an acceptable price.

 

[8literbeater]

I've called three local diff shops, and none of them have heard of it, and don't know what it is. They offer replacements, but nobody has seen a split carrier. Replacing it with a used, open carrier, is going to run close to $200.

So much for GM parts being readily available.

 

[jfg455]

Take a pick of the cover. Does it have a rubber plug in it? It could be what was called a "9 bolt" rear and was from a 3rd gen F Body. I could tell if I saw the brakes and rear cover.

*EDIT* I looked back through your thread and it is not a 9 bolt rear. It is a 7.62 rear from a 4th gen F Body. As far as power it was not a very strong rear end to start with. Just the weight of your rear tires was what probably grenaded the spider gears. These were a common failing in these cars. Even if you rebuilt it you would be dealing with a sub par diff at best. Your best bet would be to swap it out for an 8.5, 12bolt chevy or 8.8 ford rear. The first 2 you would not have to change bolt patterns on your wheels. The last you would have to redrill your axles to match but they can be had cheap and are strong. Look up the www.rangerstation.com for information on the widths, ratios and years they came in.

 

[DJ3100]

Interesting problem/discussion.

If you are going to drill axles, there is a 12 bolt Chevy here with 6 lugs. Of course it has drums-or maybe it doesn't. I don't know anything else about it. It does have wheels - a little welding would change your 5 lug to 6 lug. Diff is free - forklift rental $100. (just kidding)

 

[jfg455]

Auburn and eatons look very much alike. I would say it is an aftermarket diff that someone put in there after the factory one exploded. Your best bet for the money would be an Auburn unit. I think they are around $380 for that diff and are strong.

I can take the guts out of a 94 S10 rear I have if you just need something to get it rolling. It is an open unit but you can have it for nothing.