71 Chevelle 350, looking for direction - Page 2 - Chevelle Tech
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post #16 of 32 (permalink) Old Jul 20th, 19, 4:37 AM
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Re: 71 Chevelle 350, looking for direction

here's what you should do. new flat tappet hyd cam 270advertised duration on 108 lsa isky makes one thats close. new vortec cyl heads. hei distributor edelbrock performer and a 3310 holley. if its an original q jet car keep the carb.either keep the manifolds and go dual 2 1/2 exhaust or add 1 5/8 headers for a little more performance. some basic tuning and this thing will run great and be reliable. if you dont plan on driving much on the highway i would go 373 gears and rebuild the 350 with a good convertor. if you wanna drive on the highway go 200 or 700 r4 overdrive or if you want a manual look for a t56 out of an ls1 camaro. if you stick with a 350 this plan will cost less than 5k. check and rebuild the brakes with front disks and the front end if needed
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post #17 of 32 (permalink) Old Jul 20th, 19, 4:08 PM
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Re: 71 Chevelle 350, looking for direction

You said its been in your family since new,that's great.Is it a 2 bbl or a 4 bbl 350.It makes a difference in what you want to do with it. ----Copied & Pasted below ---
2 BBL would be the :
L65
The 2bbl carburetor 145 hp (108 kW) version of the LM1 350. It was produced until the 1976 model year. It had 255 lb/ft (346nm) of torque.

4 BBL would be the:
L48
Years: 19671980

The L48 is the original 350 cu in (5.7 L), solely available for 1967 in the Super Sport (SS) version of Camaro (1967-up) or Chevy II/Nova in 1968-1979. In 1969 it was used in almost all car lines; Camaros, Caprices, Impalas, El Caminos, Chevelles & Novas. The 1969 L48s use a hydraulic cam, 4bbl Quadrajet carburetor, cast pistons, 4-bolt main casting number 010 Blocks & casting number 041 or 186 heads. Power output was 300 hp (224 kW) SAE and 380 lb⋅ft (515 N⋅m) torque. Compression ratio was 10.25:1. The compression ratio of the L48 was lowered to 8.5:1 in 1971.

In 1972 the L48 (4bbl V8) option for the Nova was part of the SS Package. This is indicated by the fifth digit in the VIN being a "K". 1972 was the only year the SS package could be verified by the VIN.

The L48 engine was exported to Australia, where it appeared in the Holden Monaro from 1969 through 1974, and in the Statesman (automobile) from 1971 through 1974. Towards the end of the HQ series in 1973-74, due to US emissions regulations, the performance of these engines had dropped to the same or lower than Holden's locally manufactured 308 cu in (5.0 L) V8, which was not yet subject to similar regulations, so Holden's discontinued using the engine.

The L48 V8 was the standard engine in the 19751980 Chevrolet Corvette. The L48 V8 Corvette engine produced 165 hp (123 kW) in 1975. Power increased to 180 hp (134 kW) in 1976 and stayed the same in 1977. The 1978 saw 175 hp (130 kW) for California or high altitude areas and 185 hp (138 kW) for everywhere else. Power increased to 195 hp (145 kW) in 1979 and decreased to 190 hp (142 kW) in 1980.
C&P is done.

The best part is if its a 4 bbl it is probably a 4 bolt main making it an excellent basis for a strong running rebuild.If you're able to do most of the R & R yourself then $4K would probably get it done using good parts.Also if it is an L48, those engines almost always got 12 bolt rears from the factory.

John
71 El Camino SS
406 SBC M21 3.31 12 bolt
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post #18 of 32 (permalink) Old Jul 21st, 19, 9:32 PM
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Re: 71 Chevelle 350, looking for direction

Suggestions, if you have a good running engine, upgrade the drivetrain first. Going to an overdrive trans, either stick or automatic will transform the car unbelievably! The stick will make it fun to drive and the od will allow you to drive places at normal rpms and decent highway speeds. Then figure out what you want in the engine. Maybe even find a block or another engine to build and keep your numbers matching unit.

Do a TKO and add a 373 posi axle and you will be amazed!

There will be a lot of detail changes to go from a stock 350 to an aftermarket setup. Carb, headers, intake, etc will all require changes to choke stuff, cold start stuff, the head pipes, etc. I have a stockish rebuilt 350 in my 66, with a total of $1200 in a rebuild several years ago. It has some stock 70s heads, with screw in studs, and a small Comp cam. (not part of the $1200) Its fun but no powerhouse. For the money to do it again, I would not spend a dime on stock heads. I would go directly to a set of aftermarket aluminum heads with a matching intake, carb and cam. Something like an Edelbrock top end kit would be the best step.

66 Malibu Coupe, home rebuilt 350. Took me 39 years to get her!
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post #19 of 32 (permalink) Old Jul 23rd, 19, 4:13 AM Thread Starter
 
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Re: 71 Chevelle 350, looking for direction

Been taking in all the great info and researching whenever I get a chance. Heres where Im at.

Figure Ill start at the rear end up want to go with Posi 3.73. So I look back under the car and shes only got a 10 bolt and looks like its only a 7.5 and Im not sure of what the current gears are but looks like no matter whats in there I wont be able to upgrade it to support the engine mods I want. At least from the sounds of it at a cost that is worth it and have any reliability. So what should I look for? A 12 bolt? 8.5 10 bolt? Or something completely different?

Moving to the transmission, after doing some research Im thinking my converter is whats causing my current transmission woes so plan on having the transmission rebuilt with a new converter put in. And from what I gather its worth having that beefed up a bit compared to stock.

As for the engine I want to try and keep the matching numbers so going to do a rebuild on that but thinking new after market heads, cam, headers and a 4 BBL carb. and need to start researching more on that to see what will work best with the rear end and tranny. It currently only has a 2BBL so will be replacing that.

As for the end purpose of the car it will mainly be a run around car so want it to be a quick get up and go. Will have limited freeway driving, 15 minutes to work or if I want to take it on a weekend jaunt wouldnt see more than an hour of the open road. Id like to do it right the first time which means Im already going to be pushing out that budget.

Please let me know if Im off track on my thought process, once again not a gear head and in all new territory here. Thanks.
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post #20 of 32 (permalink) Old Jul 23rd, 19, 5:59 AM
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Re: 71 Chevelle 350, looking for direction

12 bolt diffs are pretty pricey nowadays and most need a rebuild on top of it. 8.5's can be hard to find and expensive to rebuild. If your diff is stock it's probably an 8.2 ten bolt. It would be strong enough for what you're doing, especially with stronger aftermarket axles, unless you put sticky tires on it.

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post #21 of 32 (permalink) Old Jul 23rd, 19, 6:12 AM Thread Starter
 
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First thought was 8.5 ten bolt but spacing on bottom bolts is closer to 3”. Didn’t look like any of the pics I found of 8.2’s.
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post #22 of 32 (permalink) Old Jul 23rd, 19, 2:01 PM
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Re: 71 Chevelle 350, looking for direction

https://sacramento.craigslist.org/pt...938261013.html

This is about the price range in our area for a good working Chevelle 12 bolt. This one already has 373 gears.

Get the numbers off the front right axel tube and we might be able to tell what rear end you have. You'll need to verify the gear ratio mechanically.

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post #23 of 32 (permalink) Old Jul 23rd, 19, 4:00 PM
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Re: 71 Chevelle 350, looking for direction

What you have is most likely an 8.5" 10-bolt, the cover does not look like a 7.5" cover. 1970 (in theory) was the last year of the 8.2" Chevy 10-bolt, and the 8.875" 12-blot car axles. I say in theory because I previously owned a 1972 Pontiac Trams Am that had a 12-bolt axle. Another thing that points to that being an 8.5" 10-bolt is that you would usually find the 8.2" 10-bolt axles behind the smaller engines such as the 307, 283 and six cylinders, and the 12-bolt was used on the larger engines such as the 327, 350 and big blocks. The 7.5" 10-bolt did not come out until 1975.

Most of the 1971/1972 "A" Body cars I have seen over the years had 8.5" 10-bolt axles, the exception being the large cube (454/455) engine cars which still used the 12-bolt. Buick, Olds and Pontiac all used the 8.5" 10-bolt in addition to Chevy - but they used different covers - each one had their own shape, and yours looks like a Chevy 8.5" 10-bolt cover.

The best way to confirm is to pull the numbers off the axle tube where shown above. That will tell you exactly which 10-bolt you have.
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post #24 of 32 (permalink) Old Jul 23rd, 19, 8:33 PM Thread Starter
 
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Re: 71 Chevelle 350, looking for direction

Ok I pulled the numbers off the axle but now Im more confused because not seeing anything that matches the code.

GAC 029 1

And yes I cleaned it pretty well to read it.
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post #25 of 32 (permalink) Old Jul 23rd, 19, 10:31 PM
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Quote:
Originally Posted by Slysharky View Post
First thought was 8.5 ten bolt but spacing on bottom bolts is closer to 3”. Didn’t look like any of the pics I found of 8.2’s.
It’s not an 8.5, no ears at 5 & 7 o’clock. 8.2 or something.

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post #26 of 32 (permalink) Old Jul 23rd, 19, 10:37 PM Thread Starter
 
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Re: 71 Chevelle 350, looking for direction

Answered my own question.

GA - 2.56:1 10 Bolt
C - Buffalo
029 - 29th day of the year
1 - day shift

But still unsure if its a 8.5, 8.2, or 7.5.
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post #27 of 32 (permalink) Old Jul 23rd, 19, 10:44 PM
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Take a pic of each side of the pumpkin and the casting number

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post #28 of 32 (permalink) Old Jul 23rd, 19, 11:06 PM
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Re: 71 Chevelle 350, looking for direction

Quote:
Originally Posted by Slysharky View Post
Answered my own question.

GA - 2.56:1 10 Bolt
C - Buffalo
029 - 29th day of the year
1 - day shift

But still unsure if its a 8.5, 8.2, or 7.5.
Since you're on a quest for knowledge I won't give you the answer. But I will give you
a hint...https://www.chevellestuff.net/qd/rear_axle_info.htm

Did you find a casting number? Should be 10-Bolt Casting #3969277
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post #29 of 32 (permalink) Old Jul 25th, 19, 7:19 PM Thread Starter
 
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Re: 71 Chevelle 350, looking for direction

So found the engine stamp and the vin matches (no surprise there since only owner) looks like it came out of Flint and the suffix is CGC which says it got 245 hp, the 2 bbl carb and the TH350 tranny. Still trying to find the stamp on the tranny to verify that matches.

So what this means is that Ill be rebuilding this one to keep the numbers matching. And from what I gather sounds like better off just spending the money on aftermarket heads compared to have the old heads machined. But still researching that aspect.
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post #30 of 32 (permalink) Old Jul 25th, 19, 8:40 PM
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Re: 71 Chevelle 350, looking for direction

Do you have the build sheet that's located under the back seat? If you can still read it, lots of good info on it.

'69 Chevelle 416" LSA TONY MAMO TFS Heads and custom Hyd roller cam.
Best 60' so far....1.34


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