327 rebuild with possible cam advice - Impala Tech
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post #1 of 7 (permalink) Old 03-18-2020, 04:55 PM Thread Starter
Join Date: Feb 2020
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327 rebuild with possible cam advice

Hey everyone. My powerglide transmission on my 66 impala is getting rebuilt as we speak. The shop is using all heavy duty parts. They said that would allow me to go with a cam if I needed one. I have the original 327 motor. It got me thinking... could I go with a mild cam and still use the original Carter AFB carburetor and stock rear end or would I have to upgrade these? I don’t absolutely have to have a cam and wouldn’t mind rebuilding to stock specs.

Also, what would be a fair price for a complete 327 rebuild, one with a cam and a stock rebuild?

Last edited by Vintage Classic; 03-18-2020 at 05:30 PM.
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post #2 of 7 (permalink) Old 03-18-2020, 07:21 PM
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If I had a 327 I would use a 350 horse L-79 hydraulic cam with new Z/28 springs. The L-79 cam doesn't have a lot of duration so you can keep your stock torque converter (1850 RPM Stall Speed) and because it is a hydraulic you lash it once and forget it. This cam offers a lot more lift than the stock cam which is why it has nearly 75 more horsepower than the stock cam (with 2.02" intake valve and a 1.60" exhaust valve 170 cc intake head). There are three different Chevy head castings that offer this combination of air flow over a stock 145 cc intake head. with 1.72"/1.50" valves.

If I were rebuilding a 327 it would be rebuilt as a 383 with a modern aluminum aftermarket head in the 215 cc intake runner range (2.08"/1.60" valves). With Chevy orange paint on the aluminum heads they could pass as stock at first glance.

The longer stroke in your 327 block really wakes up the motor to help move a two ton car.

Big Dave
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post #3 of 7 (permalink) Old 03-18-2020, 11:04 PM
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On my 64 Impala, I did a 383 stroker out of my 327. I used the stock heads, intake, block, just more cubic inches. I did use the slightly larger Carter AFB used on one of the 409's, but it all looks perfectly stock on the outside and a lot more power to the road. I do love the easy torque that the 383 gives. Of course, it does cost more
On the dyno, it made 370hp and 420tq. Stock 2-1/2 inch rams horns were very close to headers on the dyno.
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post #4 of 7 (permalink) Old 03-19-2020, 10:14 AM
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You did not state your goals for the cars performance. Many folks simply want 'better' acceleration.

'Amping' up a 327 (cam, heads, carb, exhaust, as Dave detailed) to wind to higher rpms to gain hp (in those higher rpm ranges) and mating it to the powerglide (likely mated to a 3.08 rear) will not do much except empty your wallet.

Now, put Dave's engine in a Nova (much lighter than an Impala) with 4.11 gears and a close ratio M22 4 speed, and you're ready to race!!

The +400 lb-ft of low end torque the '383' produces is a more productive solution to the 'better acceleration' quest for the 'heavy' car. That torque will 'pull' well, even with the powerglide/3.08 rear. Back in '66, one had to get a big block to get that torque, today the '383' small block does it easily.

Simply adding dual exhaust and the 2 1/2" manifolds will help the engine breathe/accelerate 'better'. And, if it's done the way GM did it, the car was built for those changes and everything FITS. And, if you're not satisfied with that much 'better', those changes support the 383.

Suggest you compare the cost of buying a crate 383, to having your 327 rebuilt into one, if you are so inclined.

In my opinion, if you are only going to 'cruise', save your money and stay with what you have. Spend it on something else the car needs to drive it. But it is your money and your choice. Good luck.

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post #5 of 7 (permalink) Old 03-19-2020, 02:24 PM
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Yes you could go with a slight up grade on that cam and get 20-40 more HP for basically the same money. You MIGHT end up needing a different valve spring to support the increased cam-lobe lift though. I'm not sure what your stock rebuild was putting in place.

As other noted though, a 327 has limited Torque at usable, lower RPM's compared to 350's/ 383's/400's so that issue combined with a Powerglide and kind of heavy car with stock rear gearing means that you're limited on any big boost of the seat of the pants feeling unless you spend more $$$. (either to go with 383 and/or do a trans with more gears and/or a gear ratio that allows for quicker acceleration.

You said you'd be fine with stock though so I have a feeling that you aren't really targeting anything other than good cruising, so the cam upgrade could be just what the doctor ordered. Will also give you a cool sounding exhaust note.

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post #6 of 7 (permalink) Old 03-19-2020, 10:05 PM Thread Starter
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Thanks. I just wanted a little better acceleration as well as engine sound. I think Iíll just have it rebuilt to stock specs since going with a cam with a powerglide and stock rear end wont give me a lot more power. The engine runs great at the moment and sounds good so if Iím gonna go that route Iíll just wait unless it gives me problems. The car only has 128K miles.
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post #7 of 7 (permalink) Old 03-25-2020, 09:01 PM
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Post 327 rebuild

The 327 is a great little engine, but if you add the L-79 cam, you need to add the compression to go with it. The factory L-79's were 11 to 1, 2.02 heads, aluminum intake and a Holley carb...cast iron intake and QJ in the final years. The L-79 was never offered with a Powerglide...that trans with the highway gears simply won't work with that cam.

You need a manual trans and at least 3.42 to 3.55 gears to make it work, assuming the engine build is correct.

You would be better off with a stock rebuild and refresh the tranny...don't waste your time and money on the L-79 cam unless you do the other upgrades.

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