300hp engine modifications.....
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Instructor
Joined: Aug 2004
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300hp engine modifications.....
Well, I have a '65 327/300 coupe with powerglide.....it is all original, Top Flight car, a couple of times. My questions is, are there modifications that can be done to increase hp, but maintain the exterior appearance of the motor???
Melting Slicks
Joined: Mar 2004
Posts: 2,964
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From: Melbourne FL
Probably the simplest one that retains it's present appearance is the L-79 cam. You could get a set of date correct heads that have the larger valves to go along with it but not sure if they would help that much if you stayed with the 300HP intake and manifold.
Race Director
Joined: May 2000
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DON'T install a L-79 cam in a PG car!
The best mod you can make is to pocket port/port match the head/manifold and a multiangle valve job. Retain the OE size valves. This will yield up to ten percent more top end power, and it will pull strong to 5500 without affecting the low end torque that is a MUST with PG.
Search on "pocket port", "pocket porting" using my screen name.
Duke
The best mod you can make is to pocket port/port match the head/manifold and a multiangle valve job. Retain the OE size valves. This will yield up to ten percent more top end power, and it will pull strong to 5500 without affecting the low end torque that is a MUST with PG.
Search on "pocket port", "pocket porting" using my screen name.
Duke
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Restorations vs. Horsepower
We've been doing an average of 20+ units a year for Island Musclecars (a resto shop) on Long Island. Both SB's and BB's combined. We are able to produce approximately 50/150 HP gains keeping EVERYTHING looking original. This includes block, heads, manifolds, (intakes and exhausts). We just finished a 350/300Hp unit with 360Hp and 390+ Ft.Lbs. torque. They all run on 89/93 octane. The only non-original internal parts on this unit was the pistons, we used a set of Ross lite-weights along with lite pins. We were instructed by the shop to use the factory L-82 cam. We would have had slightly higher numbers with our cam choice taken from dyno testing. We have a BB going on the dyno in the coming week for a '72 Chevelle 4-speed, convertible. It's a 496" oval port, cast intake, Q-jet equipped, and Hyd-Roller that we think will make close to 600 HP. There was a last minute cam swap (downward)
on this particular one due to a power brake booster issue. We seem to be able to use a factor of 1.2 HP/Cu.In. So far we're right there keeping with fuel limitations. Thanks, Gary in N.Y.
on this particular one due to a power brake booster issue. We seem to be able to use a factor of 1.2 HP/Cu.In. So far we're right there keeping with fuel limitations. Thanks, Gary in N.Y.
Melting Slicks
Joined: Mar 2004
Posts: 2,964
Likes: 419
From: Melbourne FL
Originally Posted by SWCDuke
DON'T install a L-79 cam in a PG car!
The best mod you can make is to pocket port/port match the head/manifold and a multiangle valve job. Retain the OE size valves. This will yield up to ten percent more top end power, and it will pull strong to 5500 without affecting the low end torque that is a MUST with PG.
Duke
The best mod you can make is to pocket port/port match the head/manifold and a multiangle valve job. Retain the OE size valves. This will yield up to ten percent more top end power, and it will pull strong to 5500 without affecting the low end torque that is a MUST with PG.
Duke
And I wonder if "up to ten percent more top end power" would do much to satisfy someone wanting more horsepower for a street driver. Of course a stroker conversion would do the trick and keep it looking stock but don't know how advisable that might be all things considered.
Race Director
Joined: May 2000
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The 300 HP cam makes substantially more torque in the off-idle to 2500 RPM range than ANY of the SHP cams. In fact it will make greater torque/power than any SHP cam in a 327 up to about 3500 RPM. Between 3500 and 4000 SHP cams will begin to assert an advantage that increases with increasing revs. The L-79 cam makes better low end torque compared to the mechanical lifter cams, but the LT-1 cam is not far behind. The 30-30 cam lags substantially.
You can certainly feel a ten percent improvement in top end power that mild head work will yield, but the most dramatic feeling will be the engine's willingness to still rev strongly beyond where it used to fall flat because the power will both peak higher, and stay higher longer before it falls off.
Back to the original question. It's reasonable to "upgrade" a 300 HP engine with a L-79 cam if you have a wide ratio four speed and 3.36 axle, but PG only has a 1.76:1 first gear, and even with a torque converter that can multiply torque up to about 2:1 at very low revs, unless you are doing virtually all high speed driving, you need every lb-ft of low rev torque you can muster with a Powerglide, or the car will feel doggy in normal around town driving.
Duke
You can certainly feel a ten percent improvement in top end power that mild head work will yield, but the most dramatic feeling will be the engine's willingness to still rev strongly beyond where it used to fall flat because the power will both peak higher, and stay higher longer before it falls off.
Back to the original question. It's reasonable to "upgrade" a 300 HP engine with a L-79 cam if you have a wide ratio four speed and 3.36 axle, but PG only has a 1.76:1 first gear, and even with a torque converter that can multiply torque up to about 2:1 at very low revs, unless you are doing virtually all high speed driving, you need every lb-ft of low rev torque you can muster with a Powerglide, or the car will feel doggy in normal around town driving.
Duke
Last edited by SWCDuke; Oct 10, 2005 at 12:24 AM.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
Originally Posted by 65air_coupe
I guess not owning a PG equipped car leaves me on the ignorant side of it's performance, or lack thereof. Sorry for the erroneous suggestion.
I wouldn't feel too bad about it. Your suggestion of a L-79 cam is not a bad one. It depends on what rear gear or converter you run or how you drive it.
For example, a friend in 1962 wore out the 283 Power Pack in his '58 Biscayne. He replaced the short block with a crate 327/360 short block. The thing ran like a striped a---d ape with a stock glider. He did have a 4.56 gear in it. I'd bet that L-79 cam would work great in the PG car if you weren't interested in right off idle performance. Up around 2000 or so, it would work great and sound good to boot.
By the way, I own a '63 300 hp car and I absolutley hate the torque curve it has. Reminds me of driving a Buick straight eight Dyna-Flow.
They put transmissions in cars to change gears, not drive in high gear all the time.
I also have a 327/350 in a Chevy II (L-79 cam). You can pull it down to 10 mph in high gear and pull away with no problem. No, I don't think your idea was that bad at all.
Last edited by MikeM; Oct 10, 2005 at 08:49 PM.
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Melting Slicks
Joined: Mar 2004
Posts: 2,964
Likes: 419
From: Melbourne FL
Thanks Mike, I have the same experience with my L79 with a 4 speed and 3.55 gears, pulls smooth and strong from very low RPM. That's why I thought my suggestion was okay, but as I said, I don't have the experience others may have.
Melting Slicks
Joined: Mar 2001
Posts: 2,370
Likes: 51
From: New Milford CT
How would that L79 cam work in an original 283 2x4 270hp? Paired with a 5 speed stick trans, with a pretty short first gear. I would think the original Duntov 097 is not as good all around as a more modern cam?
Race Director
Joined: May 2000
Posts: 12,712
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Better! The L-79 has about the same duration, but less overlap, which an engine with original manifolds will like, but the problem is that the Duntov cam will rev cleanly to 6500 plus. A 283 with L-79 cam would like to rev beyond 6000, but the lifters will pump up before 6500.
Duke
Duke
Last edited by SWCDuke; Oct 10, 2005 at 11:12 PM.
