Getting more Horsepower

[krscholz]

It looks to me that the L-48 and L-82 are identical except for compression ratio. What is the poor man's answer to increasing the horsepower on a L-48. At mininum milling the heads will make it a L-82 or do I need to do more?

 

[Vette79]

Here is what I did: http://www.corvetteactioncenter.com/forums/c3-general-discussion/103334-79-top-end-rebuild.html
A complete top-end rebuild of an L-48.

The main difference between the L-48 and L-82 are the heads and cam.

 

[krscholz]

So, the poor man's answer would be to change out the cam and mill the heads????

 

[JohnZ]

It looks to me that the L-48 and L-82 are identical except for compression ratio.

The L-82 uses a different cam, the valves are larger, and the pistons are different.

 

[duke94]

Here's an article about L-48 upgrades from one of the Mags.

 

[Vette79]

The L-82 uses a different cam, the valves are larger, and the pistons are different.

I did not know this. John, what is the difference about the pistons between the L48 and L82?

 

[duke94]

Here's a link that shows all the differences.

1978 Corvette Specifications

 

[krscholz]

Here's a link that shows all the differences.

1978 Corvette Specifications

Okay, I can see there is quite a difference between the 1979 L-48 & L-82. What about the 1975 year. Is is it the same as 79??

 

[krscholz]

For an easy Poor Man's fix a cam will add about 20HP. Right?

 

[Glensgages]

For an easy Poor Man's fix a cam will add about 20HP. Right?

I don't think that changing the camshaft, in-and-of itself, in a stock L-48 will result in the best-possible performance:
you'd still have restrictive cylinder heads, with low compression, and poor exhaust.

A year ago, a buddy swapped-out his top-end & cam on his '80 L-48, and went with vortec heads (64cc = increased squeeze, with better port configuration), RPM Air-Gap Vortec, Holley SA carb, the 270H CompCams hydraulic with headers & true-duals, and reports the car is totally different than before.

 

[krscholz]

I don't think that changing the camshaft, in-and-of itself, in a stock L-48 will result in the best-possible performance:
you'd still have restrictive cylinder heads, with low compression, and poor exhaust.

A year ago, a buddy swapped-out his top-end & cam on his '80 L-48, and went with vortec heads (64cc = increased squeeze, with better port configuration), RPM Air-Gap Vortec, Holley SA carb, the 270H CompCams hydraulic with headers & true-duals, and reports the car is totally different than before.

In looking at the specs between a L-48 and L-82 there is a significant difference. I spoke with CompCams and they recommended the "Extreme Energy XE262H cam that would work well with my stock rear, trans, exhaust etc. In just doing the cam we're looking at keeping the cost under $150. Adding the kit that goes with which includes gear chain etc. it adds another $300 plus to the cost. Bottom line, without doing a complete rebuild, the cost overall would run under $300, plus my time.

 

[krscholz]

Here is the best guy that I have found to talk to about this issue. His name is Mike at CompCams. Here's a guy that done the work and knows what he's talking about from experience. Keep in mind this is the "Poor Man's" route to increased HP assuming everything is stock on your car. He recommends the following cam to do the job (see the attached link): XE262H-10, Camshaft Part#12-238-2 Dyno Sheet

Read this next link with helpful information for installation of the cam.

http://www.compcams.com/Base/pdf/FlatTappetCamTechBulletin.pdf

I also asked about port and polish since everyone's been swinging this term around -Mike indicated that removing the ridge in the bowl area is much more important as the ridge restricts the flow to the cylinders.

Trust me; this guy really knows his stuff. So, bottom line if you want to increase your horsepower from your miserably under powered 350 for under $300 this may be the way. Also, make sure you get the camshaft kit from CompCams. Mike's number is 800-999-0853. (No, I don't work for CompCams I just like doing business with people that know their stuff.)

 

[Vette79]

The XE262H is what I am running and find it very mild. You should go with the XE268H. Definitely replace the heads or have them worked. Heads are where the power is at!

 

[krscholz]

The XE262H is what I am running and find it very mild. You should go with the XE268H. Definitely replace the heads or have them worked. Heads are where the power is at!

Jeff, take a look at the Tech graph from CompCams and you will see that the horsepower drops at 5,000 RPM with the 268 cam. Unlike the XE262H which maintains its higher horsepower a little longer. Go to CompCams and print out both tech reports and compare them side by side and you'll see the 262 performs slightly better. When you say mild what do you mean. Can you express the horsepower difference in terms of percentage? Are you satified with the 262 performance overall?

 

[Vette79]

Jeff, take a look at the Tech graph from ProCams and you will see that the horsepower drops at 5,000 RPM with the 268 cam. Unlike the XE262H which maintains its higher horsepower a little longer. Go to ProCams and print out both tech reports and compare them side by side and you'll see the 262 performs slightly better. When you say mild what do you mean. Can you express the horsepower difference in terms of percentage? Are you satified with the 262 performance overall?

You are absolutely correct about the numbers. I'm still waiting to DYNO my build and fine tune it so I can't really comment specifically yet.

 

[krscholz]

You are absolutely correct about the numbers. I'm still waiting to DYNO my build and fine tune it so I can't really comment specifically yet.

How difficult was it to remove the fan and shroud. Have you got a procedure you can share with us?

 

[Vette79]

How difficult was it to remove the fan and shroud. Have you got a procedure you can share with us?

I can go through my various pics during my top-end rebuild and send you some if needed. Just PM me. I thought the removal of the shroud was a PITA. You need to remove the fan and clutch assembly first which was very straight forward and easy. The shroud just needs to be manipulated a bit in order to remove and install.