Hi ,

I want to make my '74 L48 sound and run more like my '80 L82.  The '74 has an original 115,00 miles on it and a 4 speed, not an option on the '80.  After this summer I will probably spring for a rebuild of the L48 and I am researching options.  One is to go with an Edelbrock top end package, another is with a mild Thumper cam, 2000-5800 RP and a Summit engine rebuild kit.  I intend to store the stock parts in grease and plastic in case I ever want to rebuild to stock,but for now, I would like a bit more "show and go".  I really would like about a 50 HP boost, but don't want to go with headers if possible.  I now have wide open dual exhaust.  I would like to increase compression to about 9.0/1 but not go crazy.  Some of the rebuild kits are closer to 10/1.

If any one has experience with either of these or another option I would appreciate the input.  The car already has a 750 cfm
Edelbrock carb, non stock GM intake and low profile air cleaner.  Everything else original.

Thanks for any input,

Ray

I am new to this site and haven't figured out how to post photos under the message.  Something I should click on?

Thanks for the idea, Dave.  I poked around online and foumd crate engines running from $2100 which actually had a bit more horsepower than I was thinking about to $6000, which is a lot more than a rebuild.  The best price was from Summit.  I will certainly keep this in mind and store the stock engine.  I honestly don't know if a matching numbers engine would make the "74 that much  more valuabl, but it would be an ace in the hole.  I am trying to keep the car looking original, but after driving the L82 the performance seems dogged.

Where did you find your crate for the '82?

Ray

My Car


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|UPDATED|4/25/2013 10:14:28 AM (AZT)|/UPDATED|

Well I don't have any direct experience with the Comp Cams Thumper, but when I researched a cam choice for my engine I was interested in the Thumper cam too. I called Summit's tech line and spoke with a very knowledgeable person who told me that cam needs 9.5:1 compression ration to do any good and would not be a good choice for a near stock engine. The Thumper cam profile is more or less for the sound and not for power.  He advised me to go Comp Cams High Energy cam. He said the engine will run much better with that cam and he was right. The High Energy cam has a choppy idle that sounds good and runs good. I would call Summit and talk to someone about your plans for the engine and what they would recommend, they will be happy to do this for you. 

I originally was only thinking camshaft.  Don't have resources to do the work myself.  A mechanic I trust somewhat told me labor would be around $700.  Add $300 for parts.  I am wondering if it might lead to failure of my older engine .  The mechanic says it should be OK.  This is why I am looking for experienced opinions. 

Can you tell me what kind of performance increase you got with the new cam.  The '74 engine only has 8.25 or 8.5 to 1 compression.  You did not say which year engine you modified for a comparison.  Also,did you make other changes with the cam?

All opinions appreciated.

Thanks,

Ray

I purchased a slightly used (750 miles) rebuilt engine for my 74. In the process of working on the engine I discovered it over bored .040 with flat top pistons. Internally, that is about the extent of mods. Along with the cam, lifter, and valve spring kit, I installed an Edelbrock Performer intake, Summit Racing 600 cfm carb, high performance HEI tach drive distributor, aluminum water pump and headers. Unfortunately I have not had the engine dyno tested so I don't know horsepower, but it runs great. I would definitely get Summit's recommendations for a cam with stock internals or advice on a crate motor. That might be the best way to go, a lot less hassles.

Thanks for the input.  The nice thing about the L82 is the idle, the frustration is that you have to be in second gear to use the power curve, even on the 2 lane highways.  4 speeds not available in the year I have.  A power curve from 2000 to 5000 would be a lot more usable with the 4 speed Stingray. 

Now that the sun is about to shine, raining today, I won't lay the car away for improvements until the good  season is over.  We are lucky to have 6 good months here.  I will keep researching and thinking about things for a while yet.  Putting in about 300 HP of crate engine and storing the original is an idea I had not considered.  I will have to chat with Summit
Thanks,  Ray

Stock CR on the L-48 is 8.5.1
The only way to increase the CR to 9 or more is with new pistons. Any good cam is goin to need at least 9-9.5 to actually work right. Anything less, the engine will sound good at idle, but "won't pull a cork out of a broken wine bottle", so they saying goes.
You can get a really good "RV" cam, that will idle smooth, and give you goo-gobs(hi-tech term) of low end torque, but will fall on it's face above 3000rpm. Not a good choice, either.
The best money spent will be on a crate engine, in the long run, unless you have access to a machine shop, and can do the work yourself. Back in the day, we could build KILLER engines for $600....that won't even pay for machine work these days....that's what make crate engines so popular, annnnnd....they come with a warranty!

I think putting a high performance cam in an old engine will probably be a waste of money.  Trying to get that tired engine to make power will likely cause lots of blowby and you'll start seeing oil puking into your air cleaner via the PCV pipe.