Im working on my77 l48 with an auto. I am going to be doing some motor work on the car very soon... I want the motor appear fairly stock. But lets face it 185hp wont work for me. I am also going to use side pipes. I have no issue using a new cam and a new intake and carb. I am not going to replace the heads. But I will rebuild them. Any suggestions would be great. Any thoughts on the most bang for the buck? How much hp can I reasonably get to?

 

to be honest with you, if you replace the cam you will have to replace the heads. stock heads won't flow enough to take advantage of the cam. check out one of the top end power packages from trick flow or edelbrock. make decent power and it's basically a top overhaul provided the block and the rest of your car is is in shape to hold it.

 

First, Depending on the compression of the engine, that will limit how much cam lift and duration you will use. Second, use your stock heads. Your not going to be making 500+ HP, so stock head will work just fine.
Cams to use for stock set-up, Comp # K12-206-2 or K12-210-2. These are complete sets that include: Cam, lifters,Springs,Retainers,locks,stem seals,Timing chain set,lube ,and instructions. You can use either of these sets with stock gears ( rear end), and stock converter. Both sets good for low end and great midrange power.

 

The one thing you did not say was how many miles is on your engine. Reference made to compression is an indicator but so is mileage and what kind of care it has received in its past. My Dad taught me mechanics but they were just basics not performance stuff. One thing he always said was valve/head rebuild was usually problems because most engines were weak in the cylinders by the time valve issues began to show up. I understand you did not say the valves seemed to be an issue just that you wanted more power but you still need to think about it. Sealing up the top will force pressure to go down by the rings if they are the least bit weak.

As so many have said before HP equates to money. More money spent = more HP. So set down and decide what you want to accomplish and how much money you want or have to spend for the task at hand.

My 2 cents for what it may be worth--

 

the motor has about 11000mi on it. The car has 52000mi. I want to make about 325 to 350 hp. I was wanting to tap into the thousands of years of experience to see if there is a combo ie cam, intake, carb and side pipes.

 

I agree with you that I would not change the stock heads unless you want 325-350 HP. A cam change alone should be good for slightly over 300+ HP with the stock heads. I would only change the heads if you are looking for 400+ HP.

 

300+HP with stock compression and heads? Gross maybe. The OP is speaking in net HP.

 

Yeah, you are not going to get anywhere near 300-325HP with 8.25:1 compression and a cam change. If you want stock GM heads you will need to drop on a set of '186's with 64cc chambers instead of those 76cc chambers you have. Better yet would be a set of ZZ heads with 58cc chambers with your 15cc dished pistons.

 

Mike you are right that with an L-48, the op probably will not get to 300HP but with 2.5 inch true duals, a good cam like the 268H, and headers he could get real close along with an aftermarket intake and carb. I was really thinking about the 300 HP net number with the L-82 with a free flowing exhaust and a good cam. He did state though bank for the buck and the cam is without a doubt his best bang for the buck even with stock heads. So I was only half wrong. Remember that even a brand new ZZ4 GM crate engine with a roller cam is only good for 355 gross and that cost $4,000 so changing heads and cam on a stock L-48 is probably never going to that level and not be the best bank for the buck spending the additional money on heads unless as I said he is planning to go over 400 HP and is willing to change a host of other components to get there. Hope that clarifies what I was saying. Just change the cam!

 

Summit Racing - $309.00 each


http://www.summitracing.com/parts/SUM-152123/?rtype=10

 

ok so how much hp gross do you all think I would get with the summit heads for 300 each, the 286h cam and is there a suggstion on intake and carb? Oh and I am getting sidepipes with the sts baffles.

 

So, what you got there, a stock, rebuilt engine with 11,000 miles? And you don't want a race car, just make some more power, enough to make it fun to drive, right? What you need is better heads. The stock camshaft that came in your 185 horsepower '77 L48 is the same cam that came in the 300 horsepower 327 ci v-8's back in the 60's. Granted, that's net vs. gross, but still quite a bit more power from a smaller engine. Why? Two words: SMOG HEADS!!!! Basically, your heads suck from a performance point of view. A better flowing head with a smaller combustion chamber to bump up the compression ratio, an Edelbrock Performer intake manifold, (you can find 'em on ebay and craigslist for 50 bucks or less) and a set of headers, and you will be amazed at how much more peppy your 'vette will be.

In a nutshell, those crappy stock cylinder heads won't let a bigger cam do much of anything, and with better heads, you won't need a bigger cam, anyway. I am planning on doing the same thing you are on my 1980 L48, and I have decided to go with Edelbrock E-Street aluminum heads, they are about 900 bucks. Those Summit heads look nice, too, but for another 300 bucks, you can get aluminum heads with a 64cc combustion chamber that flow even better. Another choice, if you wanna stay with cast iron heads, is the vortec heads from GM Performance. You need a different intake manifold with these heads, and I think maybe different pushrods and rockers, which adds to the expense, unlike the summit heads which will use all of your old valvetrain.

You can upgrade the cam along with the new heads if you want, of course. But I wouldn't bother without a better set of heads to let it breathe. Also, you can upgrade the cam in the future, if you ever decide you want to.


Scott

 

Yes, those Summit heads will not do much for you, they still have large 72cc chambers. Buck up for some better heads like Brodix IK180s or as mentioned above. Even with 64cc heads and a .015" head gasket you will be only achieving 9.1:1 compression, thats why the zz heads with 58cc chambers are ideal for a L-48, right around 9.75:1. Depending upon your final compression you can choose a cam, I wouldn't bother with a cam swap unless you had better heads, you will loose your dynamic compression with a larger cam.

 

3 angle valve job and pocket port job and a small can will likely give you what you are looking for and the car would run on the crap gasoline were probably headed for. get a suggestion on cams from a couple came manufacturers. all have a tech line

 

http://www.carcraft.com/projectbuild...all/index.html
Kind of a cool article

 

I have basically the same engine (1980 L48) and am planning the same sort of buildup, so I've done some math regarding compression ratio, and my calculator shows that a 64cc chamber with a .015 gasket will give me 9.49/1 static compression ratio. I am assuming a 12cc dish on the pistons, and a .025 deck hieght, stock bore and stroke, are you using a different dish volume, maybe? (I'm not 100% sure about the dish being 12cc, if you are positive about pistons having different dish volume, I'd like to hear about it.)Anyway, my calculator also shows that with the stock cam and 9.49/1 static CR, the dynamic CR is about 8/1, which is cutting it kinda close to the limit for pump gas. At 9:1 the Dynamic CR is more like 7.6:1, gives you some margin for error. Unless your the kind of guy who likes to cut things close......I know I do, sometimes. I think I'm gonna run the .015 gasket!!


Scott

 

Yes I am using -15cc for the dish calculation. The Fel Pro .015" gasket for best compression ratio.

 

"The stock camshaft that came in your 185 horsepower '77 L48 is the same cam that came in the 300 horsepower 327 ci v-8's back in the 60's. Granted, that's net vs. gross, but still quite a bit more power from a smaller engine. Why? Two words: SMOG HEADS!!!!"

Not quite! Again changing heads will transform the power from the engine along with a cam swap. HOWEVER, the heads are not the whole story about the quote above:

1. If the op is looking for major/BIG HP increases (350HP) he has to change the heads and cam-as many have stated.
2. The 60's Gross rated 327 @ 300 HP is actually about 230-240 HP net (that is being generous, it is probably about 220 HP net).
3. The compression ratio on the 300 HP 327 is higher than the 8.5 on the L-48.
4. The Y Pipe exhaust and boat anchor cat that came on the L-48 is VERY RESTRICTIVE-removal of that crap exhaust and adding headers and free flowing duals will unleash MUCHO HP-that has been documented time and time again.
5. Dumping all the OEM pollution control is good for a few more horses including the OEM emissions carb, EGR valve etc.
6. Cam changes on an L-48 can add 50-75 HP with smog heads-documented

When it is all said and done, with the SMOG heads an L-48 with the changes above will easily surpass the 327's power with non smog heads.

My point is that this notion that the only way to get significant gains on these motors is to swap heads is NOT true- It is the only way to get BIG HP gains but time and time again, smog heads can be worked with and it has been done. In the 80's, I helped friends do cam changes on smog headed motors-the cam only-and there were big HP gains (50-75 net HP) with smog heads!

Bang for the buck-cam change along with other modifications! Pretty well documented that these changes can bring 100-125 HP with SMOG heads-again bank for the buck!

Just to be clear.

 

Problem with the ZZ4 heads is they flow pretty pukey out of the box but will pick up compression.

There is no way in hell with an exhaust system a cam change he can drive on the street exhuast/intake is going to get him 100hp or anywhere close to it, sorry

 

So you don't agree that a cam change on an L-48 can give you 50 HP at least?