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Discussion Starter #1
Guys, I have a 78 L-82 4 speed that internally is totally stock except Comp cams roller tipped 1.5 rockers with 65,000 miles. The engine has the OEM aluminum intake, a 650 Holley 4175 spreadbore replacement, zero pollution control (no EGR valve, heat riser valve, No AIR pump and hardware etc), shorty headers, 2.5 true duals, and Monza Turbo mufflers. The engine burns zero oil, the valve train is whistle clean, and I am going to take a look at the bottom end this spring when I replace the rear main seal for a leak there. I am also replacing the oil pump at that time since I am already in there. here is the question:

I am looking for a little more power, not big power, from the stock L-82 but I do not want to change heads-I know that the stock L-82 882 heads are 76 cc and smog heads that are not very good-but again, want to keep the engine stock and to use the OEM valve covers as well. If I keep the OEM intake and Holley carb and just port the OEM heads and change the cam (thinking of the comp cams 268H), what kind of power difference can I expect? Should I add the cam and leave the heads alone? Is it worth porting the heads and how much to do that?

I have a 2010 Z06 for big power so that is not the goal-just a decent amount of an increase with stock components!

Thanx for your responses!
 

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First off, why replace the oil pump? Is your pressure bad? If your pressure isn't low I say no reason to replace the pump. Typically bearing wear will affect oil pressure before a worn pump ever will, and from the sounds of things I see no indications that your pump would be an issue.

Porting your heads might help a little bit, but without other changes I don't think it would even be worth the effort...or cost if you're having someone else do it.

The problem is that changing just one aspect of your induction system will not get you great results. Think of it like this. Cut a small section out of the middle of an air vent pipe in your home, and replace that one section with a larger diameter pipe. You won't increase the amount of air that flows through that pipe at all.

To make power through induction, every aspect of the air in / air out system needs to be worked on.

Trust me though, I understand the dilemma of trying to make more power without making large noticeable changes. However, you can do little bits, like have already been done, to help.

To close, I recommend the following to get the best gains from what you have and what you're willing to do.

Have your carb serviced, and tuned to your goals.
If you port the heads, port the intake too, and gasket match all of it. Get a good mildly aggressive cam. I like the Comp 268H for utilizing the stock compression of an L82. It'll really wake it up with some improvements to the induction system.

Then, and this is an important step, take the car to a local shop that has the equipment to properly tune your combination by monitoring the exhaust gasses and ignition system. The carb and timing are what they'll adjust using data collected from the exhaust and ignition system. But, they have to have the right equipment so make sure you ask.

The above might net you a very noticeable difference without requiring a lot of very noticeable changes.
 

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Now this is just my personal opinion, but, I recommend that you JUNK THE L-82 HEADS!!!

Here's why: In the late 70's they were shaving material out of the heads to reduce weight, for "better gas milage". This thinned out the material where the siamese arranged exhaust valves and the EGR valve are located. This area generates alot of heat due to the EGR vavle, and will eventually crack.

This happened to mine. repaired, happened again, then I opted for a Holley SysteMax II top end kit, and swapped the Holley square-bore for an Edlebrock Performer spread-bore manifold and Q-Jet carb.

Looks virtually stock, except heads are "shiny" aluminum, and is good for 425 hp, if you run headers!

Don't wasted any money trying to maintain these flawed factory heads, go aftermarket for long term happiness!
 

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Discussion Starter #4
Thanx to both of you two above for your opinions.

I really do not want to go the aftermarket head route since I do not want to junk the heads unless I have to. I am either going to have the heads ported VERY CAREFULLY and very minorly and I like the idea of porting the OEM aluminum intake manifold. Either that or just leave the heads alone and port the intake and add a cam along with a new timing chain and gears.

What does a matched set of gaskets mean exactly? I didn't figure that the gaskets would play a big role in this change.
 

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What does a matched set of gaskets mean exactly? I didn't figure that the gaskets would play a big role in this change.

Gasket matching is a MUST if you are spending the time and money to port. Use a set of very specific gaskets that you will use for your build. They become the template for the ports on the intake, and the heads...where the two meet. The more linear the travel path is for the air, meaning it slips through perfectly where the intake and head meet at the gasket, the better.
 

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Discussion Starter #6
Gasket matching is a MUST if you are spending the time and money to port. Use a set of very specific gaskets that you will use for your build. They become the template for the ports on the intake, and the heads...where the two meet. The more linear the travel path is for the air, meaning it slips through perfectly where the intake and head meet at the gasket, the better.
Thanx for the explanation!
 

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Discussion Starter #7
Ok Guys, I have been doing some research and I am now considering a top end change for the L-82 even though it only has 65,000 miles on it since I figure that I can keep the 882 smog heads, the cam (if someone wants it if the car is sold) and intake. Just read an article in Super Chevy magazine where they dynoed a bone stock L-82 at 313 Gross HP at 5,500 RPM and 355 torque @3,800 which are right on the money in terms of RPM for a stock motor and about 250 HP Net. With the changes only described below the new numbers were 414 HP @5,900 RPM and 415 torque @ 4,100 RPM-Gross again. Here are the 3 changes:

RHS 64 CC 200 CC runners-aluminum heads-$650 per side=$1,300
Pro Comp Dual Plane manifold-$125
Comp Cams XE274H-$350

I would reuse my Holley 4175 650 CFM spreadbore and my comp cams 1.52 roller tipped rockers. I figure about $2,000 for the heads, intake, new valve covers, gaskets, 274 complete kit with Timing chain, springs etc.

Good deal? Recommendations if the combo is better than above for the same money.
 

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That's a fine combo. You wouldn't be disappointed with it at all. Please just make sure it's tuned properly. :thumbsup:
 

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Will that intake fit under a stock hood? I have the same set-up as you and I was told the 200cc runners are too big and stay around 185.
 

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Discussion Starter #10
Thanx for the feedback about the setup! I will definitely check about the 200cc runners versus the 185 CC runners to make sure that it will fit under my hood and I can use the stock air cleaner.
 

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Thoughts

650 vacuum carb is awful small for an engine with 200cc heads.

Dart iron eagles are an excellent budget line of street heads, and 190s are out there in decent quantity, so you can actually find them used.

If you're considering other heads, half the power gain you're going to see is due to the increase in compression, not from superior head flow.

Here's a different approach.........
How much would a procharger and a blow-thru carb cost in comparison? Don't even touch the L82 unless it's to install a blower cam. Blowers like low compression, and are especially good at overcoming bad heads. Hmmmm......sound familiar?? 4.5 psi on your existing engine would equal the combo you're proposing in terms of WOT power, plus have a torque curve that'd make a big block jealous. And ought to run fine on pump premium.
 

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Thoughts

650 vacuum carb is awful small for an engine with 200cc heads.

Dart iron eagles are an excellent budget line of street heads, and 190s are out there in decent quantity, so you can actually find them used.

If you're considering other heads, half the power gain you're going to see is due to the increase in compression, not from superior head flow.

Here's a different approach.........
How much would a procharger and a blow-thru carb cost in comparison? Don't even touch the L82 unless it's to install a blower cam. Blowers like low compression, and are especially good at overcoming bad heads. Hmmmm......sound familiar?? 4.5 psi on your existing engine would equal the combo you're proposing in terms of WOT power, plus have a torque curve that'd make a big block jealous. And ought to run fine on pump premium.
Slow & leaky
I am very interested in this setup can you point to a install in a c3 stock motor and tell me more about what would have to be done to complete the install. How much do you think the overall cost would be. I have a all stock 350 with quadrajet carb.

Thanks Mark:cheers:
 
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