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1978 L82 heads for 1978 L48??

srs244

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1978 pace car, 04 CE convert
i realize bore, stroke, porting and cam, etc are major components to improve engine performance, however, i have the chance to buy an original set of 1978 L82 heads that have been magnafluxed and shaved at what i perceive to be a resonable price. would changing the heads out on my original 1978 L48 automatic pace car buy me anything at all or is it just a waste of time and $$?? my future plans (time frame undetermined at this point) are to rebuild the engine ala 383 stroker type configuration.

thanks for the opinions and comments.

steve
 
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Denver, CO
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'72 Targa Blue Coupe
[An original set of 1978 L82 heads that have been magnafluxed and shaved at what I perceive to be a resonable price.]

Certainly, milled heads will raise your compression a bit-you are 8.5:1 now. I am curious if there is a difference in combustion chamber size L-48 vs. L-82? This will also play into the compression factor. How much were they milled (shaved)? I believe after a certain point (.030?), the intake needs to be milled as well to account for the change in "angle".

I also think the L-48/L-82 intakes are different. To gain better advantage you may want to consider changing the L-48 intake to something else. And, of course, a camshaft change would be in order to get the best bang for your time and effort. Hope this helps, good luck.

Rick
:gap
 
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[An original set of 1978 L82 heads that have been magnafluxed and shaved at what I perceive to be a resonable price.]

Certainly, milled heads will raise your compression a bit-you are 8.5:1 now. I am curious if there is a difference in combustion chamber size L-48 vs. L-82? This will also play into the compression factor. How much were they milled (shaved)? I believe after a certain point (.030?), the intake needs to be milled as well to account for the change in "angle"....Rick
:gap

Ditto!

Also, don't just go with advertised chamber sizes. Measure them or have someone measure them.

There are 305 heads that came with smaller chamber sizes, and I would have to go home and check for the casting number for those.

GerryLP:cool
 

Vettehead Mikey

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I believe both engines had the same head castings, so the only difference will be the diameter of the valves.

Not sure if that by itself will be worth your while.
 
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1981 HD Suspension; ZN1 Option
I believe both engines had the same head castings, so the only difference will be the diameter of the valves.

Not sure if that by itself will be worth your while.

I believe that in the early 80's, the 305's came with castings 14014416'S, 367450'S, and 14022601's. And I remember reading somewhere that the first two were 62 cc's and the 601 was 60 cc's.

Besides, weren't the early 305 heads casting 454's?

I just recall this because recently, while considering whether installing the original L81 heads, I looked into the 305 heads.

Edit: My point was that a smaller chamber should help nicely to increase your engine's CR. In the realm of "a balanced combination of engine componens", CR is king and 'quench' is queen.

GerryLP:cool
 

Evolution1980

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Steve, After reading the posts above, it looks like it's all going to come down to what it's going to cost you to have the work done. An increased CR will give you more power, but how much -vs- what it cost you in time/money. If you are going to upgrade to a 383, you might just be better off waiting and putting the money towards the 383.

I'd ask myself: What will I realistically be expecting for the money/time invested? Am I looking for significantly more oomph off the line? Am I looking to shave .3 seconds off my quarter mile time? What's the monetary value you place on those wants? Since you can't guarantee what you'll feel/experience, is the mod a good bet for your money?

...but those are just questions I ask myself because my budget is exceptionally tight nowadays.
 

srs244

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Apr 1, 2005
Messages
462
Location
the deep south
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1978 pace car, 04 CE convert
i certainly appreciate the input. mikey, i believe you are absolutely correct in that the difference was strickly in the "quality" of the head as it related to valve size. while i realize that CR wouldn't be altered to any great extent, my thinking was simply that it might just help out a bit (a kind of cheap fix if you will) without major cost and alterations at this time (i also find a very tight budget at this time. i just bought an entire interior replacement from wall to wall, ceiling to floor, to restore the interior of my 78 pace car, so $$ is a bit tight at this point).

i wasn't looking to burn up a quarter mile, chop 3 seconds of a track time, or blow the next porsche i find next to me at a light, into the weeds. as you all know late 70's C3s aren't exactly known for their "throw you back in your seat" power ratings. i have eliminated the cat on the car and replaced the exhaust system with 2 1/2" non mufflered pipes (use only a resonator in the monza style tips). went to a dual snorkle air cleaner, all the non expensive type improvements to try to help the situation out until i can fork over the $$ for the engine rebuild. my objective was to simply get a bit more out of the engine with the heads (if in fact it would help) because once again, it appears the price might be right.

once again, thanks for all the input and opinions, it is greatly appreciated.

steve
 

RUSS O'BLENES

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Aug 23, 2006
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29
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LYNN MASS.
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1970 BRONZE COUPE/WHITE 69 CONV
i certainly appreciate the input. mikey, i believe you are absolutely correct in that the difference was strickly in the "quality" of the head as it related to valve size. while i realize that CR wouldn't be altered to any great extent, my thinking was simply that it might just help out a bit (a kind of cheap fix if you will) without major cost and alterations at this time (i also find a very tight budget at this time. i just bought an entire interior replacement from wall to wall, ceiling to floor, to restore the interior of my 78 pace car, so $$ is a bit tight at this point).

i wasn't looking to burn up a quarter mile, chop 3 seconds of a track time, or blow the next porsche i find next to me at a light, into the weeds. as you all know late 70's C3s aren't exactly known for their "throw you back in your seat" power ratings. i have eliminated the cat on the car and replaced the exhaust system with 2 1/2" non mufflered pipes (use only a resonator in the monza style tips). went to a dual snorkle air cleaner, all the non expensive type improvements to try to help the situation out until i can fork over the $$ for the engine rebuild. my objective was to simply get a bit more out of the engine with the heads (if in fact it would help) because once again, it appears the price might be right.

once again, thanks for all the input and opinions, it is greatly appreciated.

steve
The chamber size on both heads are the same. 76cc. The L48 heads have 1.94 intakes and 1.50 exhaust. The L82 heads have 2.02 intakes and 1.60 exhausts. It is true that the heads are the same castings. You would notice no difference in performance unless you did some port and bowl work, and as someone else said, depending on how much the heads have been cut you could have intake manifold sealing problems. Happy Motoring.
Russ
 

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