how massive were ...
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Melting Slicks
Joined: Mar 2010
Posts: 2,731
Likes: 15
how massive were ...
the dishes in stock '74 pistons in an L48? Could a top end rework do some good? Heads, cam, intake, carb tune, etc. I would like to see a gain from the stock 190hp to 320-350hp. Without changing short block is it possible with 64cc heads or would I need to go to 58cc heads to get me near 320+hp? Thanks for any opinions!
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Go with a steel shim gasket and Vortex iron head or some other iron head, I like the WP Sportsman II head the gasket is around 20 thou, compressed so it will give you another 1/2 point.
I don't have part number handy I might have thrown it out, but made by Federal Mogul or whomever owns them now. Put in a CC270H cam or 282S solid flat tappet and top it off with an Air Gap intake and Holley 750DP and it will get you 350 + hp, very nice street driven motor, I know I built one and got nearly 300HP at the wheels
Sorry misunderstood your question, the heads aren't really worth working over because they don't flow worth a crap and you could by a new set of modern heads for what it will cost you to port those heads You should do the bottom end but, if you really can't afford it you might see 300HP with a little head work, another cam and some tuning
I don't have part number handy I might have thrown it out, but made by Federal Mogul or whomever owns them now. Put in a CC270H cam or 282S solid flat tappet and top it off with an Air Gap intake and Holley 750DP and it will get you 350 + hp, very nice street driven motor, I know I built one and got nearly 300HP at the wheels
Sorry misunderstood your question, the heads aren't really worth working over because they don't flow worth a crap and you could by a new set of modern heads for what it will cost you to port those heads You should do the bottom end but, if you really can't afford it you might see 300HP with a little head work, another cam and some tuning
Last edited by MotorHead; Aug 10, 2010 at 06:29 AM.
Race Director
Joined: Jan 2003
Posts: 15,175
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From: State of Confusion
the dishes in stock '74 pistons in an L48? Could a top end rework do some good? Heads, cam, intake, carb tune, etc. I would like to see a gain from the stock 190hp to 320-350hp. Without changing short block is it possible with 64cc heads or would I need to go to 58cc heads to get me near 320+hp? Thanks for any opinions!
My (then) new 1979 Z28 came with the 175 HP LM-1, featuring 8.2:1 compression, having deep-dish, 4-eyelet pistons, & 76cc heads:
a swap to small-valve 64cc heads, mild (.450"-lift, 218* @ .050"-lift) hydraulic cam, old-fashioned (327/365) aluminum intake, 650 cfm Holley & open headers pushed the car, which had previously run 16.4 ET @ 84 MPH, to 14.4 @ 97 times
I don't know if it made 320 HP, but nobody confused it as 'stock' anymore
Thread Starter
Melting Slicks
Joined: Mar 2010
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I was thinking a 280h cam, Vortec 64cc iron heads, Edelbrock intake for Vortecs, tune the Qjet. I wasn't sure if the '74 L48 350 had flat tops or dished pistons. If they are dished I heard some of the aluminum heads off of a C4 had 58cc chambers and would be a good fit, but I don't know much about them?!
Thread Starter
Melting Slicks
Joined: Mar 2010
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Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I don't believe flattops - more like big dish tops.
I recall the L48 piston is the same as my "Hecho en Mexico" crate motor pistons. My piston tops had a huge dish and vlv relieves inside of that. Dosen't look good for quench at all no matter what the piston to deck clearance is. I tried to measure dish volume but unable to with engine still in car. My guess at least 22cc or more.
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues.
My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.
Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues.
My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
Burning Brakes
Joined: Oct 2003
Posts: 1,090
Likes: 74
From: New Carlisle IN
I believe the first year for flat top pistons were in 1982 with the crossfire motor. That is one of the parts needed to make a good running NCCC class 2D motor. All you can do in group 2 is update/backdate parts within your class. I am not sure exactly what all parts are needed, but I know you need '82 flat top pistons and cam, '71 270hp heads, and an aluminum 81 intake. This combo produces somewhere between 300-320hp using all stock parts. One of these days, I will build one of these motors for my 73. I've already got the intake and heads so i am part way there.
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Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
I recall the L48 piston is the same as my "Hecho en Mexico" crate motor pistons. My piston tops had a huge dish and vlv relieves inside of that. Dosen't look good for quench at all no matter what the piston to deck clearance is. I tried to measure dish volume but unable to with engine still in car. My guess at least 22cc or more.
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues. My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.
Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues.
My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
With the gasket inbetween the deck surface and the head surface, what difference would it make? Where would the two different metals come into contact and cause problems?
Not being a smart A**, but I am now concerned about my build.
Thanks,
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,731
Likes: 15
I recall the L48 piston is the same as my "Hecho en Mexico" crate motor pistons. My piston tops had a huge dish and vlv relieves inside of that. Dosen't look good for quench at all no matter what the piston to deck clearance is. I tried to measure dish volume but unable to with engine still in car. My guess at least 22cc or more.
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues. My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.
Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
The problem with the small chamber aluminum heads is they are aluminum and the block deck surface should be Ra 25-50 for aluminum heads. But the stock L48 deck was machined for iron heads with Ra finish about twice the number for aluminum.
U read here on the forum where owners have install the L98 alum heads on stock C3 blocks and are now chasing head gasket leak issues.
My 2 cents here says better off with iron heads and use the FelPro coated steel shim gasket with only 0.015" crush height.Good luck tsst and let us know if u find the correct dish volume for a '74,
cardo0
Burning Brakes
Joined: Dec 2005
Posts: 992
Likes: 56
From: Baldwinsville, NY
I did a Vortec build two years ago, and the L48's had 12cc dished pistons with 4 eyelets for the valves, L82's had flat tops with 4 eyelets for valves.
At that time I stayed away from L98 type aluminum heads. Just did not want to add that to my limited experience and decided to go with cast iron.
If I were to do it again I would use non-Vortec 64 cc heads like Brodix or Dart, standard or air gap aluminum intake and make the engine look stock. Nothing wrong with the stock air cleaner, it had cold air intake.
If I had money I would go with a ZZ4 roller engine and call it a day.
JMTC.
At that time I stayed away from L98 type aluminum heads. Just did not want to add that to my limited experience and decided to go with cast iron.
If I were to do it again I would use non-Vortec 64 cc heads like Brodix or Dart, standard or air gap aluminum intake and make the engine look stock. Nothing wrong with the stock air cleaner, it had cold air intake.
If I had money I would go with a ZZ4 roller engine and call it a day.
JMTC.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Basic metalurgy - aluminum expands more and faster than steel.
Question on iron block deck finish and aluminum heads. I am running this combo, with a FelPro 0.041 head gasket. Block was '0' decked
With the gasket inbetween the deck surface and the head surface, what difference would it make? Where would the two different metals come into contact and cause problems?
Not being a smart A**, but I am now concerned about my build.
Thanks,
With the gasket inbetween the deck surface and the head surface, what difference would it make? Where would the two different metals come into contact and cause problems?
Not being a smart A**, but I am now concerned about my build.
Thanks,
cardo0
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
Apoligies for the late reply Glen. The surface needs to allow the aluminum head to move/slide around as it expands and contracts faster than the steel block. Both pieces are moving at different rate as they heat up (and down). Zero deck or +0.025 stock deck has nothing to do with this. It's the finish on the deck and head that will allow the aluminum head to move rather than tear the gasket (or what ever happens at the micro level). Again, the block and aluminum head should have an Ra of 20-50 while an iron head to iron block should be 60-120 Ra. At least thats what the professional machinists write and i just looked it up again but i'm not even a machinist so take it for what its worth.
cardo0
cardo0
I use a FelPro 1010 (I believe) head gasket that FelPro recommends for aluminum heads.
Am I looking at problems if my block and heads Ra are not the same, as you note, for cast iron/aluminum?
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
OK then just google it.
Still confused. Since the head is not riding on the bare block, what does it matter what the Ra is on the block vs the Ra on the heads?
I use a FelPro 1010 (I believe) head gasket that FelPro recommends for aluminum heads.
Am I looking at problems if my block and heads Ra are not the same, as you note, for cast iron/aluminum?
I use a FelPro 1010 (I believe) head gasket that FelPro recommends for aluminum heads.
Am I looking at problems if my block and heads Ra are not the same, as you note, for cast iron/aluminum?
But try this from Mr. Gasket as they required Ra of only 10Ra - 30Ra for thier MLS head gasket: http://www.mr-gasket.com/pdf/3130G_3150G.pdf. And here are couple of google results: http://www.aa1car.com/library/ic697.htm, and: http://www.enginebuildermag.com/Arti...s__blocks.aspx.Again i'm not a machinist or gasket expert. So i will let u decide for yourself Glen. But i feel this important enough that it needs to get out on the forum so most everyone is aware of the issue with aluminum heads.
Good night,
cardo0
