487X cyl heads ? - Chevelle Tech
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post #1 of 18 (permalink) Old Jan 1st, 05, 11:56 PM Thread Starter
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I got a set of cylinder heads 3973487X they have 1.94 1.60 valves.Mortec decodes them as 71 to 72.
Does anyone know what the port sizes are on these heads,I remember reading that the X heads had a larger port volume and therefore were a better starting point for a performance upgrade.
What about application what were these heads original to?

John
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post #2 of 18 (permalink) Old Jan 2nd, 05, 12:24 AM
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I think they have a 10cc larger intake chamber on them. They are 71-72 350 castings like you said, passenger and truck heads. The rest you probably know, 76cc chambers, 1.94/1.50 or 2.02/1.60 valves. They should flow around 215-225 cfm intake @ .500. Intake runner should be somewhere around 165cc, exhaust around 65cc. There was a time that I wanted a pair, but I have a pair of stock 487's that came on the 72 if I really want a pair. I almost bought one of the 487X's. I'm thinking it had a crack in the chamber, and the guy didn't want to part with it.
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post #3 of 18 (permalink) Old Jan 2nd, 05, 12:44 AM Thread Starter
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Thanks Trever.
They were on the motor that was in my car when I bought it.I'm going to check the casting dates.Although I'm positive the short block was not the OE engine, I'm wondering if maybe these heads are original to my elcamino.
Would these heads be used on the 71 L48 ?

John
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post #4 of 18 (permalink) Old Jan 2nd, 05, 1:07 AM
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Your welcome!

I've been thinking about that engine rpo code as well. How many 350's are there those couple of years? I know the general 487 casting (possibly both 487 and 487x) were supposedly used on the LT-1 engines. I guess it would take a person smarter than me to figure out which engine has what head.
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post #5 of 18 (permalink) Old Jan 2nd, 05, 1:16 PM
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Both my 72s have 487x heads as stock from the factory. The Malibu was originally a 2 barrel car. If you get them machined, get the hardened exhaust seats added.
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post #6 of 18 (permalink) Old Jan 2nd, 05, 3:18 PM
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To the best of my recollection the only "special" X heads were the 461X & they had about a 170-175cc intake runner.
I do not believe any other standard small block head that came on a vehicle was anything special with regards to intake port.
I am almost positive that 487 & 487x heads are the same thing although I can't recall actually measuring an intake port on one.
They are a pretty fair 76cc style head.
For info, almost all SB standard production heads are in the 155-165cc intake port range,, at least any I have measured were.

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post #7 of 18 (permalink) Old Jan 2nd, 05, 6:03 PM
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According to Mortec.com the chamber volume is only 75cc instead of the 76. Just a little more compression but not much. It says a 71-72 head as well.

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post #8 of 18 (permalink) Old Jan 3rd, 05, 3:07 AM
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The X denotes induction hardened exhaust seats !
Other than that, they are the same as 487 heads.
Induction hardened seats came along in 1972-ish.

You'll still need hardened exhaust seats installed as the induction hardened seats of the early to mid 70's are not good enough for todays fuel. Unless you want to run a lead additive all the time.

487 heads are a nice thick and heavy casting. I have seen them crack with overheating, but it takes a lot. They will stand a lot more heat than the thin lightweight 882 or 624 castings. Those are junk.

Nate
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post #9 of 18 (permalink) Old Jan 3rd, 05, 8:10 AM
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Oh no, I have the 487x on my 400 SBC (came with them) and I always thought that the x means 2.02/1.6 valves and 75cc chamber. If that's not the case I should probably get some better heads soon. I want that 400 to perform really well.

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post #10 of 18 (permalink) Old Jan 3rd, 05, 1:54 PM
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Quote:
Originally posted by SS3964N8:
The X denotes induction hardened exhaust seats !
Other than that, they are the same as 487 heads.
Induction hardened seats came along in 1972-ish.

You'll still need hardened exhaust seats installed as the induction hardened seats of the early to mid 70's are not good enough for todays fuel. Unless you want to run a lead additive all the time.

487 heads are a nice thick and heavy casting. I have seen them crack with overheating, but it takes a lot. They will stand a lot more heat than the thin lightweight 882 or 624 castings. Those are junk.

Nate
Yep, mine ran fine for years until I rebuilt the Malibu engine. No performance upgrades, just a stock rebuild. Engine developed a rough idle that kept getting worse. Every exhaust valve was damaged. The worst ones were sucked into the head.
When I had the 487x heads done on the Elky, hardened exhaust seats were added.
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post #11 of 18 (permalink) Old Jan 4th, 05, 12:45 AM Thread Starter
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There is some great info here.I was planning to add 2.02/1.60 valves and now know i'll need the hardened seats also.Just a mild 350 performance upgrade for a DD.Preferably some form of G-body.

John
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post #12 of 18 (permalink) Old Jan 4th, 05, 9:52 PM
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The 487's with the X or without came with 202/160 valves if they are off of a LT-1 motor.

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post #13 of 18 (permalink) Old Jan 5th, 05, 9:08 AM
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Quote:
Originally posted by Fathom Chevelle:
The 487's with the X or without came with 202/160 valves if they are off of a LT-1 motor.
You can't tell without removing them, or can you?
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post #14 of 18 (permalink) Old Jan 10th, 05, 2:40 AM
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the 487 x and 461 x heads have a 180cc intake runner. get the dial calliper out and measure
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post #15 of 18 (permalink) Old Jan 10th, 05, 5:29 AM
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487X and 461X are over a decade apart.
The X does not mean the same thing for both of them.
I would not build 487X heads for any performance application. You're far better off to buy aftermarket heads.

No, you cannot tell if the heads have 2.02/1.60 valves without removing them from an engine.
71-72 Z/28's or Corvettes would be the only cars to have them. That would be a rare find today.
487 heads are essentially the same as 69-70 441 and 72-up 993 heads. They are not a performance head. They are stock.

Nate
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