487X cyl heads ? [Archive] - Chevelle Tech

: 487X cyl heads ?


71350SS
Jan 1st, 05, 10:56 PM
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?

malibu man
Jan 1st, 05, 11:24 PM
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.

71350SS
Jan 1st, 05, 11:44 PM
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 ?

malibu man
Jan 2nd, 05, 12:07 AM
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.

John_Muha
Jan 2nd, 05, 12:16 PM
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.

Wolfplace
Jan 2nd, 05, 2:18 PM
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.

plain 69
Jan 2nd, 05, 5:03 PM
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.

Mr69
Jan 3rd, 05, 2:07 AM
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

71velle_malibu
Jan 3rd, 05, 7:10 AM
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.

Olli

John_Muha
Jan 3rd, 05, 12:54 PM
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.

71350SS
Jan 3rd, 05, 11:45 PM
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.

Fathom Chevelle
Jan 4th, 05, 8:52 PM
The 487's with the X or without came with 202/160 valves if they are off of a LT-1 motor.

71velle_malibu
Jan 5th, 05, 8:08 AM
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?

motown/malibu
Jan 10th, 05, 1:40 AM
the 487 x and 461 x heads have a 180cc intake runner. get the dial calliper out and measure

Mr69
Jan 10th, 05, 4:29 AM
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

bulb122
Jan 10th, 05, 11:01 AM
I admit, I don't know what the X means....but I used a set of 487X 2.02/1.60 heads on my overcammed low comp 350. I used them to replace my old heads, which were 1.70/1.50 307 heads. I also changed to 1.6 full roller rockers vs. stamped 1.5's at the same time. I picked up an average of .7 sec in the 1/4, and 7mph. :eek: Used to be 14.2ish @97, now the best is 13.50 @ 104. So they are WAAAAY better than 307 heads.... :D

I'm curious though. How do you determine the cc's of the intake runner? Is that the volume in the head between the intake valve and the intake manifold? I have the heads bolted onto the new engine, but I don't have an intake on yet. I could try to measure them, if it's easy enough. I'm just curious is all....

chris

1970SS427
Jan 10th, 05, 2:28 PM
Hey, i dont know for sure on anything but i have 2 pairs of 487X heads. I use them on my circle track car and they seem to perform much better than most other stock heads....from my experience the 487, 487X, and 441, 441X heads are the best flowing. both pairs of my 487X heads came off of corvettes. both pairs of 487X have the 1.94 valves. just my 2 cents but in my opinion 487, 487X, 441, 441X, and 993 are the best flowing of the big chamber (76cc) heads. thats all i know Levi

71velle_malibu
Jan 10th, 05, 4:47 PM
I'd love to see flow numbers of the 487x heads. I wonder if it would be worth going to aftermarket heads with a XE268HE cam or if I wouldn't benefit that much. I'm after monster torque, not monster rpm. How much would I benefit from AFR 195s, Canfields or Trickflows? The Trickflows seem to have quite a lot bang for the buck.

This is what I already have in Parts:
400 SBC / Flat-Top Pistons/ Performer RPM Airgap or Performer / Holley 3310-2 / 2400 Stall


Olli