L98 Iron heads???
#1
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
L98 Iron heads???
Is it necessary for the pushrods to rub on the heads were they pass trough the heads? I'm tearing mine down and they appear like they are rubbing excessivley. I thought they were guided by the rocker arms. There are no guide plates so do they just ride on the sides of the holes in the head??? Thanks!
#2
Moderator
Join Date: Jan 2000
Location: Mercedes Norte, Heredia, Costa Rica
Posts: 20,981
Likes: 0
Received 9 Likes
on
8 Posts
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: L98 Iron heads???
Is it a narrow slot that the pushrod passes through, or a gaping hole?
#3
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
Very narrow.
#4
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
Any ideas?
#5
Guest
Posts: n/a
Re: L98 Iron heads???
That is how most Chevy pushrods are kept in line. At some point around 88 or so GM changed to different rockers that were "self aligning". Basically where the rocker rides on the valve, there are indents on either side that keep it from sliding off the valve. I heard some engines ended up with both.
Unless the pushrods are physically worn into (check by measuring diameter) then they're fine.
Unless the pushrods are physically worn into (check by measuring diameter) then they're fine.
#7
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
I've got GM 1.6 rollers on it. They seem to be self aligning. Yes there is wear on them, you can feel it with your fingers. It just seems like more friction and metal shavings in the engine. Would it hurt if I opened the holes up so they didn't touch? Thanks!
Trending Topics
#8
Guest
Posts: n/a
Re: L98 Iron heads???
As long as there is some method to keep the pushrod in line, it will be fine. Having two is kind of contradictory and could cause issues but for some reason GM didnt seem to care. It may be that your aftermarket rockers center a little differently and is causing some bind.
Drew... why am I not surprised? Sometimes I wonder if line workers did things to try and be funny.
Drew... why am I not surprised? Sometimes I wonder if line workers did things to try and be funny.
#9
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
The rockers have 2 "washers" that keep it on the valve. So it is safe to open the holes in the head up?
#11
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
Why replace the rockers? They have less than 1k on them. They are the GM rollers, made by crane I believe.
#14
TGO Supporter
Join Date: Oct 2002
Location: Saskatoon, SK, Canada
Posts: 9,067
Likes: 0
Received 1 Like
on
1 Post
Car: '83 Z28, '07 Charger SRT8
Engine: 454ci, 6.1 Hemi
Transmission: TH350, A5
Axle/Gears: 2.73 posi, 3.06 posi
Re: L98 Iron heads???
Pics would be invaluable right about now to answer your question. What casting number are the heads though? They could have been changed at some point to a set thats incompatible with self-aligning rockers, if thats what you have. Self-aligning rockers have a little tab on either side of the end that pushes the valve down to keep it centered over the valve stem.
There are 3 ways GM used to align the rockers:
A) narrow slots in the heads, non-self-aligning rockers
B) self-aligning rockers, big holes in the heads
C) guide plates, big holes in the heads, non-self aligning rockers
You can only use one of those methods, when you combine them you will have issues.
There are 3 ways GM used to align the rockers:
A) narrow slots in the heads, non-self-aligning rockers
B) self-aligning rockers, big holes in the heads
C) guide plates, big holes in the heads, non-self aligning rockers
You can only use one of those methods, when you combine them you will have issues.
#16
Guest
Posts: n/a
Re: L98 Iron heads???
Exactly. The aftermarket ones probably have a lot closer tolerance and that may be a problem.
Are you having issues with just a couple pushrods, or all of them? What kind of wear do you have? Clean the pushrod if need be, and measure them.
Are you having issues with just a couple pushrods, or all of them? What kind of wear do you have? Clean the pushrod if need be, and measure them.
#17
Supreme Member
iTrader: (58)
Re: L98 Iron heads???
Yeah, but if they originally were dependent upon the rockers for proper alignment. Swapping to non-SA rockers will leave that job up to the heads that weren't intended to do that job.
Are the pushrods wearing from contact with the heads? Or are the rockers wearing from contact with the valves? It's not really clear from the thread so far...
Are the pushrods wearing from contact with the heads? Or are the rockers wearing from contact with the valves? It's not really clear from the thread so far...
#18
Moderator
Join Date: Jan 2000
Location: Mercedes Norte, Heredia, Costa Rica
Posts: 20,981
Likes: 0
Received 9 Likes
on
8 Posts
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: L98 Iron heads???
From the sounds of it he's got narrow-slotted heads, which will control alignment just fine.
#19
Supreme Member
iTrader: (58)
Re: L98 Iron heads???
I'd be more inclined to think the problem is the slots in the heads aren't long enough to clear the push rods with 1.6 rockers. I wouldn't trust the heads to do the job if they came with SA rockers to begin with. I'd keep the rockers, and clearance the heads. But that's just my opinion.
The following users liked this post:
Eagle223usa (03-13-2023)
#20
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
I'd be more inclined to think the problem is the slots in the heads aren't long enough to clear the push rods with 1.6 rockers. I wouldn't trust the heads to do the job if they came with SA rockers to begin with. I'd keep the rockers, and clearance the heads. But that's just my opinion.
#21
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
And new pushrods.
#22
Junior Member
Join Date: Aug 2008
Location: Bolivia, NC
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
Car: 84 Z28, 05 Mazda 6
Engine: 350
Transmission: 700R4
Axle/Gears: 3.42 Open
Re: L98 Iron heads???
Similar question don't mean to thread jack but, I just picked up an 87 TPI engine and the rockers are stamped with narrow holes on one head and the others aren't quite as small, what benefits will I see switching to roller rockers? My last engine had them when I got it is it just a reliability thing or is there a performance benefit to using them?
#23
Senior Member
Join Date: Oct 2004
Location: SE, Ohio
Posts: 965
Likes: 0
Received 2 Likes
on
2 Posts
Car: '86 Z28, '91 RS
Engine: 305ci, 305ci
Transmission: TH200c (no kidding), TH700r4
Axle/Gears: 2.73, 2.73
Re: L98 Iron heads???
I've never even heard of a special tool for elongating the push rod slots in the head.
#24
Supreme Member
iTrader: (58)
Re: L98 Iron heads???
Good to hear the culprit is identified.
Here's a link to a Louis tool...
http://www.compperformancegroupstore..._Code=Pushrods
And the backyard alternative...
http://www.chevyhiperformance.com/te.../photo_08.html
I have no personal opinion of one method vs the other. Google finds all kinds of articles on modifying heads to clear 1.6 rockers.
Here's a link to a Louis tool...
http://www.compperformancegroupstore..._Code=Pushrods
And the backyard alternative...
http://www.chevyhiperformance.com/te.../photo_08.html
I have no personal opinion of one method vs the other. Google finds all kinds of articles on modifying heads to clear 1.6 rockers.
#25
Moderator
Join Date: Jan 2000
Location: Mercedes Norte, Heredia, Costa Rica
Posts: 20,981
Likes: 0
Received 9 Likes
on
8 Posts
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: L98 Iron heads???
The Louis tool is to elongate the slot, keeping its same width so you can still use non-SA rockers. The alternative is to hog them out like Drew's backyard alternative picture, and use SA rockers.
#26
Senior Member
Thread Starter
Join Date: Apr 2006
Location: Pgh PA
Posts: 835
Received 0 Likes
on
0 Posts
Car: 89 5.7 IROC/95 LT1 Corvette
Engine: All 5.7's
Transmission: 700R4 (Roessler)/ZF6
Axle/Gears: 10 bolt Zexel 3.23's. CTW 17" wheel
Re: L98 Iron heads???
Well I used the louis tool and just finished the porting. I dropped the heads off at the machine shop. The machinist really liked my porting job! He was really surprised when I told him it was my first set! Thanks for the help Guys!
Thread
Thread Starter
Forum
Replies
Last Post
Chuck84TA
Engine/Drivetrain/Suspension Parts for Sale
10
07-15-2016 09:05 PM
ambainb
Camaros for Sale
11
04-25-2016 09:21 PM