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CorvettesHardened
push rods/guideplates or not??

68shark
Senior
Member

525 posts [100%]
Ajax Ontario

Hardened push
rods/guideplates or not??

7:22
AM 6/24/2002

I posted a while back about my cylinder head
problems (bent pushrod, rocker) which is now in process of
being fixed. I'm getting conflicting opinions on whether I
should add hardened push rods and guideplates. One mechanic
recommends this, the other doesn't think it is necessary and
indicates that some work has to be done to the heads to accept
the use of hardened rods? My heads are "461" casting, screw in
studs, comp cams springs, stock rockers.

Can anyone give me some advice??

Thanks!!
_______

Doug
'68 Polar
White Roadster L79/327-M21-3.70-Comp Cams XE262-bored .30
over-hypereutectic flat top pistons-Pertronix Ignitor and
Flamethrower Coil-K&N Filter-stock "camel hump" heads
2.02/1.60 valves 58cc chambers

gerry72
Senior
Member

691
posts [100%]
San Antonio TX

Re: Hardened push
rods/guideplates or not?? (68shark)

7:56
AM 6/24/2002

The only thing that could be done that would
indicate the need for pushrod guideplates are the machining
necessary to the stud boss to accomodate the additional pad
space necessary for the thickness of the guidplates. While it
is possible to mill the boss only for the stud, this is not
what is commonly done.

I've seen the bent pushrod syndrome on non-guideplate heads
where binding wasn't an issue. In this case, the pushrod wore
on the pushrod slot in the head, got cocked and bent when the
rocker arm went off the valve tip. Closely examine your
pushrod guides in the head and if you see any wear in the
slots, you're going to be in the position to use guideplates
or you'll have to replace the heads.
_______

72
Mille Miglia Coupe
67
Fairlane 500-XL

Gerry72's Corvetteforum web
page   email me at:
[email-masked]

68shark
Senior
Member

525 posts [100%]
Ajax Ontario

Re: Hardened push
rods/guideplates or not?? (gerry72)

8:44
AM 6/24/2002

Gerry72....thanks for your advice. It makes
sense to me and I'm going to take it. Your scenario sounds
like exactly what happened to my heads in the first place so I
want to fix it once and for all.
_______

Doug
'68 Polar
White Roadster L79/327-M21-3.70-Comp Cams XE262-bored .30
over-hypereutectic flat top pistons-Pertronix Ignitor and
Flamethrower Coil-K&N Filter-stock "camel hump" heads
2.02/1.60 valves 58cc chambers

tsw71
Senior
Member

1102 posts [100%]
san jose Ca

Re: Hardened push
rods/guideplates or not?? (gerry72)

8:49
AM 6/24/2002

quote:

I've seen the bent pushrod syndrome on non-guideplate heads
where binding wasn't an issue. In this case, the pushrod
wore on the pushrod slot in the head, got cocked and bent
when the rocker arm went off the valve tip.

I've had this problem several times in my Vette. It got to
be so common with my old set of heads that I would carry spare
rockers and pushrods in the car so I could fix it on the side
of the road if needed. I later replaced my heads and figured
that my troubles would be over..............wrong! I'm
convinced that it is caused by deflection in the soft pushrods
when using higher than stock lift cams and heavier valve
springs. If the slots have not gone too far, you can just run
the hardened pushrods without adding guide plates. Trust me,
it will work fine. This is what I do with my 461's on my
streetrod (no guideplates)and have never had a problem on this
motor with dual valve springs, over .550 lift and regular runs
past 7500rpm.

Tom
_______

71 coupe
355,S/R torquer
heads
Comp Cams 282S
TorkerII intake
Hooker
headers,
Richmond 5speed

Tom's Neverending Projects

68shark
Senior
Member

525 posts [100%]
Ajax Ontario

Re: Hardened push
rods/guideplates or not?? (tsw71)

10:29
AM 6/24/2002

Thanks for sharing your experience Tom!! Doing
both (guideplates with hardened pushrods) sounds like good
insurance for me!!
_______

Doug
'68 Polar
White Roadster L79/327-M21-3.70-Comp Cams XE262-bored .30
over-hypereutectic flat top pistons-Pertronix Ignitor and
Flamethrower Coil-K&N Filter-stock "camel hump" heads
2.02/1.60 valves 58cc chambers

Fevre
Senior
Member

1444
posts [100%]
Ann Arbor MI

Re: Hardened push
rods/guideplates or not?? (68shark)

10:32
AM 6/24/2002

Good choice. Better safe then stranded. Thought
about upgrading your rockers?
_______

73 ragtop,
temporary 350, 4 spd, MSD 6A, ProBillet Dist, Holley 4150 600
with vac sec, Aluminum Trick Flow 23 dgr heads (waiting in the
wings), Weiand Stealth intake, 3.70 rear, Two Boxers (1 male
& 1 female) and no money

68shark
Senior
Member

525 posts [100%]
Ajax Ontario

Re: Hardened push
rods/guideplates or not?? (Fevre)

10:55
AM 6/24/2002

quote:

Good choice. Better safe then stranded. Thought about
upgrading your rockers?

I hadn't actually. Do you mean to roller rockers or an
upgraded standard style?? I don't know much about
rockers....which probably shows!!
_______

Doug
'68 Polar
White Roadster L79/327-M21-3.70-Comp Cams XE262-bored .30
over-hypereutectic flat top pistons-Pertronix Ignitor and
Flamethrower Coil-K&N Filter-stock "camel hump" heads
2.02/1.60 valves 58cc chambers

Fevre
Senior
Member

1444
posts [100%]
Ann Arbor MI

Re: Hardened push
rods/guideplates or not?? (68shark)

11:06
AM 6/24/2002

I don't think the full roller will fit under
your valves covers but roller tip will. The roller tip want
give you the friction reduction that full rollers will but can
give you added lift if you get 1.6 ratio and they will give
some friction reduction. But make sure that added lift won't
make the valves hit the piston. I know very little about the
camel hump heads but I bet their are others running full
roller or roller tip rockers with heads like yours. Can your
mechanic give a recomendation?

[Modified by Fevre, 1:06 PM 6/24/2002]

[Modified by Fevre, 1:07 PM 6/24/2002]

[Modified
by Fevre, 1:07 PM 6/24/2002]
_______

73 ragtop,
temporary 350, 4 spd, MSD 6A, ProBillet Dist, Holley 4150 600
with vac sec, Aluminum Trick Flow 23 dgr heads (waiting in the
wings), Weiand Stealth intake, 3.70 rear, Two Boxers (1 male
& 1 female) and no money

clem zahrobsky
Cruise-In I Veteran
Cruise-In II
Veteran

3635 posts [100%]
delmont pa

Re: Hardened push
rods/guideplates or not?? (68shark)

4:35
PM 6/24/2002

if your heads have the pushrod double D holes
to guide the push rods you will have to open the double D
holes for clearance to prevent push rod binding with the use
of guide plates under the studs.
_______

a.k.a. MOTORMAN, 2002
torch red coupe, proud corvette owner since 1959
NCM
member#5583
NCM ambassador from Corvette Club Of Western
Pa
9TH-VETT vanity plate

73-454
Senior
Member

779
posts [6%]
Toronto Ontario

Re: Hardened push
rods/guideplates or not?? (68shark)

4:56
PM 6/24/2002

You better find out why you are breaking the
push-rods that should never happen. All push rods are made out
of Hardened steel. They should also last the life of an
engine.
_______

70-454 10.25 Comp, L88 Hood,
Crane272 Cam, Roller Tip Rockers ??, Headman Headers, Double
Roller Timing Chain, Q-jet, GM HEI, 98% Orginal," BUILT TO BE
DRIVEN"
http://temp.corvetteforum.net/c3/454rat//vette_pics_02/360_image002.jpg

tsw71
Senior
Member

1102 posts [100%]
san jose Ca

Re: Hardened push
rods/guideplates or not?? (73-454)

6:03
PM 6/24/2002

quote:

All push rods are made out of Hardened steel. They should
also last the life of an engine.

Under normal circumstances the stock pushrods will hold up,
but not always. All pushrods may be hard, but not as much as
you think. They are usually either case hardened mild steel or
chrome moly. The case depth is not very deep and while you end
up with a hard surface for wear, the steel is still very soft
when compared to the true hardened chome moly pushrods.

The likely reason(s) for these problems is that the tip of
the valve stem is not a flat surface anymore and the rocker
will want to slide to the "path of least resistance" which is
over the side. This puts a tremendous amount of lateral load
on the pushrod. The load on the pushrod slowly wears on the
cast iron and elongates the pushrod slot and causes the rocker
to sit even further from the center of the valve stem. This
keeps compounding the load on the pushrod and eventually it
will bend.The chrome moly pushrod will be strong enough to
take the lateral load.

The use of guideplates is a good idea and is what I
eventually did, but as Clem said, you will have to pull the
heads to open up the holes as well as machine the rocker stud
bosses for the added thickness of the guideplate.

If you don't want to pull the heads at this time and the
slots in the heads have not gone too far, you will be able to
get by with the chrome moly pushrods for a long time if
needed. I know this from experience.

Also, Check your rocker arm studs. It's likely that you
have a few of them that the rocker arm has started to "saw"
through.

Tom

68shark
Senior
Member

525 posts [100%]
Ajax Ontario

Re: Hardened push
rods/guideplates or not?? (tsw71)

6:05
AM 6/25/2002

Thank you all for your comments! I'm learning
more and more from all of you and I appreciate your help!!
Both heads are off and are being set up for guideplates and
hardened push rods. More money, but I do have a higher than
stock lift cam (XE262) and the higher pressure springs to
match the cam so now I'll upgrade the rest. Thanks again!!

_______

Doug
'68 Polar
White Roadster L79/327-M21-3.70-Comp Cams XE262-bored .30
over-hypereutectic flat top pistons-Pertronix Ignitor and
Flamethrower Coil-K&N Filter-stock "camel hump" heads
2.02/1.60 valves 58cc chambers

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