SBC valve train issue - help

Bobby Zlatkin · 04-07-2011, 01:05 PM

Got the car out preparing for the 1st race of the season. While setting the timing, I heard a bang, bang, bang & the engine shut off. Sounded like it came from the left side so I pulled the left rocker cover.

#3 cyl., ex. rocker off the valve, push rod bent and cracked to the point of coming apart, stud cut almost in half. Top of valve stem & retainer beat up some.

#3 int. rocker very loose, although still showing the same amout of threads on top as all the others. Made me think maybe it was pulling a stud (press-in). Again stud cut almost in half. This push rod was not bent.

Measured (compared) the length of those two studs and compared with others. Those two are longer, but not by much. If I can avoid it, I perfer not to pull the head. Can I pull and replace the studs with hand tools? If so, what?

Finally, why did this happen? The valves were lashed down properly (hyd. lifters). It's a low lift cam with stock valve strings that never sees more than 6,000 rpm.

Mike Taylor 3601 · 04-07-2011, 02:20 PM

Bobby,
First thing I would do if you have'nt already is while rockers are off, hook air hose straight in spark plug hole to make sure you did'nt bend valve when that happened,should'nt have any air come out in.or ex.,if you do tap on tip valve make sure you don't have some debris
between valve/seat. If it leaks pull it and fix valves,studs then.
You can pull rocker studs by putting washers or a spacer on stud I'd use old rod nut or grade 8 nut lubed well,tighten nut against washers/spacers and should pull stud,may have to add more spacers till you get pulled completely.
You can install new stud w/hammer install nut on threads to protect them leave just enough threads of nut above stud that you are hammering on nut.put some loctite or sealer on stud where it goes in head,drive into head carfefully so you don't bend stud with a missed lick,you can use a straight edge of some kind to measure that stud is even with other studs, BTW drain water some studs go into water.
If tip of valve is damaged where it tries to make rocker push to side, it will cut stud if it does'nt come off first.
Mike Taylor 3601 PS you can get .003 oversize studs if neeed

Ed Wright · 04-07-2011, 02:52 PM

You guys can't use screw-in studs in Stock?

Rich Biebel · 04-07-2011, 03:28 PM

You need to look at the lifters and cam.......
Press in studs in a small block used for racing is not a very good idea. Wasn't a good idea with hot street cars in the '60's

We pinned the studs in the '60's
We used cast pins as the common roll pins broke the heads before the pins broke

Not sure what started or caused your issue but it can easily cost you an engine

What engine/cam/lifters/ solid or hyd. /spring pressure?

ron mattson · 04-07-2011, 04:02 PM

Like rich said you need to look at the cam and lifters also, it almost sounds like
you have a clearance issue somewhere. piston to valve could be tight, also make sure
the rocker arms are not running out of travel on the slot.

Bobby Zlatkin · 04-07-2011, 06:37 PM

Mike, some good suggestions. Also, on the damaged valve tip, I think I'll use a LT1 self centering rocker arm hopefully to keep that out of further trouble.

Ed, I'm running IHRA Pure Stock and aren't allowed screw-in studs. Crummy rule, but that's why they call it pure stock.

Rich & Ron, I will look at the cam & lifters but, hopefully the hyd. lifters cushioned any possible damage there. With a .390/.410 lift cam at stock duration, interference shouldn't be an issue. I hope.

I know I should pull the head, and I may have to, but I'm trying to get away without doing that.

Thanks for the responses.

Greg Reimer 7376 · 04-07-2011, 07:09 PM

Good comment regarding rocker arm slot length.If the pushrod is too long, the rocker arm slot runs out of slot before maximum lift and binds on the stud. Too much of that and the stud breaks,pulls out, breaks the stud boss,bends the push rod, or commits unholy mayhem on the tip of the valve stem. Anytime interference occurs on the valve train, especially near max lift like that, the lifter and cam lobe become stressed, so check the cam and lifters very carefully.Push rods are available in a variety of lengths,try some around .150" short and go from there. I recently built a 327 with the usual stock eliminator stuff, a bunch decked off the block and a bunch more decked off the heads to get the deck height and the combustion chamber CC's where they belong, and valve lift with an OEM pushrod was over on eight valves and real close on the other eight. A set of -150" length pushrods brought the lift down to safe limits, but a set of -100" length pushrods would be optimum. When you deck a set of heads ,let's say, 065" to arrive at optimal CC's, and .045 from the block to correct excessive deck heights, you just increased the length of the pushrod .110". Not to mention, the intake is now too wide, and the distributor is now too tall. That can be corrected with a spacer between the flange on the housing and the intake manifold,and by cutting .060-.070 from each side of the intake at the gasket surfaces.It's easy to see that all engine assemblies are a part of a relationship these parts have with each other. Have you ever seen where some stocker motors might have a different length pushrod on the intakes than the exhausts? Sometimes, proper engine building is a matter of determining what it takes to do what you have to do in order to arrive at the desired end result.

04-07-2011, 01:05 PM	#1
Bobby Zlatkin Member Join Date: Mar 2003 Location: Mills River, NC Posts: 417 Likes: 0 Liked 0 Times in 0 Posts	SBC valve train issue - help Got the car out preparing for the 1st race of the season. While setting the timing, I heard a bang, bang, bang & the engine shut off. Sounded like it came from the left side so I pulled the left rocker cover. #3 cyl., ex. rocker off the valve, push rod bent and cracked to the point of coming apart, stud cut almost in half. Top of valve stem & retainer beat up some. #3 int. rocker very loose, although still showing the same amout of threads on top as all the others. Made me think maybe it was pulling a stud (press-in). Again stud cut almost in half. This push rod was not bent. Measured (compared) the length of those two studs and compared with others. Those two are longer, but not by much. If I can avoid it, I perfer not to pull the head. Can I pull and replace the studs with hand tools? If so, what? Finally, why did this happen? The valves were lashed down properly (hyd. lifters). It's a low lift cam with stock valve strings that never sees more than 6,000 rpm. __________________ Bobby & Norene Zlatkin L/SA

04-07-2011, 02:20 PM	#2
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,362 Likes: 337 Liked 279 Times in 96 Posts	Re: SBC valve train issue - help Bobby, First thing I would do if you have'nt already is while rockers are off, hook air hose straight in spark plug hole to make sure you did'nt bend valve when that happened,should'nt have any air come out in.or ex.,if you do tap on tip valve make sure you don't have some debris between valve/seat. If it leaks pull it and fix valves,studs then. You can pull rocker studs by putting washers or a spacer on stud I'd use old rod nut or grade 8 nut lubed well,tighten nut against washers/spacers and should pull stud,may have to add more spacers till you get pulled completely. You can install new stud w/hammer install nut on threads to protect them leave just enough threads of nut above stud that you are hammering on nut.put some loctite or sealer on stud where it goes in head,drive into head carfefully so you don't bend stud with a missed lick,you can use a straight edge of some kind to measure that stud is even with other studs, BTW drain water some studs go into water. If tip of valve is damaged where it tries to make rocker push to side, it will cut stud if it does'nt come off first. Mike Taylor 3601 PS you can get .003 oversize studs if neeed

04-07-2011, 03:28 PM	#4
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: SBC valve train issue - help You need to look at the lifters and cam....... Press in studs in a small block used for racing is not a very good idea. Wasn't a good idea with hot street cars in the '60's We pinned the studs in the '60's We used cast pins as the common roll pins broke the heads before the pins broke Not sure what started or caused your issue but it can easily cost you an engine What engine/cam/lifters/ solid or hyd. /spring pressure? __________________ Rich Biebel S/C 1479 Stock 147R

04-07-2011, 04:02 PM	#5
ron mattson Member Join Date: Nov 2005 Location: cloquet mn Posts: 464 Likes: 17 Liked 66 Times in 29 Posts	Re: SBC valve train issue - help Like rich said you need to look at the cam and lifters also, it almost sounds like you have a clearance issue somewhere. piston to valve could be tight, also make sure the rocker arms are not running out of travel on the slot. __________________ Ron Mattson 5015 STK

04-07-2011, 06:37 PM	#6
Bobby Zlatkin Member Join Date: Mar 2003 Location: Mills River, NC Posts: 417 Likes: 0 Liked 0 Times in 0 Posts	Re: SBC valve train issue - help Mike, some good suggestions. Also, on the damaged valve tip, I think I'll use a LT1 self centering rocker arm hopefully to keep that out of further trouble. Ed, I'm running IHRA Pure Stock and aren't allowed screw-in studs. Crummy rule, but that's why they call it pure stock. Rich & Ron, I will look at the cam & lifters but, hopefully the hyd. lifters cushioned any possible damage there. With a .390/.410 lift cam at stock duration, interference shouldn't be an issue. I hope. I know I should pull the head, and I may have to, but I'm trying to get away without doing that. Thanks for the responses. __________________ Bobby & Norene Zlatkin L/SA

04-07-2011, 02:52 PM	#3
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: SBC valve train issue - help You guys can't use screw-in studs in Stock? __________________ Ed Wright 4156 SS/JA

04-07-2011, 07:09 PM	#7
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,132 Likes: 172 Liked 698 Times in 216 Posts	Re: SBC valve train issue - help Good comment regarding rocker arm slot length.If the pushrod is too long, the rocker arm slot runs out of slot before maximum lift and binds on the stud. Too much of that and the stud breaks,pulls out, breaks the stud boss,bends the push rod, or commits unholy mayhem on the tip of the valve stem. Anytime interference occurs on the valve train, especially near max lift like that, the lifter and cam lobe become stressed, so check the cam and lifters very carefully.Push rods are available in a variety of lengths,try some around .150" short and go from there. I recently built a 327 with the usual stock eliminator stuff, a bunch decked off the block and a bunch more decked off the heads to get the deck height and the combustion chamber CC's where they belong, and valve lift with an OEM pushrod was over on eight valves and real close on the other eight. A set of -150" length pushrods brought the lift down to safe limits, but a set of -100" length pushrods would be optimum. When you deck a set of heads ,let's say, 065" to arrive at optimal CC's, and .045 from the block to correct excessive deck heights, you just increased the length of the pushrod .110". Not to mention, the intake is now too wide, and the distributor is now too tall. That can be corrected with a spacer between the flange on the housing and the intake manifold,and by cutting .060-.070 from each side of the intake at the gasket surfaces.It's easy to see that all engine assemblies are a part of a relationship these parts have with each other. Have you ever seen where some stocker motors might have a different length pushrod on the intakes than the exhausts? Sometimes, proper engine building is a matter of determining what it takes to do what you have to do in order to arrive at the desired end result.