83 Chevy 350 SB valve springs w uneven heights? Is that normal?

[docben]

I am in the process of rebuilding my 83 SB 350 Chevy and noticed the heights on the existing valve springs are different between the intake and exhaust valves. I am replacing all the lifters and cam with COMP parts and tech support asked me to measure the install height from the bottom of the spring to the bottom of the retainer to be able to size the correct springs. Well, they are different as you can see from the photos, and I am wondering why the exhaust has a different retainer/height than the intake? Is that normal? The springs themselves are the same height un-installed. Really weird to see this. Any thoughts?

 

[Scott Danforth]

are the valve stems the same height. that is what the rocker arm cares about

whats wrong with the cam and lifters in the motor?

me, personally would take the heads in, get a refresh and upgrade the springs and valve seals prior to swapping a bump stick.

 

[Scott06]

I am in the process of rebuilding my 83 SB 350 Chevy and noticed the heights on the existing valve springs are different between the intake and exhaust valves. I am replacing all the lifters and cam with COMP parts and tech support asked me to measure the install height from the bottom of the spring to the bottom of the retainer to be able to size the correct springs. Well, they are different as you can see from the photos, and I am wondering why the exhaust has a different retainer/height than the intake? Is that normal? The springs themselves are the same height un-installed. Really weird to see this. Any thoughts?

Looks like you are using different height retainers and or keepers on the valves. I ran into a similar issue on a 389 Pontiac - you never know what someone did on an older engine that has been apart.

Would take them apart - valves could have different stem lengths, seats could be receeded in the head, plus the issue of retainer to valve guide or seal clearance.

Just make sure you have proper retainer to seal clearance (assuming these have been cut for viton seals), check for coil bind, and have correct installed height.

On the engine referenced above when a valve job was done in the early 90's for some reason the exhaust guides were left .090" taller than the intake when they were cut for seals. The stock cam with .407 lift was just kissing the tops of the seals. I was putting in a higher lift cam that on paper should work with stock valve train ... ended up using Comp Cams retainers that were .050" shorter on the intakes with viton seals. Had to go back to the oring seals and splash cups on the exhaust with keepers that sit .020" higher, then had to shim some of the valve springs up for proper installed height as some of the seats were recessed into the head a bit.

Bottom line verify it is right or take it to a machinist who can otherwise you will break stuff

 

[ScottinAZ]

it looks to me that you have rotators on the exhaust valves. This would be completely normal, and they do sit a bit higher than the plain keeper. Main thing is that the stem that the rocker arm pushes on is approximately the same height.

 

[docben]

Looks like you are using different height retainers and or keepers on the valves. I ran into a similar issue on a 389 Pontiac - you never know what someone did on an older engine that has been apart.

Would take them apart - valves could have different stem lengths, seats could be receeded in the head, plus the issue of retainer to valve guide or seal clearance.

Just make sure you have proper retainer to seal clearance (assuming these have been cut for viton seals), check for coil bind, and have correct installed height.

On the engine referenced above when a valve job was done in the early 90's for some reason the exhaust guides were left .090" taller than the intake when they were cut for seals. The stock cam with .407 lift was just kissing the tops of the seals. I was putting in a higher lift cam that on paper should work with stock valve train ... ended up using Comp Cams retainers that were .050" shorter on the intakes with viton seals. Had to go back to the oring seals and splash cups on the exhaust with keepers that sit .020" higher, then had to shim some of the valve springs up for proper installed height as some of the seats were recessed into the head a bit.

Bottom line verify it is right or take it to a machinist who can otherwise you will break stuff

Looking more closely I see that the spring seat on the exhaust is lower in the head than the intake. The exhaust valves measure 4.930 inches long and the intakes are 4.860 inches. Interestingly, the install height of the springs are nearly the same (1.719 inches).

What puzzles me is why the difference in retainer dimensions between intake and exhaust? Should I reuse them and just get a new set of 981 springs ??

 

[Scott06]

Looking more closely I see that the spring seat on the exhaust is lower in the head than the intake. The exhaust valves measure 4.930 inches long and the intakes are 4.860 inches. Interestingly, the install height of the springs are nearly the same (1.719 inches).

What puzzles me is why the difference in retainer dimensions between intake and exhaust? Should I reuse them and just get a new set of 981 springs ??

Assuming they are the same spring they should have the same installed spring height. Not sure if that height is correct for the spring in question, which is key to having correct seat pressure on the valve.

as Scott Danforth pointed out - are the valve stems at the same height when installed in the head. I think someone also pointed out the exhaust retainer is a valve rotater - these were used to rotate the valve to even out heat differences to prevent burnt valves.

I would share these numbers with the tech folks at Comp cams to make sure the springs you are using work at that installed height. Usually if they are using different stem lengths and spring seat depths they are doing that to get the geometry correct so it may be just fine as is. If you can test the spring pressures given they are unknown origin you may not need new springs.

@Scott Danforth probably has better comments to add ....