Combat Intake Valve Spring Wear - Normal or Abnormal?

Longtimegone · Dec 11, 2022

Sorry for the lousy photos. Couldn't get it to focus on the wear in question, but it's the shiny area. It's worn flat at about a 45 degree angle to the ground flat, and goes all the way around the first loop. Both ends of the spring have the same type of wear. Neither the seat nor the collar show any unusual wear. Curious if this is a Combat thing, and how to avoid it. Thanks!

Combat Intake Valve Spring Wear - Normal or Abnormal?

kommando · Dec 12, 2022

Combats had 60 thou milled off the head but the pushrods were not shortened, so possibly because of the incorrect geometry that creates but maybe not. Regardless your pushrods will need to be put to the right length, the rockers should be at 90 degrees to the valve stem at 1/2 lift or just take 60 thou off the pushrod length minus any thickness taken off the cam follower face to clean them up if they are being included.

marshg246 · Dec 12, 2022

Longtimegone said:
Sorry for the lousy photos. Couldn't get it to focus on the wear in question, but it's the shiny area. It's worn flat at about a 45 degree angle to the ground flat, and goes all the way around the first loop. Both ends of the spring have the same type of wear. Neither the seat nor the collar show any unusual wear. Curious if this is a Combat thing, and how to avoid it. Thanks!
View attachment 101994 View attachment 101995 View attachment 101996

I've never seen it a Commando. Just guessing - look at the underside of the rockers to see if they are rubbing the springs. Since both ends have the wear, they may have been run and then turned over during a rebuild. Post the outer diameter of the spring so we can check if they are standard springs.

SteveA · Dec 12, 2022

kommando said:
Combats had 60 thou milled off the head but the pushrods were not shortened, so possibly because of the incorrect geometry that creates but maybe not. Regardless your pushrods will need to be put to the right length, the rockers should be at 90 degrees to the valve stem at 1/2 lift or just take 60 thou off the pushrod length minus any thickness taken off the cam follower face to clean them up if they are being included.

40 thou! It wasn't 0.060" milled off the head, just 0.040". But, you may still need to reduce the pushrod length a little more than 40 thou to get the correct geometry. Also take gasket choice into account!

ILLF8ED · Dec 12, 2022

It’s not a combat thing. I have owned my current combat for 25 years. It has over 40,000 miles on the set of valve springs with no wear like this. Is it possible you have replacement springs that were made with this bevel?
Also to above about shorter pushrods, I’m using .060” shorter that put the rocker geometry with the .040” shaved combat head back to normal. Rocker lift ratio from pushrod end to valve end is 1.13.

Longtimegone · Dec 12, 2022

marshg246 said:
I've never seen it a Commando. Just guessing - look at the underside of the rockers to see if they are rubbing the springs. Since both ends have the wear, they may have been run and then turned over during a rebuild. Post the outer diameter of the spring so we can check if they are standard springs.

Thanks Greg; I hadn't looked at the rockers, but found nothing unusual there. After doing some more checking, I think the spring OD is too big. I measure the OD of brand new KW's at 31.6mm/1.244in. That's slightly smaller than the 32.258mm/1.270in CBS shows on their website. The intake springs from the Combat head measure 33.20mm/1.307in, and the exhausts measure 33mm. They appear to just fit the seat, but it turns out they actually don't

The new KW springs have enough room to slide around on the seat. Still a mystery about the similar but not as extreme wear on top. It's possible they were flipped at some time; however, the engine is standard bore, and has not run in 30+ years. So I wonder; do the springs grow in diameter as they get shorter?

marshg246 · Dec 12, 2022

Longtimegone said:
Thanks Greg; I hadn't looked at the rockers, but found nothing unusual there. After doing some more checking, I think the spring OD is too big. I measure the OD of brand new KW's at 31.6mm/1.244in. That's slightly smaller than the 32.258mm/1.270in CBS shows on their website. The intake springs from the Combat head measure 33.20mm/1.307in, and the exhausts measure 33mm. They appear to just fit the seat, but it turns out they actually don't The new KW springs have enough room to slide around on the seat. Still a mystery about the similar but not as extreme wear on top. It's possible they were flipped at some time; however, the engine is standard bore, and has not run in 30+ years. So I wonder; do the springs grow in diameter as they get shorter?

I have a new set from AN. I measured both ends and the length in mm (caliper):

End 1 - End 2 - Length
32.92 - 32.57 - 42.61
32.98 - 32.57 - 42.67
32.93 - 32.66 - 42.47
32.96 - 32.81 - 42.48

marshg246 · Dec 12, 2022

Longtimegone said:
Thanks Greg; I hadn't looked at the rockers, but found nothing unusual there. After doing some more checking, I think the spring OD is too big. I measure the OD of brand new KW's at 31.6mm/1.244in. That's slightly smaller than the 32.258mm/1.270in CBS shows on their website. The intake springs from the Combat head measure 33.20mm/1.307in, and the exhausts measure 33mm. They appear to just fit the seat, but it turns out they actually don't The new KW springs have enough room to slide around on the seat. Still a mystery about the similar but not as extreme wear on top. It's possible they were flipped at some time; however, the engine is standard bore, and has not run in 30+ years. So I wonder; do the springs grow in diameter as they get shorter?

I just re-read what you said. If the springs didn't fit the seats then that's probably where the wear came from.

Longtimegone · Dec 12, 2022

Yes sir. Spring OD of 33.2mm and seat ID about 32.2.

baz · Dec 12, 2022

Maybe the work of a previous owner? Broken valve springs are not unusual but I've not seen a wear pattern like this

marshg246 · Dec 12, 2022

Longtimegone said:
Yes sir. Spring OD of 33.2mm and seat ID about 32.2.

Assuming our measuring devices are both accurate, it sounds like the seats and springs you have a wrong! The new springs I have measure between 32.57 and 32.98 so they wouldn't fit the seats and they are smaller than the spring you have. I know that the AN springs fit - this is not the only set I've had, and I've put a set of them in a Combat.