MF 135 Valve Springs

[1968 MF135]

Hi,

Hoping someone can help......

I have the head off my 1968 MF135, engine is an AD3 152 perkins engine. Going to get it skimmed as it has been blowing bubbles into the coolant.

Anyway, I have noticed that the valves are fitted with single springs, all the replacement kits I have found all contain an inner and outer spring.

I can open the valves by hand using moderate thumb pressure, which seems a little to easy?.

When rebuilding should I convert to a double spring setup? or leave as is?

Thank You

 

[rScotty]

I haven't run into that problem with the engines I've dealt with, but springs that weak would make me wonder too.
But it's a Perkins, right? So spring force on similar engines should be findable info in a shop manual.

If using the old valves and just refacing them or lapping them - which is what I always prefer to do, then I'd want to stay with the same strength valve spring that it had originally - hence the shop manual info. I can see the advantage with duals springs having a backup spring if one breaks - but sure don't want super stout springs hammering on an old valves, seats, & rockers.

Here's an idea but it requires getting some of the new springs to compare....Springs don't move all that much, so it might help make a decision by rigging up some sort of lever to see if the single vs double springs took about the same force to compress the necessary quarter inch or so. I've seen simple home made spring testers using a 2x4 and a tension spring gauge.

Hmm.... even better, if you have a drill press, Amazon has a nifty $60 tool to check spring rate.
This is what I would use. In fact, I will do it next time I do an engine job. Thanks for getting us thinking about spring strength.

66835 Mini Valve Spring Tester, 0-300 lbs./in. Range, 5LB Increments.​

rScotty

 

[Roadworthy]

That does sound very weak for valve springs. The bubbles in coolant could simply be a bad head gasket. You may wish to investigate further before having any machine work done.

 

[1968 MF135]

I found this comment in an online manual for 152 perkins engines:

 

[1968 MF135]

Ok so my original question is resolved - sticking with the original single spring set up.

But I now have another query.... Each valve stem has a small O ring just sat on the stem. I cant find any reference to this in any of the manuals or on parts suppliers sites. Although some refer to a stem seal on the inlet valves only - which I don't have on my valves.

So.... should I fit some new O rings to the valves, or should get some valve stem seals or just leave it without either?

Hopefully this will be my last question on valves............

Thanks in advance

 

[Dman1981]

I put valve seals on all the valves
They came in the Perkins kit years ago of course kit was only 200 dollars

 

[RayIN]

Usually double valve springs are used when the engine is turbocharged.