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Author: Subject: Engine shims and electrolysis
Ivan

posted on 16/7/17 at 03:12 PM Reply With Quote
Engine shims and electrolysis

I need to shim my valve spring seats to get the right spring height. Because of cost am thinking of using stainless steel shims as importing the right hardened steel ones is just too expensive. My concern is that the shims will be between an Aluminium head and hardened steel spring cup. Need I be concerned about electrolysis? Or is there any other reason why I should not do it?

I could get the SS shims laser cut for roughly 1/3 the cost of imported hardened steel ones.

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flak monkey

posted on 16/7/17 at 03:15 PM Reply With Quote
It'll be fine, they will be in a bath of oil all their life, no chance for corrosion.

Electrolytic corrosion is a problem in moist and warm areas, you have no moisture to worry about





Sera

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Ivan

posted on 16/7/17 at 03:27 PM Reply With Quote
Thanks Sera - I just knew you would be a valuable resource on here

Whilst I have your attention I am experiencing problems with breaking valve spring damper springs on my Chevy 383.

I sent Compcams the following email but got no help at all. What are your thoughts?

"Hi
I am confused about selecting the correct valve springs for my Chevy 383
Small Block. The current set up is as follows:
Heads: Edelbrock E-Street.
Cam: Comp Cams XE 274
Rockers: CompCams 1412-16
Push Rods: 7812-16
Lifters: 812-16

My problem:
1. Edelbrock say that using the standard Edelbrock 57567 spring you
are limited to 5500 RPM above which you can expect damper spring
breakages.
2. My head came with different springs to the standard 57657 springs
set in cups as they are smaller diameter and I have broken damper springs.
3. You recommend the 981-16 springs and comparing specs lead me to
believe that your springs will give similar problems as comparing the two
I find:

Supplier Part No Damper OD1 ID1 Spring Rate Seat Ht. Seat Pressure Seat Pressure@ 0.5"
Comp cams 941 Y 1.269 0.871 454 1.75 130 357
Comp cams 981 Y 1.269 0.88 373 1.75 105 291.5
Comp cams 986 Y 1.43 1.07 322 1.75 132 293
Edelbrock 5767 Y 1.46 1.06 328 1.8 120 284
Fitted ??? Y 1.268 0.888 404 1.75 152.308 354.308

a. The 981 spring you recommend has a significantly lower Seat
pressure than the 5767 Edelbrock spring and very similar pressure at 0.50”
lift to the Edelbrock one. This gives rise to the following concerns:
i. If the Edelbrock spring limits you to 5500 RPM with risk of
breaking the damper springs won’t your #981 springs give similar problems
and limits?
ii. In fact what maximum revs will your #981 springs support?
b. I had a look at your #941 springs and wonder if they would be a
better match and reduce the risk of Damper spring breakage. What maximum
revs would they support. I think the XE 274 cam would be best utilised if
a could rev to 6500 RPM.
i. If I removed the damper springs in the #941 springs and limit the
revs to 6500 or even 6000 RPM would there be any risk of spring resonance?
The thinking here is that I would remove the risk of damper breakage.
Your answers to these questions would be greatly appreciated."

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flak monkey

posted on 16/7/17 at 03:31 PM Reply With Quote
I ran 981 springs to 6,800rpm in my 350 with the same cam with no issues at all - they are a good spring and will be perfectly suitable for your application. Those E-Street heads will run out of flow about 6500rpm anyway.

The 981 are a single spring, they have no damper.





Sera

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02GF74

posted on 16/7/17 at 09:10 PM Reply With Quote
What sort of saving are we talking about? And what price for a new head if something went wrong.

My concern is, and it may be unfounded, is whether hardened steel and stainless steel have same properties. From what i know, stainless steel is brittle wnen compared to mild steel (but how different to hardenex is it?) so should the seats fracture, will the head be ruined and if the pieces find their way elsewhere into the engine? I think you are doing something probably noone else had done.





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Mr Whippy

posted on 17/7/17 at 05:36 AM Reply With Quote
I doubt very much electrolysis would ever occur at all considering all the components will be covered with oil...
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flak monkey

posted on 17/7/17 at 09:40 AM Reply With Quote
quote:
Originally posted by 02GF74
What sort of saving are we talking about? And what price for a new head if something went wrong.

My concern is, and it may be unfounded, is whether hardened steel and stainless steel have same properties. From what i know, stainless steel is brittle wnen compared to mild steel (but how different to hardenex is it?) so should the seats fracture, will the head be ruined and if the pieces find their way elsewhere into the engine? I think you are doing something probably noone else had done.


Stainless will be fine. Normally spring seats aren't hardened, indeed on a cast iron head they would run directly onto the head.

The reason you can't run the springs directly onto an aluminium head is that the springs actually rotate as the valves open and close, the end of the spring coil would wear away an aluminium head rapidly.

A steel spacer/shim under the spring spreads the load sufficiently to avoid this. Many modern engines have valve stem seals with the spring seat as part of them. Which also helps to positively retain the seal and stops it popping off the top of the guide.





Sera

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Ivan

posted on 17/7/17 at 02:19 PM Reply With Quote
This forum is much better than Comp Cams - at least I got answers that make sense

Just to clarify - the springs sit in a hardened cup and the spacers sit under that so failure is highly unlikely.

Sera - glad to hear the 981 springs should be good to 6500 revs. Re the E Street heads strangely enough the Edelbrock published flow figures are better than their performance head and I cleaned them up slightly, so I'm happy that they will sustain 6500 revs - using the Comp Cams CamQuest calculator and inputting the published flow figures they seem to sustain about 7000 RPM although I will limit things to around 6250 with a soft cutout at that. I hope it's true that the 981 springs don't have dampers as their catalogue say they do. (Although I have found some errors in the catalogue)




[Edited on 17/7/17 by Ivan]

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flak monkey

posted on 17/7/17 at 02:28 PM Reply With Quote
Actually you are right, the 981's do have dampers, I was being a bit of a div.

However, I had no issues with them, so you should be fine too.





Sera

https://www.facebook.com/sera.jay666

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