valves/guides Q..

[hardtimes]

Why use the 'split' guides and 'mushroom' end valves, versus using the newer style one piece guide and straight stem valves ?
I acknowledge that ....if you have still usable originals and can save $...use them. But, if wanting to reduce work and improve function , when starting to collect parts...why buy/use old vs new style , i.e.-easier adjustment; easier to install, etc.....

[Fullraceflathead]

Modern straight stems are definitely the way to go.
That Mushroom stem is Henry Ford's Patented idea to reduce the wear and help prevent the lash from getting larger as it wears.
The spring pressure is very light compared to a modern engine, I doubt much actual wear occurs in the Model A.

[hardtimes]

Fullraceflathead,
That's the way I see it also ! This all hit home yesterday, when I was working on a B short block. Well, I encountered mushroom exhausts and straight (1.825) intakes ! My efforts to take out and examine the mushroom situation , resulted in pinched digits ! Started me wondering what the heck. Then I thought of the old school auto shop teacher who made this short block. Probably what he has available, eh ? Maybe not though, as he had a model a collection and was into 'improving' performance, therefor, the huge intake valves. Being an older gentleman, my guess is that he was 'frugal' !
Best 'used' B block that I've had ,,,ever, with new standard pistons/rods/cam and standard C crank. Either he had the excellent porting job done by an expert, or he was an expert..best porting job I've seen on a B ! Best of all...NO CRACKS Since valves and job looks great, I'll have to leave these mushrooms in ? What do you think...I should change them out to straight ??

[Pete]

You can replace the mushroom end valves for various reasons but the replacements should have 5/16 stems. The engine was designed that way for a reason which should be obvious.
While going to 11/32 stems is not much of an increase in diameter, with them your engine will never develop the rated hp.
Most of the standard valves used for replacements also have more material under the head which further impedes flow.
Bigger is not always better.

[RandyinUtah]

Ever notice on the original guides there is a shoulder that the valve spring meets up against which locates the spring. The straight valve type guides do not have this shoulder so there is less spring tension. One needs to account for this with a spacer on top of the spring to get back to the original spring pressure or use longer springs.

[hardtimes]

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Originally Posted by Pete

You can replace the mushroom end valves for various reasons but the replacements should have 5/16 stems. The engine was designed that way for a reason which should be obvious.
While going to 11/32 stems is not much of an increase in diameter, with them your engine will never develop the rated hp.
Most of the standard valves used for replacements also have more material under the head which further impedes flow.
Bigger is not always better.

Thanks Pete. I will consider this information, if I change out the valves. The old timer or whoever did the porting work also worked material off of the underside of the large intake valves. He definitely had a clue. Just went so far and then used the mushrooms, which is a head scratcher.

[hardtimes]

Originally Posted by RandyinUtah

Ever notice on the original guides there is a shoulder that the valve spring meets up against which locates the spring. The straight valve type guides do not have this shoulder so there is less spring tension. One needs to account for this with a spacer on top of the spring to get back to the original spring pressure or use longer springs.

Hey Randy,
I believe that one piece guides WITH shoulder are available for some time now. Spacers are good for springs to increase seat pressure to whatever number you seek and I've used them with 'weak' springs. But, I think that a guy is better off just to get new correct springs for intended goal.

[RandyinUtah]

Hard time it's nice to learn that some manufactures have taken this shoulder issue and made the change to guides.I will look for this type in the future. Thanks for responding.

[hardtimes]

Originally Posted by RandyinUtah

Hard time it's nice to learn that some manufactures have taken this shoulder issue and made the change to guides.I will look for this type in the future. Thanks for responding.

Hey Randy,
Last evening, I was going thru some parts suppliers catalogues for stuff...I can't live without !

I noticed that they sell valve train parts as a 'set', and some individually. And, in two cases reviewed, I saw that they sell a 'modern' set ...that is the one to look at for the shouldered guide that we are discussing. Good luck