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2 or 3 spring exhaust valve?

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boc

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Could someone please shed some light on this for me.
In the process of a full restoration of a 67 TR4a. The engine has been dismantled and i find the the exhaust valves have 3 springs instead of 2. Tried to do some research but cannot find much info. From what i can tell, it appears the engine may be an from earlier tr4 or even possibly from a tr3.
Does anybody know approx when was the change made?
Why are 2 better than 3 (according to online sources)
lastly, if thats true, can it be upgraded.

many thanks for your comments.
 
According to Moss's catalog they changed during the TR4 run.

VALVE SPRING SET (with triple exhaust valve springs) TR2 thru TR4 CT21470E.

That appears to also be when they changed the exhaust valve as well as they are showing the earlier one as having a 3/8" stem and the later one have a 5/16" stem so you should measure the stem to see if what's installed matches the spring count.

What's the engine number?

Here's some information on the different heads fitted to the TR2-4A models in case just the head was changed and not the whole engine.

TeriAnn Wakeman's TR2-4A head information

Scott
 
thank you scott.
I will follow up on your suggestions, do some more research and share my findings.

BOC
 
2 are better than 3 because they cost less. Otherwise, the 3 spring setup will work just fine (providing you have the matching spring seats).
 
The engine is now completely dismantled, cleaned and magnafluxed. Suprisingly in very good condition. It did have a fair amount of sludge in the oil pan which is to be expected after some years of inactivity.

Turns out you were correct Scott. The original 2 spring head must have been damaged and replaced with an earlier tr4 version. The block appears original.

Many thanks,
 
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