TR2/3/3A Compression Question

[HighAltitudeTR3]

my compression across the board is 120, 118, 120, 120. 120 seems a little low, but they are consistent. Any reason to be worried? Thanks!!

 

[poolboy]

I wonder what they might be at sea level ?

 

[Geo Hahn]

Those number sound just fine to me.

Gauges and technique can vary quite a bit so absolute numbers are always suspect but having them consistent across the board is especially good.

Yeah, if that test was done at 8,000' they are even better.

Take up to Independence Pass and retest (just kidding).

 

[HighAltitudeTR3]

Ha. With all fairness I live at the bottom of the pass. Now if I could just get my carbs adjusted for a pass ralley.

 

[CJD]

I've been studying the carbs quite a bit while tuning mine. I learned the SU's are altitude compensating. So, unlike Holleys they should not need needle or jet changes for altitude climbing.

 

[Geo Hahn]

They do handle altitude well - unless you have them set too rich. You may get away with 'too rich' at your normal altitude but it will become 'much too rich' when you are 10,000' higher.

I'll be crossing Independence Pass (and many other 10K+ passes) on our group drive in a couple of weeks so I will get to test this out.

 

[HighAltitudeTR3]

Well I can speak first hand from experience. The needles don't change a thing! I am leaned all the way and I'm still rich. But I've almost come to terms with it.

 

[HighAltitudeTR3]

I'd love to see you guys when you come through town!! Let me know when and I'll put it on my calendar

 

[sp53]

What makes a big difference with rich running is the distributor advancement springs. If they do not move the timing up, the fuel does not burn well.

 

[HighAltitudeTR3]

SP53, are you referring to the mechanical advance springs? I thought about changing them out, but I noticed I have two different springs. After some research it seemed normal. I guess I could call Moss and get the right springs ordered. Could be a simple fix to get fuel ratio right...

 

[Geo Hahn]

Good luck finding the 'right springs'. The usual item supplied is a package of springs (5 or so) so you can find the combination that is best for you. Yes, it will be one heavy spring and one light spring - those are what create the 'knees' in the curve.

The notable running issue with the weights is if they get gummed up and do not move freely. The variation in springs is more of a tuning issue to be pursued once everything is operating as it should.