650SS intake valve size

jseng1

jseng1

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I've had some 650SS customers order 1.4 (1.406") intake valves and I've had others order 1.5" intake valves. So did some people convert their 650 heads to the larger 1.5 valves? Or did the factory make some later specials with larger valves?
 
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jseng1 said:
I've had some 650SS customers order 1.4 (1.406") intake valves and I've had others order 1.5" intake valves. So did some people convert their 650 heads to the larger 1.5 valves? Or did the factory make some later heads with the larger valves? Does anyone know for sure?
Click to expand...
Hi Jim
My research shows that the later small bolt pattern heads were all 1.4 intake. Before that it is 1.3 exh and 1.3 in. (it's on my website)
I have heard of lots of pseudo-racers hot rodding by putting 1.5 intake. The seats are all 1.5" so there is meat, yes, but it puts it so close to the cylinder wall- unlike the desaxe 750- it's not great mod IMO.
The combustion chambers seem to be the same for the S650/136 head same as the 88SS/136 head.
Some of the norton literature seems contradictory about big valve seats option yet the PN for 1.5 valves is not seen in any parts books, and I have dug plenty?
There is aparrently late mercury and 650SS valves that are rareish or unknown, by some, but they are the long stem for matching short pushrods, since the geometry was upgraded to commando configuration but retained small 1.4 valves.
 
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Just saw the post in commando area.
Haynes data is a joke.
R12/136 medium fins 1.5" carb studs
88SS/136 large fins 1.625" carb studs 88SS 1st year and 99SS
S650/136 large fins 1 manxman 1 650SS and 1 to be used on 2nd year(1962) 88SS club racers, which were rare but no evidence they were 1.5 intake from "production" . 28.5mm ports which often got factory "slip in" steel insert to increase velocity.

all 3 heads have 1.4 intake and the same part # for the valves
Every one of these heads, I own, and is sitting on top of engines less than 10 feet behind me

Seen several pix of hot rod conversions with 1.5 intakes and huge intake ports .

All the earlier heads were 1.3 ex/1.3in
 
early only on the 3 heads above, before that it was 1.3/1.3 in/ex
1.4 " 88, 99 & 650 - PRE 125871 short stem
066974

late
1.4" 125871 ONWARD long stem need short pushrods l
067942

A lot to know if hot rodding early engines/heads, lots of pitfals if you are not up to speed.
 
Of interest, the Atlas got the larger inlet valves and bigger capacity engine but never seemed to outperform the 650 ss. Early Atlas models were single carb but that changed to twin carb at some point.

Glen
 
The inlet valves were round in my 1963 650SS didn't even bother to measure the diameter of the original valves, I was only bothered with whether the the new ones seated correctly, which they did!
You can fit bigger valves but if the seat/port doesn't match the bigger valve it is not going to improve anything anyway!
Therefore bigger valves = bigger port or at least a bigger throat in the valve seat, didn't see any different parts numbers to so say there was?

Burgs
 
I suspect Doug Hele had things set up quite well in that little 650ss head.
My 650 has been played with and does go very well, but so did the original 1962 bikes. It could be that the 1.4" valve is right for this engine.
I'm not sure if any production Commando , 750 or 850 ever went quite so fast as the 650ss did at MIRA.
His 1961 Manxman/ 1962 650ss was light years ahead of Triumph and BSA at that time.

Glen
 
Very interesting info on the long vs the short stem 1.4" valves. Does anybody know what the actual lengths are? It would be useful when ordering replacement parts.
Might help avoid the following conversation: "Those valves you sent me are too short. Got any longer ones????"
I have never been into my Mercury. The guy I bought it from said he had the head off, replaced one valve, used a Commando valve, said he had to grind down the stem to make it work. Go figure.
 
Stephen Hill said:
Might help avoid the following conversation: "Those valves you sent me are too short. Got any longer ones????"
Click to expand...
Obviously you are unaware the discussion is about the end of the stem end back to the collet groove top. the collet groove to the valve seat does not change unless you are having custom valves made then numbers matter since you are totally reengineering the whole situation.
Atlas and commando valves are "functionally" the same except for the tip length only. Any diameter measurement difference is not worth chewing bubble gum over.
This stem tip difference is the same regarding the early/late 1.4" valve.
1.3 intake never existed in late version but 1949-1975 1.3 exh was both early/late, long/short version
 
I believe Commando length pushrods will work with Commando length valves in the 650 head. The Commando lengths supposedly having better geometry. So you should be able to re -cut the diameter and face Commando valves to use in the 650 (with Commando pushrods).

Found this amazing factory 650 drawing in my computer.

650SS intake valve size
 
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dynodave said:
Why not just buy them like the rest of us?
late
1.4" 125871 ONWARD long stem need short pushrods l
067942
Click to expand...
Yes I could buy them. But my current customer wants beehive springs & a cam kit with BSA lifters and pushrods. So the collets need to be raised etc and the pushrod length is worked out etc so its about the same labor just to make the valves smaller - and this way the customer gets black diamond valves.

650SS intake valve size
 
jseng1 said:
I believe Commando length pushrods will work with Commando length valves in the 650 head. The Commando lengths supposedly having better geometry. So you should be able to re -cut the diameter and face Commando valves to use in the 650 (with Commando pushrods).

Found this amazing factory 650 drawing in my computer.

650SS intake valve size
Click to expand...
Can anyone read this? copied and try to blow it up but it's fuzzy and not legible!
Might show combustion chamber radius as intended!
 
Thank you for clarifying that the difference in length between early and late valves is not overall stem length, but the length between the collet groove and end of the valve.
Would my 1969 650ss Mercury use "long stem" valves?
Does anybody know what the short and long dimensions are?
 
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top of collet groove to tip of stem
sample of one each:
approx 1/4 is the short early .240+/-
approx 3/8 is the long late .370+/-
I highly doubt the valves changed length significantly of valve seat to collet top during 1949 til 1975
intake and exhaust appear to me to be the same. approx 3.675 and it depend on how/where you pick you point.
 
jseng1 said:
I believe Commando length pushrods will work with Commando length valves in the 650 head. The Commando lengths supposedly having better geometry. So you should be able to re -cut the diameter and face Commando valves to use in the 650 (with Commando pushrods).

Found this amazing factory 650 drawing in my computer.

650SS intake valve size
Click to expand...
Jim, do you have a high res version of this?
 
Anyone else wants a higher resolution copy of this drawing. Send me your email address by PM and I'll send you a file.

650SS intake valve size
 

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