SS Head Grab Bag

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
Among the collected components in my collection with which to build a few motors, are a few SS cylinder heads, some with varying "custom touches" to them. My intention is to eventually build an 88SS and a 650SS motor out of all the components, but I'm wondering which of these heads would be best suited/adapted to each motor.

Head "S" has an "S" at the end of the casting number on top of the intake rocker box, so we'll call it that.
  • good overall usable shape, but dirty so well worth going through
  • stock size 1.3" exhaust valve
  • 750 size 1.5" inlet valve
  • inlet ports at 29.5mm
  • spigotted

Head "R" has an "R" at the end of the casting number.
  • very clean, recently rebuilt, but not run, so well worth going through
  • stock size 1.3" exhaust valve
  • stock size 1.4" intake valve
  • inlet ports at just over 31mm(!)
  • spigotted
Head "X" has no casting number on top
  • currently on a late-in-series Mercury motor. I've not removed it from the barrel quite yet but:
  • 28mm intakes
  • due to its late date, I'm guessing (dangerous, I know) unspigotted

Which of these would be best suited/adapted for a 88SS and a 650SS?

Does the 1.5" valve tangle with a 9:1-ish piston on a 88 or 650 with an SS cam?

Would it be madness to try and put 930 or 932 concentrics on the 31mm(!) intake port head on a 650?

Big single carb on the big intake?

Is the 31mm(!) intake too big for either of these? If so, is it reasonable to make sleeves to reduce the intake port down to a more reasonable size, ala the stock 88SS 28-26mm sleeve?

All the barrels I have are spigotted, other than the presumably matching Mercury, but with the Mercury being the only stock inlet size, does it make the most sense to put that on the smallest motor?

Any guidance on why the large port but stock valve, and slightly large port but oversized valve, and what could be expected for both of these particular modifications?

That's enough questions for one post...

Any help and/or insight would be appreciated.
 
Joined
Dec 22, 2006
Messages
5,083
Country flag
The late model 650ss came with twin 30 mm Concentrics. It seems a lot of carb for a 650, but it works really well. Throttle response is excellent.

Glen
 
Joined
Apr 20, 2011
Messages
4,606
Country flag
Suggest on the 31mm port you fit a pair of split sleeves and bring them back to 28mm.
The 1.5 inlet valve might be too big for a 500.
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
The late model 650ss came with twin 30 mm Concentrics. It seems a lot of carb for a 650, but it works really well. Throttle response is excellent.

Glen
Yes, I read that, but that's with a stock 28mm intake port.

I'm worried that the 31mm enlarged port on head R will slow everything to a crawl. With my rudimentary understanding of all this, it's better to have a larger carb than intake port to increase fuel/air speed through the intake valve, so with a 31mm port, I'm looking at a 32mm carb, or reducing port size with a sleeve. Does this sound right?

I've got a Triumph Bonneville motor with twin 930s, and like you said, they work well. The '69 Triumph has larger valves though.

Seems interesting that the 650 motors went from 27mm 376 monoblocs with port reduction sleeves to 30mm concentrics with no sleeves. That's quite a jump. Do monoblocs flow that much better?
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
Suggest on the 31mm port you fit a pair of split sleeves and bring them back to 28mm.
The 1.5 inlet valve might be too big for a 500.
Would the 1.5 inlet valve be reasonable for a 29.5mm port 650 with 930s, or should I sleeve those back to 28 or 26mm and run 376s?

I've got a pair of 930s and a couple pairs of 376s, but I don't want to waste a bunch of money on rebuild kits, slides, and jets, unless it's somewhat promising to do so.
 
Joined
May 28, 2003
Messages
2,113
Country flag
Well at least you have 1 desirable S650/136 head on the mercury. The racing 30 mm ports and/ or 1.5 intakes has made them ( IMO) not very desireable. Will they run, yes, nice and tractable? I doubt it.
The 22729 "SS" cam, I doubt the 1.5 intake will tangle with the exhaust.
If you try to build a 88SS be sure to measure your crank and see if it is a true SS crank. An earlier big bore sludge trap crank is more fragile.
An 88SS needs SS barrels due to the high lift cam causing push rod problems in the tunnels.
My faux 88SS is getting new 28mm carbs and even at that, I feel like a bad boy... 26 would have been better.
Are you trying to build a 12,000 rpm screamer?
 
Joined
Dec 22, 2006
Messages
5,083
Country flag
Don't know if the 1 mm from 30 to 31 will matter. My bike isn't at 28 mm anymore.
Herb Becker got ahold of it and ported it to 30 mm, also reshaped the intake bowl area further in. His description " same as we do on the racing Commandos"
It goes like stink.
The shape of the port is really important, not just size. So it's really impossible to know what the characteristics will be without assembly.
I've also ridden another make of bike that was ported, big carbs but wouldn't pull the skin off rice pudding. Bad porting job I guess.

Jim Comstock knows more on this subject than most, he's got the knack for it, hopefully he will post.
I know he likes big intake valves on 750s+ 850s, no downside ( other than cost)

Glen
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
Well at least you have 1 desirable S650/136 head on the mercury. The racing 30 mm ports and/ or 1.5 intakes has made them ( IMO) not very desireable. Will they run, yes, nice and tractable? I doubt it.
The 22729 "SS" cam, I doubt the 1.5 intake will tangle with the exhaust.
If you try to build a 88SS be sure to measure your crank and see if it is a true SS crank. An earlier big bore sludge trap crank is more fragile.
An 88SS needs SS barrels due to the high lift cam causing push rod problems in the tunnels.
My faux 88SS is getting new 28mm carbs and even at that, I feel like a bad boy... 26 would have been better.
Are you trying to build a 12,000 rpm screamer?
Yea. Not perfect scenarios that's for sure, but I enjoy using up parts that would be destined for the scrap pile, and turning them into reliable, usable bikes. Bolting up stock parts in stock configurations isn't as much fun for me. The prices were right too.

I've got a couple NOS 88SS cranks, so it'll be as up-to-snuff as you can get with a small journal, bolt-up crank. No 12k rpm screaming race bikes without a one piece, big-journal crank for me. Probably just 6-7k a road bike, as fun as it might be to brag about my $15k, 12k rpm, 500cc ridable hand grenade...

Yes, I've heard the exhaust push-rod tunnels are the ones to watch for, particularly with the barreled rods, but I've got a long 3/4" roughing end mill, and I know how to use it! Speaking of barreled push rods, where does one find those these days?
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
Don't know if the 1 mm from 30 to 31 will matter. My bike isn't at 28 mm anymore.
Herb Becker got ahold of it and ported it to 30 mm, also reshaped the intake bowl area further in. His description " same as we do on the racing Commandos"
It goes like stink.
The shape of the port is really important, not just size. So it's really impossible to know what the characteristics will be without assembly.
I've also ridden another make of bike that was ported, big carbs but wouldn't pull the skin off rice pudding. Bad porting job I guess.

Jim Comstock knows more on this subject than most, he's got the knack for it, hopefully he will post.
I know he likes big intake valves on 750s+ 850s, no downside ( other than cost)

Glen
Thanks for your thoughts. No harm in trying it out I guess. The one with the giant ports is the one that's already been rebuilt with new stock-sized valves and (what I can tell) guides and springs, so fingers crossed that the person who got crazy with the die grinder knew what they were doing.
 
Joined
Apr 20, 2011
Messages
4,606
Country flag
Would the 1.5 inlet valve be reasonable for a 29.5mm port 650 with 930s, or should I sleeve those back to 28 or 26mm and run 376s?

I've got a pair of 930s and a couple pairs of 376s, but I don't want to waste a bunch of money on rebuild kits, slides, and jets, unless it's somewhat promising to do so.
Smaller 28mm ports will speed up the gas flow, beleive it or not, it will also pickup better from low rpm, and you are talking to someone who bored out my ports to 32mm, I wish I hadn't.
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
Smaller 28mm ports will speed up the gas flow, beleive it or not, it will also pickup better from low rpm, and you are talking to someone who bored out my ports to 32mm, I wish I hadn't.
Yes, I believe it, and that's exactly my concern; spending a bunch of money and time on something that, as @worntorn so cleverly said, "won't pull the skin off rice pudding".

Out of interest, what carbs are you running on those 32mm ports?
 
Joined
Dec 22, 2006
Messages
5,083
Country flag
On the other hand- quote from Herb Becker on my 650ss before and after porting.
" The clutch held fine before but slipped after porting"
I bought the bike with slipping clutch and port job.
Tried everything to get the stock clutch to hold but right at 4 k it would bust loose every time. New plates, new springs cinched way down, no luck.
Finally put a Newby dry clutch in and that holds. It took quite a bit of spring pressure at that. On initial setup for easy clutch use it slipped too.
For a little old bike, it really romps from 4 k to redline.

Glen
 

t ingermanson

VIP MEMBER
Joined
Oct 17, 2018
Messages
135
Country flag
On the other hand- quote from Herb Becker on my 650ss before and after porting.
" The clutch held fine before but slipped after porting"
I bought the bike with slipping clutch and port job.
Tried everything to get the stock clutch to hold but right at 4 k it would bust loose every time. New plates, new springs cinched way down, no luck.
Finally put a Newby dry clutch in and that holds. It took quite a bit of spring pressure at that. On initial setup for easy clutch use it slipped too.
For a little old bike, it really romps from 4 k to redline.

Glen
Yes! I put a Newby on my pre-unit Triton a few years ago, and no other clutch will ever go on any Brit bike at my house again. Light, easy, tidy. And to quote a Texan friend of mine, they look as "cool as chrome dog shit on my dashboard". Not sure what that means, but it makes me laugh.

At this point, I can only hope I end up with a slipping clutch problem!
 
Joined
Apr 20, 2011
Messages
4,606
Country flag
Yes, I believe it, and that's exactly my concern; spending a bunch of money and time on something that, as @worntorn so cleverly said, "won't pull the skin off rice pudding".

Out of interest, what carbs are you running on those 32mm port
32mm, but I should have done it the same way as the Commando, made two carb spaces internals tapering from 32 to 28mm - that would have been OK.
 

Top