fixing a hole in a cylinder head?

I think the little hole is the least of your concern. The entire port looks to be blown out beyond usability. What does it measure now? 38mm, 39mm, 40mm?

pete.v said:

I think the little hole is the least of your concern. The entire port looks to be blown out beyond usability. What does it measure now? 38mm, 39mm, 40mm?

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36.2

I may be able to reduce that using a sleeve. if one or both of these solutions don't work, the worst case scenario is I need a new cylinder head. which is where i'm at if I don't try.

monkey wrench said:

pete.v said:

I think the little hole is the least of your concern. The entire port looks to be blown out beyond usability. What does it measure now? 38mm, 39mm, 40mm?

Click to expand...

36.2

I may be able to reduce that using a sleeve. if one or both of these solutions don't work, the worst case scenario is I need a new cylinder head. which is where i'm at if I don't try.

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36.2...! You wrote 32.6 earlier, which would be too big. But 36.2 is stupid big, unless you're building an outrageously highly tuned, balls out, 920 racer!

Seriously, I'd say you'd be much better off looking for a decent stock head (pref with 30mm ports) and put your big port jobby on eBay, it may be just what some budding racer is looking for!

monkey wrench said:

i suppose if i were to jb weld or epoxy the hole and then use a sleeve that pressed far enough into the port that it would cover the hole i'd be set.

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My thoughts are similar to yours, but I'm thinking bore the port just enough to true it up, then machine an aluminum sleeve to be a shrink fit. Heat the head to 350 F and freeze the sleeve. Once they come to equal temperature, there will be no getting them apart.

Slick

Shoot after what I've been through on alloy in my life time heat the head to like 600' F oil combustion temps to both gain full thermal advantage and distress-toughen at same time. JBW would easy hold an intake sleeve w/o any heating needed. JBW will only get slightly pliable not fail at head temps below 400' F so only needs a mechanical grip texture to stay put. If a sleeve would be more simple solution then that's what I'd do, now I know about it. Exhaust sees up to 1400' F in the most powerful tuned-run engines though so JBW may melt and blow out, but maybe not. If was mine and trying to fall asleep on a buget I'd be weighing the cost of new head ready to run vs cleaver repair with worst possible damage senario, most likely is just head air leaks and runs too bad to continue long, or repair stuff gets into chamber to beat up or just get chewed up by valves and maybe pecker texture chamber surface or even harder piston crown with undetable effect or junk hangs/bends a valve the piston strikes and most likely still run before shut down or piston parts jam the cam and sieze engine. You can not bother a Norton rod by mere piston punch through force but may ruin the rod shells even though the oil layer by Norton rod strenght. Keep in mind comnoz piston destruction this year.

I've got some experiments to do inside a head that has nothing to do with performance nor lasting long, so if ya think its only worth scrap price I'll like first refusal plus shipping.

@monkey wrench:

Bore the port to clean it up and then shrinking a sleeve in sounds good; only caveats I would add are beware of the clearance to the spring pocket and stake the sleeves so they do not move. I really see an opportunity here to develop a desirable port profile (ie. "D" shaped with a flat raised floor). Not sure where you are located but unless you have the ways and means to do this work I suggest you get in touch with Jim Comstock on this matter.

Depending upon what you are adverse to, options include a swap meet head (with unknowns), a Full Auto head or fix/modify what you have. 36.2mm intake port is well over the top unless you are going big displacement and/or short stroke. When compared to a 32mm port your 36.2mm port has 28% greater cross sectional area; when compared to a 30mm port your 36.2mm port has 46% greater cross sectional area. We know that for most applications a 30mm port serves well so unless you really think you are going to design for a 46% increase in power, the ports cross sectional area needs to be reduced.

I just noticed I have holes on the bottom of the exhaust ports of my 850 head, doesńt appear to go anywhere, as I thing they connect to the head bolts. So no leakage, they are about 8mm - 5/16" wide.

Should I mess with it and try to fix it or let the sleeping dog lie?

Jagbruno, ya got a photo of your litle dilemma ? There are 3 large studs in the head that torque down to the barrells so can only presume the 2 front ones that are tapped up into head and could this be busted through the exhaust port exit tract near exit side of exhaust valve ?

Re: fixing a hole in a cylinder head

Torontonian said:

Jagbruno, ya got a photo of your litle dilemma ? There are 3 large studs in the head that torque down to the barrells so can only presume the 2 front ones that are tapped up into head and could this be busted through the exhaust port exit tract near exit side of exhaust valve ?

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Not sure, I don't have the head near me to check, here is a picture I shot with my phone a couple of days ago:

Jagbruno , go to 3 rd. line down on forum ,how to post photos. Need to go there again myself. :|

Torontonian said:

Jagbruno , go to 3 rd. line down on forum ,how to post photos. Need to go there again myself. :|

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Done.

Looks like the blind end of the cylinder head stud hole. It looks benign to me. I would leave and run as is. If you do loosen or remove those studs for some reason, I would use some high temp thread sealant as a precautionary measure.

Yes, let sleeping dogs lie , the stud probably bottomed out in it's hole ,shattering off the little chunk. If the stud itself remains tight good enough. Fuzzy forward view shows ex.port threads may be wearing out. There are assembling lubes like never sieze and high-temp silicone to prevent more wear.

Torontonian said:

Yes, let sleeping dogs lie , the stud probably bottomed out in it's hole ,shattering off the little chunk. If the stud itself remains tight good enough. Fuzzy forward view shows ex.port threads may be wearing out. There are assembling lubes like never sieze and high-temp silicone to prevent more wear.

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Thank you, I will look into that as well!

i know its been awhile but i got the cylinder head sorted. i had a local fellow heli-arc it. total cost $0. the norton has been a back burner project but has now made it to the top of my list. hopefully i'll make some headway on it this winter.

monkey wrench said:

i know its been awhile but i got the cylinder head sorted. i had a local fellow heli-arc it. total cost $0. the norton has been a back burner project but has now made it to the top of my list. hopefully i'll make some headway on it this winter.

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Nice job.... buy this man a LOT of booze for his generous gift :lol:

Nice job.... buy this man a LOT of booze for his generous gift :lol:

no kidding. its a long story involving a local british bike enthusiasts taking pity on a guy with a true basket case.

monkey wrench said:

i know its been awhile but i got the cylinder head sorted.

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As most likely both ports have been enlarged that way you might want to have a look at the right one. There is a drain hole from the bottom of the valve spring seat to the cylinder - and this hole is very close to the RHS port. These castings generally suffer from porosity so it might be that after porting there is an oil path from the rockers' compartment to the RHS intake port. I have this on one of my heads. The solution for this is plugging the drain hole and adding an external oil drain line.


Tim

Tintin said:

monkey wrench said:

i know its been awhile but i got the cylinder head sorted.

Click to expand...

As most likely both ports have been enlarged that way you might want to have a look at the right one. There is a drain hole from the bottom of the valve spring seat to the cylinder - and this hole is very close to the RHS port. These castings generally suffer from porosity so it might be that after porting there is an oil path from the rockers' compartment to the RHS intake port. I have this on one of my heads. The solution for this is plugging the drain hole and adding an external oil drain line.


Tim

Click to expand...

thanks. i'll take a look at that.