n2omike wrote: ↑Fri Mar 19, 2021 8:12 am
I don't know why so many people insist on installing hardened seats in these old heads that won't get driven more than 500 miles a year... as this type of thing happens FAR too often. Unless it's going to see a LOT of miles under significant load... there is ZERO need for the hardened seat up-sell.
Agreed,
Years ago all the magazines had everyone upset by showing unleaded fuel damage to normal valve seats... Of course no one really realized that the pictures and field tests were from taxi cabs punishing those engines for 100's of thousands of miles and years of hard service.
Next thing you know, every hotrod driving a few hundred miles a year needed hardened valve seats...
Although I had a set in from a hot rod being driven only a few hundred miles a year, and the exhaust seats were sunk so bad the valve was seating on the flat backside of it's head. Rather remarkably it ran quite well like that. At the same time another set of the same casting number from a relatively similar application, and the exhaust seats were fine. The big question is why the crazy difference?
So with the mild cost I do put in hardened exhaust seats; in my opinion it is not worth the risk. But is sucks to hit water for sure.
It's not supposed to work but it did for me.l ported into a water jacket and mig welded it with a lincoln 140 110volt welder . Just quick trigger on off so it doesn't heat that much. My heads were chevy 416 castings from 1984 so I'm not sure on the cast iron compound difference.
I had a local welder tig it. When I cut it there was a small pin hole.
I was able to tap it to 1/4-28 so I think I am going to try a fine thread aluminum screw with sleeve retainer like a stich pin. There isn't a lot of thread support so I want something that cuts easy and with a higher expansion rate maybe it will tend to seal with heat.
Ive repaired several rare heads. I go above the seat and drill a hole directly above. I then bead blast to make sure all rust is gone. There is a extreme heat epoxy made by JBWeld. Make sure it is a 2 part epoxy with at least 48 hour dry time so there is no shrinkage. If it cures quickly, it will have much shrinkage. Go in and coat several layers, then cover with liquid weld that is made to install seta. Block off all entrances and put seat under vacuum and let it suck in the epoxy. Again cover with several thin layers. Then seal over with ceramic mix. Then tap for pipe thread and install cast iron plug. Dress it down by hand so it cannot be seen. Oh seal the pipe plug. Make sure head is cleaned thorougly before u do this so that it does not go back in cleaning tank, ever. Ill b glad to show photos if you like
reed
This would be a great candidate for using the torch and gas welding it. Pretty much a lost art but it would do it perfectly. Kent White of TMTechnologies sells a cast iron flux that is simple to use and works great. I've repaired a lot of cast iron after getting his DVD years ago. He sells the rod and flux on his site. He has a DVD on the subject for sale or rent, that covers all you need to know.
Seems to me as though the risk-to-reward ratio is leaning the wrong way on this job.
If the repair starts to leak at some point down the road it could easily become a hydro-lock situation...... that ends up with a bent rod and a damaged engine.
If the head is really that valuable, it should worth having the casting properly welded up by a place that does that type work daily.
PRH wrote: ↑Sun Mar 21, 2021 5:01 pm
Is this some rare unobtainaium head?
Seems to me as though the risk-to-reward ratio is leaning the wrong way on this job.
If the repair starts to leak at some point down the road it could easily become a hydro-lock situation...... that ends up with a bent rod and a damaged engine.
If the head is really that valuable, it should worth having the casting properly welded up by a place that does that type work daily.
Or stick the valve in the guide.
Any type of stitch repair success is contingent on having sufficient threads to maintain seal.
I have had good success with old castings like that when you get a pin hole is to just use everdur 656 bronze and tig the land up and re-machine it a bit higher and top the seat down to suit the height needed.
It will work in both Intake and exhaust. I see old mopar heads that have had seats put in them and numbers matching stuff is always worth the effort to save for show queen cars.
Even daily drivers had the same issue with an old 1959 383 head and thats a daily summer ride for the last 7 years now still going.
Silver solder and everdur 656 bronze rod works wonders on cast iron
It is a numbers matching head for 1970 and it is going to a customer in Finland. There are other castings with the same number available but I had these two just about done except for cutting a couple seats and correcting the intake side for intake alignment so I really want to fix it if I can. These heads are crack prone on the outside and these two are the second pair because the first two were cracked
According to the customer, inspectors check all numbers and they need to be accurate for the car or it does not pass.
ProPower engines wrote: ↑Mon Mar 22, 2021 1:09 am
I have had good success with old castings like that when you get a pin hole is to just use everdur 656 bronze and tig the land up and re-machine it a bit higher and top the seat down to suit the height needed.
It will work in both Intake and exhaust. I see old mopar heads that have had seats put in them and numbers matching stuff is always worth the effort to save for show queen cars.
Even daily drivers had the same issue with an old 1959 383 head and thats a daily summer ride for the last 7 years now still going.
Silver solder and everdur 656 bronze rod works wonders on cast iron
I've done similar repairs with 656 from cronatron. Unless you bring the head to 700* approx before brazing and completed a very slow cool down procedure afterwards, the cast iron will be very hard and abuse you seat pocket cutter. Good news is you will now have opportunity to install a shorter and smaller od seat than initially used and you will never touch the iron. The neighboring intake seat will lose its press fit, so yank it out after fixing the exhaust and replace after measuring it's counterbore.
Opened up the hole to 5/16 and got decent thread engagement. Coated the threads of a 5/16 bolt and screwed it in then machined it down. Going to pressure test it today but it looks like it is going to work.
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I did a set of BBC large ovals about 17 years ago to go on a stroker boat motor.
I installed hardened ex seats to accommodate 1.88 valves. No issues discovered during that operation.
They also got 2.19” intakes and “new everything” for parts, & bowl blended.
On the dyno there seemed to be a weak cylinder.
Pulled the plugs saw moisture(water) on one plug.
Pressure tested the system, water running into the cylinder.
Pulled the head, pressure tested it........ leaking from around one ex seat.
Cut the seat out...... no hole to be found.
Pressure tested with the seat out to see where it was leaking....... coming right through the casting.
Whacked the area where the bubbles were coming out with a punch....... it was pretty solid(punch didn’t go thru).
