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Old 08-16-2018, 07:03 PM   #41
Talkwrench
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Default Re: Piston to head clearancing

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Originally Posted by JSeery View Post
You could, but it would be difficult to know where you were on the piston dome. The clearance will vary around by location. When you do this check, you do it in several positions for each piston. You can attemp to modify the head for more uniform measurements or use the tightest measurement for your reference.
correct.. You need to check around the edge of the piston, piston center/ dome area has plenty of clearance.
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Old 08-17-2018, 10:56 AM   #42
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Default Re: Piston to head clearancing

Kenny Kloth told me many years ago, that at .035" his pistons would barely touch when 7K rpm was reached by accident.
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Old 08-17-2018, 12:04 PM   #43
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Default Re: Piston to head clearancing

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Yes, you can use a tighter piston to head clearance, if you use a lighter piston. The heavy 4 ring pistons have a tendency to stretch the rods a little. Especially is you running a good cam at run over 5000 RPM;s Just remember ONE thing: There;s always a reason for making a modification. Some work, some don't.
I sometimes wonder about "rod stretch". Is a rod elastic enough to stretch at high RPM and return to original length? Or could the crankshaft be flexing enough to allow piston contact? Has any research been done on this?
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Old 08-17-2018, 12:07 PM   #44
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Default Re: Piston to head clearancing

I have not seen any test data, but rod stretch is a common concern in high RPM engines.
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Old 08-17-2018, 12:45 PM   #45
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Default Re: Piston to head clearancing

Any metal can be stretched within its limit and go back to what it was from start.
Then it can be plastic deformated getting stretched permanently.
And finally loading it beyond its tensile strenght it will snap.
Terms might be off...pardon my swedish...someone jump in and correct whats needed.
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Old 08-17-2018, 02:46 PM   #46
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Default Re: Piston to head clearancing

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You are talking about a stress-strain curve for steel. Here is an example.
Attached Images
File Type: jpg Curved-Steel-Stress-Strain-Curve-Ratio.jpg (23.3 KB, 50 views)
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Old 08-17-2018, 03:56 PM   #47
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Default Re: Piston to head clearancing

I've used rosin core solder on industrial engines before to find what the firing order was, some of them can have the flywheel put on in different positions and have timing marks all over the place. I worked for an industrial ignition, hydraulic, and mechanical governor co. and have seen just about everything that can be done wrong. I wish there was a distributor with the point contacts sealed in a glass tube ( one for each cyl.) and closed by a magnet on the rotor like the Altronic ignition system uses. It had a small alternator built in the housing and I never had a problem with them and I converted many a industrial engines over to it, up to 10 cyl. That should get some of you younger guy's thinking about how to do it, I'd by one for my Flat Head 41. Al
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Old 08-17-2018, 05:18 PM   #48
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Default Re: Piston to head clearancing

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Kenny Kloth told me many years ago, that at .035" his pistons would barely touch when 7K rpm was reached by accident.

Thanks, that's the sort of info I'm looking for. Do you have any idea what stroke, what rods, what pistons, etc? You know I have to ask, right?
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Old 08-17-2018, 10:05 PM   #49
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Default Re: Piston to head clearancing

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Kenny Kloth told me many years ago, that at .035" his pistons would barely touch when 7K rpm was reached by accident.
That is quite true with stock rods and crank.
We can run a little closer with modern rods, pistons, billet crank and girdle.
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Old 08-17-2018, 10:41 PM   #50
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Default Re: Piston to head clearancing

The rules for sportsman engines back in the late 50's was 1/8 overbore max, stock 3 3/4 crank. ahy cam stock valves, heads and intake..
In an effort to get max acceleration off the corners. WE ran the 38/42 crank, 21A rods and Silverlight pistons. The rich guys tried Thomas mag pistons. I had a set for yhe 4" crank. but they never became league.. Light rear drums and anything else that spun around. This is when we discovered rod stretch.
We also ran alum clutch and flywheels. Cheating was the name of the game, but getting caught could loose your number. The best mod was a hollowed out 33/34 intake and 2GC carb. Now on a short track, non of this was very importan,FI, You didn't have the ***** to use it,
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Old 08-19-2018, 06:00 PM   #51
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Default Re: Piston to head clearancing

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The rules for sportsman engines back in the late 50's was 1/8 overbore max, stock 3 3/4 crank. ahy cam stock valves, heads and intake..
In an effort to get max acceleration off the corners. WE ran the 38/42 crank, 21A rods and Silverlight pistons. The rich guys tried Thomas mag pistons. I had a set for yhe 4" crank. but they never became league.. Light rear drums and anything else that spun around. This is when we discovered rod stretch.
We also ran alum clutch and flywheels. Cheating was the name of the game, but getting caught could loose your number. The best mod was a hollowed out 33/34 intake and 2GC carb. Now on a short track, non of this was very importan,FI, You didn't have the ***** to use it,
Ron,
Why did you use a 33-34 intake and anything special about the carb? Would these modifications be useful today?
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Old 08-19-2018, 09:09 PM   #52
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Default Re: Piston to head clearancing

The 33/34 "Camel back" Intake is a large casting, and can be hollowed out, The Bore can be increased to the size of the 2GC carb the carb can have a third bolt added where the PB port is filled with JB weld Noe it's a legule carb because it in the original place. The inside of the intake is formed with epoxy and fiber glass Then filled with foam to shape the runners. After the Epoxy hardens just pore some gas into the intake and lall the foam will melt away. I still have one of the last intakes I made. I;ll take some pics and try and post them. This was one mod that really worked quite well. It's nice when something work better than planned.
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Old 09-17-2021, 07:39 AM   #53
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Default Re: Piston to head clearancing

I am interested in this process , any more detail or pictures?
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Old 09-17-2021, 09:21 AM   #54
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Default Re: Piston to head clearancing

They make some rosin core solder that's about 1/8" in dia. Just feed this thrugh the spark plug hole and turn the engine over and you'll get some accurate piston to head clearance.
Over the years I've done allot of experimenting with the flathead combustion chambers and for street use found the compression and turbulence. In the early 90"s I bout a milling machine and used flathead aluminum heads were a dime a dozen. I made sa fixture that allowed me to rotate the head to any angle I wanted and began machining heads. With a flow bench I could check some of the results. I cabe to the delusion that clearance over the valves should also be .050" at a 4 degree angle. The transfer angle at 8Degrees and the exit at 45 degrees. Angle milling a set of EAB heads .070" and following the above numbers will give yiu a head with a chamber around 60cc. I also made a fixture to relocate the spark plug to clear the exhaust valve, but this isn't working right YET@!! At present I'm working on creating a Vortex/LS intake port. The bowl adapter is finished and a new powered file has bee made to shape the port. Getting old prevents me from getting much done. Right now I've finished the new disk braking system for the roadster, hope it works. Running out of time???
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Old 09-17-2021, 10:29 AM   #55
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Default Re: Piston to head clearancing

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They make some rosin core solder that's about 1/8" in dia. Just feed this thrugh the spark plug hole and turn the engine over and you'll get some accurate piston to head clearance.
Over the years I've done allot of experimenting with the flathead combustion chambers and for street use found the compression and turbulence. In the early 90"s I bout a milling machine and used flathead aluminum heads were a dime a dozen. I made sa fixture that allowed me to rotate the head to any angle I wanted and began machining heads. With a flow bench I could check some of the results. I cabe to the delusion that clearance over the valves should also be .050" at a 4 degree angle. The transfer angle at 8Degrees and the exit at 45 degrees. Angle milling a set of EAB heads .070" and following the above numbers will give yiu a head with a chamber around 60cc. I also made a fixture to relocate the spark plug to clear the exhaust valve, but this isn't working right YET@!! At present I'm working on creating a Vortex/LS intake port. The bowl adapter is finished and a new powered file has bee made to shape the port. Getting old prevents me from getting much done. Right now I've finished the new disk braking system for the roadster, hope it works. Running out of time???
So if i am understanding you correctly, you are milling the head at a angle taking more off the cylinder side? If so what angle are you doing it at and did you ever do it to cast iron heads?
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Old 09-17-2021, 10:26 PM   #56
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Default Re: Piston to head clearancing

I do this just to see if I cam make it better, and improve preformance and econmy.. Most aftermarket heads add material to the transfer area ti increas compression. Then we relieve the block to improve flow. YET! The transfer area controls flow. I ran a flow bench teat on the angle of the transfer area and found a 10/12 degree angle provided the beat flow. However there isn't enough material there to t remove much. It would also reduce compression.
I only take about .010" over the dome area of the head. The rest comes off the valve area. The clearance the area over the valves at a 4 degree angle with matches the angle of the valves.. Now this depends on the lift of the cam. now removing more material from an *ba style head, material should only be removed from the block sursurface of the head as the uppre portion is very thin..
Last but not least the aftermarket heads are very expensive and only have an aesthetic value.
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Old 09-18-2021, 08:19 AM   #57
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Default Re: Piston to head clearancing

Gramps,
Great post, My head is spinning with information. The last set of heads i did were milled at a shop to get .050. I plan on doing my 59a heads on my mill and have been contemplating how to hold them to the table at an angle. Can you share a photo of the fixture you made to hold the head?
Thank you ya’ll !
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Old 09-18-2021, 05:53 PM   #58
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Default Re: Piston to head clearancing

I loaned the fixture out a few year back, I'll try and get it back, don't think it ever used anymore.
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Old 09-18-2021, 09:43 PM   #59
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Default Re: Piston to head clearancing

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Using head gaskets over, has been a practice since the stockcar days. I have a stack of old copper gaskets and I can't remember buying a new one. Same with bearings. I use Hi tac or copper coat. In the future I'll use Latex paint on the aluminum side. For the new builders, better check the cam bearing clearance, Some of these are way out. Now I measure them before i remove them. Gota admit, they're well lubricated.
OK Ron I'll bite! what's with the latex paint and bearings?
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Old 09-19-2021, 08:52 AM   #60
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Default Re: Piston to head clearancing

Copper and aluminum creat an electrical current which caused the errosion of the aluminum. When you remove the heads after they have been on awhile, you can see where the aluminum has been removed. After beed blasting you can fill the area with Devon F, providing the fire ring is original. I was told by a fellow engine builder that painting the heads with Latex paint will insolate the two materials and prevent erosion. Might work, can't hurt.
As for the cam bearings? I don't usually measure the clearance of the cam bearings , However, back in the 90's someone, might have been Walt said he founf .006" clearance with a new bearing. (max is.003). Since then I've been checking all my cam bearings and have found several loose ones. Now when I receive a block in fair condition I measure the cam bearing before I remove them. If they check OK I leave them in the block if I'm not having it bake cleaned.
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