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Valve reliefs info request - 16v

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the poi

the poi

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Jan 5, 2003
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Pasadena, CA
Lets say I had a matched set of b23ft pistons... I'd like to just take them into a machine shop and let them carve some reliefs out of em to match the b234 pistons...unfortuantely, i Have no b234 piston. Short of finding a b234 motor in a junkyard and stripping it to pieces just to remove a piston...anyone have any idea how I could get what the shop would need to cut the reliefs?
 
A b234f piston probably wouldn't tell them a whole lot, other than where to put the cuts. You'll need to know the depth of the reliefs. Deck height, head gasket thickness compressed, and cam lift come to mind as factors to consider when making your calculations. Might find info on the process here, although not with a B23:

http://bertone.wynott.ca/htm/dohc16v.htm
 
I have asked for this information in many places numerous times. Never got an answer. You might ask Diamond Pistons what specs they used for the Turboford guys.

I might have to break down and actually measure the heads i have.

Matt
 
I think you might not need reliefs. I was under the impression that the dished turbo pistons already had enough clearance.

I have some B234F pistons lying around. You could borrow one if you need. BTW CR for B234F is 10.0:1
 
An old hotrod trick is to place a thin layer of clay on the piston and bolt down the head. Turn the motor over a couple of times and remove the head. You now have impressions on the clay to exactly locate valve reliefs. Use junk intake and exhaust valves modified by grinding the edges to make a sharp surface, the place them in a grinder or high speed drill and use the edges to machine the valve reliefs. Correct angle and depth could be calculated from cam lift and head dimension. Polish off the sharp edges and you have a piston that could be used as a template for the other three.
If you have a B234 piston it would be even easier to calculate relief cut depth and angle. Just scan the piston on a computer scanner and copy on clear acetate. Place over the B230FT piston and you have a template to position valve reliefs. Place your valve cutter on the B234 piston in the valve relief and mark the depth with a sharpie. Grind to mark and you are done
Low tech and low buck solution to the valve relief problem
 
Hoggster said:
I think you might not need reliefs. I was under the impression that the dished turbo pistons already had enough clearance.

I have some B234F pistons lying around. You could borrow one if you need. BTW CR for B234F is 10.0:1
Click to expand...

yo yo

i live in virginia any possiblitly that you send me a piston so i could borrow it and make a casting of it. In return ill send you a vadis dvd? :x:
 
Sure I'll send you one that you can keep for a month or so. PM me with your address and I'll UPS it to you. I'm going to send you a rod with piston and you can seperate them if you need. I already have VADIS but thanks.
 
Hoggster said:
I think you might not need reliefs. I was under the impression that the dished turbo pistons already had enough clearance.

I have some B234F pistons lying around. You could borrow one if you need. BTW CR for B234F is 10.0:1
Click to expand...

I had both pistons side by side. I dont believe you can get away with out cutting the valve reliefs, as the reliefs extend PAST the the dish into the shallow part.
 
jord9308 said:
An old hotrod trick is to place a thin layer of clay on the piston and bolt down the head. Turn the motor over a couple of times and remove the head. You now have impressions on the clay to exactly locate valve reliefs. Use junk intake and exhaust valves modified by grinding the edges to make a sharp surface, the place them in a grinder or high speed drill and use the edges to machine the valve reliefs. Correct angle and depth could be calculated from cam lift and head dimension. Polish off the sharp edges and you have a piston that could be used as a template for the other three.
If you have a B234 piston it would be even easier to calculate relief cut depth and angle. Just scan the piston on a computer scanner and copy on clear acetate. Place over the B230FT piston and you have a template to position valve reliefs. Place your valve cutter on the B234 piston in the valve relief and mark the depth with a sharpie. Grind to mark and you are done
Low tech and low buck solution to the valve relief problem
Click to expand...

That is a good method.
I have also seen carbide cutters brazed in notches in valves, but I have not personally done that.
 
My old Ross piston specs included: Inlet valve pocket depth 0.200", Exhaust pocket depth 0.160". Looking at a Ross piston and valves in front of me now I measure: Valve reliefs 41.5mm C/C for both inlets and exhausts (20.75mm either side of piston C/L).
Flycuts need to be 36mm dia to suit 34.2mm OD inlets, and 32mm dia to suit 31mm OD exhaust. Each flycut finishes just inside the outer edge of the piston crown. You will have to measure in the head the angle of each row of valves from normal (90 degrees) to rod axis. These numbers should allow an engine shop to make the appropriate flycuts.
Dick Prince Ovlov.net
 
Yerah- that's a good pic- I was trying to get some idea of scale.
I had another thought- Could a dish be machined into the B234 piston to match the B230FT dimensions? I think someone cut a B234 in half and it had plenty of metal in the crown area. Just a thought.
 
hmm..... so what is that piston? I'm going the b23 route, but piston availability is low... only can go 1st overbore w/o ordering something from europe... maybe aftermaket is the way to go.
 
I may wrong on this but won't stock b234 pistons fit in either the b23 or b230 blocks. Maybe some of the experts will clarify this.
 
WeezilUSA said:
hmm..... so what is that piston? I'm going the b23 route, but piston availability is low... only can go 1st overbore w/o ordering something from europe... maybe aftermaket is the way to go.
Click to expand...

Its a 3.800" bore custom piston from Diamond Racing. As mentioned above, they have the info on the valve locations in their database already.
 
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