103 x 76mm crank

[pnikas]

Hello everybody, I was thinking of building a 103x76 type 4 using 914 heads with 44mm intake valves and 36mm outlet valves. will a stock 914 clutch be able to handle it? Will probably use a 86b webcam and around 9.7:1 compression . Stock rods , stock head studs, is there something wrong in my plans ? Should I keep it 103x71?

[cal 67]

86B wants to make power till ~6800 rpm. If you plan on just bolting on the AA 914 heads you'll probably run out of steam by 5,500 rpm with that large of an engine. So either choose a smaller cam or get your heads worked to match your combo. Your headstuds might be a weak link in sealing the chamber. Keep the step in the heads and run your piston flush with the cylinder. Use the quench area for your deck clearance.

[wreck]

That should work well , consider using a crank with type 1 or Chev journals , then you can use the type1 rod which are cheaper than type 4 rods . I was driving with a stock 215mm Sachs clutch with 170whp on the street , it only was an issue with drag racing type starts on a track . Street was fine . I'm using stock head studs also . 10.5 compression with a CB2300 (274 degrees @0.050"). I use annealed copper gaskets with 30 ftlbs torque .

[Type 4 Unleashed]

The suggestion of keeping a step in the head and run the piston flush with the cyl won't work, the piston will hit the step, and if the step was the same size as the cyl, the step couldn't provide enought support to seal the cyl .

I would recommend Chevy or 2.0 ltr jrls, and there is nothing wrong with stock head studs, and the only time I change out stock studs, is if I need longer ones for longer rod & stroke combinations.

[cal 67]

The suggestion of keeping a step in the head and run the piston flush with the cyl won't work, the piston will hit the step, and if the step was the same size as the cyl, the step couldn't provide enought support to seal the cyl .

I would recommend Chevy or 2.0 ltr jrls, and there is nothing wrong with stock head studs, and the only time I change out stock studs, is if I need longer ones for longer rod & stroke combinations.

Zero cylinder deck, bore head to 115mm only to the height of the step, then bore step diameter to 103 + whatever you want to account for cylinder stagger. I've done it several times. This way your head has more material to resist flexing. More material is better than less. I don't understand the last part of your statement. As long as the step diameter matches the barrel more or less, it'll seal.

[GARRICK.CLARK1]

Get the cylinder lengths exactly the same too , make sure the cylinder spigots are parallel to the case mating surface as well

[Type 4 Unleashed]

I agree more material is better than less, but cutting a step in the head makes for less, and increases the chances of the heads flexing and reduces cyl sealing. The only material that needs to removed from the heads, is what it takes to clean the decks of the heads to seal the cyl's, which could be any where's from .002 to .005".

There is no difference to running the pistons @ 0.0 deck, then cutting a .040" step in the heads compression pads for clearance, or running the pistons @.040" in the cyl and not cutting steps in the heads, other than leaving the heads stronger by not cutting steps in them.

[Wally]

I'am with Richard on this one: machine as little as possible from original style castings.

[Ephry73]

The suggestion of keeping a step in the head and run the piston flush with the cyl won't work, the piston will hit the step, and if the step was the same size as the cyl, the step couldn't provide enought support to seal the cyl .

I would recommend Chevy or 2.0 ltr jrls, and there is nothing wrong with stock head studs, and the only time I change out stock studs, is if I need longer ones for longer rod & stroke combinations.

Zero cylinder deck, bore head to 115mm only to the height of the step, then bore step diameter to 103 + whatever you want to account for cylinder stagger. I've done it several times. This way your head has more material to resist flexing. More material is better than less. I don't understand the last part of your statement. As long as the step diameter matches the barrel more or less, it'll seal.

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