96mm Big Bore P/C Kits

[URY914]

There are several retail vendors now selling the 96mm big bore p/c's. Are they all selling the same thing or are there several manufacturs suppling these now? If there are several is one better quality that the others? I currently have a set made by NPR and want to do a rebuild.

[john walker's workshop]

big bores in general are thin walled and have trouble staying round. premature smoking is the result. they're not for motors that you expect to get a lot of miles from. some smoke at 20K. the contact surface at the head is usually narrow, so you can't use a head gasket, and it cuts into the head eventually, causing the initial torque to decrease, and oil leaks. just my 2¢.

[Jake Raby]

The cylinders are ALL crappy.....Radial and longitudinal inaccuracies are most always found in them, and are sometimes are worse than those found on a 100K engine.....

We use 94mm original, used cylinders, and torque plate hone them to 96mm, this way we can double check everything and set our own skirt clearance.(very important to those who hate piston slap)

[Conrad W Peden]

On the otherhand, I've got over 200k on my bigbore kit and have only done the rings and hone once.

Cant remember who made them , i think its COFAP, sound familiar to anyone.

It depends on how the motor was put together in the first place if you ask me. Done right the first time will always last longer. The only reason I redid the cyls. etc was a detonated cam follower.

But John is right, to get a bigger cyl. you are going to have a thinner wall. At 96 mm, this isnt as big a problem as 103's or 105's but can start the motor 'on its way to a better place' early.

Personally, I like Jakes solution to bigger bore.

By the way Jake, what pistons do you use for your 96's if you do the cyls yourself?

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CWP/VIR
72 914 L20E in rusto.
73 914 L20E 2.0L in resto.
a914lover73@hotmail.com

[URY914]

So Jake, I would be better off using your 94's re-worked to 96's to slip in my 1.7 case? Sounds better than taking a chance with parts made in the third world. I'll contact you via your web site, thanks.

[JmuRiz]

Speaking of Jake's 96mm P/C's...how much power are those things putting out in the 2270 kit? Just interrested to see how they stack up to a 6 cyl...also considering the MASSivE would be a simple fit.

Thanks,
Nathan

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'73 2.0 914

[Jake Raby]

We do not sell our big bore kits except in our engines, they are labor intense and we could never justify all that time if we sold them individually. I can help walk you through the process, though.

96mm cylinders do NOT promote head leakage, we never have a problem with them, running directly on the head surface, without a head gasket.

200K is very possible with 96's, however those are probably NPR units, and about 90% better than this new "JUNK" that we see from third world countries.

As for the power of the 2270, our standard version makes about 150BHP, and our new "Higher revving" version will probably make another 15 on top of that...It is not tested yet, but is first on the list for the dyno, when we are finished.

[Conrad W Peden]

Jake, my 96's are about 6 years old and came from a respected local german parts supplier(BOW-WOW Parts of BC). They probably are NPR.

When mating the cyls to the head do you do anything in place of the gasket? It was recommended to me that i lap the cyls to the head after lapping the cyls on a plate.

------------------
CWP/VIR
72 914 L20E in rusto.
73 914 L20E 2.0L in resto.
a914lover73@hotmail.com

[jabez]

Conrad,

That's what I did and so far, no leaks and 130 psi on compression all around.

[rmcelroy]

Originally posted by jabez:
Conrad,

That's what I did and so far, no leaks and 130 psi on compression all around.

Jabez-describe lapping the cyls. for me if you would. Do it all by hand, thickness of plate-anything you think is important would be appreciated.

Thanks

[jabez]

I took 400 grit paper and laid it on thick glass. Used figure 8's and lapped until the top of the cylinder was true. Had the heads cut clean and then took lapping compound and put in the head area where the cylinder fits. Inserted cylinder in the head and rotated back and forth until I got a true pattern. Once I thought that was good enough, I soft blued and made sure I had 100% contact between each cylinder and valve.

[Conrad W Peden]

You also have to make sure the cyls are all the same length after doing this. And clean too.

------------------
CWP/VIR
72 914 L20E in rusto.
73 914 L20E 2.0L in resto.
a914lover73@hotmail.com

[jabez]

Clean is good. I put my cylinders in the dishwasher (without my wife's knowledge). That really cleans out the machining grit and dirt from the pores in the cylinders. DON'T let them sit long afterward without oiling them or you will have a rust problem and need to hone them out and have to start all over again.