Interference, Non-Interference.....

If I am right our engines are an Interference engine?

Is there a way to get a piston made that would keep the 8:1 compression and make it so that it is a Non-Interference engine? So that way your engine could just run like shit until timed right and not destroy valves or worse, your engine?

How far off are the pistons with deeper grooves for "Enlarged Valves"?

Would these larger valve groove pistons with stock valve sizes require much to make it work?




And on an off note, when you get a rebuilt block that has 8:1 pistons(that has been decked), and heads that have been rebuilt(and decked) what is the compression really now?

These motors are interference motors.

I don think there aer pistons out there that would make these non-interference motors and really if you have the time set right then you shouldn't have to worry about the dreeded valve/piston kiss.

It would depend on how much the heads and block were decked as to the rise in compression.

Sohc is non-interference.

DOHC NA / DOHC TT = Interference
SOHC NA = Non

my suggestion:

buy a 96 stealth base & pester SSM for a sohc >tt kit.

lol. No, I was just wondering. It would save a lot of heart ache, if jumping a tooth happened or something of the like.

only the sohc motor is non-interference. ssm is supposed to be working on a kit which allows stock vr4 tt parts to bolt onto the sohc...

Who is SSM?

split second motorsports. they're a forum sponsor. chatzvr4 is your man.

Quote:

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Originally Posted by EvanH

lol. No, I was just wondering. It would save a lot of heart ache, if jumping a tooth happened or something of the like.

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you’re not going to bend any valves if you jump a tooth, and you can probably even get away with jumping 2 teeth. its when the belt snaps (EBay belt), your tensioner fails, or the tensioner pulley slips that causes the belt to jump several teeth and bend valves.

plus you notice a huge loss of power when the belt jumps 1 tooth, let alone two teeth. my RT felt like turtle one day, when I checked the timing marks all the cam gear marks lined up with the marks on the head but the crank was 1 tooth off. honestly I’m not sure what caused it to skip a tooth, but I just redid the timing belt and the car went back to its normal 'peppy' self.

I also had a Mazda 929 in which mice decided to build a nest right on the timing belt. when I fired up the car it jumped 7 teeth but the car still ran for a little bit. Even though the belt jumped 7 teeth the valves didn’t look too bad. When I took of the heads and checked it out you could only see a tiny amount of light in-between the valve and the head.

Just do your 60K with OEM parts and you’ll be fine. plus a 60K is cheeper than custom 'non-interference' pistons.

One tooth is enough to damage the valves on our engines. Just depends on where the valves are when it happens. There are certain piston designs that have indentations where the valves would hit, but I'm not sure if there is enough clearance with those to call it a non interference engine with them. If you really want to make it non interference it can be done, just need to check out a few rod/piston combos that will do it.

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Originally Posted by thor'svr4

you’re not going to bend any valves if you jump a tooth, and you can probably even get away with jumping 2 teeth. its when the belt snaps (EBay belt), your tensioner fails, or the tensioner pulley slips that causes the belt to jump several teeth and bend valves.

plus you notice a huge loss of power when the belt jumps 1 tooth, let alone two teeth. my RT felt like turtle one day, when I checked the timing marks all the cam gear marks lined up with the marks on the head but the crank was 1 tooth off. honestly I’m not sure what caused it to skip a tooth, but I just redid the timing belt and the car went back to its normal 'peppy' self.

I also had a Mazda 929 in which mice decided to build a nest right on the timing belt. when I fired up the car it jumped 7 teeth but the car still ran for a little bit. Even though the belt jumped 7 teeth the valves didn’t look too bad. When I took of the heads and checked it out you could only see a tiny amount of light in-between the valve and the head.

Just do your 60K with OEM parts and you’ll be fine. plus a 60K is cheeper than custom 'non-interference' pistons.

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Its a gamble on jumping teeth. My NA jumped 7 teeth without bending a single valve but Ive heard of others only jumping 2 or 3 with bad damage.

The TT engines are definitely interference engines. When my A/C belt shredded and wrapped around the front pulley and got inside the front cover wrapping around the crank timing belt drive gear i instantly lunched 24 valves. Every one of them was bent and hanging open. Zero compression, zip, nada, none.

One big factor is getting the belt tensioner at the proper setting. If it is to loose and not enough tension on the belt it could slip under certain conditions.

Do it right the first time.