16V GZE pistons and a 20V head

[matt dunn]

You can use 16V 4AGZE pistons in a 20V engine and they do run and clear the valves.

BUT>>

If you have a cambelt failure or a cam timing problem they will touch and the pockets do not line up with the valves.

here are some pictures of the result.
(hope the pic sizes are ok)

See where the valves contacted the pistons,



and what happens to the valves,



and the valves still in the head.




The engine was running fine, had done about 2 hours at the track when it had a cam timing problem up the back straight.

made no weird noises, just stopped like the key had been turned off,
and then had no compression.

Matt

[crnkin]

hehe. awesome

[bluemaumau]

noob question, are either of those two pistons reuseable?

[soopachargen]

i vote FAQ!!

[Dell'Orto]

i vote FAQ!!

I concur I'll give it a couple of days then move it.

[TRD_ZERO]

What head was that silvertop or blacktop? And how long had it been running for until it kicked the bucket?

[Lloyd]

Looks like silvertop, and it says 2 hours up there though that could be just track time and not overall time

[matt dunn]

Looks like silvertop, and it says 2 hours up there though that could be just track time and not overall time

Yes it was a silvertop,

and it had only done 2 hours since a full rebuild and it was all track time.

Most of it at low boost setting, 10 psi or so, and the last 1/2 hour at 18psi.

And all four pistons are marked the same, and are all being reused.

Matt

[I SL1DE]

Are you going to change anything to prevent this happening again or are you just doing to replace the valves and put it all back together? Did anything else get damaged in the head when this happened?

[flygt4]

ah the question is answered. id always wondered if they became intereference when used with the silvertop head.

[matt dunn]

Are you going to change anything to prevent this happening again or are you just doing to replace the valves and put it all back together? Did anything else get damaged in the head when this happened?

The cause has been found and fixed, and the whole head was replaced,
not just the valves.

To cut a long story short,
it broke the key in the crank that drives the camgear.

Matt

[TRD_ZERO]

Keyway in the crank? Im not too sure what that is? Little bit of a newbie here. Did you just replace it with a factory one or upgrading it to something better? Oh and do you know what power output your engine was making?

[Lloyd]

Keyway is that groove, supposed to be only as wide as it is in the back. A "key" fits into it. The key is basically a rectangular block of metal which also fits into the keyway in the pulley. Its a way of locating the pulley onto the crank. As you can see in this pic there is a step worn to the right, that means the pulley can move on the crank and throw timing out. If it wears right out or if the key gets out/breaks then you can end up with valves touching pistons.

[Bazda]

i think he actually broke the crank pulley, so then the crank key fell out of the timing pulley. this happened to me but i didnt do any damage

[matt dunn]

i think he actually broke the crank pulley, so then the crank key fell out of the timing pulley. this happened to me but i didnt do any damage

Yeah, keyway/key failure was a generalization(?).

The key is rounded shaped at the bottom.
the lip on the front pulley broke off and the keyway rocked and came out.
When I pulled the front pulley off the key was stuck in the pulley.

[TRD_ZERO]

Oh ok i get it now thanks. Are you just going to replace the factory keyway or upgrade it somehow, and the pulley are you upgrading that and if so where do u get an upgraded one and how much do they go for and where do you get them? Like Baz got one custom made i think....... so im guessing it wont be too cheap.

[Bazda]

guy on trademe sells custom alloy ones, they are pretty cheap at around $200

[TRD_ZERO]

SO the custom alloy ones on trademe will stand up to the task of turboing a silvertop motor? Thanks Baz

[Bazda]

SO the custom alloy ones on trademe will stand up to the task of turboing a silvertop motor? Thanks Baz

yes they are made from 6061 alloy.

[matt dunn]

Ok,

so we strapped on a new head and bolted it back into the car.

went to NZEFI again for a dyno tune and too see how it would go.

Was starting to make good power at low boost's
and was hoping to make some reasonable power out of it.

They had finished most of the tune and were just goint to do the final part and up boost from 14-15psi up to to 18 19,

and then we had a moment from the fast and the furious,
amnd we blew the welds on the intake manifold.

Probably from old age and vibration, it cracked it open and we had a loss of boost pressure so we could not get up to the pressure we wanted.

So in the end we made about 270hp at 15psi,
using my modified T28 and stuff from my old engine.

Manifold is now all fixed and there is a race day tomorrow at Levels,
so will run it and see how it compares to my old engine.

Looks to me that high comp is the way to go,
so if it does the business like I think it will,
I will put raise the comp on my other race engine up from 7.8 to the 8.9 this one is, and combined with the headwork and cams should hopefully net more gain again.
May even get carried away and use a BT head with the setup too.

Will post some results of tomorrow and maybe some vid's too weather depandant.

Matt