PeasantDSM said:

So I've been told by one half of people that the 420a is interference and the other half say it isn't... So on that note 2 questions.

1). Is it or is it not an interference engine.



2). Assuming it has jumped one singular tooth but the t-belt is still intact will it have bent valves?

TIA....

-Peasand DSM

Click to expand...

The 420A is an interference engine. My 1995 Eagle Talon with the 420A engine was one tooth off and it ran poorly, but it did not bend the valves. After I replaced the timing belt and timed it correctly it ran much better. I also replaced the water pump, tensioner, idler pulleys at the same time. I am not sure how far off it has to be before it bends valves but I suspect not much. Better to set the timing correctly than to chance bent valves.

My 90 GSX was off 2 teeth on the exhaust cam when I got it. The tensioner had failed letting it jump. If I hadn't bought the car when I did, I suspect the owner would have tried to drive it more and it would have jumped more and I would have been doing a head job.
My Red 90 Talon had its crank pulley work forward from a loose pulley bolt and it ate ALL 16 VALVES. That was late in 2017 and I STILL don't have her fixed yet.
Have you done a compression check yet? I would get some numbers from each cylinder and then post the results.

The 420a is a LOT more forgiving than the 4g63 when it comes to timing. I cannot fully confirm that it is okay being off 1 tooth although I highly suspect it will only mess with operation with little to no damage to the valves.

I have seen people post on here with varying issues at idle and their timing ended up being 1-2 teeth off. They did a timing job and it fixed their issue.

That being said the only way to know if there is damage is to inspect the engine internally.

EDIT: and yes it is an interference engine, if someone is saying that it isn't they are ignorant on the 420a