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Re: Engine fails to start after rebuild.

Posted: Wed Nov 03, 2021 6:17 am
by paul c
That's the next job on my 4.6. I bought a degree wheel now just need to make a piston stop and find the cam specs, I'm using a 4.2 cam. Always like to check as often the cam can be a few degrees off from the keyway.

Re: Engine fails to start after rebuild.

Posted: Wed Nov 03, 2021 9:38 am
by DaveEFI
Must admit I've never understood this. They can machine a cam so all the valve timings are correct for each cylinder - but get the keyway position wrong?

Re: Engine fails to start after rebuild.

Posted: Wed Nov 03, 2021 12:19 pm
by GDCobra
DaveEFI wrote: Wed Nov 03, 2021 9:38 am Must admit I've never understood this. They can machine a cam so all the valve timings are correct for each cylinder - but get the keyway position wrong?
I guess the answer would be that all the lobes are ground in one operation so maintining the relationship is reletively straightforward but the keyslot is produced at a separate op' hence the relationship between this and the cam profiles depends on the setup accuracey.

It is a pretty poor excuse though?

Mind you 12 degrees is probably a whole tooth out on the cam gear rather than inaccuracy of the grind

Re: Engine fails to start after rebuild.

Posted: Wed Nov 03, 2021 1:13 pm
by DaveEFI
What we need is the cam driven by a servo motor, so MegaSquirt can adjust the timing. :lol: