Usually the decks are not 100% flat on stock blocks. And didn't you assemble this from scratch?

Second if you have a custom ground cam. While the Profile should be similar on all lobes, the grinding wheel wears during the grinding process, Especially if the grinder is aggressive removing material.

So with 6 and 8 being at the back of the cam it is possible those lobes are fatter as the wheel was worn more then at the front.

Did you Check the pre load when you assembled it?

 

Yes i assembled it from scratch, i checked preload and cant remmeber what it was exactly off top of my head but it was within spec, wouldnt have put it together otherwise! Wouldnt the misfire be on 5 and 7 as well at roughly the same rate?

 

Not necessarily. Like I said the decks are not flat and alot of the time. The core could be shifted to 1 side or the other. The piston is usually further out of the hole on the shorter side.

It's possible that the passenger side is the shorter side and that combined with the a slight variance its entirely possible that is the issue.

A lot of builders will measure pre load on each lifter and use multiple length push rods through out the engine to achieve proper pre load. There is a few guys that recommend it on the Tech side. Especially since the rockers are not adjustable.

 

I went with a set of 7.4" pr, i checked preload on 3 pushrods on each side and all were fairly close. I didnt properly measure piston extrusion (or whatever its called) but i did turn the engine over stopping at tdcof each piston and none of them where in or out of the hole any vast amount over the others that i had noticed... Matter of fact they all seemed pretty well even. When i put the spark plugs in i put one box of four in each bank, i did drop one if the boxes, and then dropped one of tbe idividual plugs.. However both pr length and faulty plug would cause misfires off idle too i would think..not just at idle... Being an idle misfire was thinking vacuum leak or weak injector or coil...

 

I had a bad plug that did something similar.

Maybe try another or swap them and see if they change or stay with cylinder.

 

Figured recheck electrical connections swap wires around measure injector resistance... Check plugs, and for ***** and grins/ peace of mind do a leakdown test...

 

A leak down would be a good Idea to rule out a mechanical issue.

Are you done yet?

 

Actually... just got done about 30 minutes or so ago.... Leakdown was decently good, most of the decently was user error! However i found the cause of the miss and had a moment..... Apparently after 9 hours of working on it, on my one day off and having the wind knocked out of my sails with the harness modification, i somehow missed going back over the intake bolts after i tightened it diwn with my 1/4" electric ratchet, the two center bolts on the right side of the intake were about 1/4 turn past finger tight, and same with the back two on the left side... Still has a random misfire but is truly a random misfire now... Which is to be expected on a stock tune with a cam....

As far as the leak down it was good as far as percentage of loss goes, once i figured out i didnt have the adaptor screwed in as far as i should have or thought i did....
And all the injectors measures right at 13.3 ohms, and all had fairly equal drop when i did the balance test... Now to tune her ***.... Just need to get out for a long enough drive to actually do what i need to

 

Well Get on it!!!

 

Kinda requires gas.... And remembering which file i have loaded in the ecm at the moment... Have a file i copied and pasted everything out of a denali and a file that is basically my stock 5.3 file with some changes for injectors etc and it runs better on the 5.3 file,...

On another note, i need to find a way to force the calibration for tu/td into my bcm from a denali, i know chrysler has diagrams of their modules internal circuits, but i have yet to find it for any gm modules... Any idea where to find those schematics?? Or an hptuners type programmer for the bcm, i have the calibration file numbers, but tac said the only way they can introduce a different calibration file is if there is a bulletin or policy for it, which tells me it cam bedone they just arent allowed to