2010 Burb Misfire

[solli5pack]

I have what I consider a smooth idle.. Maybe just the misfire making it rough for you?

Even before the misfire sitting at a stoplight it always had a little bit of a stumble that bothered me. I was told it's just the way these trucks are.

 

[Geotrash]

Even before the misfire sitting at a stoplight it always had a little bit of a stumble that bothered me. I was told it's just the way these trucks are.

It is. Most of them seem to do it. Some raise the idle 50-100 rpm with a tuner and say it helps a lot. I really don’t even notice it anymore.

 

[iamdub]

I'm pretty sure you need push rods. I've not done it, but the afm lifters look longer to me? maybe at least new ones for the lifters being replaced?

They are a hair longer. But, the AFM lobes on the cam have a smaller base circle. This is why you can't keep the AFM cam and just drop in regular lifters when doing a delete. You'll have four cylinders running weakly enough to show up as misfires.

If using a non-AFM GM cam or specifically-made aftermarket cam, you can use the stock push rods. Many, if not most aftermarket cams modeled for performance have a smaller base circle, requiring longer push rods. The common performance cam's base circle is .050" smaller than that of the factory cam, requiring a .025" longer push rod to compensate. The factory rods are 7.380". Since most rods are made in .025" increments, a 7.4" is the standard drop-in rod. That .005" difference is negligible, especially with the rather wide acceptable preload range for the factory lifters.

 

[j91z28d1]

They are a hair longer. But, the AFM lobes on the cam have a smaller base circle. This is why you can't keep the AFM cam and just drop in regular lifters when doing a delete. You'll have four cylinders running weakly enough to show up as misfires.

If using a non-AFM GM cam or specifically-made aftermarket cam, you can use the stock push rods. Many, if not most aftermarket cams modeled for performance have a smaller base circle, requiring longer push rods. The common performance cam's base circle is .050" smaller than that of the factory cam, requiring a .025" longer push rod to compensate. The factory rods are 7.380". Since most rods are made in .025" increments, a 7.4" is the standard drop-in rod. That .005" difference is negligible, especially with the rather wide acceptable preload range for the factory lifters.

you know that's the first thing that's made sense. I did quick search and all I got was some miss some don't.

reason I'm curious is the hybrid cam is different grind. there's not a non afm one avaliable for it. maybe able to get a custom grind, but not sure and expensive. if a lifter did ever fail and I could drop normal lifters in, measure push rods, order up 8 and go. that would be interesting. not something I'd do until a failure thou.

 

[iamdub]

you know that's the first thing that's made sense. I did quick search and all I got was some miss some don't.

reason I'm curious is the hybrid cam is different grind. there's not a non afm one avaliable for it. maybe able to get a custom grind, but not sure and expensive. if a lifter did ever fail and I could drop normal lifters in, measure push rods, order up 8 and go. that would be interesting. not something I'd do until a failure thou.

I forget you have a hybrid. I think the L9H cam would be your best bet for a "factory non-AFM cam". It'd probably run just fine on the stock tune. Not optimally, but fine. You could reuse your original push rods unless any are damaged in an AFM failure.

 

[Geotrash]

They are a hair longer. But, the AFM lobes on the cam have a smaller base circle. This is why you can't keep the AFM cam and just drop in regular lifters when doing a delete. You'll have four cylinders running weakly enough to show up as misfires.

If using a non-AFM GM cam or specifically-made aftermarket cam, you can use the stock push rods. Many, if not most aftermarket cams modeled for performance have a smaller base circle, requiring longer push rods. The common performance cam's base circle is .050" smaller than that of the factory cam, requiring a .025" longer push rod to compensate. The factory rods are 7.380". Since most rods are made in .025" increments, a 7.4" is the standard drop-in rod. That .005" difference is negligible, especially with the rather wide acceptable preload range for the factory lifters.

Your post made me go back and double-check my notes to make sure. Somehow, I got the notion that the factory pushrod length on the L94 is 7.400", but it's 7.385". So my memory was wrong because I used 7.400" pushrods for all 3 of the aftermarket cams I had in there (which at the time I thought was the stock length). I did confirm the correct preload upon install with the adjustable length pushrod checker tool I have. I stand corrected. Thank you.

 

[swathdiver]

@solli5pack

Whatever you do, use new GM OE lifter trays only. The only other that works without wrecking motors that I know of is one sold by Summit Racing.

It's rare that a 243 head cracks, probably a blown head gasket.

Almost all replacement camshafts sold for the 5.3 is the old LM7 grind which makes 10-15 horsepower than your engine. These do not have VVT either which your engine does.

The LH8 and LH9 camshafts are the LM7 grind with VVT. Don't let anyone sell you that one either unless you don't mind the power loss!

The L9H camshaft that Chris mentioned has VVT and is marginally bigger than your original and makes over 400 horses in the 6.2s.

 

[mikez71]

So the L9H camshaft is better than stock for the 5.3 with VVT? Will it run well on stock tune?
(Main reason I wouldn't want to tune is smog checks)

Are one of those you mentioned a stock LMF cam?

 

[solli5pack]

Just a heads up. The oil pressure sensor for our trucks is on sale on Amazon. All GM websites I checked wanted at least $50

 

[Onlyone]

Just a heads up. The oil pressure sensor for our trucks is on sale on Amazon. All GM websites I checked wanted at least $50

View attachment 402757

Good catch. I just ordered one to have it.

 

[iamdub]

Your post made me go back and double-check my notes to make sure. Somehow, I got the notion that the factory pushrod length on the L94 is 7.400", but it's 7.385". So my memory was wrong because I used 7.400" pushrods for all 3 of the aftermarket cams I had in there (which at the time I thought was the stock length). I did confirm the correct preload upon install with the adjustable length pushrod checker tool I have. I stand corrected. Thank you.

It seems there's a 50/50 split between them being 7.380" and 7.385". There's also explanations for why there are these two specific measurements: One is the full sphere dimension for the ball tip and then that .005" shorter measurement if you put the caliper over the holes. It's flat there, costing you .0025" on each end. Since the ball tips fits in the cups so that they're the actual contact points, my personal belief is that they should be considered 7.385" since that's the effective length. But, it's such a minute difference when you're dealing with hydraulic lifters that have something like a .040" allowable preload range so I just round it off to 7.380" to make the quick math easier.

Even then, the cylinders vary a lot between the corner ones and those in the middle. I have it documented somewhere in my thread from about a year ago, but I ended up with three different lengths of push rods in mine to get them away from the minimum and maximum preload figures and to tighten the variance across all of them.

*EDIT* I couldn't let it go so I looked it up: https://www.tahoeyukonforum.com/threads/growing-up-doesnt-have-to-suck.93510/post-1669150

 

[j91z28d1]

It seems there's a 50/50 split between them being 7.380" and 7.385". There's also explanations for why there are these two specific measurements: One is the full sphere dimension for the ball tip and then that .005" shorter measurement if you put the caliper over the holes. It's flat there, costing you .0025" on each end. Since the ball tips fits in the cups so that they're the actual contact points, my personal belief is that they should be considered 7.385" since that's the effective length. But, it's such a minute difference when you're dealing with hydraulic lifters that have something like a .040" allowable preload range so I just round it off to 7.380" to make the quick math easier.

Even then, the cylinders vary a lot between the corner ones and those in the middle. I have it documented somewhere in my thread from about a year ago, but I ended up with three different lengths of push rods in mine to get them away from the minimum and maximum preload figures and to tighten the variance across all of them.

*EDIT* I couldn't let it go so I looked it up: https://www.tahoeyukonforum.com/threads/growing-up-doesnt-have-to-suck.93510/post-1669150

depends on the push rod checker used. if you set the geometry correctly and then measure a checker with a flat part like the actual ones have then I want that measurment. if i one without it, I'd like to order based on that.

like you say thou for stock ls stuff it's not big of a deal. the ls7 I'd be picky about.

 

[iamdub]

So the L9H camshaft is better than stock for the 5.3 with VVT? Will it run well on stock tune?
(Main reason I wouldn't want to tune is smog checks)

Are one of those you mentioned a stock LMF cam?

Compared to the '10-'14 LMG cam (with VVT), the L9H cam has negligibly more duration but .019" more lift. LSA is 1° tighter. I don't know how close the VVT cams run the valves so I can't say how that .019" more lift will act.

By comparison, my LMG ('07-'09 pre-VVT) originally had a 193/193, .482/.482, 116 LSA cam. The TSP Stage 2 it has now is a 212/218, .550/.550, 114 LSA. So, 19°/25° more duration and .068"/.068" more lift.

Mechanically, I think the L9H cam would be fine in your LMG. So, "better than stock" by a hair. IMO, not worth it for performance but might be okay as an AFM delete cam.

 

[j91z28d1]

I forget you have a hybrid. I think the L9H cam would be your best bet for a "factory non-AFM cam". It'd probably run just fine on the stock tune. Not optimally, but fine. You could reuse your original push rods unless any are damaged in an AFM failure.

yeah I don't know, something about late intake valve closing and higher compression for it. hptuners, allows for zero ve table or maf table turning.. all I got is the wot target air fuel ratio. so at this point, besides it seems silly to chase hp in a hybrid designed for gas mileage, I think I'd give normal lifters with correct length push rods a shot over trying a normal cam with zero tuning access. like I don't think I even have access to idle speed.


sorry totally off topic.

 

[iamdub]

depends on the push rod checker used. if you set the geometry correctly and then measure a checker with a flat part like the actual ones have then I want that measurment. if i one without it, I'd like to order based on that.

like you say thou for stock ls stuff it's not big of a deal. the ls7 I'd be picky about.

Other than Prince Randy @randeez, We're all bums here messing with scrub-level truck engines. I'm sure I'll never have my fingers in an LS7!

I used the laser-engraved marks on the checker rod versus measuring with a caliper. For my 6,000 RPM turd, it's precise enough.

 

[j91z28d1]

Other than Prince Randy @randeez, We're all bums here messing with scrub-level truck engines. I'm sure I'll never have my fingers in an LS7!

I used the laser-engraved marks on the checker rod versus measuring with a caliper. For my 6,000 RPM turd, it's precise enough.

honestly I won't either.. I have friends that have had them. they all drop valves stock if not fixed pretty quickly. only one friend of a friend is having one rebuild now and he went iron block. but people that can afford those don't really do work themselves. they drop them off shops and pick them up a year later.

 

[j91z28d1]

Just a heads up. The oil pressure sensor for our trucks is on sale on Amazon. All GM websites I checked wanted at least $50

View attachment 402757

I feel bad even saying this but I've had 2 of the "so called" Amazon acdelcos fail on me. one in each car I used them on. it's probably just my bad luck, but if in a month or 2 your oil. pressure goes wacky, don't freak out till you confirm it's not the sensor.

I put one or the dealer 50$ sensors in both and they haven't failed since.

sorry, but I thought I'd bring it up just incase. they do have tons of 5 star ratings. I just have 1 star luck haha.

 

[iamdub]

I feel bad even saying this but I've had 2 of the "so called" Amazon acdelcos fail on me. one in each car I used them on. it's probably just my bad luck, but if in a month or 2 your oil. pressure goes wacky, don't freak out till you confirm it's not the sensor.

I put one or the dealer 50$ sensors in both and they haven't failed since.

sorry, but I thought I'd bring it up just incase. they do have tons of 5 star ratings. I just have 1 star luck haha.

With all the other pricey maintenance items being counterfeited, or are low-quality brands being sold as genuine factory parts, I'd be suspicious.

 

[solli5pack]

With all the other pricey maintenance items being counterfeited, or are low-quality brands being sold as genuine factory parts, I'd be suspicious.

Actually since I've been doing a lot of research about all the parts I need I'm getting very suspicious. Look at this lifter kit that someone is trying real hard to look like genuine GM performance lifters. Same part# and everything.

 

[solli5pack]

I feel bad even saying this but I've had 2 of the "so called" Amazon acdelcos fail on me. one in each car I used them on. it's probably just my bad luck, but if in a month or 2 your oil. pressure goes wacky, don't freak out till you confirm it's not the sensor.

I put one or the dealer 50$ sensors in both and they haven't failed since.

sorry, but I thought I'd bring it up just incase. they do have tons of 5 star ratings. I just have 1 star luck haha.

Thanks for the info. It really doesn't make sense that they can sell the same senor for $17 vs $50. I'm going to look real close at it when it shows up. AC Delco is supposed to be AC Delco though right? Could they possibly put inferior products in the box? And it's coming from the AC Delco Amazon store..