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.