I was planning to put the engine in the truck this weekend, but instead I have taken about 4 or 5 steps backwards......
I didn't think it looked like the balancer was installing deep enough. The gap between the cover and balancer looked like more than I am used to seeing. I bolted one of the accessory brackets on and the crank pulley was not lining up to one of the idler pulleys. I asked
@Capt Ron and
@doubletrouble to check the gap on the L29 engines they have access too and they confirmed my suspicions.
I think most of you can probably see the problem pretty easily in the picture below:
After doing some internet research I was finding that it looks like the aftermarket timing chains do not take the crank sensor reluctor into account. Apparently they assume people aren't running double rollers with factory EFI. I even found a post by
@skunked in the Sancho thread where he had found his aftermarket crank sprocket was thicker but in his case it was perfect because he's not running factory EFI.
I only found 1 aftermarket timing chain for the Gen VI that said it wouldn't work with factory EFI; that was CompCam. After reading some forums, it sounds like up until about a year ago it was mentioned this was the case as a few people had run into this issue.
Here are the numbers that will hopefully help someone else in the future that has a similar issue with their L29 Gen VI vortec 7.4L 454 (I listed all of the possible nomenclature because my searching has taught me you have to use about all of the variants to find answers).
- Factory timing chain crank gear width: 0.456"
- Howards 94309 timing chain crank gear width: 0.558"
- Crank sensor reluctor wheel width: 0.2"
Anyone quick with the math will notice the crank gears are only 0.1" difference but the reluctor is 0.2" thick. Here is the other part of the equation:
- Gen VI harmonic balancer depth: 2.562" as measured by me
- Mark IV harmonic balancer depth: 2.686" per RockAuto Dayco unit
So you can see the other 0.1" comes from the balancer.
At this point I'm either running the factory timing chain or I could have 0.1" taken off the reluctor. The only concern I have there is clearance between the reluctor and the timing chain which you can see in the picture below thru the crank sensor hole.
I put a feeler gauge between them and just 0.1" just fits.
I did think some about taking 0.1" off the balancer, but I have some concern about the sensor properly reading the reluctor. As you can see in the picture, it's pushed off center in the hole.
I guess another option is to consider taking a little off the reluctor and the balancer. Only thing I don't like about this is that it does make the balancer unique but I should be needing to replace balancers in the future.
My biggest lesson from this project is that just because a part is listed for the Gen VI 454, it doesn't necessarily mean it will work. Especially not with the factory EFI. Not only does this problem happen with the timing chains, but if you search for balancers on Summit Racing, it will give you several of the deeper MarkIV type options and really only 1 or 2 that are true factory replacements for the Gen VI.