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Tech guys- could a stretched chain cause KR?

M

Maximum Gnarnage

New member
currently running a 3.4 pulley on the following setup and still getting 2-3* KR at the top of 2nd.
s1x cam w/ crow 105's, FSIC, headers + supporting fuel system and air intake mod's.

When I assembled and installed this motor(late on a Sunday night) I noticed the stock chain was stretched about 1 mark off and couldn't find an open parts store to replace it so I had to drop it in.
Not sure if a stretched chain could/would cause any sort of KR due to mechanical timing being off etc. But I can't help but wonder why i'm restricted to such a big pulley for my setup. AFR and timing are low 11's and 18* so i'm not being overly aggressive their.

There's a couple other symptoms that lead me to believe it could be the stretched chain. I had to bump up the idle speed and command about 13.5 afr at idle to avoid misfires. haven't heard of too many people running the s1x having to do that. car takes a couple cranks on a cold startup to turn over and fire up.

Could use some help with diagnosis to get her running strong again so speak up!
Thanks
 


No idea on the chain, tons and tons of high mileage motors out there with stock everything internal that are modded and don't see this issue.

Why not lower the timing to 15º at WOT and see what happens to the knock, some cars just don't like to run high timing. And bumping the idle rpm to 750-800 isnt uncommon for cammed motors, and they already command stoich at warm idle like any car.
 
Fivefingerdeathpunch said:
No idea on the chain, tons and tons of high mileage motors out there with stock everything internal that are modded and don't see this issue.

Why not lower the timing to 15º at WOT and see what happens to the knock, some cars just don't like to run high timing. And bumping the idle rpm to 750-800 isnt uncommon for cammed motors, and they already command stoich at warm idle like any car.
Click to expand...
i'm running open loop so actual afr at the wideband is around 13.5 with idle at 775. the block I replaced the original motor with is a 60k L67 as of 2 years ago. it replaced the factory L32 that had about 115k at the time it threw a rod. on that motor I was able to run a 3.2 with more timing and 1.9 rockers (stock cam) with all other mods the same-kr free.
just seems strange to me. my crow 105's may be a little exhausted so could possibly be getting valve float at high rpm's. don't know if that would cause any KR either tho?

Isn't their a setting in DHP you can lower the sensitivity of the knock sensors?
I will probably lower the timing a bit as well to see if it goes away

thanks for any help
 
I'll never understand why people run open loop on a grand prix, it's far more accurate with a maf sensor and closed loop working. These pcm's are so retarded compared to a v8 computer with a proper VE table that you can actually tune.
 
BillBoost37 said:
What do you consider high rpm?
What elevation are you at?
How many miles on these springs?
Click to expand...
1-2 shifts around 6200-no kr. 2-3 shift just over 6k and that's where the kr occurs. i'm in Denver so elevation is roughly 5280 depending on location. I bought the springs used and ran them on my rockered setup before I got the cam. I've ran them for ~50k.
 


Fivefingerdeathpunch said:
I'll never understand why people run open loop on a grand prix, it's far more accurate with a maf sensor and closed loop working. These pcm's are so retarded compared to a v8 computer with a proper VE table that you can actually tune.
Click to expand...
I'll never understand why more people don't! if I ran in CL and idled at stoich my car would be sitting their misfiring all the time. plus I've been able to get better mileage running leaner while cruising. I like having full control over my afr at specific maf ranges and not having to ever look at fuel trims.
 
It sounds like you certainly know there's a few issues.

Mechanical timing is likely from that chain and while you could tune around it.. sounds like a chain is in order.
The springs.. 50K of high shifts like that.. yeah, I could see them weakening and causing float.
 
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