I have a very small displacement SBC V8, it's only 240 cubic inch 3.50" bore (SBC 267) x 3.10" (SBC 262) stroke using a 7730 ECM. This custom SBC engine has a similar bore x stroke as the Chevy 2.8 V6. Should I use a Knock Sensor from an engine with a similar bore stroke? Should I use a Knock Sensor from a SBC 305 / 350?

dave w

 

i've read that you match it to bore size. but thats all based on what other people say.


i don't really know..

 

I tend to agree with the bore size ... the 305 / 350 share the same stroke, but different bores.

dave w

 

i think i've done a search in the past and there is a lot about knock sensor's on here.

the big thing is if you're using a knock module or its on the memcal. i think your options are limited by using the memcal type of ecm. but i even saw a thread about how to use a knock module type of setup and wire it into the 730 ecm bypassing the memcal. that may open you up to more bore size motors to chose a knock sensor from.


but i don't know if it really matters or not unless you are running a dead stock motor. as soon as you add even roller rockers its changed stuff. and i can tell you a 305 knock sensor seems to work pretty well on a 406ci motor. i can see it retard timing before i can hear any knock if i hit a lean spot to add in few * to much timing. so while it may not be 100%. it still works pretty good to me.

 

I have an interesting idea ... the 7730 was also used on the 2.8 V6. Maybe I should use a modified V6 memcal with the stock V6 ESC / modify for V8 res-net / custom V8 PROM?

Larry's Electric re-works the V6 for V8 TPI. http://www.larryselectricsite.com/prom.html

The engine is balanced, but I am using 6" rods ... makes me think that the knock sensor I end up using is not really going to be an ideal choice?



dave w

 

For the longest time I always said that your memcal needs to match the motor for that reason, but after reading a post by Fast355 saying he was using a V6 memcal with his V8 without problem I decided to not worry about it, I too am now using a V6 memcal in my truck (I couldnt bring myself to hack up my one V8 memcal when I had a pile of V6 ones when I converted to MPFI.)

 

I was told the V6 knock sensor is less sensitive than the ones in the V8 cars. I may swap mine out for it. Right now it is disabled as too sensitive. I am getting false knock 2000rpms at 50 map under moderate accelleration. That should not be.

 

Ronny, Now what? Discontinue tuning SA or try to fix KS?
Who has tuned SA without KS?

 

Something tells me to tune SA effectively you need to be on a dyno. Or at the least a use a stop watch and a measured 1/4 mile. My recent changes were idle SA and a low crawl in first gear (manual) to decrease bucking. I am pretty much using stock EBL SA table other than those changes I made and mentioned. I did take advantage of another members SA table for similar setup as mine and compared it to stock EBL. The only changes I see that member did is add SA(one point) in those areas of 80-100MAP or WOT.