On my old motor i was right at 20 and now its right around 15-16. Its a fully built motor now. We checked for potential vac leaks and found nothing. any clues? Any disadvantages of running such a low vacuum?

 

with ac on it will be at 15

 

what's the A/F at idle? what cams? is timing set?

 

My built motor idled around 15 inches right after I did it.....after beating the living **** out of it on the dyno it was right there @ 20 inches of vac.

 

i dont know the a/f at idle. Mase tuned it a while ago. CTR cams. and yes timing is set. I had these cams last time.

 

Do you have a vaccum box anthony? Man when you coming down here?

 

my vacum see to change with the weather. cold out its like 20 and when its warm it like 18

 

is the motor broken in yet? you will see slightly lower numbers until the ring seal gets better.

 

For some reason my car always has a lower than normal vacuum. I think maybe my gauge is just off because it literally reads -26-28 in/HG sometimes at idle.

 

Both my buddies D series are reading less then 18 right now, I know for a fact one has a lil bit of leak but on the other one (both are boosted) I have no clue why it reads 14-12 @ idle. That one has a t25 on it so maybe its tryin to build boost @ idle, who knows....

Blaze

 

no its not because of the size of the turbo. My turbo is just as small as a t25.

 

What vacuum source are you using for the boost gauge?

Sometimes I see people use the same source for the gauge, BOV, wastegate, whatever...

If you have a good clean vacuum source and it's still reading low I would think it's because the engine is not broken in yet.

Maybe the boost gauge is bad? Have you tried a different one?

 

for a vacuum source im using a manifold from GE. The gauge isnt bad. I was just using it with the other motor and the vac source never changed. Im guessing its because of the new motor and the seals not fully sealing. i think i can live with 16 for now. just hope it doesnt drop any lower.

 

You gotta beat on it a little bit in order for the rings to seal up. The first 20 miles or so are the most critical, so don't loaf around at 2500 RPMs. The rings will seal up if you don't baby it.

 

i didnt beat on it at all. to 5k at most but 50% throttle. The rings will seal eventually. Im not smokin or anything though.

 

I just started my built motor for the first time about a week ago. Motor properly borken in.

Initial start up vacuum was around 24hg

After warm up sits around 21-23hg.

My old setup it was right around 17hg all the time.

vacuum is a small indication on how well you rings are seating. Low number like 17 mean they aren't toast but they have seen better days.

edit: I wonder if compression has anything to do with vacuum reading???? My C/R is rather high. (10.1)

 

My CR is 9.2:1 in an 84mm LS block.

 

It was in the tune. Its at 20 now.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1SlowSi &raquo;</TD></TR><TR><TD CLASS="quote">It was in the tune. Its at 20 now.</TD></TR></TABLE>


was it running leaner at idle than before?

 

yes

 

mine sits at 20,somtimes 18-19 when warm.

 

tune was the finall out come?

 

yup