Howdy all,

Got my new rebuild idling pretty good now at 1,000rpm, but its only pulling between 8 and 10 inHg. Is this normal for a 0mile rebuilt engine with a largish street port with a fair bit of a overlap(for a street port)?



Or should it be pulling more than this even though its not got any k's on it yet?



I only ask because i've had to richen up the idle maps on the microtech a bit to get it idling i've looked for vac leak i dunno how many times and I can't find any, even when I spray water over suspect areas I can't find any.



So, should it be pulling more than 8-10inHg?

If you think you have a vacuum leak, get some carb cleaner and start spraying around where you think the leak may be. If the rpms drop, then the leak must be somewhere in the area where you are spraying.

Run it for 1000 miles and then see what happens. Obviously check it thoroughly first to make sure there really aren't any vac leaks.



8-10 does seem a little low- but it may be that the seals haven't bedded in properly, especially if you re-used the rotor housings. You haven't got load on like an A/C compressor- that will drop the vac as well...

I think mine is more like 18 inches of vaccum. Quite possibly a vaccum leak, or your running really lean at idle. When I lean out my idel it jumps up to about 14 inches of vaccum.

Yikes!



I did a milder SP than what you probably have and it was pulling roughly double that vacuum @ 1000 rpm after a few tanks of gas through it. Something is amiss!

my engine did that until i had about 150 miles that it started to get more vaccum, now that have 1k miles on it pulls a nice 22hg of vaccum and it sound nice

yeah look for vacuum leaks, i hope you find some https://www.nopistons.com/forums/pub...#>/biggrin.png

White

Where do you have your map sensor hooked up at. If it is hooked to the UIM then move it to the port on the LIM. The one that pulls vacuum from the two primary runners and the nipple faces the fire wall. If your vacuum reading is the same and your idle is around 1000rpms and you still feel you have a vacuum leak then it is your intake manifold to engine gasket. If you sprayed carb cleaner where you think there is a vacuum leak and the idle did not increase then you do not have a vacuum leak. Your using a stand alone right? Ported rebuilt motors with new seals and used housings should pull less vacuum when first started. Mine pulled -10 when first started, now after a week it pulls -12. As long as the motor starts and idles fine I personally don't care what the vacuum is on a newly rebuilt motor.

chuck

It's hooked up to the UIM, but im SURE I don't have any vac leaks..



BUT I am happy, its upto 12inHg now at 1,000rpm, and its only done 1.5km.. https://www.nopistons.com/forums/pub...IR#>/smile.png (thats 1.5km, not 1,500km... https://www.nopistons.com/forums/pub...DIR )



So i'm figuring it just needs to be broken in some more..

Will keep you guys posted, so far it drives great, bit of oil smoke, wonder if that will go away? maybe I _should_ have replaced the oil control ring springs... https://www.nopistons.com/forums/pub...IR#>/smile.png





Ah well it's all a big learning curve isn't it..



Cheers guys

-Nathan