vacuum levels for 400?
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From: ponoka,ab
vacuum levels for 400?
hi. what should the vacuum level be for 400cid at idle? im getting 14 which i thought was low. when i time the engine i should have the vacuum hose to the distributor plugged,right? what would it mean if i have it unplugged and there is no differnece? if i hook my vacuum advance up to the manifold vacuum source my idle jumps up so im assuming the vacuum advance is working and i also used a hand help vacuum pump to check to see if it moves when i pump it. it runs alot better when i have the vacuum advance hooked up to the manifold vacuum port than the ported vacuum.
i read in other posts that timing can be done with a vacuum guage? is that right? what i read was advance the dist.until max vacuum levals are reached? the more i advance the more vacuum i get until the distributor vacuum advance hits the thermostat housing and vacuum kept going up. my timing gun is broken so i thought i could try this method but it seems odd to me but im not the brightest bulb on the tree so...lol.
thanx in advance for the help/info
i read in other posts that timing can be done with a vacuum guage? is that right? what i read was advance the dist.until max vacuum levals are reached? the more i advance the more vacuum i get until the distributor vacuum advance hits the thermostat housing and vacuum kept going up. my timing gun is broken so i thought i could try this method but it seems odd to me but im not the brightest bulb on the tree so...lol.
thanx in advance for the help/info
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From: chicago burbs
give yourself some credit, you think it's an odd way to set your timing. the vac reading will continue to climb as timing and rpm increases, until you are way over advanced. there are a bunch on here that time by ear, OK with experience but should still be verified by the light. and for total timing. sounds like it's time for a new light! mine is a resurected piece held together with hose clamps and elec tape, built from two that had different problems. one had a bad button and the owner threw it against the wall and cracked the pick up magnet. i had a pick-up from one that got hit by the fan and i bypassed the button. anyway, 14" of vac isn't too bad. what is the idle RPM? (you need a tach too.) you can check the mech advance by disconnecting the vacuum and watching the timing marks with the light. if the timing doesn't change, your mech isn't working. total timing should be around 36*-38*
Last edited by grclark351; May 16, 2004 at 01:26 PM.
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From: ponoka,ab
hi there. im going to go get a light today. but the rpm is around 800. should i set timing first then mess with the carb or the other way around? the intake is an edelbrock open plenum type with an edelbrock 600 cfm carb. would an open plenum have an effect on vacuum lsignals? i have no idea what the cam is.thanx again
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Freshman User
Joined: Jul 2003
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From: ponoka,ab
timing
hi. i'm replying to myself.lol. i have a digital timing light now and set the initial to 15deg but will slowly decrease and see what happens.rpm is 800. this is with the vacuum advance plugged or the vacuum line on the ported vacuum from the carb. it made no differnce. so how do i figure out my total advance,do i increase revs up to a certain rpm? oh yeah. my vacuum level is now at 15-15.5.. thanx
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From: chicago burbs
clean off the balancer real good and make some marks with a dab of paint or white-out or whatever. i have a timing tape on mine so the degrees go around far enough to read total. not sure where they stop on the stock markings? to check total, disconnect/plug the vacuum advance and slowly bring the rpm's up until the timing stops advancing while watching with the light. i adjusted my vacuum advance to around the same as my mech total also. the vac advance doesn't work because the vac will drop to 0 when you have the gas pedal pegged while driving, but when you let off the gas the vac will pull to it's max allowable. i just don't want mine going off the scale.
