normal straight six idle

just got my L6, 250 back from a valve adjustment($400). guy set idle at around 700+ which i understand is fairly normal. my question is, how low can i set the idle and still be healthy for the motor? (i like the way it sounds lower)plus only got a cheapy sunpro gauge, don't know how accurate. also is it possible to have a perfectly quiet valvetrain or is there always gonna' be a little clatter?

Valve job or valve adjustment? If not a valve job & only an adjustment who ever adjusted them screwed you man!

HandiVanMan! Was a valve adjustment, timing, and carb adjustment.(monojet) crappy cork gasket too. carb is o.k. but not great. He set timing at 12 degrees top dead center, I guess 2 more than my Haynes manual says for the high altitude here in CO. Obviously need to learn how to do all this stuff myself but don't have the $ to go back to school right now. It is a little quieter but of course I want it silent. Are you saying' this was too pricey or I should have better results or both? Finally got the attention of another vanner onsite here in CO and hopin' he can steer me in the right direction next time. (sorry for the pun)

Well I was quoted $110 by a machine shop to rework my 250 L6 head & $300 for the engine pulled & re installed once the head was ready. Most service stations will set the timing for $15 -$20 no more than $30 tops. Adjusting the carb is pretty simple so I would say $20 no more than $25.

HandiVanMan!definitely have buyers remorse but i gotta' plead ignorance. never do nothin again without talkin to you guys.hopefully HOTRODVAN will clue me in to some righteous local people. Still, what is the lowest base idle i can healthily run my L6 250?

donivan65 wrote:A 1st Gen idles at 500 RPM,,,,,and then you need to adjust the mixture screw to have the smoothest idle for that speed,,,,,,Should be pretty quiet if they adjusted the valves correctly,,,,,,,

Just go by what Don says & you should be good to go!

I'm sec. gen. 67 block , 68 head. probably same thing? air mixture screw in or out? and by the way my valvetrain is still clickety-clack, down the track. will they go silent, or does that mean the valves are TOO tight?

Here some info on the Monojet carbs.
http://www.scribd.com/mobile/doc/82845902
Maybe it will help you.

You might want to drop the gas tank & pull the sending unit to see what shape it's in. The old gas tanks gets pretty rusty inside. I would also replace the filter in front of the tank & also replace the one inside the fuel inlet at the carburetor. I would suggest that you run 93 octane gas in it and see if the valve chatte quiets down.

Thanks Gentlemen! definitely had a rad. place do my tank after the motor rebuild. new line, filter in front of the fuel pump and the normal filter on the carb. Original sending unit but pretty clean. Lousy Haynes manual says 4 degrees top dead center so this guys got me way out in front. Carb is off a '73 so i'm not sure if the idle should be set for the motor('67-'68) or the carb. stupid haynes says (manual trans) 500 high and 480 low for '68 but 750 high and 700 low for '73. always seems more right with the 500ish setting than the 700ish. will reset the timing early tomorrow but what's your opinion on the idle speed? (gotta drive to wyoming tomorrow so want to get it close) I'll call and find out valve lash tomorrow as well

RPM from the factory is decided by the following demands, in order...
Customer happy with the smoothness (tends to be higher than necessary for the other demands).
Low enough so the vehicle does not jump when dropped into gear (tends to be under 900 RPM, except when the cam/carb/compression will not allow smoothness at this level).
Must be high enough to maintain oil pressure, coolant flow and charging system ouput and not stall under load (many mild engines can idle below 500 RPM, but will tend to suffer one or more of these).

One more thing that affected idle RPM specs after our vans were built is emissions. A low idle tends to produce more emissions than an idle that is 1-200 RPM higher. This is especially true if the idle mixture is lean to meet emissions.
On most early chevy 6s, they tend to have a mild state of tune. I'd suggest 500-700 in gear. These early engines a much better at telling you when they are 'happy'. Listen to it when cold, warming up and hot. If it does not stall, doesn't diesel when shut off, restarts easily at all temps and is smooth, you have found it's happy spot.

can't even get my "craftsman advance inductive timing light" to even flash. rip off shop wont even spare 5 minutes to tell me if the light is a piece of shit and/or bring the timing back down to 4 T.D.C. without charging me again. this after paying them over $400 for a valve adjustment and it still sounds like im shakin' a spray paint can in the valvetrain. sorry to complain boys but i'm shit out o' luck and can't scare up any local reputable advice. i will not drive this this thing for any significant period of time 'cause i'm terrified of effin' up the motor and the dude that rebuilt it did an excellent job and i aint got the $ to eff around. (he's back in PA)any suggestions you guys got are greatly appreciated. i guess i'm essentially just bitchin to the choir at this point. after this i'll never make a move without consulting you guys. thanks again

I suggest that you go to court and file suit against the garage for not doing the job right!

Gonna' make sure they suffer disrepute online (as well as the other screwups from which i've suffered) doesn't really solve my problem but like they say, "ya want it done right ya gotta do it yourself". Only problem is I don't know how to do it. can't even get my "fancy"craftsman timing light to work. van really runs great essentially it's just time to quieten up the valve train now that the motor's broken in. I'm tryin to network, get a recommendation from the only other Colorado G guy I know of on the site but I'm afraid he doesn't check in too often or need to. guess I gotta go back to school.....

also the pick up on some timing lights need to be clipped on in the correct direction,,,,there might be an arrow that says TO SPARK PLUG,[/size][/quote] i never paid attention! just clipped on #1. now i am curious, will have to check both ways and see if there is a difference.

O.K. Donivan, guy says valves are 1/2 turn from zero lash. Craftsman advance inductive timing light has no directional marking. manual has numerous hook up instructions. tried almost all. will straighten out tomorrow with more reputable shop. i'll let you know how it turns out

That's the deal. I will say that a full turn is a lot. I try for 1/2 to 3/4 turn. You do not want just zero lash. This will beat up the lifter snap ring. The greater the amount of preload, the more the lifters can 'pump up' at high RPM and limit the max revs the engine can safely handle, all other limitations being equal and engineered to handle the higher RPM.
I knid of doubt you will be zinging that straight 6 to the moon, but it's nice to know that you also will not be inducing an artificial lower limit.

The engine is fresh, so I hope that they are new lifters and the oil is clean and at the proper level.
Adjust the rocker arms, then double check the dwell (points) timing, then final adjust the carb. Set RPM, then adjust mixture. Readjust RPM if needed, then mix. Mix is always set last. If it's an auto, always drop it into gear at idle to make sure it's smooth and will remain idling. Then shut it off, wait a minute of 2 and start it again. It should start easily and settle back to the same idle RPM. If it kicks back on the starter, the timing is too advanced. If it cranks a long time, there is probaably a mixture issue.

Motor was rebuilt about 20,000 miles ago. doesn't leak or burn oil hardly at all unless i'm really hittin' it. dude did a great job. just drove to Idaho from Denver and back, 1000 miles or so and it basically rocked! averaged 70-80 mph and only burned a little more than half a quart. you're right though, Donivan, the valve job should be redone and that manual page really helps. gonna try to get HOTRODVAN's attention and convince him to recommend someone local 'cause he's around here and seems to know a lot more about blocks and heads than i do. thanks for all the help folks!