Thread: tappet adjustment 350

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Hi, I'm new to this forum, and not an engine expert. I have just replaced a head gasket on the 350 chev in my ski boat. I am not sure how to adjust the hydraulic tappets. In case it matters, the block is a 3970010. According to the suffix code (CKL) the engine was first put together 1973.

Help would be appreciated (I must get a decent workshop manual).

welcome to the fourm grahamO, these people are great to talk to. never did it to a boat, but on a auto. some people do it hot and some people do it cold, i do it hot. turn the motor over and adj. all the rockers down to 0 clearnce and then start the motor up and give the lifters time enough to pump up, then back off the adj. until you hear the rocker tap then tighten the rocker back down a turn to a turn one half , the motor will run rough until the lifters adj. themselves, then it should leval out, if it dont then you have the lifter to tight, every body has an opinion on how tight they should be but this should work out just fine. this is not the professional way of doing it but it works. oil will go everwhere so you need to control that some how. good luck thanks, mike

ps- hope these people dont run us off here with your boat and my 97 chev. truck. we are a little out of place

Buy a set of these , they'll help to keep oil from going all over the place

simple to adjust...if the motor runs

idle motor with one valve cover off. best done at op temp if possible.

back off one rocker nut till the rocker taps loudly, then tighten it until the tapping just stops, then go about 1/2 turn more.

repeat 7 more times. turn off motor, replace cover, remove other cover and repeat.

you will have some oil mess, and check the level when you are done. the pic of the 'key ring' is the tool that helps stop the oil mess. Last time i did this (about a month ago) on an 80psi oil pressure motor, i had lost less that 4 oz of oil.

the non-running adjustment might be more accurarte, sure is more complicated, and easier to screw up.

Well mines close to that, I cut the whole top off the spare set, don't loose more than a few drops, I also use the 0 lash+ 1/2 turn hot method

Thanks for your quick replies. I also found some info on the net about doin it cold. ie Set engine rotation so lifter is on heel of cam for each respective valve, then adjust until no play in push rod (can use .0015" feeler gauge instead of testing by rotating push rod), then tighten 3/4 of a turn more. I need to do at least an initial set this way, since I have just replaced one head and everything is way out.

Does this sound OK. I'm not too keen on getting oil throughout my boat, and I don't have spare rocker covers.

Cheers

yep, that shoudl work
remember - boat and oil both float, so don't worry about it.

This is a great thread for me with two new ideas, namely setting valves when hot and the idea of holes in old valve covers to prevent oil spray. I recall studies/papers on setting the valves on 1300-1600 VW flat fours with mechanical lifters that showed that setting the valves close to the limits (tight) when hot produced about three more H.P. and recently I have seen comments on other sites that one can set the hydraulic lifters close to the tight limit so as to get the maximum duration of a given cam. However those articles said to gain a few added H.P. to only tighten the nut 1/4 turn, but this would require more frequent adjustments. I don't understand in the sense that if one tightens to 3/4 turns after contact of the lifter I would think that is TIGHTER and more likely to follow the cam profile more closely????? Anyway I guess after reading that I would compromise with 1/2 a turn while hot. Have there been any proven H.P. gains based on the 1/4, 1/2, 3/4 turns idea which is the optimum, 1/4 or 3/4 turns (hot)?? On the VW flat four there is little use for a hydraulic lifter with a horizontal lifter orientation in which the oil would form a bubble so they use a mechanical lifter, but I guess there is some "convenience" in the vertical (45 degrees anyway) orientation of the V8 lifters, assuming you keep the shiny side up! Thanks for the idea of the holes in the cover, I am learning a lot from this site! Streets and Tech1 and others really can comment on a lot of important little tips that might take years to learn on my own.

Don Shillady
Retired Scientist/teen rodder

OK, I can also attach a small broom to the horizontal antenna and perform a public service by sweeping the gutters at the same time and maintain a perfect ground! Now what about the question of 1/4 or 3/4 turn on the hydraulic lifters? Holy Valvecover (x8) Streets! I give you a little compliment and you give me a grounded antenna! Actually your idea would work if the tires were perfect insulators, but those with positive ground systems such as the '48 Cadillac and early MGs know that tires do conduct a little bit AND the Earth is actually NEGATIVE, not ground=0 volts. This is because negative electrons from the Sun are trapped by the Earth's magnetic field whereas positive protons are more massive and whiz on by the Earth so that overall the Earth has extra electrons and is actually negative and that means that the ground cable of an auto electrical system should go to the negative pole of the battery; otherwise you are bucking the whole Earth! That also explains a lot of difficulties with British car electrical systems that have positive ground. Now what about the 1/4 versus 3/4 turn on the SBC valves?

Don Shillady
Retired Scientist/teen rodder

Originally posted by Don Shillady
OK, I can also attach a small broom to the horizontal antenna and perform a public service by sweeping the gutters at the same time and maintain a perfect ground! Now what about the question of 1/4 or 3/4 turn on the hydraulic lifters? Holy Valvecover (x8) Streets! I give you a little compliment and you give me a grounded antenna! Actually your idea would work if the tires were perfect insulators, but those with positive ground systems such as the '48 Cadillac and early MGs know that tires do conduct a little bit AND the Earth is actually NEGATIVE, not ground=0 volts. This is because negative electrons from the Sun are trapped by the Earth's magnetic field whereas positive protons are more massive and whiz on by the Earth so that overall the Earth has extra electrons and is actually negative and that means that the ground cable of an auto electrical system should go to the negative pole of the battery; otherwise you are bucking the whole Earth! That also explains a lot of difficulties with British car electrical systems that have positive ground. Now what about the 1/4 versus 3/4 turn on the SBC valves?

Don Shillady
Retired Scientist/teen rodder

on the 1/4-1/2-3/4 turn bit - you apy for the dyno time, i'll supply the car and labor and post eth results here.

so, when the earth's magnetic feidl reverses, as it has many time n the past, will the earth then be - and the 'air' +? I s'pose we won't know that till then

I am suspect of the antenna idea. Each freq has a specific optimum antenna lenght for best reception. I beleive FM radio is 21". I know that my lincoln, with a rear deck mounted antenna does better for some reason than my cars with hood/fender mounts. Japanes cars useed to have them in the A pillar on the drivers side and the extended above the roof - not truly vertical so the roof would not have made a good ground plane. Sticking tthe antenna 'under' the car if a 'glas rod might be ok, metl on a steel one i would bet teh reception sux.

I have to put a CB antenna on my Wrangler..any thoughts on best placement on that one?

Don,

My understanding of the 1/4 vs 1/2 vs 3/4 power difference is as follows. We are talking about a hydraulic lifter that has a cavity that fills with oil to allow for expansion and contraction in the valve train due to variences in temperature. In a solid lifter valve train this variation id dealt with by a small clearance, usually .014-.030, adjusted between the rocker arm and valve tip. Back to the hydraulics, The cap inside the lifeter has a range of movement inside the lifter and that is what you are adjusting. The less you tighten the hydraulic lifter the more oil will be allowed into the cavity there by making the lifter a little taller and increasing net lift to the valve. It's a very little difference that could be made up for by changing the cam grind if you were starting from scratch. The downside is you take some of the hydraulic adjustment range out of the combination. That's pretty simplistic but that's how I understand it.

Pat

Streets,

I was TRYING to say your trick with the holes in the valve covers is really neat, and of course a milling machine would really do a clean job! In thinking it over I will try using a hole saw and hope it doesn't snag. You often give amazingly good suggestions mixed in with some other information which I don't always get. Here's my explanation, I find with every piece I add to my 350 that I am on totally unfamiliar ground with little transfer from VWs, MGs or flatheads, particularly all the brackets and so forth that I did not get with my bare block. Thus I try to trade some relatively abstract information that might apply to automobiles for information I need on SBC and TH350. I thought that anyone who might have struggled with a positive ground system would appreciate knowing why and to most British car fans the Lucas electrical system is infamous, but those who already have negative ground didn't even know there was a problem!

Screamer63,

If the picture on your signon is your jeep I can see why you have a question. Most CB antennas are "dipole" antennas consisting of a whip and a coil on the base. The EMF signal to the base coil energizes the whip during transmission, BUT the whip is only the top half of a figure-eight shaped oputput wave. On most vehicle mounting a mirror image of the top half is generated by a reflection of the EMF wave off the metal of the body shell. In your jeep you have a roll cage instead of a smooth metal trunk lid or cabin roof, AND on a jeep there is little space for a mount on a side of a fender. There is another consideration. If you mount the whip on the back of the roll cage you will have to make some modification of the soft top for rainy weather? If you mount it on the tail gate it should be vertical so that the figure-eight shaped wave is vertical. Maybe the most efficient location electrically would be in the middle of the hood since that would have a nice surface to reflect from, but I have never seen a jeep with a CB whip in the middle of the hood! Then again the hood would be near ignition parts which might interfere. I would ask around among other jeep owners and find out what they are using. In "theory" I think the best place for a CB antenna on a jeep might be somewhere along the midline of the hood, but you probably would have to use RF-suppressing ignition wires! As a practical matter you might have to install it vertically on the lip of the tail gate and hope the small surface of the tailgate will form the other half of the dipole figure-eight EMF field. One good thing is that CB antennas seem to work on a variety of mounting surfaces anyway somehow, but the signals will be cleaner/clearer if there can be a reflected wave. Then again I seem to recall that you can buy a CB antenna which is a whip with the coil half way up the whip (a bulge in the middle of the whip). In that case the antenna forms the full dipole figure-eight shape and would work anywhere you install it, even on the top of the back pipe of the cage. Try to get that kind of an antenna if you can. Then again, the military certainly solved this problem long ago using radios on the earlier jeeps before the Humvee, although they used other wavelengths with whips optimized for those wavelengths, some of which required fairly tall whips. Finally, if there is no other option just mount the whip to an angle iron next to the trailer hitch, but I doubt if that is optimum.

StuCool,

OK you say that the 1/4 turn gives slightly more duration, but may require more frequent adjustment. That is what the earlier article said but I guess that means that the oil trapped in the lifter is "hard" enough. I was confused (just slightly) in that I thought the slight pressure leakage in the lifter would provide a "squishy response" and it might be better to work from the bottom of the lifter. Anyway StuCool has answered the question and so 1/4 turn should give slightly longer cam duration! I guess I will ball park the settings cold just like the boat motor and then try the 1/4 or 1/3 turn when hot using my very own valve covers with holes!

Don Shillady
Retired Scientist/teen rodder

Streets,

That's the point, negative ground is good no matter what brand, but the early British cars and some early GM cars had positive ground and hence a constant battery leak through static transfer of the otherwise nonconducting tires. Negative ground, good; positive ground, problems! Yes Lucas got the point too somewhere around 1970, possibly 1968 as you say and changed their grounding, but the earlier cars had electrical systems that led to discovery of new swear words! My '73 Midget had negative ground, but in and around other owners of earlier British cars they would always ask me how I liked the Lucas electrical system with a smirk on their face and I would say that I had the newer negative ground. While we are chatting, can you tell me exactly how you had the horizontal antenna mounted, the orientation is not the question. You are saying you connected it to the frame?

Don Shillady
Retired Scientist/teen rodder

What i have seen most Jeepers do is to use the Cb antenna with teh midway coil and then they mount it with the aprre tire or other tailgate area mounting. I will make sure i get the miday mounted coil not base loaded and go from there.

Tappets to antennas:

Today I stopped in to a local Radio Shack and looked at their CB antennas. Almost all were the type with the coil at the base, but they did have one with a coil at the base and an inductor choke coil in the middle intended for a "glass mount" (rear I suppose) and that design probably puts out the full figure-eight wave since the simple coil in the middle would separate the top and bottom to some extent electrically and the kit was only $43. Still as Screamer says a power coil in the middle would be better, although probably more expensive. Regarding tappets, I torqued the 882 heads on my short block 350 today and lubed the cam with the special stuff followed by liberal dollops of STP on the cam and in the lifter bores. I used new lifters and I was surprised how tight the lifter bores were, although the block only had about 80,000 miles on it before the rebuild. I squeezed the air out of the lifters under oil so they start out filled, and ran out of time before I got to the rockers, but I slathered STP in the lifter bores and on the bottom of the lifters since it may be six months or so till I actually start the engine. Next I will be right at the step asked about in the original question of this thread where I set the rockers cold. Having once been interested in restoration as well as rodding, it occured to me that if everyone cuts holes in the old "orange SBC valve covers" in a few years restorers will be paying top dollar for "original valvecovers" while the rest of us are running aftermarket valvecovers with holed-originals hanging on our garage wall! Strange! Still I thank the folks on this forum for the trick for setting the valves hot without spraying the garage walls with oil. Regarding Streets' horizontal antenna, I see the horizontal space-saving part, but I am still trying to understand grounding to the frame which depends on the insulation of the tires. Streets do you remember if the radio worked better or worse in the rain when there would be less insulation by wet tires? I have heard of amateur Ham radio people shooting arrows through the trees with a fine wire attached to the arrow and then using that extended wire as an antenna even though it was in contact with the trees. Still the way I learned to make an antenna, starting with a crystal set, was to isolate the antenna from the ground with glass insulators so I am surprised Streets' setup worked! Sorry about the wordy description, I am depending on Streets to tell me when I do something wrong on the SBC rebuild!

Don Shillady
Retired Scientist/teen rodder