Tappets

[Richard Coutts-Smith]

Anyone know the best (that means easist) way to set the tappets on my 235? ( I assume its the same as a 216). More recent vehicle manuals tell you at which point to check each one, and I have been told that you can do it with the motor at a slow idle, (The guy I spoke to years ago would do it by ear as well) but I fear that with todays technology this is a dying art.
I know you should do it with a properly warmed motor, any other tips?
Finding out what a pain it is to remove the engine cover with seats in and a roof on, no wonder they were thrown away...
Rich

[Mike K]

Originally Posted by Richard Coutts-Smith

Finding out what a pain it is to remove the engine cover with seats in and a roof on, no wonder they were thrown away...

Richard.. you dont know how lucky you are - try doing it on a cab 11 . First, you spend an hour removing myriad bolts and screws and then the three engine cover panels come off. A circus contortionist would be a good job for this mechanic. You lean over seats, battery box , gear stick and under the dash panel . The bonnet measures about 10" X 10" . Luvly stuff. Thanks Syd. Swallow: we you

Mike

[Keith Webb]

Originally Posted by Mike Kelly

Richard.. you dont know how lucky you are - try doing it on a cab 11 . First, you spend an hour removing myriad bolts and screws and then the three engine cover panels come off. A circus contortionist would be a good job for this mechanic. You lean over seats, battery box , gear stick and under the dash panel . The bonnet measures about 10" X 10" . Luvly stuff. Thanks Syd. Swallow: we you

Mike

Don't you mean disconnect electrical wiring, remove cab to frame bolts and lift cab off frame?

I wonder whether you can do the tappet clearances on a sidevalve V8 in situ.

[Keith Orpin]

Richard,
Do them with a cold engine, don't mess about with it being warmed up. The reason I say this is that the clearences hot and cold are the same, the worst scenario is with a warm engine as the clearences are at their tightest, so short of keeping the engine running, in an enclosed area, there is no easy way of adjusting them hot, (co-effiecience of expansion on different metals etc). The other thing is how good are your feeler gauges? i.e. are they new or an old set, as the old set will probably give you a smaller clearence, because they will have been flatten though use,and, lastly, it all depends on what sort of feel you have when pulling the gauge through.
Rule of 13 works well, i.e. (valve No 1 being the valve nearest the water pump, and 12 being at the back of the head)

when valve No 1 is fully open, adjust valve No12
when valve No 2 is fully open, adjust valve No 11
when valve No 3 is fully open, adjust valve No 10
when valve No 4 is fully open, adjust valve No 9
No 5 No 8
No 6 No 7
No 7 No 6
No 8 No 5
No 9 No 4
No 10 No 11
No 11 No 2
No 12 No 1

There is another way, which relies on two valves rocking and you adjust the opposing ones, i.e. valves 1 & 2 rocking , adjust 11 & 12
valves 3 & 4 rocking, adjust 9 & 10
valves 5 & 6 rocking, adjust 7 & 8 , reverse the above for the last 6 adjustments.
Hope the above makes sense !
Have fun, and don't rush it
Keith

[Phil Waterman]

The reason that I ask, is that depending on the year and if it has been rebuilt or worked on, a lot of 235s in the states have hydraulic lifters even if they did to begin life with them. So as a starting point knowing that you have solid lifters is key because they are adjusted completely differently from the solid lifters.

While a lot of people with many years of experience feel that you can adjust the valves cold vs. hot while the manuals say it must be done hot to get best performance. I seen old line Chevy mechanics do it by ear. My experience with the 216s and now 235 and 261 would say it depended on which truck, fuel and how hard you drive. The HUP with an engine that you actually used the gas pedal to control the speed; you could probably do the valve adjustment cold and not have any problems. On the C60 with the engine working a lot harder I don’t think so.

The trade offs on getting the adjustment correct are, too much clearance more valve noise and less power as the valves don't open as soon or as far, and the engine can't breath as well. Too little clearance and a valve will probably burn or you will get back firing in the intake.

Anyway you look at it doing a valve adjustment job on a CMP is difficult. First off it really takes a long time for the engine to actually equalize. Idling the engine alone just won't do it so if driving the truck for half and hour is not an option then I agree with Keith Orpin set the engine completely cold. By the way Keith your tip about the order is interesting; I've printed it out to try in the shop the next time I adjust valves. One tip I would suggest is that you attach a vacuum gage to the engine manifold as you will see quite a difference as you get the valves dialed in. One thing for sure you will be able to spot real quick is any valves that are not closing completely. Strangely enough you can spot a burned or open exhaust valve as a flick in the vacuum gage on the manifold.


I just pulled the Chevy Manuals US car truck1939, Canadian Car Truck 1940, MB-C1 1942 and MB-C2 1943 all of them have significantly different information about adjusting the valves. Someplace I remember a manual that listed both cold and hot valve setting I'll try to find that one and then post all the valve adjustment information.

[Richard Coutts-Smith]

Keith,
That is exactly the info I was after, will print it out and stick it in the back of the manual. Much appreciated.
Phil,
I built the engine, solid lifters. Set everthing up cold,and I think the tappetts are pretty close, but now it has done a couple of miles things have probably settled, and I would like to make sure. I will run it for a bit, do a couple of miles in it then whip the cover off while it is still hot.
Thanks for the input guys
Rich

[jim sewell]

Richard
I strongly recommend you do several adjustments now that you have started your engine ,
1) Retension your cylinder head , bring the engine to operating temperature and working from the outer ends of the engine slacken off the head studs about 1/8 th of a turn then working from the centre retorque the heads studs down to the correct torque .( the reason for backing off is to break the lock of the thread )
2) Making sure the engine is at operating temp adjust the valve clearances by iether of the sequence methods referred to in earlier replies.( using feeler gauges with a slight drag )
From memory the book species are 006'' for inlet and 016'' for exhaust and an option of 020'' for h/duty operation , you may want to go to 018'' as an in between for l/duty operation in Aust.
3) Tighten the manifold bolts to head including the hot box ones.

I have assumed you have used a convential head gasket and not one of the no retorque ones.

The above was a standard procedure when these engines were in common use.
Some workshops used to retorque the cylinder head and check the tappetts again after 300 to 500 miles as a precaution against blowing head gaskets .
p.s. I have just done my 235 after it's rebuild and the head came down part of a stud turn.
Regards
Jim S.

[Keith Orpin]

Richard,
Glad to be of help, after all, that's what we are here for, to help each other.

Phil, Never thought about using a vac gauge, good idea. I'll store that idea away for another day. If you happen to have a spare camshaft lying around, you can see how the rule of 13 works ( it also works on a 4 cylinder in line engine as well, only you follow the rule of 9 !)
Trouble is, that most modern mechanics would not know how to adjust tappets, let alone dwell angles and point settings !
Regards
Keith

[Richard Coutts-Smith]

Jim,
Thanks for your advice, have retourqued manifold and head already, but have not tried the turnback first. Have not heard of that one, but will do it when I have a go at the tappetts.
Regards
Rich