Compression Check and manual timing help.

howdy! I'm working on a 1989 Mighty Max 2.0(G63B) and I finally found a new head after burning up the old one. but now I'm doing a compression check to make sure I didn't destroy any other internal parts. I have the head back on but I need to know how to time it without having to take everything off again. I'm still new to working on these cars. thanks for any help.


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There are alignment marks for the belt timing pulleys. On the oil pump pulley, there's a notch cut out on the edge of it that faces a tapered pointer on the oil pump housing. The crank has the timing marks and should be set @ TDC on #1 cylinder. The cam sprocket has a dimple on the outer edge that aligns with a small bulge/ridge on the head. It is located on the head just below the valve cover seating edge @ 9 o'clock - it's not 'on' the face of the timing belt recess but on the inner face of it aiming towards the sprocket teeth. Last is the secondary counter balance shaft timing belt. There is an access bolt on the side of the block about in the centre of the balance shaft (IIRC it's a 14mm bolt). Remove the bolt and place a screwdriver through it. If the screwdriver hits something, the shaft is out of timing. Rotate the shaft until the screwdriver is able to pass through and install the belt. Pull the screwdriver out and reinstall the access bolt. Set your ignition timing. If you need a visual guide, check the manuals section. If you get stumped by it, someone will find the pictures (if I don't first...)

Thank You very much! I'll check it out this weekend. may get up the manual and try to get 'er goin'. I plan on doing a propane conversion later on down the road like my other D50

OK, now I'm having an issue. I have the head on and I tested the compression, but I didn't get anything UNTIL I took the rocker arms and assembly OFF, after that I started getting compression. it didnt look like the arms were keeping the valves open but I'm stumped. has this happened to anyone else?

Check the timing marks are set correctly. It would have to be way out for you not to get a comp reading. Luckily the G63B is a non interference engine... On your last post the pic has the timing sprocket dimple facing straight up and I'm guessing that is where you are attempting to set TDC #1. That dimple should be facing about 9 o'clock at a casting ridge on the inside of the cam recess on the head.

Oh I set the timing after your last post and referring to the manual like you saidhttp://www.mightyram50.net/vbulletin...id=27026&stc=1, which was very helpful, after I set the timing, still no compression, it wasnt until I loosened the rocker arm assembly that I got a compression reading at all. I have a feeling something is compressing the valves.

Did the marks align once the belt was tensioned? It can be tricky to get right. On TDC the rockers on #1 cylinder should have a little play in them, meaning the rockers aren't pre-loading the valve springs. Both intake and exhaust cam lobes should be facing downwards on #1 TDC. This is kinda weird...

Hey geezer! sorry for the no show on your last reply, Holidays and getting covid knocked me out for a while. but I'm back at trying to figure out this no compression business. (it's not letting me post any photos) but I have it timed and we managed to get SOME compression after loosening up the rocker arm assembly and poring a little oil down into each cylinder. after tightening the assembly back up...*fart* we get nothing. it doesn't look like its compressing any of the springs that would keep the valves open. but I'm stumped. any thoughts?

you are setting the valve clearance on the radius of the cam and not the lobe right, sounds like its too tight
should be able to wiggle the rockers a little until the lobe comes up and presses on them

when you remove the rocker gear, all cylinders have compression? so it must be holding the valves open. You didnt change the valves? if not, and the engine ws running before, then they are probably the correct valves with correct length, none of the rocker gear was changed?
gotta be your clearances too tight. Back them right off and reset. confirm you are using the correct feeler gauge thickness

hey hey! back again after trying to figure this out, something is definitely holding the valves open...

I found out the old valves were too long so I took the head back off, lapped and replaced them with shorter valves, NOW I'm getting compression in-

1(150psi), 2(145psi) and 4(about 40psi) but nothing in 3.

I took off the assembly and they all close perfectly, I slowly put the rocker assembly back on (keeping a close eye on 3) and its just barely pushing the exhaust valves open.

the tappet is completely pushed in with no wiggle room even when the exhaust is on a closed cycle and the intake is completely open.

seems like I'm only having issues with 3(not closing) and 4(just barely closing) exhaust.

---also, I have those lifters that set inside the rockers that compress as the rocker moves, I have no clue how to adjust those, but
the manual says
INTAKE 0.003 in (0.07 mm)
EXHAUST 0.007 in (0.17 mm)
jet 0.003 in (0.07 mm)

Is there a mismatch of hydraulic and mechanical valves and rockers going on here? I wasn't aware there was a difference between valves (not AFAIK) but there is a difference in cams and rocker ratios between hydraulic/mechanical

heres the exhaust and intake, so far the only thing I see that I can adjust are the jets on the intake. and exhaust 3 no compression and 4 little to no compression. I bought an adjustable rocker arm just for 3 to help let off some tension on the spring.
thanks again for your help. really means a lot.
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There is something definitely up if you are getting that much spring compression. Do all of the rocker arms look the same? We need some background info on the history behind the engine/truck. To me it looks like there are a mix of different hydraulic rocker arms and this will screw things up (has someone used rockers from a 2.4 or a 2.6 etc) I would consider looking for a complete set of rocker rails for the G63B.

When I bought the truck it ran fine (never worked on by me) until the one of the freeze plugs sprung a leak, over-heated and blew the head (crack on 3)
I bought a replacement head from a salvage yard
took the valves off the old head, cleaned and lapped them to the new head (I took off the new head valves because they were too long)
I put the original rocker arm assembly back onto the new head.

all of the rockers look the same for the intake and for the exhaust.

now were at the stage of checking the compression to make sure I didn't burn up any internal parts,
I loosened the assembly and I got compression in all 4.

saying all this all out loud, I fear that I might have grabbed a 2.4/2.6 head from the salvage yard? and maybe the assembly isn't working with the new head.

also. would something like this be worth investing in?

https://www.ebay.com/itm/32434953290...Cl-ycTkSGVLJ_Q

thanks!

Quote:

---

Originally Posted by clunkheads

When I bought the truck it ran fine (never worked on by me) until the one of the freeze plugs sprung a leak, over-heated and blew the head (crack on 3)
I bought a replacement head from a salvage yard
took the valves off the old head, cleaned and lapped them to the new head (I took off the new head valves because they were too long)
I put the original rocker arm assembly back onto the new head. all of the rockers look the same for the intake and for the exhaust.

now were at the stage of checking the compression to make sure I didn't burn up any internal parts,
I loosened the assembly and I got compression in all 4.

saying all this all out loud, I fear that I might have grabbed a 2.4/2.6 head from the salvage yard? and maybe the assembly isn't working with the new head.

also. would something like this be worth investing in?

https://www.ebay.com/itm/32434953290...Cl-ycTkSGVLJ_Q

thanks!

---

In a nutshell - no. You could get a whole used head (a WHOLE engine...) for that price. If the rocker journals are ovalled out, the assembly is TRASH and you won't know til it got into your hands. Being that gummed up with old oil is not an indicator this has come from a maintained engine. Are you getting full valve travel without the rockers installed - no signs of valve guides being damaged etc? How were the donor valves too long for the head they were originally from? A 4G64 head is EFI and has no provision for a carb'd fuel pump. The head from a 2.6/4G54 is a timing chain driven head and isn't compatible with the G63B or 4G64 engine.

the donor head came with valves and springs and I just put the whole thing the block at first and when I wasn't getting any compression I noticed they were longer than the old valves, so I swapped them thinking that was the problem. I hope this can confirm my confusion... as it sits right now old valves with new(ish) head.

left, that came with donor head
right, from the blown head

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