serious timing issue

[22dodge]

OK, I have been struggling with these 2.6 engines. I've milled .120" off the head. I'm at 11:1 compression. Cam lift is .540" I had to cut valve reliefs .180" deep. I put everything together, start the car and while I am adjusting ignition timing, the engine started making noise and quit. I went to crank it over and hear a lot of bad noise under the valve cover. I pull the cover and find 3 broken intake rocker arms and all the cam tower bolts pulled out of the head. I go to check cam./crank timing and found it off 2 teeth. I pulled the head, checked the valves all ok nothing bent. Then I put helicoils in for the cam cap bolts and new rocker arms. put it all together checked cam timing 10 times. All is good. I start the car up, runs strong, checking ignition timing all good, then I rev'd the engine to 3500 rpm and bam, same thing, started running weird and making noise. I shut it down then pulled the valve cover. I cranked the engine over with the starter and a rocker arm brakes sending part to the ceiling of my garage.

How in the world can I be jumping timing? I got the idea for milling the head .120" from people on this board. What are you guys doing to prevent this problem?

[webby]

Did you put a half link in the timing chain to take up some of the slack?

[C_Fernance]

Did you shorten the chain? I'm pretty sure you need to take a link out of it. If its too loose even when the tensioner is all the way out it may be able to jump over those couple of teeth.

[GLANT]

coilbound valve springs??? breaks rocker arms.. (and sometimes valve collets) .and maybe thats locking up cam causing it to skip.....
you cant shorten the timing chain...too hard... modify guides to use more chain .....to take up slack.

[webby]

Don't see how it's too hard, all you need is a chainbreaker. Push pins out, take a link out, press the pins back in?

[GLANT]

its riveted chain....i wouldn't...plus i think that would make it too short...its only a small amount of chain that needs shortening...head was machined 120 thou....so,120 thou x 2 =240 thou ???

[22dodge]

I don't know where to find a metric spec timing chain ½ link that could hold up to the speeds/pressure that it would be under.

I've had this cam for over 6 years in 2 different motors and never had a problem The head it's in now was in there for 3 years. I finally decided to just mill the snot out of the head for compression. Tired of the Neon's blowing my doors off.

I got the idea of milling the head this much from many members on this board that stated they milled even more than .120" (3mm). What are you guys doing that I'm missing?

[Superscan811]

In Cheater's post, he said he puts a spacer behind the chain tensioner to make sure it initially stays out further to take up the slack (before the oil pressure forces it out).

Another thing to note, Mitsubishi, in the later oil pumps, puts a cylindrical piece of rubber inside the spring of the hydraulic tensioner, to reduce the volume of oil that is needed before the tensioner starts to work.

Cheers.

[cheaterparts]

I don't know where to find a metric spec timing chain ½ link that could hold up to the speeds/pressure that it would be under.

I've had this cam for over 6 years in 2 different motors and never had a problem The head it's in now was in there for 3 years. I finally decided to just mill the snot out of the head for compression. Tired of the Neon's blowing my doors off.

I got the idea of milling the head this much from many members on this board that stated they milled even more than .120" (3mm). What are you guys doing that I'm missing?

as superscan811 said you need to put a spacer behind the plunger on the chain tentioner
the timing slips only when there is no oil presure in the motor ie on start up

I will have a post on here somewhere about it
but what you need to do is when you dail your cam in - which needs to be done with the timing cover off and the head on
to get your timing right
measure the distance the chain tentioner is out of the oil pump - ether fit a small stack of 9/16 flat washers to pack the punger out or as I do machine a small aluminium spacer
this spacer or washers do not need to carry full tention of the chain it just needs to stop the plunger going right back
on start up as soon as the oil presure comes up it will still tention the chain as normal
from memory its about 1/4" long ( but you can work it out on your motor )

If you machine 3 mm off the head and have the engine assembled with the timing chain cover off push the
timing chain adjuster back into the pump ( it has a light spring so is easy enough to do ) then check how much slack there is in the chain
there is easy enough slack to jump the timing
however with a std head pushing the plunger back into the pump although there is a little slack in the chain
theres not enough to jump the chain
so all the spacer is doing is stoping the chain tention from going loose enough to jump the chain with no oil presure

I also found out the hard way 10 years ago and I just looked at the way the engines chain tentioner worked which was fine except when there was no oil presure ( on start up ) - and I machine 3.5 mm from the head as normal to up the comp
you could find a 1/2 link to fit the chain but I have been using full lenth chains and the spacer in my circuit car
with no problems

hope that is some help

[astronturbo77]

you would have to run a adjustable cam gear with this much machined off the head and a spacers behind the oil pump tensioner? wouldn't it retard the cam timing if you didnt have a adjustable sprocket when dialing in the cam?

[cheaterparts]

by astronturbo77

you would have to run a adjustable cam gear with this much machined off the head and a spacers behind the oil pump tensioner? wouldn't it retard the cam timing if you didnt have a adjustable sprocket when dialing in the cam?

yes the cam retards about 1 deg per mm removed from the head

but I think with the cam that 22dodge is using it would already some kind of adjustable gear

[22dodge]

I'm well aware of the effects of milling the head on cam timing. I modified my cam sprocket to use Chevy offset busings. I degree'd the cam and have it advanced 5° (3.5° for milling and a bit more. I like to advance the cam for more power off the corner)

Over the weekend, I pulled the head, checked all the valves (all OK), replaced the broken rocker arm, then I modified a new set of guides. Now with everthing back together (minus the front cover), I used the starter to crank over the engine for a few minutes. All looks aOK. I'll finish up assembling this week and hope it runs. I ended up welding tabs on the guides and drilling new holes to get the slack out. now the tensioner doesn't come out as far which should also help.

[81GL]

I've been running 3.5mm off the head for a fair while now.
-Unlike cheater suggests, I haven't got the tensioner packed to take up the slack at idle, which is rather foolish of my self. But I'm still running factory 2lt cam etc etc, so no extreme loading of after market springs and aggressive ramps of the lobes.
Mind you, planning to build up a more manly engine soon and will be doing something about it then.

Also, you can't just put a half link in unless you take 5mm off the head to allow a full links worth of slack.
-I've got links here to suit - was hoping that would work, but not able to get enough slack.

Which tensioners have you modified to take the slack? got a couple pictures?
Be good to hear how you get on with it.

Nick.