Engine timing change due to head or deck milling

[Legacy777]

Was just curious what other's thoughts are in regards to the timing change caused by milling the heads or the deck. I can't imagine it to be much, but in my quest for new block alignment pins I pulled up Crawford Performance's website for their phone number and ran across a cam timing adjuster.

http://store.crawfordperformance.com/store/products/566

Of course the guy I talked to said, oh yeah you want to use this adjuster if you'd had the heads or the deck milled at all and they are outside the Subaru specs. I'm just not sure how much timing might be off.

Additionally, with my Link, I'm not sure it even matters at all since I can adjust the base timing offset.

Any thoughts/comments on the subject?

[93forestpearl]

I see the surface grinding limit is .004", so maybe if you are over that? I've thought about the change in cam timing, but I haven't seen this product before.

[Legacy777]

The machine shop said they took .007" off the heads and .010" off the deck. So I'm way over the factory specs.

[PhyrraM]

It's the cam timing that I would think might cause more of a problem than the ignition timing. One bank will be off twice the number of degrees as the other bank. The only way I can think of other than the Crawford eccentric idler is with oversized idlers or fully adjustable timing sprockets.

I wouldn't worry about it too much unless there are drivablity or dyno issues. Of course, $150 for the Crawford idlers is pretty cheap compared to the cost of building the motor in the first place.

[beatersubi]

With the factory tensioner taking up the slack on the driver side, you'd really only need one for the passenger side to time it correctly, no?

[cj91legss]

That's actually an interesting point. i guess it does seem like you would only need one for the LH Cam gear. Also someone posted in the DOHC thread about different head gasket thicknesses... Josh have you thought about a thicker headgasket to compensate? i decided to go with the cometic head gaskets on my 22t/20h. the thickness was 0.51 so maybe you could get some extra clearance there? i don't know the stock headgasket thickness

[macipusy]

Can't you get a custom HG made by Cometic to bring everything back to original specs? I have not looked into this, but it's also an issue I will be having to some degree.

[cj91legss]

I remember a friend telling me something about Wiseco was making head gaskets now too. i think he said they were 5 layer or something like that..

[93forestpearl]

Extra thick headgaskets would be counter productive with the loss of compression ratio and the screwed up quench area.

[Legacy777]

I would tend to agree with Dan on the extra thick head gasket. I'm not sure that's the way to go.

I need to do a little more muling over this to think how much it will affect things.

[cj91legss]

well all jokes aside, since you're still running SOHC do you think it could have possibly become interference? i don't know what clearance is between the valves and pistons and whatnot.

[Legacy777]

I highly doubt it would become interference. Until you actually look at how small 0.017" is on a caliper, it's just a number.

I'm sure Subaru's specs are what they are due to the change in timing.

[PhyrraM]

OK, so the theoretical "right" way of doing it would be to:

1st, deck your block and heads the minimum neccisary.

2nd, spec your headgasket thickness to put the cams at the correct "height" to keep timing unchanged when using stock components. This would be: (Stock gasket thickness) + (amount taken off the block) + (amount taken off the heads).

3rd, spec your piston compression height (or rod length) to maintain proper quench and compression ratio with the dimensions decided on in step 1 and 2. This would likely mean slightly protruding pistons, like a stock EJ22T.

I don't think ANY builder goes through all that on a used block. It's easy to spec a single piston/rod design if you never have to deck a block or heads...every motor is essentially the same.

I know my builder ordered my pistons AFTER he measured the new deck height and CCed the surfaced heads. However, there was no "custom" headgasket to bring timing back in line. I'm thinking I will try the Crawford adjusters.

[93forestpearl]

The local engine builder that does most of our local "big dawg" cars uses beeswax to check piston to valve clearance. Most of those motors run the Kelford cams with 11.5mm of lift, so clearance throughout the stroke is even more critical.

[beatersubi]

A little bit higher compression isn't necessarily a bad thing, though, if you one has the means to tune for it.

[Legacy777]

More info from Nabisco

http://forums.nasioc.com/forums/showthr ... ?t=1985028

http://forums.nasioc.com/forums/showthr ... ?t=1984605

[93forestpearl]

In your case, they might be a wise investment. I might get them next time I need a belt, or take it apart for that matter. I might pull the covers off and take a look, actually.

[Legacy777]

Yeah I'm more than likely going to get them. I just want to fully understand how to adjust them.

[93forestpearl]

I wish they would sell them without the bearings. I don't need the bearings, unless they have a different ID or something.

[Legacy777]

I'll take some pictures when I get them.

[Legacy777]

I worked on the timing belt items today. I tried utilizing a degree wheel, but there's just not really any good ways to attach to the cam pulley and get everything aligned and setup. So I had to just align things as best as I could by eye with the timing marks.

I will say that these things are not very easy to hold in place or adjust....it was a little frustrating to say the least. It's not an easy task to adjust them once the tensioner has been released. I pretty much had to set them tighten the bolt most of the way, and then do any fine tuning with a socket. The correct wrench needed for these is 1-1/4" offset boxed wrench. Which is not a common item at hardware stores, not to mention it's not going to be cheap. I ended up picking up a 1-1/4" open/boxed wrench at Northern Tool for $8. A buddy and I are going to hack/weld it up next weekend and make our own wrench to suit the application.

From what I did get to play with these today, I'd say I got them about as good as I'm going to get them. The passenger side cam was pretty much on the money, but the driver's side cam was about a 1/2 tooth off from the mark. I believe I was out of adjuster too. I'm not sure if there's another way to configure the top and bottom, but here are some pics with the adjustable tensioners.

Crawford Idlers



Crank


Passenger Cam



Driver Cam




For reference, here are where the marks sat with the stock idler pullies. Honestly, they looked pretty darn close IMO. Also, that's about what they looked like before the heads & motor were decked.

Stock Idlers


Crank


Passenger Cam



Driver Cam

[beatersubi]

I couldn't fully rely on the marks on the rear timing covers. They are flimsy plastic, after all.
You can loosen the bolts, move it around, re-tighten the bolts and be off half a tooth.

[evolutionmovement]

You can't get a 1 1/4 socket on there? You should be able to find that locally. If you have any marine supply places, they MIGHT have one if a hardware store doesn't. I think I got mine at Sears (IIRC, I needed it for prop nuts on outdrives).

[Legacy777]

Relying on the timing marks on the plastic casing is about all you can do. There's no other marks on things.


Steve, I can get a socket on there. I've got one. But then you can't tighten the center bolt holding it to the motor. A buddy helped modify a wrench from Northern Tool. I don't mind hacking up an $8 wrench. It works perfectly for what I need it for. Unfortunately one of the pullies got damaged with the die grinder. I'm hesistant to use it.

Here's some pics

http://main.experiencetherave.com/subar ... adwork/22/

[beatersubi]

I guess what I'm saying is: unless you degree the cams in the motor, you don't really know where the timing is anyway.