Challenger

I've got a 85' 22re with a Downey mid range cam in it. I did not install the cam and this is the first time i've tried to do a tune up on it. I noticed that the head has these measurements engraved into it. Hot Cam - IN 015, EX 016 - BTDC 10-12. I know what all these mean but does this change anything when I go to do a normal tune up?

xxxtreme22r

nope, but sounds like your lucky the P.O. engraved those valve lash requirements for you.

peow130

10 degrees really isn't that far before tdc..
Just runs it advanced so that the engine probably runs best and to pass smog.
Also, no vehicles in history run at 0 b/atdc.. so even if cali does notice it I doubt they'd fail you for it

xxxtreme22r

peow130 I know your a smart buy and all and have helped me in the past but, spec on a carb'd 22r is 0 BTDC

peow130

Yes, but its adjustable for when the tchain (or belt in other situations) stretches. Thats the point im getting across. If the timing wasnt adjustable then all engines would need a solid sprocket timing set, and we all know how noisy and unpleasant those are.

xxxtreme22r

yah I understand why the timing would chang depending on how much the chain has stretched, but the motor is supposed to run with the ignition timing @ 0 BTDC on a carb'd 22r.

If I am thinking correctly right now, if a chain stretches the timing will end up retarded from where it was originally set because the cam would be slightly behind the crank. I don't see it being more than a half of a degree or so though.

peow130

As cam's wear down, timing changes.. Also, rockers get out of spec, valvesget covered in goop, etc etc.
Engines don't stay the same forever.
And i run my timing on my pickup advanced for a reason, it runs about 5x better, lol.
Now, i'm not saying that specs for a carbed 22R are 0 degrees. But at some point or another, the timing will change, and you'll have to adjust your distributor.
It's that way with every engine in the world..
And you'd be surprised how much a chain can stretch. The chain on my dirtbike has links that are about 20% longer than when they were new.

xxxtreme22r

I fully understand what you were saying but that comment was kinda out of context and at least threw me off a little bit. FYI I have tried to run mine at 3-5 BTDC and it runs like crap, haha. probably because my cam timing is not perfect due to block shaving. Trying to save up to get LCE's cam gear.

peow130

Lol yeah, i guess i worded it funny on my phone.
I coudnt go back and edit it cuz i was on my phone and my internet was out for my pc..

herpestes

"IN 015, EX 016"

would this be valve lash.......... if so wouldn't it be kind of noisy?

peow130

No, he has a mid range cam so the grind is different on it. The valves open and close at different times compared to stock.

Challenger

Ok, so I did the tune up and now the engine has started revving up from about 950 to 1000 up to 1400 and then back down again over and over. What happened?

PismoJoe

I dunno man, sounds like you must have messed with the TPS or misrouted some vacuum lines