fredrx7

So the car is an 87t2 and it has some stuttering issues under low throttle and I have spent forever and a day trying to figure out why. I have spent a lot of time replacing, checking and rechecking the tps settings. Anywhoo I noticed the other day that the cas is set to all the way clockwise. I thought this a bit odd so want to check out the timing but the pulley has no paint on it worse yet it has no visible knotch or grooves to go by. I should mention the motor was rebuilt by the previous owner.

How can I check the timing (find tdc)? There must be a way but my searching has revealed nothing useable.

DC5Daniel

iTrader: (10)

You sure the pulley is not just dirty and hiding the marks? They are very small grooves.

fredrx7

yeah there are deff no marks on there, I looked really closely. I have found some info in my searching on finding tdc by matching the flat part of the flywheel to the side of the block, this supposedly lines up the front pulley to tdc. But I am a lil hazy on how I set it to 5degrees as thats what the timing should apparently be. Forgive any of my ignorance as I have never had to do anything with the timing on any of my rx7's in the past. Once I find tdc do I make a mark 5degrees from there and thats where the timing light should flash on, or does the timing light have a setting I can put to 5 degrees and it will shine on the tdc mark I will have made? Again forgive me for my ignorance.

fredrx7

so fwiw, tonight I retarded the timing a bit by cranking the cas back (counterclockwise) to the near center area of its range and the idle smoothed out a bit. Correct me if im wrong but there is no potential danger in retarding the timing without a timing light until I get one this way is there?

DaBrkddy

Lack of power, and possibly excessive exhaust temperatures are the only negatives that come to mind from retarding the ignition timing to far. And since it's a rotary engine, it already has both of these conditions anyway.

All joking aside, the *easiest* way to get your timing marks would be to get a stock pulley and either install it, or better yet borrow one and transfer the marks to your pulley.

Edit: if you run a catalytic converter, it could possibly be prematurely destroyed by excessively late ignition timing due to incomplete fuel burn and high EGT's. It may also damage your turbo's hot side if you manage to get the EGT's high enough. However we all know the alternative when you go with too much advance...

Aaron Cake

iTrader: (1)

You are looking on the correct pulley for the marks? It's the rear most pulley in the pack, on the rear most sheave. There's no stock pulley produced without the two notches so it may be an aftermarket underdrive pulley. Probably the easiest way to fix this is to get both a stock pulley AND HUB (they are a matched set!) from the same series engine and then use that to re-mark. Or swap in place as underdrive pulleys are stupid on the street.

kborro01

iTrader: (3)

I had the same problem and I found this helped find TDC. From there is was a matter of measuring around the pulley and determining how far on the pulley was the timing marks should be from TDC and marking them.
Finding TDC - NoPistons -Mazda Rx7 & Rx8 Rotary Forum

fredrx7

Thanks for the help guys! You all are the best! I am looking at the rear most pulley on the motor and theres no marks or indents anywhere. I am pretty sure its not the original pulley that came with the motor, in the least it's definately not the whole set. Assuming I can get my hands on a set of pulleys from a friend, will I need to remove my existing pulley to match it up to the new one or can I simply rest the borrowed one against mine while still installed to transfer the marks? I know there is a key way behind the pulley that can be referenced but Id rather not remove that big *** bolt if possible.

FWIW...Whoever rebuilt the motor only installed one pulley with two ribs and not all the accessory pulleys. When I bought the car it had a dual belt pulley on the alternator and these two belts occupied both "slots" on the main pulley. I have since replaced the alty pulley with a single one that doesn't under drive it.

MjhRotor

iTrader: (1)

As aaroncake mentions the pulley and hub are a matched set. You cannot copy marks from someone else's pulley alone.

Removing the hub is going to be pretty involved.

Also if you don't have an air pump you will want the dual alternator belts to help prevent the water pump slipping from lack of belt wrap with a single belt.

fredrx7

only reason I didnt reinstall my dual pulley onto my new alty is that I couldnt get the nut off. In the past I had stuck a couple screwdrivers into it to keep it from turnng, but this nut is on there so tight that it was going to bend the fins inside. Any ideas how to get this nut off the alty without damaging the internals?
I adjusted the timing back towards the center of its range and its running much smoother, should I just leave it be or continue trying to open this can of worms? What would you guys do?

PinkRacer

Wrap a belt around the pulley and hold it tight, then use an impact on the nut.

clokker

iTrader: (2)

Your can of worms is already open, you're trying to gather them up now.

You really need to quit guessing and do whatever it takes to get a timing light on that thing.
I too thought I could get away with setting the timing "by feel" on both the FC and the Z, and they were running quite well, I thought. A timing light showed the error of my assumption and they both run noticeably better now.

As Aaron said, if it's a stock pulley (and wouldn't an aftermarket pulley be aluminum and thus, easy to spot?), the marks are there, you just can't find 'em.
I'd remove the pulley from the hub and take a closer look.

fredrx7

cool, thanks for the replies guys. I shall pursue getting a timing light, and I will check the pulleys again tomorrow for marks.

Is there any risk in removing the pulley from the hub/anything I should know first?

clokker

iTrader: (2)

Nope, no risk, but...
The pulley is held on with four bolts into the hub, the bolts are not equally spaced and the pulley will only go back on with all four bolts one way. It can be frustrating finding the correct alignment, so make your life easy.
Make a temporary mark on the pulley that lines up with the timing pointer on the engine cover. As long as you don't turn the engine over, you can replace the pulley using your temporary mark and the bolts should line up.

In the future, just use the real timing mark on the pulley to do the same thing.

trickster

I tried to set my timing a couple years ago based on guides on here looking at the position of Rotor 1 as it goes past one of the spark plug holes but I recently finally found my original timing marks on the pulley once I knew what to look for. The mark that I made based on the guides was about ten degrees off from the actual L1 mark so I wouldn't recommend that method. The grooves are on the outside circumference of the pulley and look like small notches. Even with my extremely rusted corroded and banged up pulley I was able to see them as the were close to the mark I made, but not exact. Google some images of what the marks look like so you know exactly what you're looking for.

SpAm@FC

iTrader: (4)

one warning here:

If you change your main pulley together with the hub (as those parts are matched together), you have to open the center main bolt of the excentric shaft.
Removing your hub can possible drop the axial bearing behind the spacer.
You will not notice this problem, to be safe jack the front of the car up AS HIGH as possible, I mean, REALLY high!
After changing your pulley/hub package, check for correct axial endplay of the engine assembly. If there is no play you have droped your axial bearing and you are ready to toast your complete shortblock
Too many engines died because of this

ben.farnath

Isn't the trick to wedge your clutch pedal fully down til you replace the hub? But you're right. One lunched motor if that Torrington bearing drops

KompressorLOgic

iTrader: (6)

Front Pulley / Thrust Bearings very detailed explaination of what to do, and explained what actually happens, when removing the front main hub bolt.

have you tried taking just your pulleys off( the 4 10mm bolts) and inspecting the rear one very closely, to see if theres two slight divits, or do u have a few pictures of the pulley on all sideS? ive never had a pulley so bad u could not tell where the mark was....

fredrx7

man I have stdied it with a magnifying glass! That shi&T has no marks on it!

RotaryEvolution

iTrader: (30)

i sell reconditioned pulleys, or you can send me your old hub and pulley pair and i will set and stamp it at a perfect 5/20ATDC instead of stock that has about 5 degrees of possible variance in it.


there is no accurate way of setting TDC without a good pulley set. last thing you want to do is start *****ing with the timing without knowing for sure on a turbo car. even then, after all these years one can't be sure that a mismatched pulley hasn't been installed on the incorrect hub, i have seen timing marks as far off as 45 degrees with various combinations.

the spark plug method is the worst method(the plugs are not symetrically placed in the combustion chamber), using the keyway is probably the best and closest but still not close enough for a turbo engine, 10 degrees of timing in the wrong direction can cost you an engine. i did testing with an test engine and found there is no accurate way of finding TDC with the engine actually assembled without a known good timing hub/pulley, ie i couldn't find a good alternative method without a fabricated test tool from a disassembled engine that i physically set at true TDC.

out of 10 pulleys i put on the test engine set to TDC, 1 was accurate within 2 degrees, about 3 within 5 degrees and several were over 10 degrees off. the original pulleys that i could tell had never been taken apart from a set were the ONLY accurate ones within 5 degrees(factory spec for slop in the drilled holes in the hub).the factory ECU timing is aggressive enough, once you start raising boost and add in these factors you can see why people tend to lose engines for no apparent reason.

unfortunately no one seems interested in returning core pulley sets, so eventually i will run out completely. i still have a few left though. you can still buy them from mazda, or if you can live with underdriven accessories the racing beat one i verified as accurate on the 2nd to right most mark at 5 degrees(going by memory, since they don't actually document the degree stamps but i could verify it again for anyone who needs to know, i know i put the notes in the thread i made years back on TDC and the rotary engine).

edit: ignore what i said about the RB pulley, my notes are in this thread though the pictures have died.
https://www.rx7club.com/2nd-generati.../#post10898182


technically you could use my notes from the spark plug method and offset the amount of advance that it will put your mark at. that's as good of an alternative as i can give, you also must be able to know 100% for sure that you have the narrow split S4 USDM plug housings or the S5+Jspec S4 wider split housings, if you just guess, you could be wrong. this should theoretically put you closer than any other assembled engine TDC setting method, but i never actually tried it myself, so i won't be held responsible for the accuracy of it, my degree wheel i made for these engines takes all the guesswork out of it.

fredrx7

RE,
I will definately take you up on that offer once it warms up in my area a little bit, thank you. In NH its cold as a mf right now.