Keaponlaffen

Hey, all of the timing marks on the main pulley are worn off on my car ... I have to time it by ear and it still backfires (which means I've probably got a pretty bad ear). How would I go about replacing those timing marks? Thanks in advance....

Jeff

rxseven

Do you have backfiring on warm-up, deceleration or all the time? I have yet to see a 1st gen that didn't backfire atleast a little.

JIMMY54

iTrader: (2)

I'd say clean that area (pin and the pully) very carefully there should be some tiny trace of the timing marks. Even with timing set to factory my car backfires. I was told as soon as you change the stock exhaust that is a problem that will arise. But I noticed that cars around you have no idea where that sound comes from. I was driving behind an rx7 during a meet and I thought I had blown something on my car. Only after awhile did it set in that other rx7's backfire too and they where the cause. It really sounds different when you are in a car following. As long as it doesn't bother you in the car, don't worry about it. I bought a header and it helped cut the backfiring in half, (in sound, and even accurance). So timing won't really solve the problem, it might help, not a definite cure.

SilverRocket

Lol that was my car hehe.

I had major backfiring and flammage (with full RB exhaust) until I removed all my emissions junk. I think my shutter valve was acting all fucked, causing my backfires. As of removing that crap, my car NEVER backfires or shoots flames anymore, EVER.

Bottom line - your RX-7 should not backfire, at least not with stock or RB exhaust. If it does, something is wrong. Fix it or get rid of it!

stinkfist

It would be strange for your timing marks to wear off. Nothing touches them. Your pully is probably just dirty. clean it off and see if you can't find them. Rub your fingers across the back edge of the pully. you should be able to feel them if you can't see them.

good luck,

Mike

FJ

Here you go:

To find TDC :
http://www.teamfc3s.org/info/articl...ifying.html#TDC

To mark degrees on pulley :
http://personal.riverusers.com/~yawpower/pultime.html

Shouldn't take more than a half hour.
:p
-John.

mar3

iTrader: (8)

The Yaw Power timing tips are the best especially when you consider how easy it is to get the pulley off. He gives a blow-by-blow instruction on how to do it, just follow the directions and shake well. Regarding backfire, my current Rex does NOT backfire EVER so it's not a normal characteristic of a carb'd 12A even streetported like mine. Check to see if you have any leaks allowing fresh air to mix with the exhaust when it's just exiting the housings. The exhaust is hot enough to re-ignite the "spent" mixture flying outta there. Joy.

Keaponlaffen

K, thanks for all the help... the timing marks are almost not visible. I cleaned the pulley, but it is all marked up like something rubbed on it?! Oh well... it's not damaged in any way... But I'll try to find the problem. I do have exhaust leaks though, and that could be a problem, as it is only on deceleration (even if I put the clutch in). Hopefully I'll be able to fix it. It is a lot quieter than it was before though, as I plugged the two bottom exhaust ports that weren't covered by my manifold. I can actually hear my girlfriend talking to me when It's going :p.

One More thing... Will the backfiring hurt the car? or is it just the noise that's a problem. Like will I huck an Apex or Corner seal quicker because of backfiring...?

Jeff

Pittdp

Is it backfiring or just making the funny decelerating noise that they all make.

SilverRocket

Just a cautionary note. This has been said several times before, but be very careful if you decide to advance your timing and set your split to 8 degrees as he recommends. A few of us on here, myself included, have dangerously broken sparkplugs doing just this.

My favorite timing settings are the Racing Beat recommendations - 2 degrees BTDC leading and 19 degrees ATDC trailing, set at idle.

mar3

iTrader: (8)

There is a solenoid on the carb that is supposed to prevent the throttle bracket from snapping back when the gas pedal is abruptly lifted. I don't have my manuals unpacked yet (just moved into a new house...) but I believe it gets its "signal" from a vacuum source. Make sure it's functional and it'll stop 80% of your backfires. I lost an engine from a backfire when it still had that gawdawful thermal reactor bolted to it. Coupla PEPOPs and then sickening white smoke (surprise! NOT oil!!) came bellowing out as the cooling system drained into no.2 housing. It was an old engine, anyway...:p

Pele

iTrader: (28)

I thought a lot of our backfires are from shoddy shutter valve repairs.

RXcetera

Mar3, the only part on the carb that "slows down" the closing of the throttle is the Dash Pot. It's on the engine side of the carb, towards the firewall. It's threaded into a U bracket. It doesnt work on carb vacuum. It's adjusted by threading the unit up or down into the bracket.

mar3

iTrader: (8)

Solenoid was a bad choice of words. Like I said, I didn't have my manuals to give the correct term and my Rex is getting painted right now so I couldn't wander out to see the beastie on the car. The point was this, however. With or without the shutter valve working, don't let the butterflies abruptly shut during shifts or spirited driving. Teach thyself how to maintain revs and you won't have a backfire problem. Prior to the engine setup I have now from Rotary Performance, I had to do this all the time and never had the problem unless I was rushing myself and let the carb butterflies snap shut. Pepop!