Finding TDC

Tech tips and how to's

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kt

Finding TDC

Post by kt »

I'm trying to set new points.
I hooked up a timing gun over the weekend only to find
out that whatever markings i'm looking for have been
painted over on the crank pulley.

I have an idea, but wanted to put it out there to get some
more suggestions:
What is the best way of finding TDC?

Thanks,
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SLOroadster
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Joined: Sun Dec 08, 2002 2:53 am
Location: Napa Ca

TDC

Post by SLOroadster »

You should be able to see several cut outs in the harmonic balancer, the large one is TDC. look on the back side on the edge. I'm guessing its just like a 2L.

Will
oilleak

TDC

Post by oilleak »

As Will said, the marks on the crank pulley are cut into it so it's difficult to paint over them. Get the engine near TDC for #1 - both valves closed and assuming the dist is in the car correctly, the rotor pointing at the #1 tower. once your close, look the pulley over carefully, and use a shop light. You may need to put some bright paint on the marks or clean them up to make them more visable. If you really can't find them you can use what's called the positive stop method of finding TDC. Remove the plugs so the engine spins easily. You'll need to make somthing that will thread into the #1 spark plug hole and will protrude down into the cylinder a bit further than the plug does. Once in place, you turn the engine over (by hand) until the #1 piston hits the protusion. Mark that spot on the crank pulley. Turn the engine in the opposite direction until the piston hits the protrusion again - mark that spot. TDC will fall exactly between the two marks that you just made on the pulley. Mark the TDC spot as permenantly as you can. Try to be as precise as you can with the marks or you'll wind up a degree or two off of real TDC. The only other way I know to do it is to remove the head and put a dial indicator on the piston. That's extremely precise but I don't think you'd want to do that just to put new points in.
kt

Post by kt »

Found the hash marks! Thanks!
New points are in, engine is running great!
Really strong.

In hooking up the timing gun, I found out that
the PO set up 14degrees of advance at the crank.
I verified this at the dizzy, it shows about 7degrees
of advance.

Problem is, I have a 69 1600, which is suppose
to have 0deg BTDC.
I checked out the dizzy's cam, it's a 17.5, not 7.5.

This results in too much total advance.
I've read that if you have this setup, you'll run into
engine problems. But even at higher rpms(4000), the
engine seems to run fine.

Should I reset the dizzy back to 0deg BTDC???
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SLOroadster
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Posts: 5338
Joined: Sun Dec 08, 2002 2:53 am
Location: Napa Ca

advance.

Post by SLOroadster »

Have you de-smogged your car? You might want to check the compression just to make sure nothing is wrong. If it runs with out pinning you might reduce it just a little bit, just ot be on the safe side, otherwise go for it. Just listen carefully for it to ping. Also run premium gas. No need to fix what doesn't appear to be broken.

Will
Sorry, I find modern engine swaps revolting. Keep your G, R, or U series in your Roadster!
oilleak

Advance

Post by oilleak »

You really need to set it at 0 degrees until you put a 7.5 cam in it. 34-36 degrees of total advance is about the most you want to run on most engines. All of that is in the distributor right now. You can advance the timing safely once you've got less advance built into the distirbutor. If you drive it as is, be very careful to notice any pinging and back off right away. I'd make the new dist. cam my wallets top priority.
kt

Post by kt »

Well, I guess the vehicle has been partially de-smogged.
The air holes on the intake manifold has been plugged.
The nipple on the balance tube has been plugged.
Needles are probably not de-smogged needles. (Is it possible to verify this?)
Dizzy is stock, 17.5deg cam, probably stock springs and weights too.

I will handle the dizzy asap.
Needles, I guess the best place to get that is from a vendor?

I've had my roadster since sept. Never heard it ping at high rpms.
When the engine is cold, it does backfire. so I usually don't run it
until its all warmed up. Its fine at that point.

I think I'll set the dizzy back a few degrees just to be safe.
I always run premium gas.

Thanks,
oilleak

Distributor

Post by oilleak »

The vendors will have carb needles - I seem to remeber a thread on the list about Dean having the "right" needles - can't remember if that's the N17 or N25 needle but any of them should have them. Also, before you buy a recurve kit (which is a new cam, and a set of springs and weights) check how much play is in the distributor shaft. If you can wiggle it noticabley the bushings are shot. That can be fixed too but if that's the case you may be better off buying a new distributor. Woody bought one for his car for $145 if I remember correctly. I think he got it from either Ross or CDM - it may have been a sale. Might also be a good time to swap over to one of Gary Boones EI distributors. I just built my own and put it in the car. Seems very nice. After building it myself, I'll tell you that I wouldn't recomend doing it unless you want a month long project. For the amount of time I spent doing it, I'd have been better off buying one from Gary cost-wise. I just like doing that sort of stuff myself.
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