How do adjustthe timing?

[Guest Grenade300]

I just got a 73 240Z and it needs a tune up. I am somewhat far from a book store that carries a datsun manuel, so until I can get on ordered I am goingh to ask a couple of questions. I used to search function, but could not get a strait answer.

 

Correct me if I am wrong, but the way to adjust the 240's timing is to first make sure the car is warmed up and put the 1st piston to TDC. The initial advance while the car is off should be about 5-8 deg, I think???. disconnect the vaccume advance and plug the side leading to the engine. Start the car. Just running the mechanical advance at idle, it should be about 12-15 deg, I think???. Then reconnect the vaccume and check that the timing is advancing more than with just the mechanical (It should maxout at about 30deg, right???). Please correct me if I am wrong.

 

I am going to LA in a day or two and I will pick up the "How To Restore your Datsun Z-car" If there is a better book to use please tell me.

 

Thanks

[Wide260z]

A Hayes manual could help you alot as well. Any local parts house could order it for you.

[Guest Grenade300]

I am heading down to the auto parts store to order a the book as soon as I am done typing this. I just wanted to give the car the best tune up possible in the mean time. It could take a few days for the book to arrive, postal system here is slower than a ford festiva with a fried clutch.

[Clifton]

The initial advance while the car is off should be about 5-8 deg' date=' I think???. disconnect the vaccume advance and plug the side leading to the engine. Start the car. Just running the mechanical advance at idle, it should be about 12-15 deg, I think???. Then reconnect the vaccume and check that the timing is advancing more than with just the mechanical (It should maxout at about 30deg, right???). Please correct me if I am wrong.

 

 

Thanks[/quote']

Correct. I've always checked total timing. That to me i more important as it effects power, usually 32-35* is good. I would try 35* and retard it from there.

[Guest Grenade300]

Thanks for the info Clifton. I adjusted the timing today and set it to about 10 deg advance at idle with the vaccume disconnected. I decided to not put very much advance on it because I would rather play it safe for now. I will probibly adjust it more this weekend. I will check the total timing like you said and go off of that.

 

The guy who owned it prior to me had the timing set to 0 deg advance at idle!!! No wonder it ran like crud! I still need to adjust and synchronize the carbs. I did check the compression. All cylenders were between 140 and 150 psi.

 

Thanks again,

Scott

[Guest Grenade300]

I adjusted the timing some more today. It is now set to about 15 deg advance at idle without the vaccume connected. The engine runs a lot better (When I had it set to 10 deg advance, the engine coughed and sputered below 2000 rpms) however it dies off hard at 5500 rpms (comparable to a rev limiter) and still coughs on occasion, however I do need new spark plugs. I think the hesitating at 5500 could be caused by any of the following.

 

-Fuel starvation

-needs yet more advance

-valve float

-the points in the distributer floating

 

Tell me if I missed anything?

 

I tried to adjust off the total advance, however the timing marks don't go that high. I am thinking of getting a protractor and making a mark at 30 and 35 deg on the pully with white out.

[Clifton]

Tell me if I missed anything?

 

I tried to adjust off the total advance' date=' however the timing marks don't go that high. I am thinking of getting a protractor and making a mark at 30 and 35 deg on the pully with white out.[/quote']

 

You could just use calipers and measure out the marks. I use the timing light with the adjustable timing knob. it makes adjusting total timing alot easier.

[Cody 82 ZXT]

I use the timing light with the adjustable timing knob. it makes adjusting total timing alot easier.

 

 

Totally with you here. Much easier. I tried to use a buddies at the track one night that did not have the knob and it was much less friendly.

[Nismo280zEd]

if you have a stock cam the Z's give out about 5500. Alos, less advance will give you mor power you advance too much you cut your redline down. You have a 240 so i can't tell ya much to correct that other than a biger cam and upgraded springs to prevent valve float. My EFI 280 i bumped up the psi that gave me damn good top end.

-Ed

[JMortensen]

if you have a stock cam the Z's give out about 5500. Alos' date=' less advance will give you mor power you advance too much you cut your redline down. You have a 240 so i can't tell ya much to correct that other than a biger cam and upgraded springs to prevent valve float. My EFI 280 i bumped up the psi that gave me damn good top end.

-Ed[/quote']

 

Less advance = more power??? More advance will make it EASIER for a NA engine to hit redline, not harder. Maybe if you factor in the vacuum advance AND the mechanical advance that might be too much advance. But when you're WOT the vacuum won't be doing much, and if it does it's a bad thing. That's why I just disable it (I'm not looking for mileage and I don't care about stop and go driveability either though). IIRC the 240Z distributor has something like 20 or 22 degrees of mechanical advance. I'd suggest you ditch the vacuum and run about 12º to 14º at idle. That should get you really close to where you want to be.

 

You can see if your distributor is listed at the guy who can't weld's site: http://home.att.net/~jason510/dizzy_specs.htm. If your distributor is in there then you can figure out idle setting will get you into the low to mid 30s.

 

Stock Z valves and springs don't float until 7500 or more rpm (lots of personal experience and friends with Z's and 510s on this one). Valve float isn't really a problem for most people since the induction tends to limit rpms to well under the valve floating rpm unless you just sit on the gas and wait for it to get there. BUT, the springs coil BIND at anything over about .480 lift on the cam so the aftermarket springs are usually necessary for that reason. Smaller cam would tend to reduce valve float too. And you say you "bumped up the psi" and got more top end??? Did you build a higher compression motor? Installing a larger cam will bump DOWN the psi.

 

Not trying to pick on you Ed, I just disagree with everything you just said. I think you're getting confused by turbo guys who crank down the timing and crank up the boost to get more power. Doesn't work that way on NA.