A concerning timing issue.....

[d510addict]

It Is pointing to number 1 wire, the motor is at top dead center and these are the pics I snapped while it was at TDC.

[datzenmike]

Ok here are my pics of things, to start off I approximated tdc based on the end of the compression stroke (cyclinder 1 cam lobes in a V shape) then gently held a screwdriver in the spark plug hole and wiggled the crank back and forth until i was absolute tdc.

 

First off my timing plate/crank pulley

It is tough to see but it is lined up exactly

I agree. It's at TDC compression stroke.

 

Here is my cam timing

I think this is correct but say something if I am wrong

Again I agree this is close enough. V should be just below or slightly to the right of the horizontal etch mark on the cam thrust plate. This just says that the chain isn't stretched too bad. It would still run if over on the left side but not as well. Has nothing to do with ignition timing but good to know.

 

Here is my Dizzy

While the Dizzy is clocked nearly all the way counter clockwise it can go far enough to get me to like 20 deg btdc right now I am at 3. So it is def off a bit but does that make a difference? 

As long as the adjustment range is able to be set at 12 degrees it's good.

 

 

Maybe borrow a second timing light that doesn't have adjustable advance. I've never used one so I wouldn't know if you are using it properly or not.

[Sealik]

Hmmmm....seems like excessive lateral movement at the top of dizzy...between the reluctor and magnetic pick-up????

[datzenmike]

Yes but how much is too much?

Ok I have an l20b bored .030 over with an A87 open chambered head that has something around .040 taken off of it. I use an EI dizzy and a 32/36 weber everything else is fairly stock. My problem is when I set my timing to 10 deg btdc my 521 won't do anything past an idle. It basically wont run. So I set it back to 5 deg and it pings highest ive run is 3 deg btdc without pinging.

That's a 0.030" overbore and a head shave of 0.040"???? If so I run the numbers and the compression is 9.222. Even that high you should be able to run more than 5 degrees.

You say it idles at 10-12 degrees but above idle it's crap???

TRY RUNNING AT 12 DEGREES BUT LEAVE YOUR VACUUM ADVANCE HOSE OFF.

 

Maybe the vacuum advance goes full advance as soon as you go above idle? Instead of one or two degrees it goes right up to full?

[d510addict]

I will try this and let u know wont be till tomorrow though.

[datzenmike]

I think there is a spring the vacuum pulls against inside the advance pot. If the spring was broken the advance would be easier and faster. Maybe too fast.

[Sealik]

Yes but how much is too much?

 

I'd say (guess) that's a little too much and would swap in another dizzy

[ssnapz]

Adjustable light set at 10 + marks at zero = timing at 10. If you don't understand the light put the dial at 0 and pretend it doesnt adjust, set timing and they move dial so you can learn the light

[banzai510(hainz)]

I think your motor is mechanically set fine.

Its a carb or dizzy issue.

 

if you can adjust between 0-20 Deg BTDC your OK

 

 

carb main jet maybe be plugged?

Try running with the CHoke ON and see if the RPMs go up(maybe run it cold whole the choke is still On if you have a eleltric choke or pull the elelctric wire to the choke. this will enright the carb thru the 2nd barrel and maybe make it run above idle.

[d510addict]

Well the problem isnt rpms above idle its like it cuts in and out of power and surges/lurches real bad when i accelerate, makes me think this is a dizzy issue.

[d510addict]

So I fucked up my control test by putting premium in (been going back and forth for 6 months trying to compare) and heres what happened. The car was drivable at 10 deg of advance but it was surging and pinging badly, at 5 deg it runs like a top. I tried both settings with vacuum advance on and off and nothing changes. Maybe the head has been taken down more than I thought?

[banzai510(hainz)]

you readjust your mixture.

7 degs should be ok also.

 

go back and forth and mess with it.

 

 

you can always do a feel test on coil if its HOT

 

thats a nice rotor and dizzy cap you got there. Standard Motor Products?

[d510addict]

Oh I have no idea just got it at baxters. My coil hasnt felt hot (coil is from an EI z car so it should be correct), and after driving at 5 deg btdc for a bit I am noticing pinging. I'll do some more messing around with it. I have another head I could try out after a quick refresh, yall think that it would be a wise choice do to so? I am starting to second guess some of the stuff I "know" about the current head as I've had many other problems with it.

[datzenmike]

With valve lash properly set and...

Ignition timing properly set...

 

 

Set the idle speed screw as low as you can. It's the one to the back and near the throttle.

 

Find the idle mixture screw just forward of it on the base of the carb body. Turn it in and out finding the middle point where the idle speed is smoothest and fastest.

 

Turn the idle speed down and repeat the mixture screw adjustment. 

Turn the idle speed down and repeat the mixture screw adjustment. 

Turn the idle speed down and repeat the mixture screw adjustment. 

Do this as many times as needed to get the idle down at about 750-800RPMs... and when you can't improve on it any more you're done.

[d510addict]

Ive already set everything a few times now, while I do not follow that process of setting the carb I have it set to about 800 rpm but ill try that way to reset it.

[banzai510(hainz)]

are these .030 over pistons flattops stock dished type?YOu didnt say.

If stock dished it should be OK.

 

If flattops on open chamber head then I think thats the proplem, I say I think.

 

only way to know for surew is try 100 octane and if you can get 10-12 degs and not pinging aI say its that.

 

But this is a best arm chair guess Im doing.

[d510addict]

They are dished pistons, the head is old and has been abused for many many years. It very well could be that it has more meat taken off than what I can account for. Grandpa had it shaved .030" 18+ years ago then ran hard in a 620 for years. When I got it it was sitting for 7-8 years so I took it in had it pressure tested and checked for straightness. All but 1 valve guide was fine that guide was basically replaced with a custom guide. So that .040" I listed was basically me taking a guess at what has truly been removed. Its been milled twice as far as I know post that .030" shave so .040" ought to be a good guess.

 

I set my carb per Mikes instructions but it was about as spot on as it can get by my ear, I checked the zcar coil for signs of heating up and it was at an ambiant temp. I had to drop my timing back down as it was pinging at 5 deg. I'd like to try out a known working EI dizzy to see if maybe that is the issue but I don't know anyone that can help and I havent been able to nab 1 at the PnP. If I cannot solve the issue I think I may look for an operable head and send it in for a refresh.

[banzai510(hainz)]

Try another dizzy first.

maybe try to find soem 100 octane gas and see if you can up the timming.

 

If they pressure ck the head you have to assume its good.

 

open chamber pistons and .040shave  should not make it that high compression. Im thinking youd be lucky to even hittin 9 to 1 compression if you bout l20 11.35 cc pistons. as a stock L20 is about 8.4 to 1

[d510addict]

Hate to ressurect this but my timing plate teeth go blank 0 5 10 15 20, shoudlnt it be 5 10 15 20?
 

[racerx]

try this:  http://www.davidcmurphy.com/olddat/620tech2.htm#TM

[d510addict]

I purchased and installed another dizzy, this one is from an l20b. Pinging is just is bad if not worse and now it pings badly when cold (likely because of the different advanced curve) trying nee head next.

[d510addict]

Updated