Tuning a DZ 302

[Tony_H]

Guys this is my first post. I've always loved this forum but never have had a super car that fits in. I do have a 69 Pro Touring Camaro but that's for different forums. The reason I'm posting is because I work on classics as a side job to my real job. I have a 69 X-33 that has been sitting for a few years I am in the middle of getting it back in shape for a customer. One of the questions that I have is setting the timing at 4 degrees. Most small blocks I set at 14 to 16 initial and shoot for 32 to 34 total. This 302 runs lazy at 4 degrees initial, if I bump it up to 14 or 16 it sends my total over 45 degrees I don't want to modify the dist. on this original car. What are you guys doing? Also the dwell seems to like 25 degrees over the recommended 30 degrees. Plug gap is at 35 degrees.

[Kurt S]

Modify the distributor. The advance is way lazy in that era - comes in way too late.

[Tony_H]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tony_H</div><div class="ubbcode-body">Guys this is my first post. I've always loved this forum but never have had a super car that fits in. I do have a 69 Pro Touring Camaro but that's for different forums. The reason I'm posting is because I work on classics as a side job to my real job. I have a 69 X-33 that has been sitting for a few years I am in the middle of getting it back in shape for a customer. One of the questions that I have is setting the timing at 4 degrees. Most small blocks I set at 14 to 16 initial and shoot for 32 to 34 total. This 302 runs lazy at 4 degrees initial, if I bump it up to 14 or 16 it sends my total over 45 degrees I don't want to modify the dist. on this original car. What are you guys doing? Also the dwell seems to like 25 degrees over the recommended 30 degrees. Plug gap is at 35 degrees. </div></div> Thousandths I meant.

P

[Salvatore]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kurt S</div><div class="ubbcode-body">Modify the distributor. The advance is way lazy in that era - comes in way too late. </div></div>
I agree with Kurt. Set the points at 30 and the timing at aroound 12 at idle. Try to have your distributor guy bring the advancement in around 2,500 to 2,800 rpm's. That will be easy once you have the distributor on the machine and redo the curve. I say run some R44 plugs or that equivalent gaped at 32 and set the valves cold at about 25 lash. Make sure carb is not leaking and I would change the fuel filters too. 302's are lazy not matter what unless you change some gearing around. Of course fresh gas with maybe a couple gallons of high octane &quot;leaded&quot; fuel mixed with 93.

[Tony_H]

Thanks guys.

[ZLP955]

I found optimum for my conditions is 12-14 initial, and 36 total coming in at around 2,500 rpm.

[COPO PETE]

what he said ^^^ 14 initial. 36-38 total. Have it all in 2500-3000rpm.

Plug gap .028-.030.

WE dont even run vaccume advance anymore. Plug it off.

[ZLP955]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: COPO PETE</div><div class="ubbcode-body">what he said ^^^ 14 initial. 36-38 total. Have it all in 2500-3000rpm.
Plug gap .028-.030.
WE dont even run vaccume advance anymore. Plug it off. </div></div>
What plugs do you find work best? Currently using AC R45S......

[Salvatore]

R44S work good for me. I also think I have used Autolite 85's??? I believe.

[Mr.Nickey Nova]

You can also try NGK XR5 V-Power plugs,thats what i use.Heard good things about NGK plugs.

[PxTx]

X2!

[COPO PETE]

NGK V power plugs work good. Usually run 7's.

Also keeping the carb absolutly clean of varnish and in tip top shape I have found is a must for peak performance.

[Tony_H]

Found the bushing that controls the amount of total timing was gone along with a couple of other little issues. Ended up with 14 initial and 38 total with the vacuum advance blocked off with a BB in the line. The Sun machine he ran it on was from the 60s. It was pretty interesting.

[Plowman]

That is so cool looking. Look's like he knows what he is doing. Good job.

[Salvatore]

its where you gotta be Tony!

[Kurt S]

38 deg total at what rpm?
You want that vacuum advance hooked up - remove the plug. And make sure it's connected to manifold vacuum, not ported vacuum.

http://www.camaros.org/pdf/timing101.pdf

[Tony_H]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kurt S</div><div class="ubbcode-body">38 deg total at what rpm?
You want that vacuum advance hooked up - remove the plug. And make sure it's connected to manifold vacuum, not ported vacuum.

http://www.camaros.org/pdf/timing101.pdf </div></div>

All in by 3200 RPM. That is a good write up and makes allot of sense. A Z28 has 3.73 to 4.11 gears and turns allot of rpms when cruising. I know your vacuum drops out under acceleration but when you are cruising at 2800 RPM with a load on it wouldn't the vacuum come up and add more timing causing detonation that you may not hear. With 11.1 compression and todays fuel I would be worried about that.

[PxTx]

Tony, you can place a temp vac gauge to verify this but the highest vac will always be with your foot out of the throttle. Light cruise with a slight load should not allow the vac advance to add enough timing to detonate with a proper tune.

My dad has always made a point with theze timing 101 articles to note that the vac advance needs to be limited to no more than 10 degrees due to the typical pump gas we have. I'm on my phone and don't want to go into details. Though engine tunes and config vary- they all act surpisingly similar in off throttle conditions (highest vac)..

[Plowman]

Having vacuum advance at light cruise will help with cylinder temp's to cool down. The cylinder at light cruise will be the leanest and cylinder temp will go up. Having manifold vacuum advance at 10 deg max at idle,with a &quot;Hot camshaft&quot;,will help to have leaner mix at idle and won't load up. Also help's at cruise too lower cylinder temp by add timing.

[Kurt S]

John (who wrote the article) runs his Z that way on pump gas - no issues.
As do many others.

I think you could have the advance come in sooner that that, btw.

[Tony_H]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kurt S</div><div class="ubbcode-body">John (who wrote the article) runs his Z that way on pump gas - no issues.
As do many others.

I think you could have the advance come in sooner that that, btw. </div></div>

You guys have me convinced. Ill hook it up and see how it performs.
These forums are very educational, don't know what we would do without them.
Thanks

[Salvatore]

after I had my distributor done about 12 years ago I never rehooked my vacuum advance with no issues. All advancement is in around 2,800.

[COPO PETE]

Iv never had issues running vaccume advance unplugged. I find running with it off the engine runs cooler. The only down side is it takes a few extra minutes to get the car to &quot;warm up&quot; vaccume Advance builds heat and can cause pre detto if you run poor fuel with a true 11:1.

[danachevroletfor1967]

When my 1969 Z/28 was idling poorly and almost stalling at a stop sign or red light my mechanic, in addition to other things he did to the carb, made the vacuum advance inoperative. The car has run fine and no longer has the decreased idle or stalling at a stop.

[Tony_H]

I hooked up the vacuum advance. I had to turn the idle down because of the extra timing. It seems to run pretty good. I do have to shoot a little extra fuel in to get it to start.