502 timing after ignition tune up
 

Hello,

decided to replace ignition components on my 502 mpi. Cap, rotor, plug wires, pick up coil, module, coil and spark plugs. All the parts are from boats unlimited.

Got the boat to TDC, marked the distributor to block with a line as well as the distributor under the cap before taking it apart.
Replaced everything and lined up the marks on the block and have a hard starting rough idling (with the throttle bumped up) engine. I have the a and b pins jumped in the dlc plug. Rpms don’t hold too steady (-/+ 300 rpm) at 1,500 rpm and making it difficult to check set timing. Cleaned off the timing marks, and even painted them and still no luck.
Any advice is appreciated.

thank you

check your plug wires. firing order

I have verified they are the right spots. When I set my timing gun to 8 degrees and shoot the crank, it’s past 60°, when I twist the the distributor and start getting to 50 and 40 the rpms start climbing much higher.

if you never removed the distributor there is no need to mark things or move it to adjust the timing, why did you need to get it to TDC ?

I removed the distributor to replace the pick up coil when I was doing the ignition tune up.

So I have it running and idling good now. However my aligned marks before removal and now are probably 1/2” off clockwise or better. I set my timing light to 8° and rotated the distributor further than I thought I needed to and got the tdc line on the crank and the timing cover mark aligned. Is this normal to be that much different?

I’d post a picture but can’t until I reach 10 posts

if you had to reclock the distributor and its that far off then I think the wires were one hole off when you replaced them

Hmmm. I’m looking at my old cap with the wires still on. I removed one wire at a time, and pulled them back, ran the new wire to the plug and put it on the new cap accordingly. I also looked at the new cap for any markings to indicate cylinder 1

I’ve looked at drawing of the distributor, but does anyone have a real photo with the #1 cylinder highlighted or circled for reference?

#1 can really be any place on the cap if you wire it correctly, but most aim the pointer towards #1 cylinder, if you had to crank the engine to get the distributor to fall into the oil pump ? then it wasn't in the same place as when you removed it

Didn’t have to crank the engine to get the distributor in. Just have to rotate the distributor slightly to fall into place.

Well what you've described doesn't make sense to me, I guess all this is above my pay grade and its 5 o'clock time for a :ernaehrung004:

could
i have the rotor off 180° inside the distributor? Wouldnt think it’s even fire though

I edited the photo to make it easier to see, but the white marks where my reference marks originally





https://cimg1.ibsrv.net/gimg/www.off...b4ad606b2.jpeg

NO, the rotor is keyed just like the cap, maybe you were not on the compression stroke when you were thinking its TDC, if thats the case then you were 180* out

EDIT: your picture as I said before looks to be 1 hole off all the way around the cap when replacing the wires, good thing is its fixed

yea like I had the rotor and key flipped 180° Inside the distributor. But if It flipped would even start or run?

But now looking at other pictures their distributors sit how mine is now in relation to the block. Picture I found
https://cimg0.ibsrv.net/gimg/www.off...8001b3980c.png

And even this illustration has it sitting similar



https://cimg8.ibsrv.net/gimg/www.off...2e7314fc3d.png

Picture of the distributor in relation to the engine now.
https://cimg7.ibsrv.net/gimg/www.off...cb4df00c5.jpeg

Anybody have a picture of their 502’s distributor positions? Thanks!

You almost never get a dist to fall back in after lifting out. As you lift it up the cut of the gear rotates the dist which turns the oil pump drive and then it doesn’t line up going back in without rotating the engine. I think you’re a tooth off which will work if you can turn the dist that much. I would reset it.

that makes sense. What would be the way to go about that

why does the #7 wire look out of place

thats the bottom of the #2 your looking at

you need to turn the oil pump drive w/ a long flat headed screw driver.then the distributor will drop in,if its still off,turn it a little more and try again.hope your on the #1 compression stroke and not #6.

had it running in the driveway with it set as is right now.

This ^^^^^
I have Never dropped a dist back in a chrvy V8 without having to turn oil pump rod a hair back to get dist back in same place. Use a big long flat blade screwdriver.

Looking at your picture compared to mine(502 mag) you are off a tooth. The 2 electrical connectors I thing face almost straight back toward the transom. I definitely remember the cap hold down screw ends up almost under the intake plenum and difficult to get too.

so can I pull the distributor up and rotate it back counter clock wise?

you need to turn the oil pump drive a liitle back so distr. will go back to where it once was.

Turn the engine over till the timing mark is on 8* compression stroke. Take the cap off and see what wire it is pointing at.

Bstocky, get your boat going?

How old is your balancer? I've seen balancers way off too.

Pull # 1 spark plug. Place your finger in the hole. Have someone bump the starter until you start to fell compression and stop at this point. Note how the timing marks are lined up on the balancer then hand rotate the engine to align the balancer mark-groove with the pointer. Pull distributer cap and note which wire location the rotor is pointed at. If not at #1 or REAL CLOSE remover the distributer and re install it so it does point to # 1. You will need to slighlty rotate the rotor counter clockwise to account for the gearing. As stated it may be necessary to rotate the oil pump slot to line up with the dist.

Mark

Spark timing