Switched from Marelli to Bosch

sammygon1 · 10-21-2003, 07:40 PM

My marelli broke it's distributor cap and I am switching to a Bosch. Only problem is I cranked the engine over when I had the Marelli out and the Bosch not in. So now (correct me if I'm wrong) I have to:

#1 set engine to TDC. The mark to the right in the set of two close marks on the crank pulley.

#2 Align the rotor tip with the notch in the distributor and point the rotor tip towards piston #1.

#3 Bolt everything down adjust timing and I should be good to go, right?

Just double checking to see if I'm missing anything as I plan to do this tommorrow. And yes I've read the 101 projects, and the engine rebuilding book. Any hints would be appreciated. Thanks, Sam

Tim Walsh · Tim Walsh's Garage

err make sure your cams and distributor are in alightment as well. aka you're at TDC before your power stroke

sammygon1 · 10-21-2003, 07:51 PM

Okay, I'm not quite sure what you mean by: "make sure your cams and distributor are in alignment.." Care to shed some light on it for me. Thanks, Sam

sammygon1 · 10-21-2003, 08:26 PM

Okay I know you guys have to have some tips for a porsche newbie.

Tim Walsh · Tim Walsh's Garage

sammy,
there are 2 TDC's. One "on" cam and one "off" cam . I don't remember which one you need to set it to. What you need to do is open up your intake valve cover and watch what the camshaft for cylinder #1 is doing. I think you need to set it to have the rotor point to #1 when you have TDC and both valves are closed on cylinder #1 aka just before it's power stroke (just leaving the compression stroke and about to fire for the power stroke)

Hope this helps

sammygon1 · 10-21-2003, 09:13 PM

Is there an easier way to determine TDC for #1(not pulling off a valve cover), can I just install at TDC try to fire it up, if it doesn't run, pull distributor rotate crank pulley 360 degrees reinstall and try again. This can't be the most delicate method but is it possible to do this way, or am I risking damaging or breaking something? Thanks, Sam

Fishcop · Fishcop's Garage

Set your crank to Z1 and observe where your rotor is on the distributor. There is a notch at cylinder 1. If you are on Z1 and cylinder 1 start it up and tune with a scope.

sammygon1 · 10-21-2003, 09:58 PM

My pulley does not have a Z1 mark only a pair of marks, and then a couple of marks unevenly spaced.

ajserrano · ajserrano's Garage

Hello Sammy! Is your "Marelli Twin-Plug Distributor" for sale? What size engine is your Marelli installed in? Early or late style case?

Does your distributor look like this?

here is another photo...

Please let me know.

THX!!!

Armando
http://www.pbase.com/9146gt

Wayne 962 · Wayne 962's Garage

I would guess his is a single-plug distributor.

Sammy, if your engine is at Z1, it could be at TDC for cylinder number one, or TDC for cylinder number 4. The best way to tell where it is located is to remove the valve covers on the left hand side and check to see if the rockers wiggle when you're at Z1. If they wiggle, the valves are closed, and you're at TDC for cylinder number one. They shouldn't both wiggle if you're on TDC for cylinder number four.

-Wayne

-Wayne

limble · 10-22-2003, 06:18 AM

To find TDC can't you also hook up a compression tester to #1 and turn the engine over until you see the highest pressure readings? I did that when I replaced my dizzy. Compression testers aren't that expensive.
Mike

Zeke · 10-22-2003, 06:21 AM

Another way to tell TDC w/o removing covers is to monitor compression on the upstroke while turning the crank with a socket on the fan nut. All plugs should be removed and you will need a compression tester. You have to be able to turn the crank with fairly rapid motions so that the air will move the gauge. On the exhaust stroke, you will get nothing on 1, but a jump in the needle on 4. After a couple of trys, you should know that you are TDC compression for no. 1

Rot 911 · 10-22-2003, 06:29 AM

Or if you don't have a compression tester and don't want to remove the valve cover then do just as you describe in your initial post. If the car won't start or runs incredibly rough, you are 180 degrees off on the distributor. Pull the distributor, turnt the rotor 180 degrees and reinstall. You will then have it in correctly.

Early_S_Man · 10-22-2003, 06:42 AM

Sammy,

Don't try to run the engine with the timing 'guessed at' ... an engine fire can result if you set the timing to fire on all the cylinders while the intake valve is open!

Your crank pulley should have a total of three notches associated with cylinders one and four ... as you rotate engine clockwise there will be two notches close together for 35° and 30° Before Top Dead Center, then a bit further over, the Z1, or TDC notch. There are isolated notches for Z2 and Z3 for cylinders #3 and #6, and #2 & #5, respectively.

Jack up the left side of the car 8" - 10" ... and pull both valve covers, then turn over engine until both rockers are loose on cyl #1, and look for the third mark/notch as decribed above. Use a test lamp to see when your points open, and rotate distributor body until points open when the TDC mark coincides with the notch on the fan housing or crankcase vertical split ... as you turn the engine over with a wrench on the alternator pulley nut.

Check your work by turning the engine over a few more times and MAKE SURE the test lamp comes on each time the TDC -- Z1 notch comes up for cylinder #1!!!

limble · 10-22-2003, 07:52 AM

Quote:

Originally posted by sammygon1
My pulley does not have a Z1 mark only a pair of marks, and then a couple of marks unevenly spaced.

The Z1 mark is really hard to see. I cleaned the entire pulley with degreaser. I took a small mirror and was able to locate it.Then I put a little paint on a piece of foam and ran it over the mark. Came back with more foam and wiped off the excess.
Mike

Early_S_Man · 10-22-2003, 08:27 AM

Sammy,

Maybe this will help ...

john walker's workshop · 10-22-2003, 08:31 AM

remove #1 plug. turn engine clockwise by hand and notice the resistance as each cylinder pumps up it's compression on the way to TDC. when you reach #1 there will be no resistance. line up the Z1 on the pulley to the fan housing mark, and install the distrubutor with the rotor tip ponting to the notch on the distributor body. you will be in the ballpark enough so it will run. then set the timing with a light.

sammygon1 · 10-22-2003, 08:46 AM

Excellent, thanks for all your advise guys I'm going to go ahead and pull the valve covers and give it a try today. Sam