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east tx skier
02-23-2006, 12:43 PM
I installed a new distributor cap on my 351W HO (Prestolite w/ electronic ignition screw down cap). Looking for something unrelated, I came across an archived version of this forum where someone had raised a question pertinent to my situation. I didn't really think it got resolved, so I'm repeating it here. The original question involved timing, but someone mentioned turning the distributor. This is where I started getting confused.

From all I can tell, my distributor cap was whatever came on the boat. New one is tan (PCM). Same as DIM sells.

Quesiton. Is there a front and back (right and wrong way to screw it on)?

Question. Do the receivers line up like the old one did (I'll be fishing the old cap out of the trash when I get home)?

Question. Anyone who has made this swap from the old black cap to the tan one, did you make any adjustments to keep everything firing the same.

/edit. Here's the link to the archived discussion.

http://www.tmcowners.com/teamtalk/archive/index.php/t-478.html

//edit 2. Just reread it. Thinking that turning it might be more specific to clip down caps.

The tan one had a tick mark on the inside of it. I instinctively put that toward the front of the boat/engine. Now I'm wondering if that indicates the "1" in the firing order, which is aft. :confused:

grease
02-23-2006, 02:02 PM
Timing (turning the distributor) should not change because you changed the distributor cap. As long as you have the wires in the same postion as the old cap and going to the same cylinders every thing should be OK. I have made the change, but my new cap was also black. If you squat in from of the engine, cylinder #1 is the first one on the left side (Left side cylinder 1-4, right side 5-8). Bring the engine to top dead center and see if the rotator button is lined up with the cap going to cylinder #1. The fire order of your engine with left hand rotation is 1-5-4-2-6-3-7-8. Hope this helps

east tx skier
02-23-2006, 02:40 PM
Thanks, grease. One question though, my manual says the firing order is 13726548. :confused:

grease
02-23-2006, 03:03 PM
Sorry, your mannual is correct. The firing order I gave was for a big block 460. It seems I remember my cap had a notch on it so that it would only go on one way. I will check it tonight

east tx skier
02-23-2006, 03:08 PM
I'm told mine should only go one way, too. Since it's on, maybe I got it right, but it looked as if it would go on either way. Let me know what you see.

Workin' 4 Toys
02-23-2006, 03:32 PM
I didn't know there was an order other than 18436572;) :rolleyes:

east tx skier
02-23-2006, 03:41 PM
Let me guess, Chevy?

Leroy
02-23-2006, 03:50 PM
Way back, they would go either way I'm pretty sure. I alway just pull off the wires and put back the way they came off.

You'll know if you did it right as soon as you do the key test.

east tx skier
02-23-2006, 03:57 PM
Leroy, that's exactly how I did it. Unscrewed the old one with the wires still on and moved it forward of the distributor. Installed new one. Moved wires to their new location one-by-one. Then I replaced the plugs and as I did this, I replaced the wires one at a time.

Will it not start or will it just run extremely crappy?

roddydog
02-23-2006, 04:15 PM
Just jumpin' in. If you got the order right, no problem, if you didn't it will start and yes it will run extremely crappy. No harm should come to it but you will know right away.

martini
02-23-2006, 04:24 PM
Usually the screw down caps for the Prestolites have a notch on one of the mounting ears that are attached to the cap. The corresponding distributor body mounting flange has an "L" looking bracket on one side, were the other side is just flat. Hence making it near impossible to put it on wrong. It should line up and seat flat, where as if you tried it the other way around it would appear to be ill-fitting.

NSXBill
02-23-2006, 04:35 PM
There are automotive replacement parts for the cap and rotor on the clip-down Presolite for Ford. I used to get them at NAPA for a LOT LESS than boat parts. Take your old parts to NAPA or where ever and have them match up to old MOPAR cap and rotor (same for cond and points for anyone still using them). CAUTION - some automotive caps have a very small vent hole in them. Fill it with silicon caulk (to block flame path) and drive on. Be sure to retain the old cap gasket and use it though, auto won't come with one.

east tx skier
02-23-2006, 04:55 PM
Usually the screw down caps for the Prestolites have a notch on one of the mounting ears that are attached to the cap. The corresponding distributor body mounting flange has an "L" looking bracket on one side, were the other side is just flat. Hence making it near impossible to put it on wrong. It should line up and seat flat, where as if you tried it the other way around it would appear to be ill-fitting.

That's what the mechanic told me, too. I could've sworn it could have gone on either way. Maybe I got it right and should not worry about it.

Nah, I'll worry about it just for good measure.

NSXBill
02-23-2006, 04:57 PM
Clip-down cap (has screws holding clips on) has a notch.

east tx skier
02-23-2006, 04:57 PM
There are automotive replacement parts for the cap and rotor on the clip-down Presolite for Ford. I used to get them at NAPA for a LOT LESS than boat parts. Take your old parts to NAPA or where ever and have them match up to old MOPAR cap and rotor (same for cond and points for anyone still using them). CAUTION - some automotive caps have a very small vent hole in them. Fill it with silicon caulk (to block flame path) and drive on. Be sure to retain the old cap gasket and use it though, auto won't come with one.

NAPA was out and my local CC dealer (I have no local MC dealer) had it for less and in stock. They beat NAPA on every part price, but the rotor.

Workin' 4 Toys
02-23-2006, 10:55 PM
Let me guess, Chevy?Yes, sorry, I thought you had your answer already. I was just kidding.

SKI*MC
02-23-2006, 11:13 PM
I really wish i could comment on this, i went through all the same things here, but everyone else seems to have nailed it. Job well done!

east tx skier
02-23-2006, 11:49 PM
WFT, I knew you were kidding. I was just guessing. Got home and looked and, indeed, there is a flat side on one of the mounts through which the screw goes. I had it right. Set the old cap over the new one and the towers line up exactly the same. Supposed to get close to 70 this weekend. I may take it out and run it just for kicks.