advanced distributor settings

[RallyBob]

Well, since the photos aren't there, I can guide you to the original content. It was in the 'Turbo EFI Manta' thread.

http://www.opelgt.com/forums/27331-post148.html
http://www.opelgt.com/forums/27332-post149.html
http://www.opelgt.com/forums/27333-post150.html
http://www.opelgt.com/forums/27335-post151.html
http://www.opelgt.com/forums/27338-post152.html
http://www.opelgt.com/forums/27341-post153.html

These posts show the pics and the descriptions you are looking for.

Bob

[opeletti75]

Originally Posted by soybean Thanks Bob, Gary. Jarrell

bob what size drill did you use to tap the limit scews on an advanced distributer make up.

[RallyBob]

Originally Posted by opeletti75 bob what size drill did you use to tap the limit scews on an advanced distributer make up.

I have no recollection...whatever worked with a 4mm set-screw!

[Paul]

Try a 3.3 mm or a #30 drill..... or maybe even 1/8"

[jordan]

4mm x.35 fine thread in steel would use a 3.60mm (0.141") drill bit.
4mm x.7 coarse thread in steel would use a 3.30mm (0.129") drill bit.

[Paul]

a #30 drill is .1285"
a 3.3mm drill is .1299"

a #28 drill is .1405

[opeletti75]

thanks for all your help guys,got it.

[opeletti75]

Originally Posted by RallyBob I have no recollection...whatever worked with a 4mm set-screw!

what advance would you use on a 1.9 motor with flat tops ,425 lft,268 dur,sprint man,and big head valves,i have everything together on the advanced dist.mod except for this dont want to be hastey.thanks for all the great info,cant afford to buy much.

[hrcollinsjr]

Quick question. I thought "street" engines worked better with the vacuum advance still functional. Yes or no?

Years ago before I knew about this list I set up three different distributors, two for the track and one for a street engine. I kept the vacuum advance function for the street engine. It really came to life after the modification. It had a 32/36 Weber, Isky OR66 Hyd. cam, and flat top pistons. I set initial timing at 5 deg. adv. and total at 38 deg. I set the race car up similarly but with the vacuum advance plate "pinned" to prevent movement. The owner was setting it by total advance only before. With the engine hot it was hard to start and he would have to readjust the timing to get the engine to start easier and then reset it until I modified his distributor.

Harold

[2 Fast 4 U]

Originally Posted by opeletti75 bob what size drill did you use to tap the limit scews on an advanced distributer make up.

M 4,0

Pitch 0,70
Inner Ø 3,442
Drill Ø 3,2

Pitch 0,50
Inner Ø 3,599
Drill Ø 3,5

Here are some other metric thread sizes and the drill Ø in mm & "

[Paul]

Originally Posted by opeletti75 what advance would you use on a 1.9 motor with flat tops ,425 lft,268 dur,sprint man,and big head valves,i have everything together on the advanced dist.mod except for this dont want to be hastey.thanks for all the great info,cant afford to buy much.

The distributor for the 1975 models works well with your specs above. It has a total advance of 25*, it has no vacuum advance so its all mechanical. The vacuum pod that is on it retards 5*. Helps the engine return to idle and for emissions, I think. With this distributor you can set it up with ~8 degrees advanced for improved throttle response and keep total timing below 36*.

[RallyBob]

Originally Posted by opeletti75 what advance would you use on a 1.9 motor with flat tops ,425 lft,268 dur,sprint man,and big head valves,i have everything together on the advanced dist.mod except for this dont want to be hastey.thanks for all the great info,cant afford to buy much.

The camshaft is the determining factor. That cam has pretty low duration (214* @ .050" as I recall), so you should retain the vacuum advance. You could limit the total mechanical advance somewhat, and increase the static timing a bit. Not knowing what year distributor you have, it's hard to say how much to limit things. But as a baseline, I'd go with somewhere between 6-8 degrees at idle (900-1000 rpms), keep the vacuum advance, and limit the total to 36-38 degrees. Just how much vacuum advance you will have depends on the vacuum cannister....early ones (71) had a lot more timing compared to the later ones (73,74).

I only contemplate removing the vacuum advance cannister when the duration @ .050" approaches or surpasses 225*. Below that you should have enough manifold vacuum to comfortably retain the vacuum advance mechanism.

Bob

[opeletti75]

Great info as always, want to give you some more info, I have a 75 distributor and a streetsports cam from c/r 6 to 8 degrees still sounds good right? The old catalog from the 80's says 425 lf 268 duration, thanks again merry christmas Bob[/QUOTE]
I hope your not mad for saying merry christmas, but I know you're not jewish so I'm not going to say have a nice Hanukkah.

[RallyBob]

Originally Posted by opeletti75 Great info as always, want to give you some more info, I have a 75 distributor and a streetsports cam from c/r 6 to 8 degrees still sounds good right?

The 1975 distributor already has NO vacuum advance. It only has a vacuum retard. It has 25 degrees of mechanical advance already. So, if you set it at the stock 1975 setting of 5 degrees BTDC, you will have 30 degrees of total timing. This was done to reduce emissions (limiting the total advance that is). If you set it at 8 degrees, you'll have 33 degrees total. This should work okay with that cam. While you could probably add another 3 degrees of timing to get the total up to 36 degrees without running into detonation issues, I'd be concerned that 11 degrees of timing at idle might be too much....it would probably be tough (slow cranking) to start, especially when the engine is hot.

The old catalog from the 80's says 425 lift, 268 duration

That is the advertised duration number, not the @ .050" number. It also depends when you bought the cam...the older cams were designed when Carl and Smitty ran C & R. The 'street/sport' cam was also called the CR-149, which was .425" valve lift, and 268* advertised duration, with 212* @.050" duration. I changed the 'street/sport' cam to a different profile in the early '90's, called the CR-149A. It had a little less valve lift, but two degrees more duration. It idled smoother, which was the primary reason I changed it.

Bob

[jeff denton]

I hope everybody studying all this is catching the importance of understanding and checking TOTAL timing. The initial timing and various advance and retard devices are just for comfortable idling characteristics.
Total timing is kind of important for getting the most performance out of your engine when it is not idling, and what kind of gas you buy for it, and how long your engine will last!