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Guest Anonymous

74 tii question...

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Guest Anonymous

My mechanic has pinpointed what he thinks my problem is in not getting full power between about 2000-3000 rpm. On the '74tii, it's got a vacuum advance distributor with a decel valve sitting on top of the air cleaner. The decel valve is an emissions device that slows down how fast the engine returns to idle after coming down from acceleration. He thinks this valve is leaky, and I am losing vacuum. The two possible fixes are: 1) replace distributor with a new mechanical advance dist, and bypass the vacuum; or 2) somehow find a new or good condition decel valve.

My question is which is the better alternative? If distributor, which one? If decel valve, are these available? Does anybody out there have either one in good condition for sale?

Many thanks,

Andy74tii

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Guest Anonymous

there is such a thing as a decel valve on a tii. Well mines a 73 model so i can't say how the 74 differs. I have a cold start valve located on the intake plenium that has an fuel hose from the K-pump attached to it. I have nothing resembling that on the air cleaner. Do you have the stock tii setup? or a retrofited EFI from another model? The tii's dizzy is always the mechanical advance unit.

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Guest Anonymous

The 74's do have a slightly different setup than the 72-73 tii's.

My quick answer is that if you don't have emission checks, then just get a correctly-curved vacuum-only distributor and junk the emission setup. You'll probably happier with that in the long run than spending money on a new valve (if they're even available).

However, before spending money on that, I would question the "thinks this valve is leaky" line from the mechanic. Vacuum leaks are simple to diagnose so he better know for a fact that it is leaking before sending you down that path.

Matthew Cervi

'73 tii

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Guest Anonymous

URL: http://www.my2002tii.com

Andy,

As a fellow 74tii owner, let me pass along some thoughts.

Historically the 74tii was a victim of some unfair lobbying with exhaust emissions. The Feds thought it was a polluter, and were under some other pressure by the lobby of the Big 3 auto makers to put harsher controls on foreign auto makers to make them more expensive or less of a performer than the cars they competed again. Hence, BMW gave up and quit selling them for the 75 model year in the USA. Elsewhere but here, there are 75 TIIs which as I recall reading are more like the 73 engine setup with respect to emission controls. Unfortunately our 74's were whacked in some way in being a one-off setup for smog stuff compared to our round light TII brothers. You can de-regulate your car and make it more reliable!

If I were you...

First of all, I would get a second opinion. Call Jack Fahuna in LA. He knows TII motors inside and out and can most likely tell you what your options over the phone. Explain what you are posting here, and that will be a starting point for next steps. That will get you to the root cause of whether the emission stuff is your problem or not.

THEN...

Going forward, unless you have to pass smog on your car in Houston (I can't remember if that's required or not) I would ditch that smog stuff anyway.

usa-tii-smog.jpg

On my rebuilt Stella, I will have converted all of my engine over to Euro late model TII components which have no smog plugs.

euro-tii-smog.jpg

Up top, you need a different top log manifold that only has the brake booster hose. Your 74 air box has some hose plugs in it, you need to cap those off or find a 72 -73 air box center section (the part without the snorkels) without those and use it. End result is a simpler engine to diagnose and less vacuum leaks to deal with, plus it just looks better. WIN-WIN.

Distributor - unless it is worn, don't consider replacing it. WORST CASE: A new one does not have the precious timing curve required for a TII, so you will be creating new problems. I had Jack rebuild me one to TII spec, without the 74 vacuum retard mechanism which you are speaking to. A simple plate covers the old spot where it was. The car did excellent with that setup before I tore it down. A new distributor must be put on a Bosch distributor machine and have the TII curve applied to it. This is a tedious, somewhat manual process. Jack's the ONLY guy I know who still has a machine who can build one from scratch. Consider that kind of work $350 or more to have a ready to go replacement distributor to replace the one you have. It was amazing how much better the car ran before I put in the right distributor. Somewhere before I owned the car, a mechanic, unknowingly put a replacement dizzy in there without the TII advance curve, and the thing was not running up to it's potential.

I have another complete with runners 74 TII Euro log manifold if you're interested, drop me a line. The air boxes are hard to come by. I have been buying up all I can get my hands on the center sections. I only have one for my own use right now, but a 73 or 72 unit might be found by some of the 02 places (2002 Haus, 2002 Ad, Double 02 Salvage, or Ebay or HERE)

I hope that helps!

Keith

'74tii-Stella

http://www.my2002tii.com

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Guest Anonymous

Before you tear into this, spend a lot money and change a lot of things, replace the vacuum lines and bypass or replace the decel valve. If that improves driveability, you problem is solved.

Delia Wolfe

'73tii

Inka (aka "Orange Julius")

#2762756

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Guest Anonymous

I had a bad decel valve on my '74tii. I also had a bad dist. On advice, I went to a regular 008/002 dist. so that I wouldn't have to worry about the vacum stuff. Worked out. Car idles well. I had been told that my k-pump was set up different because of the vacum stuff. I've heard varying opinions on that.

Hope that helps.

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Guest Anonymous

Read: I didn't know any of this stuff! Thanks for

sharing

Michael

72 tii

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Guest Anonymous

but Keith is spot on, accurate and the only thing I can add is the 74 is a vacuum retard distributor, retarding the timing on trailing throttle and at idle to meet the emissions requirement, it advances mechanically. But again Keith is correct, this is the only dizzy to give your tii the correct curve, may want to read my thoughts on Roadfly too.

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Guest Anonymous

Keith, excellent information as always. I do trust this mechanic (he's Bob Murphy's mech as well), but I like your advice. What do you think of this plan:

1. Remove decel valve, remove all vacuum hoses to and from dizzy, intake, decel.

2. Block up openings on intake

3. Take off vacuum retard on dizzy; fix metal plate to close opening.

Are you saying that my car should run well under this setup, without any vacuum advance at all. I think Pikachu mentioned that the vacuum on this dizzy is only for backing off acceleration, the rest of the time the advance is mechanical, yes? This of course assumes that the dizzy is fine, which I believe it is.

Later, I would like to try to retrofit a '72/'73 center section air box and an intake.

What do you think?

MANY MANY THANKS!!!

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Guest Anonymous

Excellent advice from you and Keith. You both seem to be recommending I keep my distributor, and bypass the smog stuff. I did not realize this was an option. In Texas, of course, my car is not subject to emissions testing. So, that would work here. I didn't realize that the distributor would still work without the vacuum feed.. . THANKS ...!!

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Guest Anonymous

Andy,

You're almost right, Pikachu is totally right on. The 74tii distributor is vacuum retard, not advance as I stated before. It's easy to get the advance/retard terminology mixed up until you've dove in and worked on it yourself before.

Second, as I stated before, I didn't rebuild my distributor, Jack Fahuna did. Hence just covering up the hole where the vacuum pot was may not be all he did. It's worth a call to have either you or your mechanic call him for the details.

All those things you sound like a plan. Plugging up the big holes in the manifold are not as easy as they look. Ask me how I know!!!

Good luck with the project.

Keith

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Guest Anonymous

up the vacuum ports on the intake log with rubber vacuum plugs from your local parts store. They are really not plugs, they are more like caps or 1" hoses that are sealed on one end. They secure on the vacumm boss with a small hose clamp.

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