High RPM rich 1st Gear

[vande17941]

Ive got my 230sl idling perfect, running high speed freeways perfect, starting perfect, etc. But, I have one weird issue.....if I accelerate hard in 1st gear, so the revs are rising fast, at around 5800 the car goes rich and bogs and blows a nice rich smokescreen. It cruises high RPM fine and accelerates through that Rev range in all other gears fine.

Pertronix Ignition on 051 distributor with hotter coil
TIMING at 30 btdc deg at 3000rpm
NGK plugs one range hotter
Recent valve job clearances right on
Leakdown/compression  excellent
Injectors perfect spray pattern/open when they should
The WRD closes when hot
The CSV doesn't leak
The solenoid on the FI pump is working like it should.

My guess is that it has something to do with the fuel injection pump and the spinning weights because it only happens when rapidly accelerating through the rev range in first gear at about 5800 or higher or the vacuum/mechanical advance on the dizzy

Somebody who knows more, please give me some ideas! Thx

[Benz Dr.]

Set your ignition timing to 38 degree full advance at 3000 RPM.

[Tyler S]

Not saying this is your problem but I had an issue with it breaking up like that under high load, High RPM. The Pertronix had issues. If you have a timing light, rig it up so you can see the strobe while your driving. If the light starts flashing inconsistantly (cutting out) while breaking up its ignition related. Having a passenger helps.

[vande17941]

Benz Dr? 38btdc at 3000 RPM on a 051 dizzy with California 91 gas 10% ethanol?

Just making sure...don't want to go kaboom!

[Benz Dr.]

You won't. Set your idle timing to 8 degrees BTDC. Since the distributor is supposed to advance 30 degrees you should end up with a total of 38 degrees. Many people forget this initial 8 degrees advance and set their timing at 30 degrees because they get it confused with distributor advance. These two settings work together but are still two different specs.

[vande17941]

I'm exactly at 3000rpm @ 30deg btdc and then at idle roughly about 2 deg after top dead center at idle(moves slightly with varying idle rpm). Unless I'm missing something, I dont see a swing of 38deg in the specs unless we see 8deg atdc  at starter speed.......but it should still be 30deg btdc at 3000 like the specs suggest?

If I'm correct, 30deg btdc at 3000  and +-02 at idle is with vaccum. Vacuum is zero at 3000rpm. At idle without vaccum +-2 and without vaccum about 8deg atdc.

[Benz Dr.]

Run your engine up to 3,000 RPM and then turn your distributor until you see 38 degrees on the front hub and lock it into position. If your distributor is working properly you should see roughly 8 degrees at idle. What you want is 30 degrees of distributor advance plus the extra 8 degrees of initial timing at idle. Leave all of the vacuum lines hooked up - that's the way it will run while you're driving.


  I believe this is a common misunderstanding while setting timing. Looking at the specs for our engines, it will say something like 30 degrees at 3,000 RPM. This is a spec for the distributor and it doesn't include the basic idle timing. Your engine shouldn't ping at 38 degrees because mine won't at 40 degrees. If you set it to only 30 degrees full advance, your engine will run OK but it will lack power and use a lot more fuel.  MB engines are such that they require as much advance as you can run before they will make good power.

I let a number of guys drive my car last fall at PUB. Maybe one of you would like to comment on what full advance feels like.   ( Joe ? )

[vande17941]

I will try it based on your expertise.....but, that much advance still scares the cr@p out me. The car kills it right now power wise.  If it's faster, doesn't ping, and doesn't cut out at high RPM that would be great. Right now at 30deg it is getting 20mg cruising 65-70mph.

I will report back...hopefully not having to report that a top of a piston is glued to the head....ha ha.

Would having the idle retarded 8 degree cause the car to misfire and puke rich at high rpm on a 230sl with 051?

[vande17941]

Those sure look like specs for a 050 and not a 051.

[Benz Dr.]

Those specs are for a 051 distributor. I've been rebuilding distributors for 20 years and that's the info I would use to get the proper advance curve. In the second chart it actually shows the 8 degrees I was referring to and the retard at idle is the amount the vacuum pull rod inside the distributor moves when vacuum is applied. The 8 -14 degrees is the vacuum portion ( of distributor timing ) variation you can have and still be within specs. I should note that you won't be able to see these small variations on your front hub ( timing marks ) and only a distributor tester can give you this sort of fine adjustment.
 
Some distributors will only produce 18 degrees of mechanical ( flyweight ) advance. In that case, I would lengthen the pull rod so that the vacuum portion would move 12 degrees instead of the normal 10. As long as total distributor movement is 30 degrees, ( and this is important ) your distributor is working as designed. Along with this 30 degrees of distributor movement you also need to add 8 degrees of initial timing at idle. Your distributor doesn't produce that extra 8 degrees of advance - you have to adjust it (add it ) yourself. Trust me, your engine won't blow up.

Listen for pinging and retard by 2 degrees if you hear anything. Lots of black smoke at full load may not be ignition related and may be throttle linkage or IP settings. Personally, I wouldn't be pushing my engine past 4,500 RPM unless I was very confident of the internal condition. 

[Naj ✝︎]

I will try it based on your expertise.....but, that much advance still scares the cr@p out me.

I will report back...hopefully not having to report that a top of a piston is glued to the head....ha ha.

No need to be that scared.
Just look at the dizzy spec of a similarly engined earlier 230 SL with vacuum advance and 046 distributor.
30 degrees advance at 3k rpm without vacuum. With vacuum a further 8 to 10 degrees.

naj

[georgem]

What  scares  the beegeezes out of me in all this tech talk, is the thought of the engine of my Pagoda revving out to 5800..I know, I know, the red line is at 6500 but I`m with Joe, treat her with a little dignity - 4500 and she still sounds good. At 6500 I would be waiting for the old whaling call.....................THAR SHE BLOWS CAPN

[vande17941]

I bought mine to drive! And I do! If it blows, that's the price of fun. I drove that thing up Mt. Baldy on a zero traffic weekday morning and the tire tread melted together (205/70-14s don't come in a high performance variety). The motor handled 50min of race driving just fine. The brakes...perfect. the 50 year old car...no problem. Current tires....couldn't handle it. That's technology for you.

I'm going to warm it up, hold the rpm at 3000 and set it with a timing light at 38deg btdc with vacuum hose still attached.

If that doesn't work, I'm going to pop another Pertronix in it just to get the two most obvious solutions out of the way.

I will report back if the motor did not blow me and the rest of the shabang into pieces.

[Benz Dr.]

When you advance your timing you will find that  your idle speed will increase. This is normal and you will likely need to adjust your idle settings to reflect this change. I would also do a split linkage test to see if you have a rich condition at various RPM ranges.

 How many miles are on this engine?

[Benz Dr.]

What  scares  the beegeezes out of me in all this tech talk, is the thought of the engine of my Pagoda revving out to 5800..I know, I know, the red line is at 6500 but I`m with Joe, treat her with a little dignity - 4500 and she still sounds good. At 6500 I would be waiting for the old whaling call.....................THAR SHE BLOWS CAPN

 I very confident that I could give you a more complete technical explanation but my eyes are starting to glaze over.

[vande17941]

Thanks for your help and time.

54,000 original miles with a complete valve job 3000 miles ago.

Now....we have to figure out what a split linkage test is.....

[Jonny B]

Try the main search page, use "split linkage" (with the quote marks) and you get three pages of hits. Read through the first couple and you should find out what you need to know.

The first "sticky" at the top of this section of the forum is "Linkage Tour" read through that, it was one of the hits from the search.

[vande17941]

Thank you for the search tip....that helped.

I don't understand how the split test would affect or diagnose an engine running over 5000 rpms. It appears to me that it verifies idle mixture?

[vande17941]

Woooooo hooooooo! I set it to 38 btdc and it pulled all the way to redline like a banshee.

Once I adjusted the timing, I went through setting the idle again. Had to bring it down 8 clicks and use a vacuum gauge to get the mixture right.

Question: does a car start easier with more advance, or is it the other way around? It starts great right now when it's warm.

THANK YOU THANK YOU. The Benz Dr. Is king!