Can't rev past 4500

[Fishcop]

Okay here's what I know. I've refreshed the engine with new gaskets, dialed in the cams, rebuilt the carbies, new fuel and air filters, plugs etc...

I cannot get the engine to run past 4500 rpm, timing light indicates that I'm definitely NOT getting full advance and the tacho goes wild as I hit 4500. The distributor is the original Marelli and is on my "must change to Bosch" list. Engine definitely advanced before rebuild.

The one screw up I did make was to put the red + wire to the coil onto the black - wire's side. The result was smoke from the distributor and a burnt insulation wire on the new set of points. I could not see any real damage to the points, so I shrink wrapped new insulation around the white wire and reinstalled.

What do you all think, could this stupid mistake have (a) damaged the points irrepairably (b) stuffed the coil (c) nothing at all, and my problem is fuel or something else?

The car is running really well at low to mid revs, but still has the previous flat spot off the lights. My wrench has gone over the car as best he can, brilliant with later 911's, but being my age (30's) has not really worked on older 911's with carbs and points.

Let me have it, brain-storm!


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John Forcier
69 911T

[roGERK]

OK here's a couple of obvious ones to check out first:

1) Are you sure the throttle linkage is OK i.e. - goose the throttle from the engine compartment not from the gas pedal.

2) Have you checked the rev-limiter in the rotor arm? Its a very simple mechanical device and if that little er... "fire" in the distrubutor damaged the arm, it may be malfunctioning.

Here's some other general points. One of the really nice things about old 911s is the tach is hooked up to the distributor. One of the first signs that the points are misbehaving is the "bouncing tach" syndrome. You've already established that the dizzy isn't giving you full advance, so I'd check every connection to the dizzy you can, and if that's no good replace the dizzy asap. Sorry about the cost -new dizzys aren't cheap. The only consolation is they are Bosch and have a lifespan of at least 100,000 miles - possibly 200,000 with proper lubrication and care.

Good luck to you.

- roGER

[Fishcop]

Thanks for the advice roGER. I'm sure that the problem is not a throttle one. I will replace the points today with the set I removed.

I'm also confident that it is not the rev limiter, although this is how the car feels at 4500. I dismantled the rotor arm and checked the spring and contact, both seem fine with no evidence of recent "contact".

Any one have Bosch distributor they're willing to post to Australia?

[john walker's workshop]

the old bosch distributors are real hard to find. a solution i came up with is to modify a 73-77 unit to fit the early engine. the distributor needs to be disassembled, and machined on a lathe down to the size of your marelli. a new o-ring groove must be cut. the large hold-down bracket is cut off. now you can use the easier to find points/cap/rotor. the vacuum unit is a retard, so it's not used. set timing for 35° total and you're off.

[Fishcop]

Thanks John Walker, I'll start looking for a later distributor. Do I need to have it re-graphed?

Cheers

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John Forcier
69 911T

[pacmyster]

I had the exact same symptoms on my '91 VW 16V GTI.. At 4000 rpm it would go nuts. The engine would buck wildly and the tach would freak out.. Turned out to be a bad wire between the battery terminal and the alternator.. It was not too visible.. Just a littly frayed..
Pete

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'77 Carrera3.0
Citrus Region PCA
www.geocities.com/pcafaro2000/carrera30.html

[Fishcop]

Thanks everyone for your help. I replaced the fried points with my old set and .... perfect!

On closer inspection I'd fried the points soooo bad that the spring had changed colour and lost it's tension. The plastic parts had also melted and deformed.

So I can officially call myself a knob! At least it was a simple fix after all



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John Forcier
69 911T