Engine not reving out.

[MikeB]

Gents

OK here's my problem, my engine pulls well but runs out of puff at 6000 and won't rev much over that certainly not to the 6500 red line

So here's the engine spec, as far as I know. It's a standard 240 unit, still on the Hitachis, now fitted with SM needles and K&N pancake filters.The exhaust manifold is a 6 into 1 with a 2.5 inch single box system, all ex MJP I believe. It has a ZX distributor (DSK 08-02 with an E12-80 unit), running with vacuum advance

Had it on the rolling road on Friday, and made a solid 120 at the wheels. Slightly rich in the middle, lambda of 0.80 but getting rich at the top end with 0.70. But would that cut the revs high up.

Any thoughts?

What ignition timing would you suggest

Cheers

Mike

 

[Rob Gaskin]

Mike, has it just started to be like this, if so have you altered anything?

Timing needs to be around 35 degrees max advance.

Won't it even pull beyond 6k in 1st gear?

 

[MikeB]

Rob

From memory it has never been happy to rev past 6k. Initial though was fuel starvation, but the rolling road showed it was getting plenty, so isn't that. It has a Facet electric pump by the tank, no mech pump fitted.

As a rough guide, with the vacuum advance disconnected what sort of timing setting should I be getting at idle (700 rpm) ?

 

[MikeB]

Just checked the ignition timing. With the vac disconnected it is 12 degrees at 800 rpm and max at 33 at 2500 or so. With vac attached this goes to about 32 tick over and about 54 at max advance ! Is this correct. Does the e12 module retard the ignition at higher revs to get it back to more reasonable levels?
I went for A quick blast up the road and tried it with the vac attached and it went to 6 k and then wouldn't go any further, then with the vac disconnected and blocked off and it went to about 5700 before cutting. Now the rev counter needle started to waver at this point, when I tried holding the revs there.

Cheers

Mike

 

[jonbills]

As Rob says, you want it about 35 or so all in, and I think you should get that by around 4k rpm. Don't worry too much about what it's doing at idle.

Have you tried it without the air filters, just as a test?
Also is the timing of the spark steady as it gets up to 6k?

 

[rallymanDP]

As jonbills and Rob have said, the total advance needs to be a maximum of around 34-35 degrees, and if your Timing light says that it is going up to 54, I'm surprised that the Pistons haven't got big holes in them by now - so check that that is indeed the correct reading.

If, once you have set it correctly and it is still struggling to get over 6,000rpm, try checking the Cam Timing - as per the Haynes Manual. it should sing up to an indicated 7,000rpm quite happily

 

[MikeB]

Duncan

I checked the cam timing and you had it spot on, the little dash on the cam is bang in the middle of the slot. I'll try another timing light tomorrow, totally agree the figures are odd and need verified, the engine doesn't sound that advanced.

I've moved the distributor through about half of the movement that the bolt clamp permits, it was originally pretty close to the max advance side and have tried is towards the middle of the setting i.e retarding it, but no particular change.

 

[Nigel Brook]

Duncan

I checked the cam timing and you had it spot on, the little dash on the cam is bang in the middle of the slot. I'll try another timing light tomorrow, totally agree the figures are odd and need verified, the engine doesn't sound that advanced.

I've moved the distributor through about half of the movement that the bolt clamp permits, it was originally pretty close to the max advance side and have tried is towards the middle of the setting i.e retarding it, but no particular change.

I think you need to verify what cam you have in the car because it sounds like cam timing to me. If you can't verify try playing about with the different holes in the sprocket, but be careful not to release the tension on the chain!

 

[andrew muir]

Hi Mike
I have had all sorts of issues with not reving out, the clues are the wavering or jumping tach, sounds like ignition, get a really good timing lamp eg snap on etc, which can be adjusted for timing total advance should be as already stated 34-35 at 2700 revs, If the timing starts jumping about etc at hi revs it will be the coil or similar, is it using a standard dizzy? with points, if you can, get a set of points to eleminate the electronics.
Also try testing the timing with headlights etc on as my car had a problem at high revs but showed up under load more, does it feel like a solid cuttout almost like a revlmiter?
Traced my fault to an alternator would you believe it. Now ignition is solid as a rock to beyond 6000 car is getting flat by then anyway happy to 6000 but not beyond, lower grears till 6500.
It is a 260 though.

 

[MikeB]

Well some progress this morning.

I took the air filters off and ran open trumpets, didn't like that and wouldn't go over 5700, so I put the standard Z filter unit on, then it went to 6k, as it had before. Finally I disconnected the vacuum advance and advanced the idle timing to about 16 degrees, which gave an circa the 34 degree max advance at circa the 2500 mark. Now the car will pull to 6500, but it definitely struggles from 6k to 6.5k. So whether the vacuum advance is knackered I don't know until I pull the dizzy apart


Nigel, it's a standard engine, built by Duncan, so it has the standard cam in it, I believe. And as I said above the timing dash on the cam plate is smack in the middle of the groove on the cam, so I assume that's near perfect as far as timing goes.

Andrew as above it's a ZX dizzy with electronic inners and the E12-80 spark unit, my timing light is an adjustable one.

So half way there, reving higher but definitely not singing as it gets above 6000.


Cheers

Mike

 

[Mr.F]

NGK plugs gapped to 1.1mm?

 

[MikeB]

Mike

35 thou so slightly less


Cheers

Mike

 

[Mr.F]

The 280ZX system does run a different plug to a standard points system. The bigger gap allows a fatter spark from the extra voltage available. The NGK plug has the suffix -11 to show that the side electrode is extended to allow the wider gap.
May have some bearing on top end revs...?

 

[MikeB]

Mike

It has the 11 marked NGKs in it, and I've opened the gaps up to just over 40 thou, but usually smaller gaps aren't a prevention to high revs.Will try Andrew's high electric load test to see if tthere is any difference, so I can rule that out.

Cheers

Mike

10 mins later, - no electrical charging issues, head lighs on, wipers on and heater blower on full and went to 6300 as before.

Should I see if the cam advance is an answer? Or is that a No No?

 

[MikeB]

Well, after many experiments and a bout of misfiring above 4000 rpm and the tacho needle jumping about, I think I might have traced it to a fault / short in the loom to the E12 unit on the distributor. Have removed the loom tape and seperated the wires and with the vacuum advance removed the engine seems altogether keener to rev up to 6500.

More runs tonight with the vacuum refitted and some tinkering of the carbs to see if I can get it even better, but pretty happy as it is now.

Does anyone know how to get the wire terminals out of the black two pin connector that fits onto the E12? I would like to refresh the wiring but still use the connector as opposed to two loose leads


Cheers

Mike

 

[Nigel Brook]

Should be two small spade connectors if I remember correctly.

 

[MikeB]

Nigel

Yes it's two spade terminals inside a block connector like this

I'd like to try and keep the connector block, so was wondering if anyone knows the trick for releasing the existing terminals.

 

[Rob Gaskin]

Nigel

Yes it's two spade terminals inside a block connector like this

I'd like to try and keep the connector block, so was wondering if anyone knows the trick for releasing the existing terminals.

Slide a small screwdriver between terminal and case.

 

[morbias]

If you accidentally damage the connectors you can get new ones from vintage connections

Bear in mind they have a minimum order policy of $10, otherwise they cancel your order.

 

[SKiddell]

http://www.autoelectricsupplies.co.uk/product/45/category/7

And they sell things in pounds