Toyota 4AGE into Eleven will go (one way or another)

[erictharg]

So, thought all was well, finally. Had done my bedding in miles. Got the good oil in. Then the misfire re-appeared. A hard low tension cut, still. And seemingly random. Not speed or heat or lead related. So ordered the Aldon ignitor rotor and pick up and spent a day installing it in my spare distributor (including having to file the Denso reluctor rotor to something similar to a Lucas 4 cyl points cam profile!). Can think of no reason why the Lumenition trigger set up would be causing the failure but it eliminates one possible problem. All now fitted and feeling good. So far. Also going to replace my battery cut off switch as they don't last for ever and can be the weak link in the low tension ignition circuit. Genuine Autolec switch this time. Was mentally compiling my packing list for heading up to Anglesey this Friday, then got a text yesterday saying the race has been cancelled due to too few entries. Aaargh!
So next race is now Silverstone Aug 20/21. On the International circuit - a good thing. Hope to get test day in before then if only to dial in the new brakes. Anyone fancy a trip to Silverstone 20/21 Aug?

[erictharg]

Almost forgot: Rear brakes need improving now. Got to thinking a set of MGB drums would do the trick ... and less hassle than going to dics maybe? May even be overpowered, but can fix that with the bias bar. Might give MGB Hive a call and see what they can do...

[Westfield 129]

Check your electrical system voltage stability. Spikes and dips in the output can cause all sorts of random ignition problems.

As for improved rear brakes...There are also alfin rear drums you can use, though the do widen the rear track somewhat.

Disc brakes are not that hard (or even that expensive) to do. The big problem is the hand brake system. At least one builder here has done a Sprite disc conversion to the W11, trimming the hand brake system of the Nissan rear caliper slightly to fit around the Panhard rod mounting.

Still another builder is doing a new rear brake caliper mounting to rotate the caliper mounting to get the brake lever system out of the way of the suspension.

A pressure lock valve can be used on the rear calipers to maintain rear brake pressure when parking, as used on many light aircraft. I can see where this may be problematic in light of your IVA (you have to depress the brake pedal, then pull the valve knob to set the "park" brake with no mechanical system at all). This eliminates the mechanical brake entirely, and allows the use of any of the aftermarket calipers available (or even a pair of Spridget front calipers), while using the available Sprite rear discs from the existing kits. I have been thinking of doing just such a system, as it really simplifies the installation.

[erictharg]

I've got a power conditioning module for the Amethyst that ensures it only sees voltage within spec. Minifin drums are, as you say, available but only with a cast in 1" spacer and I don't want that. It's more load on the rear wheel bearings, plus if I go up to a 525 section rear tyre at any point in the future it will cause them to rub the bodywork. And they only give you a marginal cooling improvement. The pressure lock valve won't pass the annual MoT test as it checks the parking (emergency) brake on the rollers so you need to be able to apply it gradually and it needs to be independent of the main (service) brakes.
I can run the car without handbrake as long as I only use it on the track, but its nice to have it road legal, if only for ad hoc testing.
The off the shelf kits for discs are too expensive, but as mentioned before Fiesta Mk1 discs and pretty much any caliper should work.
I'll see how the testing at Silverstone goes on the 5th Aug.

[jonclancy]

Hi Charles,

FWIW, I had an intermittent misfire a few years ago. Turned out to be that the Lumenition optical "chopper" had taken a cut out of one of the wires under the dizzy cap. The engine torque on acceleration pulled the wire slightly tighter and the two chopped ends apart. Was a difficult find, but the repair and re-routing has left it reliable now.

Cheers

Jon

[erictharg]

I suspect it was something similar Jon. Would run fine for a hour or more than decide to start missing, or might just randomly give a "cut" as you are cruising and then fine for a while. Given the amount of non-standard work to get it to fit and run I figured it safest to use the "correct" Aldon rotor and trigger.

[Westfield 129]

My R5 Turbo T300 German tuner special has a separate master cylinder connected to the hand brake that acts only on the rear brakes, independent of the main brake tandem master cylinder.

The modified hand brake lever doesn't have a ratchet, so I use a pin to lock the brake if a parking brake is necessary.

This is a standard sort of vintage rally setup, and likely available from the vintage rally specialists. My setup came from Renault Sport's catalog of 1984.

If you use your hand brake lever and cable to actuate the secondary rear master cylinder, you will have a separate system that will gradually apply braking to the rear, and lock using the internal ratchet in the hand brake unit.

Just a thought.

[erictharg]

I wonder what the dictionary definition of "despair" is? I think I'm getting close to it either way. Did a test day on Friday at Silverstone. All had gone well up to that point. About 150 miles on the road. Aside from a rear crank oil seal leak (there was a slight wear groove on the crank) everything was good. Went out for the first test session and built speed up gradually and slowly but surely after about 10 laps the oil pressure starts to drop again. Not catastrophic this time but noticeable. Came in to check everything over and it's down to 20 psi at idle. Still getting up to 50 - 60 psi at 4000 but way off what it was before (and should be). Let it cool and tried again but the same thing happened. Checked oil temp (using an infra red thermometer on the filter housing) and reading about 98 deg C. So actual oil temp maybe 100 - 102 deg. Not a problem for decent oil. Also checked the cooler was doing its job OK. Let it all cool down over lunch and tried again. Same story. Once hot the pressure drops. Decided to call it a day before too much damage done.
Dropped the sump Saturday and pulled one of the main caps. Sure enough the bearing was showing signs of scoring and wear. After maybe only 30 laps on the track. Engine now out again and stripped. No big debris so hopefully the pistons and head are OK. I'm struggling to understand what is going on. If I were paranoid I'd say someone had been dosing my engine with abrasive.
The only thing I can come up with is that I'm getting some really bad crank vibration at 5000-7000 due to not running a damper. So on the road its fine but on the track, where it's at that speed all the time, there is bad enough vibration to cause the bearings to make contact with the journal and start wearing.
So, off to the machinist Thursday to see what they suggest. Also sourcing a complete spare stock engine which I may just rebuild with fresh shells and my cams.
On the positive side the new rad has the coolant temp down to high 80's, and the car is going well with better bite from the brakes. I was staying with V8 Morgans down the straights. That's enough to keep me going! Won't be able to make the 21 Aug race sadly.

[Westfield 129]

Were the block main oil galleries opened up and flushed?

Was the crank trued?

Were the bearing clearances checked during assembly? End play?

No damper? That will usually result in very early crank failure. Those dampers are there for a reason. This may be the root cause of your problems.

But, going on...

How much block work was done? Were the mains line bored?

Condition of the oil pump?

How are the rod bearings?

With this being rebuild #3, in very short order, I would consider a new machinist.

[erictharg]

Need something more creative from you Jan!
Oil gallery plugs removed and flushed out.
Crank was re-ground because it was not perfectly straight.
Clearances Plastigaged on assembly. 0.002" for mains; 0.0025" for big ends.
Mains not line bored but crank spun easily with fingers on assembly when torqued up, so not big problem there.
New OE oil pump.

So, as you suggest, I'm coming to the conclusion that it can only be the omission of a crank damper that is causing the problem. Need my machinist to tell me if the wear is due to bearing to crank contact (and if so, likely the result of the crank vibrating out of shape due to resonance) or dirt ingress. If dirt I'm struggling to know where it came from.

Collecting a spare 90k mile ex MR2 engine Monday. If it all looks good I might just throw some fresh shells in it along with my cams and see how it goes...