Engine and Transmission Tech

My 215 running an Edelbrock 500 with perhaps the wrong jets/needles, I took the plugs out yesterday.

Most of them are Champion NY12C, they were sooted.

In the even bank, for reasons now obscure, there are two Bosch BP5ES which had quite a nice colour.

The Champion and the Bosch have supposedly the same heat range.

So are the Bosch plugs telling me the mixture is OK, or are the Champions telling me it's rich?
After I get the trans rebuilt, I will be putting it on a rolling road to tune the carb, just curious in the meantime.

Springs... when I changed from #1463/6755 with primary 083, and 095 sec, to #1448/6852 primary 083, 089 sec, I went to the pink springs just in case the new settings were too weak. Idle vac is 13" .
No flat spots.

Have you found a lot of difference in mixture from changing the springs?

Ivor



Edited 2 time(s). Last edit at 08/13/2022 11:11AM by 88v8.

I found that the silver step up springs are the ones that worked best in my E-brock 1403. They definitely cured the sag at tip-in.

So, I put my Gastester in the pipe and checked the CO at idle. Surprised to find it's around 4.8% (AFR 12.7).
The factory range for SU carbs is 3%-4.5% so on that basis it's a bit rich at idle, and I have no idea what it's doing on the power step.
The idle is optimised with a vac gauge.
I ordered some 7052 rods to lean the idle but leave the power step unchanged.

How long would I need to run on the power step to colour the plugs?

Ivor

PS... the plugs are NGK, not Bosch.... doh...

Ivor, changing the metering rods won't affect the idle mixture.
The rods control the off idle or cruise mix and the power mixture.
The carb does have idle jets but they shouldn't need to be touched on a mild street engine.
The idle mixture screws are the only adjustment that you should need to make. And setting the idle mix in the 1 to 2 % range will stop any off throttle stalling that you might have. ( make sure that you are using timed vacuum to the distributor and not manifold vacuum)
The springs are there to time the lifting of the metering rods into the power stage.
Not like the SU's where they influence the entire mixture range.
You want to use the lightest spring that won't cause a hesitation on acceleration.
I don't trust plug readings on pump gas anymore. Too many additives mess up the reading. And any ethanol at all will wash the plugs white.
Your best friend will be a wide band O2 gauge. It lets you know where your fuel mix is at any time. I have a standard Autometer one that has a clamp I made that lets me insert the sensor into the tailpipe and I power the gauge from the cigarette lighter. That way I can use it on any vehicle to tune the fuel system.

Fred, thankyou very much.

I set the idle screws for the max vacuum (manifold) but I suppose I could tweak them for the CO reading not that it matters as my car is exempt from the govt test. I did run ported vac but apart from a nice loping idle I can't say there was much difference. The manifold vac was a little higher and the idle a little faster before I adjusted it.

At the moment I don't have any off-idle problems with no 24 squirters in the bottom hole and pink springs, I'm just trying to get the mixture right so I don't empty my wallet or burn the engine.
I had assumed that the idle mixture tracked through the whole economy step, thanks for clearing that up.

Is this the Autometer gauge you use? [www.amazon.co.uk]

I didn't realise there were stand-alone gauges, thought they had to be hooked up to a computer. I should get out more...

Ivor

That is the exact gauge that I use.
Its mounted in a Pelican case and I usually just set it up on the passenger seat while I'm tuning.
Rather than purchasing individual metering rods, pick up a Performer carburetor calibration kit for your carb.
It will come with a variety of metering rods, jets and springs to let you really dial in your carb. Or screw it up enough that you wished that you had never opened the hood.
If going to the pink springs made no difference to the tip in ie. no hesitation then I would suspect that you are too rich on the cruise mix and wasting fuel.
When you switch from manifold to ported timing you need to bump up your initial timing. This is due to the loss of the extra advance that manifold vacuum gives at idle. The advantage to ported timing is that the idle becomes much more stable. This is because the timing no longer hunts around due to vacuum changes. You also benefit for a much crisper tip in due to the timing bump just off idle.
Both are capable of the same ultimate HP I just find that ported is much more drivable and is capable of better mileage.

cheers
Fred

Thankyou. I just ordered the gauge.
£220, but with premium fuel at £9 per gallon imp ($8.50/US) it seems worthwhile, given the option is dyno time at >£100/hr.

And after all, a dyno is only a tool and it's always been my preference to buy tools rather than borrow or hire them.

I don't have great confidence, changing the timing. The factory setting which I'm running, was back in the days of proper petrol, so I feel I'm already pushing my luck even on premium fuel.

Yes, I have the #1476 kit, and some extra rods. Hopefully one step at a time I shall manage not to mess it up.
It's remarkable, looking at cars for sale over here with a 215 & 4bbl, how many are running on out of box settings.I think many people, like me, are just nervous of getting into it.

Anyway, the gauge will come from the US, so 10 days to wait.

I can get some Peli cases over here - the 1200 looks as if it might be the right size, which one do you have?

Ivor

Mine is a 1400. It's what I had on hand at the time.
The gauge is mounted in foam in the upper right. The rest of the case houses some tools, extra sensors and cords.
I think the original timing was 5' btdc. You should be able to tolerate at least 10' initial with the ported vacuum. The original timing numbers were very conservative to keep NOx numbers down. So detonation shouldn't be much of a concern.

Misfiring, the #1 plug was sooted, so I changed it for a new BP5ES.

The wideband AFR has arrived, I put the sensor just behind the tailpipe on a mounting. It read 14.9 at idle, whereas my CO meter was reading 3.8% which is 13.08.
Ran the engine a while, the gauge still read.a constant 14.9 even when I revved the engine.

Perhaps the sensor is too cold, but I'd have thought there should be some variation as the engine warmed up.

Ivor

"The wideband AFR has arrived, I put the sensor just behind the tailpipe on a mounting. It read 14.9 at idle."

Out in the air, Ivor? That will certainly read too lean. Mine claps on the end of the tailpipe, but I have a 16.5 inch copper extension that goes inside the tailpipe to counteract reversion.



Edited 1 time(s). Last edit at 07/25/2022 05:29PM by MGBV8.

Oh! That sounds ingenious.
So is the sensor plug soldered into the copper? Copper slipped into the tailpipe, sensor, then a few inches more copper...?

Yes, mine is in the air, I was thinking as it was swamped with exhaust gas it would work OK, but no.

I'm hoping to get a local garage to weld the plug into the downpipe, problem is there are four downpipes and the final two-into-one is a long way back. If it's important to have the sensor heated, the plug will need to go into one of the downpipes so it's only going to be sampling two cylinders.

Ivor

Like Carl said the sensor needs to be as far up the tailpipe as you can reasonably get it.
Mine has a piece of 1/8th stainless rod with a hoop in the end. the hoop is bent 90' and the sensor is held into that with a nut.
I slide the sensor up inside the tailpipe and clamp the rod in place with a small pair of vicegrips.
No need to worry about heat for the sensor , it has it's own heat source.

cheers
Fred

Yes, the O2 sensor has a built-in heater filament.

I use the Innovate LM-2 that has a Bosch wideband oxygen sensor. With the copper extension it tested spot on with the dyno shop's.

OK, thankyou, I was imagining a different arrangement.

The gas collector on my CO meter inserts about 6" into the tail pipe, so I can see how it corresponds with the copper extension.

The exhaust clamp is not available over here. I wonder if it would take the Auto Meter sensor. The thread o/d is 0.7".
Be nice to know before I spend $80 on it.

Auto Meter say the sensor should be as near the cylinder head as possible, they evidently want it to be hot, but as you say it has its own heater....

Fred, if I put the sensor up the pipe, the wiring will get heated and the holes in the sensor will be facing the gas stream... do they not get blocked?

Meanwhile, I have another idea....

Ivor

The Innovate clamp accepts the standard M18x1.5 wideband oxygen sensor.

For a permanent mount O2 sensor, from Auto meter:

"The oxygen sensor should be
installed in a spot where exhaust from all cylinders flows past
it. The oxygen sensor should also be installed as close to the
cylinder head as reasonably possible so that the sensor reaches
operating temperature quickly. If headers are used, the oxygen
sensor should be installed in the collector. If cast iron manifold(s)
are used, install the sensor in the pipe just below the manifold."

The wiring for the sensor is more than up to the task. I have used this setup for years now without any issues.
Carl's setup is excellent, but for me it has limitations. I work on an array of different vehicles so sometimes a straight shot into the pipe is not available. I'm able to bend the stainless wire to fit varying configurations. With the sensor 12 to 14 inches inside the tailpipe it reads spot on.

Auto Meter do reply quickly to questions... very good.... the tech confirms their sensor will fit the clamp.... and says the sensor should be welded into the pipe ahead of the muffler, well that would be almost at the end of the exhaust because that's where the muffler is so perhaps the heating isn't so crucial.

I have a cunning plan which should be ready by Friday, watch this space...

Ivor

"says the sensor should be welded into the pipe ahead of the muffler, well that would be almost at the end of the exhaust because that's where the muffler is "

Surely they do not mean that far back. On a modern car, they are before & after the catalytic converter. On muscle cars, street rods, etc, about 6 inches past the header collector.

I suppose it depends where the muffler is. Mine is perhaps unusual, I just have a Hooker Aerochamber right at the back.
But then, you and Fred seem to do OK with the sensor at the tailpipe, and the Govt emissions test collects from the tailpipe... so in theory it should work anywhere.

I imagine one reason for putting it nearer the front is simply to minimise the cable run.

Ivor

Most dynos use a tailpipe sniffer. I bought one so I could use to tune other cars....and motorcycles.

My MGB only has the rear muffler. Ditched the middle one years ago for additional ground clearance.