Special getting closer...

911hillclimber · Post by **911hillclimber** » Wed Aug 03, 2011 6:17 pm

Me? Slackin'?

Probably....

Day job getting in the way of my mental health and will to live.

Maybe check tonight as i was going to see the Harry Potter film but too hot.

I do hope the jets are the same, but the temp difference is really big.

I have a set of new jets to the sizes from PMO's Richard Parr for a stock 3.2 so the number comparisons will be interesting.

I have to wait to the 21 Aug hillclimb to find out if things are ok.

The engine has independent headers, no X link, and have a lambda sensor bung in each as close as poss to the heads, Bob put them in for me so easy to see how close they are to combustion ideal.

The emission read-out on the rollers show a very good efficiency indeed.

This car is nothing but hard work.
My 911 73T/3.2 is exactly the opposite.

WHY did i bother doing the Lola!

A pic to cheer me up!

911hillclimber · Post by **911hillclimber** » Wed Aug 03, 2011 8:59 pm

Good sweaty hour in the garage tonight looking at PMO jets...

All jets are the same across the engine.

Actual:
Idle: #55
Main: 155
Air: 180
Emulsion: F11
38mm venturi dia

Mixture 2.25 turns out 3 chokes on the drivers side, 3.25 turns out 3 chokes on the other. Interesting difference.

PMO jetting:

Idle #55
Main: 155
Air: 190
Emulsion: F11
38mm Venturi dia

So, the only difference is the position of the mixture screws on one side to the other!
Thinking of bringing the rich 3.25 side to the 2.25 of the other.

Will do this and run the engine to full heat and see if that changes anything, but too late tonight, next doors children gone to bed i think.

To the fan:

It is central to the engine/cylinders with a very 'hemi-spherical' distibution duct under it.

I now stink of petrol.

= double session of washing up for me.

MikeB · Post by **MikeB** » Wed Aug 03, 2011 9:46 pm

Graham

Remember that PMOs have air adjuster screws as well as idle fuel screws ( see the PMO Installation instructions). Bob would have set the carbs using these two sets of screws and balancing the throttle linkage to get it idling properly when he set them up before.

Are you getting the car back to him before Shelsley?

911hillclimber · Post by **911hillclimber** » Wed Aug 03, 2011 10:05 pm

Probably not.
If I can take it down and do a quick check and onto the rollers in the same day i am tempted.
have to get time off work etc.

Bob wants it back to check it.

The screws all look very equal (number of threads showing).

Having an idle that is out of sorts is no problem of course, just about the real engine running range, 2K to 6K rpm, but esp over 4K where people say it sounds flat under load.

911hillclimber · Post by **911hillclimber** » Fri Aug 12, 2011 4:17 pm

Still waiting for the 21 Aug and Shelsley Walsh.
In the mean time, Xmas rebulds are looming so some planning needed.

Where in the UK can i source G80 cams and high comp pistons?
Are there other cams for the 3.2 when on PMO carbs?

hot66 · Post by **hot66** » Fri Aug 12, 2011 5:09 pm

kent cams will grind you cams to that spec

911hillclimber · Post by **911hillclimber** » Sat Aug 13, 2011 7:17 am

Thanks for that, I only know they come from Anderson in the USA.
I'm sure some say 964 cams do the same job..

steve wright · Post by **steve wright** » Sun Aug 14, 2011 11:23 am

Hi Graham. I've not kept up with this thread for a few months and reading about the trials and tribulations got me thinking. I'm no engine expert and there are plenty of people in this club with a lot more experience than me, but a few things struck me:
1. There are too many variables at play here - eliminating potential issues by temporarily replacing components is the way to go (e.g. replacing the T dizzy with an S or the PMO's with webers)
2. A 911T dizzy is never going to work with your set up/configuration and is going to give results that will strangle the engine: it's only designed to work on a low-revving, restricted engine
3. There are plenty of exhaust set up's for 911 racing engines that meet noise restrictions. Although you've got a mid-engined configuration which might complicate things you should be able to get a temporary set up, even if it's nothing more sexy than a set of SSI's and a rally exhaust (two-in, two-out) to see if that unleashes things!
4. The engine getting hot on one side is either cooling fan (or tinwear) or a mixture issue. Eliminate the fan, etc and temporarily replacing components should fix this. just keep checking the temps. when you're changing components!

hope this helps and good luck with hunting down the gremlins. Keep your chin up, great thread, and I've no doubt you will get there.

911hillclimber · Post by **911hillclimber** » Sun Aug 14, 2011 9:00 pm

Thanks for your thoughts.

I have a dizzy from Mike Bainbridge in the wings to try.
Changing the carbs to webers I've done (to no effect)
I had a cobbled SSI style header system originally but same silencers before the Techcraft ones, and the new exhaust made a big gain on Bob's rollers.

The temp issue has always been there, and to change that to a cinventional one is a huge change on this engine.

The car will run in anger at Shelsley Walsh next weekend with the straight through silencers for the first time, so will be interesting.
I can think of saner plces to try someing new.

steve wright · Post by **steve wright** » Mon Aug 15, 2011 11:29 am

Hi Graham, just looking back at the photos I noticed how much lower the fan is than the factory flat-fan arrangements on the 935, etc. I know it would be a major pain but are you confident it's directing airflow evenly across the 6 cylinders? Maybe there's some way of measuring the airflow, even if it's just sticking something under the engine where the hot air exits to check it's the same each side?

Have you considered pulling the PMO's and having them sonically cleaned, as that could very well explain a lack of power if everything else is okay?

Cheers,
Steve

MikeB · Post by **MikeB** » Mon Aug 15, 2011 12:10 pm

I think the thing to remember is that Bob ran the car on his rolling road earlier in the year and got 260 ish HP out of it. The spec is as the engine is now, PMOs, dizzy et al, if I recall correctly. That was with the first set of silencers on it.

Hence the spec of the engine, exhaust and inlet set ups was pretty good.

As we know something happened to the silencers and they restricted the exhaust flow. That has now been cured by putting on proper Techcraft ones.

The jetting of the carbs is also nearly spot on, as can by seen by the ones Richard Parr supplied, and 3.2 engines are his bread & butter.

Graham can confirm if the above is correct.

If the engine is now not producing power it is because something has gone out of setting ie ignition timing has slipped, carbs are out of sync, there is a restriction in the exhaust system or maybe a cam lobe has worn It has to be something of that ilk or else Bob's power reading wasn't correct in the first place.

The bottom line is the engine did produce the correct power, hence something has changed since then.

gridgway · Post by **gridgway** » Mon Aug 15, 2011 12:16 pm

MikeB wrote: As we know something happened to the silencers and they restricted the exhaust flow. That has now been cured by putting on proper Techcraft ones.

I'm probably losing track (on many fronts), but do we know that? I thought that Graham took the silencers off and got a raised tickover and thus inferred a restriction. But I don't think we know the exhaust became more restricted after the RR run? Or am I way out?

MikeB · Post by **MikeB** » Mon Aug 15, 2011 12:32 pm

Graham R

Yes I am assuming that the silencers became restrictive after the RR test, as this is basically a std 3.2 on carbs, and 260 would be the sort of figure you'd expect.

But my main point is that with all the current ancillaries attached, at that point the engine made good power. So overall the spec of the engine is OK, so you only need to change defective parts, if there are any.

Something has since changed to apparently reduce the output.

steve wright · Post by **steve wright** » Mon Aug 15, 2011 6:13 pm

Mike, that makes sense and the logic follows. Graham what's changed that you're aware of. If nothing then you're looking at more intrusive diagnosis....

911hillclimber · Post by **911hillclimber** » Mon Aug 15, 2011 6:15 pm

Just to clarify:

When I first built the car up 3 years ago now the engine was as i bought it, 40mm Webers (old) and cut-n-shut -to-fit 2.4 headers and the big Custom Chrome silencers.

It made a miserable 180 bhp on bob's RR.

I then made my own equal primaries free flow headers and left the rest.
About 190 bhp....and a LOT of back firing etc.
I changed the webers for a set of 46mm one, about 2000 road miles old.

Lots of back firing and got very fed up 'I am going to sell it' at the end of last year.

Spring this year took the car to Bob's.

The engine was leak tested and the BEST cylinder was 14% leak rate.

I re-ringed the engine, ground the valves and it went back on the rollers.
Bob spent a day on it and it ran 269 bhp and 240 Lbft.

That is good for a 3.2.

This is with the same silencers and headers, the same dizzy and same Shell V power fuel rating.

The car just does not go well. Simple as that.

My 911 73T with a stock 3.2 in it is nearly as fast on a hill as the Lola., that is 200 bhp/ton verses 440 bhp/ton.

The difference should be electric.

An experienced racer drove the car on a private day at a sprint track and came back in to say it has about 180 bhp, certainly not 270.
So, the car is down somewhere.

Incase you think I'm scared to drive it, I've been faster up the hills I've run for 20 years now in my hot Impreza and gone much faster in the Scooby, so for 3 years I've gone quicker.

The issue is the apparent lack of pick-up-your-skirt-n-run!

i have now fitted the very exhaust the engine used when it was first hillclimbed so absolute straight through Techcrafts.

It sounds great.

The engine was run with the Custom Chrome silencers off as an experiment and the tick-over went up from 1000 to 1600 rpm.

As to the temp difference, it must be the fan as the carbs are jetted the same, balance of them is more to do with slow speed 'road' running, hardly an issue in competition where full bore is the main engine position.

The dizzy will have locked-up above 2 or 3 K and Bob has checked the timing right through. Ignition is by coil and an Aldon automotive electronic system that replaces the points.

Shelsley Walsh is next and it is a track where you can certainly stretch any car.

Next weekend will see if the silencers were killing the engine by the times recorded.

This car should be seriously fast at 440 bhp/ton.

It is a great car, but the mood I'm in I'm about ready to sell and go back to my wonderful 911.