mk2 head wrecked?

[sparky_spit]

Top man Bruce! I didn't realise you had been off the road more or less since Cadwell last year? I think you're gonna need Roy to remind you which one's the clutch pedal and what all those switches do.  Well done, I'm really chuffed for you after all the pain you've been through.

[thescrapman]

GT6boy wrote:

If Gareth wants to put them online- thats up to him.  

We won't hold our breath then.. :-)

[GT6boy]

GT's current work has produced some stunning results :).
Pre-work testing of an existing race engine Spit showed 130bhp on Maynards RR. The 1300 Spit road engine he's just put together is putting out the same power on the same RR being trialed in the same race car as a hack 8). The gasflow figures supporting days of testing show step-change improvements.
It's very refreshing to see new developments to our old bangers 8).

[99176]

Are you at Silverstone Bruce?
Proof of the pudding and all that.

[GT6boy]

Hi Keith. That's a bit soon(financially) for me, sadly. Still got to get it MOT'd (needs new screen) in readiness for Stoneleigh and I reckon the diff should be replaced before it goes on track again....
Must get our two cars together for a picture. Should have done it 2 years agao at CC when it was just you and waiting 1st thing in the pit area.
Looking to haunt CC(July) again this year and Goodwood(Nov?) looks promising ;).

[99176]

Be good to see how hi-tec mods compare with 'old school DIY'
CC sounds good to me.

[Deleted User]

Bruce, are you going to do any events this year with the rebuilt car? The replacement for the La Cannonball in June is a must and not expensive

[Brian 93957]

I dont know the exact circumstances of your machining work but in 15 years of working for a long standing engine machining firm, ive never heard of someone taking 020" in one pass.
Usually most machinists would take this amount off in a number of passes to reduce heat build up or chatter of the machining stones or fly cutter.
Most heads can be saved its just a case of finding the right approach, but it can be expensive.
Good luck hope you get it sorted

[GT6boy]

bobyspit wrote:

Bruce, are you going to do any events this year with the rebuilt car? The replacement for the La Cannonball in June is a must and not expensive

Aside from CC and Goodwood Trackdays, i don't have anything else pencilled in. I'd like to give some thought to the RBRR though. I enjoyed the last one, the Scottish bits particularly 8).

[GT6boy]

93957 wrote:

I dont know the exact circumstances of your machining work but in 15 years of working for a long standing engine machining firm, ive never heard of someone taking 020" in one pass.
Usually most machinists would take this amount off in a number of passes to reduce heat build up or chatter of the machining stones or fly cutter.
Most heads can be saved its just a case of finding the right approach, but it can be expensive.
Good luck hope you get it sorted

Hi Brian
The head was a skimmed accident waiting to happen. It would have been fine if left at the standard CR, but undiagnosed core shift meant anything over a .010" skim would have found this defect.
The head repairs by two very(VERY) experianced cast iron welders came to nought. The only likely effective repair would have been to do it properly with a cast iron repair(heat head to red hot and let in new metal. Fine for a £100 000 Bugatti, but wholly inappropriate for our value cars :B.

[GT6boy]

  A quick note. More detail later.
Just spent a fun filled day with GT and a few runs on the rollers at Maynards. Whilst I wasn't looking, he must have swapped my engine out for another one! ;D
To watch him working is fantastic. He is an absolute marvel to watch. His ear for tuning is marvellous to behold. 8)
The new head/inlet manifold/balance pipe mods all amount to the car now easily pulling from 1200rpm in O/D top!!!
Those who know the large A46 hill up out of Nailsworth will be aware of how steep that is. Coming back I was stuck behind a pootlin' Fiat 500 doing 30mph, I was in O/D top all the way and the car was perfectly happy. Job well done. :)
Really spins nicely now. All the frustrations of my last years shennannigans is finally coming together. Still a little fine tuning to do to needle selection, so even more scope for more power 8).
Time for a bath I think!

[Royboy66]

(cool) Mojo back ! ;)

off to polish me rear view mirror!! :B

[GT6boy]

A little more info on yesterday.
Car was running hot getting there(no mechanical fan now, but Kenlowe was on whilst motoring, although the engine stayed at 85 degrees.
First thing on arrival we set to getting it into the best possible tune before the RR started. Turned out I was running the needles to high in the jet and the engine was running lean.
Then the simple operation of getting the carbs to open in unison- oh dear. All new build componants in the throttle linkages, but there is a lost motion in there and you have to set it up by eye, once you've allowed for the rotational losses in travel. This took some considerable time, but Gareth cracked it by perceveance 8) .
Then the map I was running was a little extreme, so we started off with Steve A's GT6 map. This was quite an improvement and enabled a good tickover to be established.
But the engine was hesitating on pickup, this was confirmed on a blast up the road outside. Lots of fettling and this improved with the Megajolt being altered to give more advance low down below 1500rpm, as well as the mixture being changed. But, changing the piston springs to a heavier weight made a step change and there we were: instant pick-up!
So, onto the RR.
First run went well, mixture a bit rich still(eyes smarting!), but a massive decrease in fuel vapour stand-off as compared to previously :).
The engine is losing about 10lbs of torque through the 3000-4000rpm band, but it is improved on previously. Looking at 153bhp at 6340rpm.
Can't remember where the torque was! I'll dig out and scan the printouts.
Further runs were effected to improve the mixture and then to knock back the advance around the area of the torque dip 3000-4000rpm(Megajolt- bloody marvellous! )
There remains further work to be done to refine the needle profile and tighten up the map so it is spot-on all over. That is for another day though.

So, what of the mods?
The new head/inlet manifold mods were allowing so much more vacuum by virtue of their better flow rates, that the self same pistons springs that were fitted previously were now woefully inadequate. The nescessity for stiffer piston springs speaks volumes.
The power is up on last years projected 130-135 session on these rollers to 153 yesterday. I'm happy with that .
Irrespective of any power figures, the car is transformed. The tuning and remapping means it will now tickover at 600rpm if I want it to- it never did that before on my TH5/TTFR83 comedy cam, always had to settle for 1000rpm!
The engine is, for the first time, really tractable. Press-on and its bye-bye Diff time.

I'd like to thank Gareth and Mark for doing such a great job on the car for me. I know full well that the cost I paid them for the work of the last few months, didn't in any way match the amount of time and effort they both put in.  
Anyone wanting some tuning work- you know where to go! To say they have my seal of approval is an understatement :) .
http://www.maynardltd.co.uk/automotive/site1/index.htm  
  

[GT6boy]

Hopefully, this will bring an end to this thread and I can put it all behind me now- just get on driving the car! :)

[GT6boy]

This was a subsequent run, but not taken as far. After this, we altered the ignition advance to improve the mid-range spike(TH5 cam and Phoenix 6-3-1 charecter traist). Easy-peesy Mr Lemon-squeezy on the laptop! ;D

[GT6 M]

Good bit of extra  GG,s  and torque there Brucie

It must be down to the exhaust , but every chart i seen, always have a dip about 3-4 thou rpm,
the torque shows it up more than the HP charts,

Intresting to see, that although you got some good GG,s, the torque is lagging way behind a similar  HP  2.5 engine

now you can have fun,

rgds Marcus