New block worries

[DangerousDerek]

Put the crank and pistons in the new block. Offside looks ok and i am seeing about 7 thou deck height on all 4 pistons. But looking on the nearside they are not square. The fronts of each piston sits flush with the deck and the rears of each are 8 thou under. How can this be?

[DangerousDerek]

QBee said:

Do you get the same result if you rotate each piston 180 degrees? (assuming you can do that)

I suppose i could as an experiment. But i would have to take the pistons off the rods and getting those spring clips out is something i dont want to attempt if i dont have to.

[DangerousDerek]

carsy said:

Derek its quite normal that the pistons are not completely square with the top of the block. I put it down to the pistons having offset pins which i assume yours have.

1 bank all 7 thou down and the other bank flush at the fronts? Seems very wrong to me.
Not only something amis geometry wise but means i would have higher CR on 1 side of the engine.

[DangerousDerek]

I just swapped piston 4 into pot 3 and its the same.
So i guess the rods are fine and it must be down to the new block.

Back to ACR with it tomorrow!

[DangerousDerek]

All the chevy rods are chamfered so its obvious which way they go.

[DangerousDerek]

I swapped 2 and 3 over just as an experiment and they were the same.
Swapped them back now.

I have found that a good bit of thumb pressure on the front of the cock eyed pistons can get them flat to the deck but it cant be right they sit the way they do while 'resting'

[DangerousDerek]

Having had a nice chat with a respected engine builder it seems I may not have a problem after all. There are a couple of checks I still need to do but it looks like the build is back on.

[DangerousDerek]

Apparently it's not unusual for forged pistons in a cold build to have a slight tilt here and there. The deck heights are the same for all 8 when the pistons are flat. Like I said I still want to double check a few things such as the big end bearings but it should be fine.

What was wrong with the numbers Simon? I measured about 7 thou deck height when they are flat all round. Skirt clearance in the bore is about 5 thou. It's normal to have a lot more at the top of a forged piston.

One thing I haven't got my head around yet is the CR calc, it doesn't add up. Can someone do the calc for me and see if I am getting the same. 96mm bore on offset crank for 5.0. Just 7 thou deck height. Are the Elring composites 40 thou? My heads should be 28cc but I intend to remeasure as they have had a few skims and the chambers worked. Roland tells me the pistons are 20cc.

[DangerousDerek]

Sardonicus said:

Pupp said:

But if Dereks description is this I assume then I am still

Ok to clear this up. That pic is the wrong side so front and rear are opposite for pistons 1 3 5 and 7

All these pistons are sat tilted so the front are flush with the deck. Having slept on it I think this is still a serious issue that needs investigation.

On another note and getting further information off Roland that my pistons are 20cc bowl and designed to sit at 7.5 thou deck height I have calculated that my CR would have been 11.26:1 when I melted the piston. I had 50 thou MLS gaskets. This is assuming 28cc heads. Mine have been skimmed a few times but the chambers have also lost a little. I will be measuring these properly as soon as I can. Any tips or the use of a plate etc

[DangerousDerek]

neal1980 said:

Derek with greatest respect I cant believe you have built an engine of completely different parts and not measured your compression ratio.

This is engine building basics, I trust NO ONE. if im building an engine I measure and re-measure everything until IM happy.

You need to know your CR anyway to optimise the setup.

Have you been following my antics this year at all?
It's not as though I have had the car in the garage for a few years with all the time in the world to plan everything to the finest detail. I've been racing, braking the car, fixing it before the next race meeting and doing the best I can.
With the wasted time I had on the old cast pistons that didn't last due to ill fitting on what were probably worn rods I picked out a forged set up from ACR. Little did I know that Roland made a wrong assumption and assured me I would be about 10.4:1 CR. I did not care if I was a little higher or lower. Then the cam choice came in to play, then I had a great offer for the roller rockers. No plans, the build just developed and grew. My thoughts were to have an NA set up that could run 11,s and still able to take a decent shot of nitrous when needed to beat any turbo LS challenges that may come up.

I think I can get the cr down into the 10,s and retain squish. Watch this space.

[DangerousDerek]

Sorry guys if I appear to be ranting, moaning etc. Been a stressful couple of months.
I think it's obvious I am not ashamed too much to air my dirty laundry in public. That's pretty much the point of threads like this. To make people aware that modification is not so simple. We have all sorts of problems with mechanicals, suppliers, experts etc. I believe miscommunication is one of the biggest culprits.

Keep the comments coming please. Good bad or just plain taking the p1ss.
All stories have ups and downs. I am sure this one will have a happy ending.

Looking forward to getting home and measuring those chambers.

[DangerousDerek]

Chamber volume = 28cc. Sheet of acrylic and a medical 60ml syringe did the trick.

Check my maths
bore 96, stroke 86.3 = 624.66cc
piston bowls 20cc, top ringland 2cc, 7,5 thou deck clearance 1.38cc, gasket (1.28mm) 9.26cc, head chambers 28cc = 60.64cc

624.66 + 60.64 = 685.3 / 60.64 = 11.3

60 thou MLS gaskets would give me an extra 1.89cc which would drop the CR to 10.99

Decisions?
Any thoughts?

[DangerousDerek]

Confirmed and measured the CR is 11.3:1 with Elring 1.28mm gaskets. A little chamber work and 60 thou MLS gaskets will bring the CR into the 10's. On Vpower at least and VP racing fuel for the strip it will be fine (famous last words).

As for the left bank of tilted pistons I am still not happy and will be talking to Roland some more and may have to take the engine back to him to investigate and put right. May even have him build and dyno if the price is right.

[DangerousDerek]

The engine is going back to ACR and they have agreed to build it free of labour charge. Now considering an ECU upgrade. Either Omex710 or Pectel which I've never heard of.

[DangerousDerek]

neal1980 said:

Good to see it progressing again

Why you considering the change in ECU???

I want more control and reliability.
When at Dales we tested the map switch and it wasn't working so I wasn't getting a retarded map on nitrous. It turned out to be a wire cam loose in the ECU.
The other 2 are recommended by Roland and what he prefers to work with. I am thinking to letting him build the engine as he said for free and to map it on his dyno.

[DangerousDerek]

BoostedChim said:

DangerousDerek said:

When at Dales we tested the map switch and it wasn't working so I wasn't getting a retarded map on nitrous. It turned out to be a wire cam loose in the ECU.

Do you think you ran the normal NA igntion timing when the piston melted then?

Dale made the repair and I am confident it was working on track as it did on the rollers. Still a worry that this can happen.
On reflection not the greatest idea to rely that the map switches on nitrous activation. It would make more sense to make sure the nitrous only works if it's on the retarded map.

Such changes and safety measures will be put into place.

[DangerousDerek]

I am sticking with the MS2 guys.

[DangerousDerek]

Ready to go back to Roland at ACR.
Lets hope he sorts it properly. He made a very kind offer to build it for me for free.
The engine will also be tuned on his dyno when its done.





seems to take up a lot of space in a 1 series BMW!

[DangerousDerek]

Sardonicus said:

Nice one Derek running soon then.

I will be happy to have it running at Christmas giving me time to getting miles on it and race ready for easter.

The car is getting trailered to Teeside next week to have a full MSA spec cage fitted.

[DangerousDerek]

Sardonicus said:

Keep me posted on the drag dates Derek I fancy some next year along with a few others am sure

We will have the usual meet at the pod and Shakey at least once.

I really hope i can convince that a journey to Yorkshire will be worth it.
York have a meeting mid summer that includes the Street Racer championship. Its a great meeting to come along either to RWYB or join in the racing. I think Neals car could stand a good chance of taking the £1000 prize money.

I would love to see a turn out of modified TVRs at ten of the best at Elvington. Its a fantastic weekend, with 1/4 mile drags, a short but testing handling course and the famous flying kilometre. Get to stretch the legs somewhat on that one!