New block worries
Discussion
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.
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.
Take the time to burette the heads etc - still think the unanticipated increase in CR resulting from the greater swept volume of the bigger bores will be a key factor in the failure last time around; was maybe just enough to tip you into det when you were previously safe on your set-up
Pupp said:
Well assuming the rods were on the crank, and the pistons on the rods and in the holes the right way round and the right way up, it's not that is it? 
Exactly hence the confusion previously fitted/used Elrings are 1.28mm and 1.3mm BN loose/not fitted Derek, what I cant get my head round (forged pistons or otherwise)is if you have those kind of figures from one bank to the next your static CR's are going to be odd 
7 thou/.18 mm difference is a lot in relative terms 
Edited by Sardonicus on Tuesday 25th August 09:27
Pupp said:
I understood the description to be that the pistons were tilting along the line of the thrust and non-thrust face (ie at right angles to the gudgeon pin)
Thats my confusion then Gary bloody internet nothing like being there or pictures we all have differing descriptions 
Derek shed some light and tell me my pic opinion is wrong then it all becomes clearer Sardonicus said:
Pupp said:
But if Dereks description is this I assume then I am still 
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
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.
And although de-compression plates are hated by the world remember they were used in my old rover engine which has never missed a beat for over 15,000 miles now. Just use ARP's and the special compound and you will be fine should you decide / need / have no choice to use these.
Have you decided what your doing on the new build yet, nitrous or turbo, Supercharged ???
Good Luck
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.
And although de-compression plates are hated by the world remember they were used in my old rover engine which has never missed a beat for over 15,000 miles now. Just use ARP's and the special compound and you will be fine should you decide / need / have no choice to use these.
Have you decided what your doing on the new build yet, nitrous or turbo, Supercharged ???
Good Luck
Graham said:
you can get mls to a wide range of thicknesses iirc i had to get a 60 thou cometic to get my CR right after a head skim as its already very high, Although i suppose you could say an mls is essentially a decompression plate lol
Not if it retains some squish and is the only head gasket :-).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?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.
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 said:
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.
I have been following your antics all year Derek....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.
Although I fail to see the point...you cant be that busy you dont have a spare half hour to measure your engine!
Look forward to seeing the new build anyway and if all goes well mine should be MOT'd in the next 2 weeks then that challenge will be there
Are you going to Neil Garner day ??
Derek, I do believe Neal is trying to help by being honest. Really not putting you down here mate but having folk say things like, 'that's bad luck' or 'what a bummer' etc is nice, but it doesn't help you get to the bottom of the problem. Having parts supplied with an approximate/assumed CR is a bit scarey. Remember my pistons? we thought they were around 8.5:1 with standard gasket, yet they turned out to be 7.45:1 and I had to do some work to get it up again [ohh, err] Even the standard TVR block has 9.35:1 stamped on it and we know that's not right.
Really wish you all the best with it bloke and I'm sure you'll be beating all comers again soon.
Really wish you all the best with it bloke and I'm sure you'll be beating all comers again soon.
Edited by macdeb on Wednesday 26th August 10:18
Edited by macdeb on Wednesday 26th August 10:20
macdeb said:
Derek, I do believe Neal is trying to help by being honest. Really not putting you down here mate but having folk say, 'that's bad luck, what a bummer' etc is nice, but it doesn't help you get to the bottom of the problem. Having parts supplied with an approximate/assumed CR is a bit scarey. Remember my pistons? we thought they were around 8.5:1 with standard gasket, yet they turned out to be 7.45:1 Even the standard TVR block has 9.35:1 stamped on it and we know that's not right.
Really wish you all the best with it bloke and I'm sure you'll be beating all comers again soon.
Agreed that's what were here for Really wish you all the best with it bloke and I'm sure you'll be beating all comers again soon.
I want to see Derek & Tiv kicking arse again 
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.
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.
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?
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?
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