1970 GT6 MK2

[JohnD]

SpeedySix,  just noticed your comment on chamber sizes, above.   "Plus or minus a cc or so"   will make a big difference to the CR in different cylinders!  

That wont do, only +/- less than half a cc is acceptable.    Only needs a little work with a die grinder to equalise them.

John

Edited June 9, 2024 by JohnD

[Speedysix]

On 6/9/2024 at 3:06 PM, JohnD said:

SpeedySix,  just noticed your comment on chamber sizes, above.   "Plus or minus a cc or so"   will make a big difference to the CR in different cylinders!  

That wont do, only +/- less than half a cc is acceptable.    Only needs a little work with a die grinder to equalise them.

John

Thanks John, yes I'll be repeating the test with somthing over the chambers as I fill them up, that was where the uncertainty in the measures was coming from. Hopefully they all should be spot on!

Jacob

[Speedysix]

Small update.

Pistons all in block and torqued to spec. I put two flywheel bolts in the crank and used a small 30cm long bar to turn it over. It's moves nicely, there are a few spots I'd describe as flat or tight, but I mean very minor. I'd expect this on a reground unit with new bearings?

Cap no4 had been removed and thrust faces cleaned of graphogen. I have orderer an oversize thrust from rimmer so come the end of the week the end float should all be squared away.

[Nick Jones]

Crank with torqued up mains should turn smoothly and completely evenly. Fit pistons without rings and torque big ends and it should be the same (though few would do this in a standard engine build - I only did it to determine deck height for block skimming).

However, once the rings are fitted, that changes. Points where all pistons are around mid-stroke are highest torque.

[Speedysix]

I'll give that a try tomorrow. I did spin the crank after torqueing down the mains and it was perfectly smooth. Every time I added a piston and torqued the big end I gave it a little rotate and that feeling of it having resistance only increased with more pistons so I assume it's just the rings gripping the cylinder at diffrent heights.

I'm slightly fearful of removing the rings, I have done this once and broken one

I also managed to re cc the chambers tonight, all except no6 which has the valve seat issue. An average from 5 should be enough. Averaged out at 33.7cc. That seemed on the low side to me? This head is definitely thinner than the other vitesse one I recently acquired but not by much. I've yet to work out the cr from this

[Speedysix]

Cr calculated, if someone's able to confirm..

1998 / 6 = 333cc 

Bore + 0.020" (0.508mm)   = 75.208mm  radius 75.208/2 = 37.604mm

compressed head gasket thickness  = 3.5cc

non decked volume = 2.7cc

swept volume 3.1416 x (37.604 x 37.604) x 76÷1000 = 337.6234cc

combustion chamber volume (actual arrived by via pippette method) = 33.7

CR calc
(337.6234 +3.5 + 2.7 + 33.7) / (33.7+2.7+3.5) =  9.4617 to 1

[JohnD]

 Suggest you check your final division calcs!   I get a CR of 9.16.  Much better than OE but not 9.5.

John

PS I used "337.6".   Ten thousandths of a ml really aren't significant!

[Speedysix]

4 hours ago, JohnD said:

 Suggest you check your final division calcs!   I get a CR of 9.16.  Much better than OE but not 9.5.

John

PS I used "337.6".   Ten thousandths of a ml really aren't significant!

Not sure what I'm doing wrong, using the formula from your guide,

"CR = Stroke volume + Compressed volume / Compressed volume

(Remember that Compressed Volume = Combustion Chamber Volume + Gasket Volume + In Block Volume)"

Stroke volume 337.6 cc

Combustion chamber volume 33.7cc

Gasket volume 3.5cc

Non decked volume 2.7

So CR= 337.6+(33.7+3.5+2.7)/33.7+3.5+2.7 

Still gives 9.46, how did you get 9.16?

[JohnD]

Simon, my apologies.  You are quite correct!

I did the calculation  several times on my pocket calculator (remember those?) and got 9.16 every time.

I thought to do it by long division on paper (remember that!) but life is too short, so I did it on my phone's calculator and got 9.46!   And using the Google calculator!   

 it's solar powered, so it's not a battery problem.  Then I looked again and realised:  some of the segments of the calculator's LED  digits are 'ghosted'!  That "1" is the upright of where it was trying to show me a "4"!  And its getting worse!   I need a new pocket calculator!

[Nick Jones]

21 hours ago, Speedysix said:

I'm slightly fearful of removing the rings, I have done this once and broken one

I’m absolutely not suggesting that you pull it apart and remove the rings to check at this stage!

6 hours ago, Speedysix said:

Still gives 9.46

Pretty much factory. Suggest that’s a good place to leave it.

[RedRooster]

https://www.computinghistory.org.uk/det/65624/Casio-HS-8G/

39years old. 

[yorkshire_spam]

10 hours ago, RedRooster said:

https://www.computinghistory.org.uk/det/65624/Casio-HS-8G/

39years old. 

That one comment just wasted about 30 minutes of my time... down the rabbit hole of trying to work out which Casio models I had at home/school over the years. (FX-140 at home, FX-451M for school) 

[Speedysix]

On 6/11/2024 at 9:53 PM, Nick Jones said:

I’m absolutely not suggesting that you pull it apart and remove the rings to check at this stage!

Pretty much factory. Suggest that’s a good place to leave it.

I got to the bottom of it in the end, was perfectly fine, just me not factoring in the rings in the bores. Rotates as it should!

Yes agreed. It will need a reface but that will hopefully bring it up to 9.5 ish, shouldn't need too much off to get a good surface.

[Speedysix]

On 6/11/2024 at 6:54 PM, JohnD said:

 

I did the calculation  several times on my pocket calculator (remember those?) and got 9.16 every time.

I thought to do it by long division on paper (remember that!) but life is too short, so I did it on my phone's calculator and got 9.46!   And using the Google calculator!   

 

Aha no problem John, yes Calaclators Lie sometimes! Some like thst don't follow the bidmas rules and you can't use brackets. Anyway we got to the bottom of it

[Speedysix]

Bottom end mostly together! Enfloat i managed to do one of the tricks suggested on here

glass shelf from the fridge and some 240 wet and dry. Wd40 for some lube and just took down the steel face with a few passes.

Cleaned and refitted:

absolutely perfect

And for sanity again, definitely the right way around

Frustrating evening yesterday, was hoping to continue but my hylomar didn't arrive in the post. Hopefully today!

Lastly the oil galley plugs, what's the general feeling, a blob of hylomar or loctite, or dry? 

[egret]

18 minutes ago, Speedysix said:

Aha no problem John, yes Calaclators Lie sometimes! Some like thst don't follow the bidmas rules and you can't use brackets. Anyway we got to the bottom of it

Due to an old habbit of rushing calculations I got into the habbit of using excel for almost all of them now.  It allosw you tp split the calculation up into sections to help check and interrogate the answer rather than have to keep stuff in your brain, or lose steps in the brain of the calculator!

Also, some advice from my recent engine rebuild is that I didn't use any sealant around the oil feed to the head when I put head on.  I now have a small oil weep at the back of the head and regret not doing the sealant trick!

[Speedysix]

3 hours ago, egret said:

 

Also, some advice from my recent engine rebuild is that I didn't use any sealant around the oil feed to the head when I put head on.  I now have a small oil weep at the back of the head and regret not doing the sealant trick!

This is a trick I learnt from minis! Guaranteed to weep from them even with perfect faces. Hylomar blue does the trick nicely!

[Speedysix]

Today I aimed for more progress, but couldn't due to parts.

Sealing block in and I think the last time when I rush built the engine, I kissed a very important trick with this... making sure the block is flush with the front of the engine! I didn't realise there was some movement in it. This would explain the oil leak.

The next one stumped me. I was about to fit my new seal into my rear seal housing

i wondered how far the seal should be as its a straight machined hole in the plate, so i checked my vitesse one from the engine i just bought... suprise suprise, they are slightly diffrent! The vitesse one has a shoulder for the seal to mate up to. The only advantage I can see here is that it can't go anywhere, and ensures the seal is at the correct position. I might use this one, seems like a better thing to me?

[Nick Jones]

Top one is old style. You have to remove the housing to renew the seal and the seal does have pretty much have only one possible position. Which is fine if your crank has no groove worn in it.

The later(and by far more common) one at the bottom allows the seal to be renewed without further dismantling and some adjustment of position, which can be helpful if you have a wear-groove to avoid.

Don’t be afraid to use a decent quality silicon sealant (in moderate quantities!) -  it works!

[Speedysix]

22 minutes ago, Nick Jones said:

Top one is old style. You have to remove the housing to renew the seal and the seal does have pretty much have only one possible position. Which is fine if your crank has no groove worn in it.

The later(and by far more common) one at the bottom allows the seal to be renewed without further dismantling and some adjustment of position, which can be helpful if you have a wear-groove to avoid.

Don’t be afraid to use a decent quality silicon sealant (in moderate quantities!) -  it works!

Thanks Nick, I think I'll stick with the existing newer one then!

Frustrating my tube of silicone stuff has dried up!

The oil galley plugs, the little Allen head ones and bigger threaded ones, smear of sealant/loctite on these or dry?

[Nick Jones]

I do use a lock / seal compound on the gallery plugs.

Typically just blue loctite, though there are also products with the same basic chemistry, but a little more viscosity that claim to be actual sealants. Hylomar probably effective too.

[JohnD]

While Nick's suggestion of fitting the seal in slightly different places works, there is always the SpeediSleeve approach.   https://www.skf.com/uk/products/industrial-seals/power-transmission-seals/wear-sleeves/skf-speedi-sleeve

[Speedysix]

13 hours ago, Nick Jones said:

I do use a lock / seal compound on the gallery plugs.

Typically just blue loctite, though there are also products with the same basic chemistry, but a little more viscosity that claim to be actual sealants. Hylomar probably effective too.

Typical, went to use mine earlier and also all dried up. Will have to wait now until postie delivers more.

[Speedysix]

24 minutes ago, JohnD said:

While Nick's suggestion of fitting the seal in slightly different places works, there is always the SpeediSleeve approach.   https://www.skf.com/uk/products/industrial-seals/power-transmission-seals/wear-sleeves/skf-speedi-sleeve

I've seen these a while ago, a really good solution! I've yet to actully check if my new crank has a groove but I doubt and hope not

But good to know there's a solution!

[Speedysix]

Last night was a bit of a mish mash of jobs, ticking off various bits and slowly getting more done.

spare wheel, my wheels are 5.5, I assume this is the wheel width? 4.5's fit the gt6 fine right? Can get one for 15 quid delivered from Dave at spitty graveyard, which is a steal.

A few misc other jobs that I wanted to address, sunvisors.

this was before, they sat too low and the friction between the pegs and mounts on the sunvisor was not enough. So as you saw me earleir, I shortened the pegs and attempted to nickel plate them. On thr whole not bad, required polishing but they're passable

After remaking the brackets on the sunvisors and a bit of fettling, I'm much happier with the results. Before they used to flop down from the single mounting point on the car, so I closed the hole up a tad with a hammer and chisel, such that the self tapper grips much better....

They have. Seems to be staying up so far, if it flops down I'll dab some loctite on them.

Next was the seatbelt refurb, the buckles have been sticking to the vinly in the car and ruining the paint on them. 3 years later, they look like this

They need stripping off and repainting or coating in matt black, I just want to avoid this annoying sticking again