Exmo Revamp

[Guest 2b cruising]

Don't just have 14 though taken off the head.

Measure it first, engine reworkers should know minimum depth of head allowed.

If it has been done before, it could end up with valves saying hello to pistons in a much to friendly manner. (Kissing on first date)

[brumster]

Friendly manner?! In Glasgow, maybe !

[richardm6994]

Where did the 14-thou figure come from because you can't just randomly guess this kind of measurement.

 

If the head has been skimmed before, and you take more material off, you could end up needing a cometic MLS head gasket to build the thickness of the head back up to avoid valve contact with the piston or too high compression ratio ......these head gaskets are around £130 each!

 

When skimming an unknown head...................the surface grinder's first pass needs to remove the least amount of material as possible off in order to clean-up the face (there shouldn't be much warping but if there is then the first skim must also true-up the head face) and gives you a good-clean datum.

 

After the first skimming-pass, you then need to calculate what the combustion chamber size is that you are left with so you can then work out what compression ratio you'd be running.........remember that a pinto on standard pistons can only run a max 10.5 compression ratio.

 

Depending on what combustion chamber size that the first skim leaves you with will then determine how much more material can come off the head.........if it was a clean / straight head.....then the first skim-pass should only remove 3 or 4 tho........

 

You also have to be mindful of piston to valve clash when removing material from the head......which I think also depends upon the duration of your cam?

 

 

 

 

From what I remember......40-50 thou is a good rule of thumb as being the most material that can be removed from a standard head with a standard cam (if removing this amount of material then its best done on a vertical milling machine and not surface grinder).........this should give you around 10:1 compression.

Edited October 5, 2015 by steamer

[jaimo]

It's going headmasters so they check first but from experience doesn't look to of been skimmed before but there the experts just rule of thumb 14 thou rich due to advice from stu

[richardm6994]

You're seriously taking advice from this man?!?!.....

Edited October 5, 2015 by steamer

[Guest mower man]

Not wanting to be too techy but c/r can altered /lowered by working the chambers also equalising them ,ok its extra work but is worth it [smoother engine performance ] . My 2.1 ran v6 flat tops less than 1mm deck clearance but a 1,5 mm gasket compressed and was some where between 10.5 and 11.0 cr after mods, you have nearly all my secrets its up to you to build it PROPERLY!!! NO SHOT CUTS ETC

[biksz]

Rich how dare you take my weekend pic lol I was advised to have 40 thou took off but after speaking to head man he advised unless racing it don't go more than 20 thou for road use so I decided if not a lot was took off to go 14 thou which I think has improved the engine if he did take 14 thou off he might of only took 8 thou as he said what do I want to do so I told him to what he could.

[jaimo]

Decided to stick with Weber 32\36 for now so ordered new manual choke Weber 32\36 as I really wanted to stick with the phlenum as it is a work of art done by steamer

Also took delivery of cycle wings kindly donated by john still building so gone are the clam wings just got to paint and fabricate some mountings and cut down suspension mountings

[theduck]

Got any pics of the plenum?

[jaimo]

[theduck]

Ooh I like. Might have to get him to make me one

[jaimo]

Yeah its a top job and that nice keeping it over bike carbs

[Guest 2b cruising]

Once I get the z20 in I will look into having a plenum along the side of engine cutting away the bonnet side so it can be seen and shown off. Not even started the conversion yet as car is going back to GBS.

[jaimo]

Well the Weber never happened due to no supply's from retailer so got some r1 bike carbs for a bargain price

 

So now just got a few other pics to source then when we get keys for new house got few jobs in there to do then on with revamp of engine and hopefully a few other jobs before stoneleigh

[jaimo]

heres the latest purchase