1.9 Head Skim Of 0.75Mm - Do I Need A Vernier Pulley ?

[sharpm 1]

hello

 

 

my first real post, so be gentle with me ............. yes ive searched and all that but cant find a definitve answer.

 

 

as per the title, i'v just finished rebuilding the engine and just wondering before I fire it up at the weekend whether I'll need a vernier pulley or not ??

 

Its a standard 1.9, standard cam with 0.75mm off the head and a standard thiickness head gasket.

 

 

 

thanks.

[daneldridge23 15]

All a vernier pully is, is to advance an retard your timing more precisley, it makes no difference if you have had your head skimed.

75 thou sounds alot tho, i had mine done and had 25 took of wich i thoight was alot? Or is that just me

[Tom Fenton 1,526]

All a vernier pully is, is to advance an retard your timing more precisley, it makes no difference if you have had your head skimed.

75 thou sounds alot tho, i had mine done and had 25 took of wich i thoight was alot? Or is that just me

 

Wrong and wrong.

 

I know you are just trying to help. But please make sure 100% you know what you are on about. There is a clause in the forum rules about this.

 

When the head is skimmed, it moves the cam towards the crank, and hence can throw out the cam timing, hence if you are meticulous and check the timing, you may find a vernier pulley is required to correct it back to standard.

 

Also 0.75mm is not 75 thou. 75 thou refers to 75 thousands of an inch. Which is 1.905mm.

[daneldridge23 15]

I stand corrected! But i must ask, if its just a standard engine that has had a skim, is a vernier pully a bit excesive for it? Or unless like you say if you are very meticulos about your engine and dont mind spending tje extra cash

[welshpug 1,626]

not excessive at all if you want it to work as it should, a pulley isn't that expensive, plus with the raised compression a hefty skim gives cam and ignition timing is even more important.

 

if you were talking a minimal skim (say 0.2mm) and were using a repair gasket (+0.2mm) rather than a standard one then your overall crank to cam distance and hence the timing will be unaffected.

[daneldridge23 15]

Logged into brain! So while were on the topic, my head has been skimmed 25 tho i have fast road cams, what gasket should i use then as i want the highest compression i can get, and am i going to have any clerance issues with my valves and pistons. Im glad i bought my pullys now!

[sharpm 1]

forgot to say that when i fitted the timing belt the 10mm dowels fitted perfectly in both timing holes on the crank and cam pulleys - so the 0.75mm (30thou) skim couldnt have thrown it off too much.

 

obviously the skim will have upped the compression slightly so is there any change to the ignition timing needed and how do I do set it ?? - there are marks on the crankshaft pulley already.

 

want to get it up and running then get it set up properly on the rollers, but just didnt want to get it on the rollers to have the guy tell me that he couldnt set it up properly without a vernier - thats why I initillay asked if I needed one.

[welshpug 1,626]

the pins will probably fit fine but the front of the belt will be ever so slightly slack, easiest way to set the timing is by lift @ TDC, just adjust the cam till its within spec, it wont be a massive amount.

 

Dan -

 

you say you have "cams" and "pulleys" in the plural... what engine do you have?

 

with the 8v you do have a fair amount of clearance but specifically I don't know, should be able to find something on the search though, I know a PTS gravel cam will work in a standard head.

 

with the 16v you're on the limit for the XU10J4RS head and unless you have forged pistons (or modified standard pistons) will need to use a repair gasket or ditch your "fast road" cams, depending on which cams you may not be able to use them at all.

 

 

anyway, get your own topic

Edited December 9, 2011 by welshpug

[daneldridge23 15]

Lol its xu9 mi

[feb 47]

the pins will probably fit fine but the front of the belt will be ever so slightly slack, easiest way to set the timing is by lift @ TDC, just adjust the cam till its within spec, it wont be a massive amount.

 

with the 8v you do have a fair amount of clearance but specifically I don't know, should be able to find something on the search though, I know a PTS gravel cam will work in a standard head.

 

 

If the cam is timed as per cam manufacturer's spec but the head is very slightly skimmed and using a standard thickness HG, wouldn't this mean that you would have to retard the timing as the valves are now closer to the pistons?

Edited December 9, 2011 by feb

[welshpug 1,626]

only if valve to piston clearance is an issue.

[daneldridge23 15]

Need to get the plastigauge out then me thinks

[kyepan 291]

Need to get the plastigauge out then me thinks

what for?

[kyepan 291]

what gasket should i use then as i want the highest compression i can get

 

Have you checked the liner protruderance? as it may not last very long if you wind up the compression without making sure that is at least within factory tolerance. I have been told by Maxi that the iron block 2.0l mi's respond better to increased compression.

 

check back and search for drsarty, he used a copper head gasket to up the compression, it lasted a few thousand miles, perhaps less.

 

might be worth checking things first, or alternatively, wind it up and pray it doesn't pop.

 

cheers

 

J