Shimmed valve clearances. Set during build?

Shimmed valve clearances. Set during build?

Author
Discussion

Megaflow

Original Poster:

7,643 posts

193 months

Thursday 27th May
quotequote all
A question for the guys with pass car engine assembly experience. Engine that use shims to set valve clearance’s, how do they select the required size shim during assembly?

Do they dry build, measure, strip and then build with the required size? This seems highly unlikely to me. Or do they use a nominal size shim that is designed to land within the middle of the tolerance range?

Thank you.

ETA: title should say build. Bloody phones…

Edited by Megaflow on Thursday 27th May 13:14

Scrump

14,774 posts

126 months

Thursday 27th May
quotequote all
Title corrected for you.

Boosted LS1

20,077 posts

228 months

Thursday 27th May
quotequote all
If possible I'd measure the existing clearance and then change the shims to suit what I needed. It's the lobe to follower clearance that's beng measured/shimmed.

Megaflow

Original Poster:

7,643 posts

193 months

Thursday 27th May
quotequote all
Boosted LS1 said:
If possible I'd measure the existing clearance and then change the shims to suit what I needed. It's the lobe to follower clearance that's beng measured/shimmed.
Sorry, that’s not what I was asking, I’d like to know how the do the very first build in the factory. 100% brand new components that have never been introduced to each other before. So there is nothing to measure.

stevieturbo

15,502 posts

215 months

Thursday 27th May
quotequote all
Megaflow said:
Sorry, that’s not what I was asking, I’d like to know how the do the very first build in the factory. 100% brand new components that have never been introduced to each other before. So there is nothing to measure.
OEM know every measurement, they build them, they machine them...they have the equipment to get it right.

There is always something to measure if you have the right tools.

If you have no lifter...there is a gap to measure. If you have a lifter that's too big...there would be an open valve to measure etc etc

DVandrews

1,190 posts

251 months

Thursday 27th May
quotequote all
It’s easy to establish shim thickness, I do it all the time, assemble the valves springs and caps to the head. Normally you use a control shim and do the followers one at a time, if the control shim gives no gap, go down to a thinner control shim, check the gap, select the appropriate shim to give the correct gap, go on to the next lobe/follower.

Dave

Edited by DVandrews on Friday 28th May 08:54

Yuxi

528 posts

157 months

Monday 31st May
quotequote all
I was lead engineer on an engine assembly line instalation in the Philippenes,I was responsible procurement, technical sign off and instalation of a machine to do exactly this.
It was a 4 cylinder petrol engine, 16 valve DOHC engine. Cycle time was 3.85 minutes.
Heres the process -
Engine with head already on (with cam caps attached, these have not yet been removed after machining the cam bores) arrives in station, in parallel the pair of cams for the that engine are put into a gauging machine which measures each journal diameter and each lobes base circle diameter and distance to journal center. The engine goes into a machine that measures cam bore diameter and valve tip to cam bore center.
With this information the machine control works out the ideal tappet thickness for each valve.
An operator takes a fixture with 16 holes in it and places it on a slide in front of the tappet storage rack. Lights on the rack then guide the operator to select the correct tappet for each valve and place it in the fixture.
Once the fixture is full its then taken to another machine which measures the thickness of each tappet to ensure the correct tappet has been selected.
Next the cam caps are removed then the fixture with the tappets is placed on top of the head locating in two reamed holes. The tappets are then pushed through the fixture and into the tappet bores.
Next the two cams are fitted, then the caps are fitted using 20 electric spindles.
Then each position is checked manualy by an electronic gauge which works by measuring the distance between two balls which locate on the face of the tappet and the base circle of the cam.
Any out of limit are replaced manualy.
Its not an exact science and there is always a "fudge factor" built in to get the correct result.
The machine cost 1.3 million Euros 15 years ago.
I also did the conrod weight grading, piston, and main and big end bearing liner selection equipment.


Edited by Yuxi on Monday 31st May 08:03

Boosted LS1

20,077 posts

228 months

Monday 31st May
quotequote all
^ Fascinating. I wish there were more posts like this.

RizzoTheRat

21,054 posts

160 months

Monday 31st May
quotequote all
Interesting post, thanks.

When I did the shims on my Yamaha some time back I noticed that the original ones were to 0.01mm, while replacement ones are to 0.05mm. Do they assume the gaps will change in one direction (closing up as the valve/seat wear?) and set them further the other way initially?

Evoluzione

6,312 posts

211 months

Monday 31st May
quotequote all
Yuxi said:
I was lead engineer on an engine assembly line installation in the Philippines, I was responsible procurement, technical sign off and installation of a machine to do exactly this.
It was a 4 cylinder petrol engine, 16 valve DOHC engine. Cycle time was 3.85 minutes.
Here's the process -
Engine with head already on (with cam caps attached, these have not yet been removed after machining the cam bores) arrives in station, in parallel the pair of cams for the that engine are put into a gauging machine which measures each journal diameter and each lobes base circle diameter and distance to journal centre. The engine goes into a machine that measures cam bore diameter and valve tip to cam bore centre.
With this information the machine control works out the ideal tappet thickness for each valve.
An operator takes a fixture with 16 holes in it and places it on a slide in front of the tappet storage rack. Lights on the rack then guide the operator to select the correct tappet for each valve and place it in the fixture.
Once the fixture is full its then taken to another machine which measures the thickness of each tappet to ensure the correct tappet has been selected.
Next the cam caps are removed then the fixture with the tappets is placed on top of the head locating in two reamed holes. The tappets are then pushed through the fixture and into the tappet bores.
Next the two cams are fitted, then the caps are fitted using 20 electric spindles.
Then each position is checked manually by an electronic gauge which works by measuring the distance between two balls which locate on the face of the tappet and the base circle of the cam.
Any out of limit are replaced manually.
Its not an exact science and there is always a "fudge factor" built in to get the correct result.
The machine cost 1.3 million Euros 15 years ago.
I also did the conrod weight grading, piston, and main and big end bearing liner selection equipment.
Fast forward to today and some bloke is rebuilding it with a hammer and a bent spanner on his drive biggrin

Very interesting post and thanks for writing. I bet you could write about that kind of thing all day and some of us on here would love to read it.
I do not have a clue how the engines I work on today were originally made and put together, but sometimes ponder over certain things I see. I do wonder how much was done by robot and where the human intervention came in.

Penelope Stopit

8,854 posts

77 months

Monday 31st May
quotequote all
Yuxi said:
I was lead engineer on an engine assembly line instalation in the Philippenes,I was responsible procurement, technical sign off and instalation of a machine to do exactly this....................................................................................................................
Great post

Thank you very much

Megaflow

Original Poster:

7,643 posts

193 months

Monday 31st May
quotequote all
Yuxi said:
I was lead engineer on an engine assembly line instalation in the Philippenes,I was responsible procurement, technical sign off and instalation of a machine to do exactly this.
It was a 4 cylinder petrol engine, 16 valve DOHC engine. Cycle time was 3.85 minutes.
Heres the process -
Engine with head already on (with cam caps attached, these have not yet been removed after machining the cam bores) arrives in station, in parallel the pair of cams for the that engine are put into a gauging machine which measures each journal diameter and each lobes base circle diameter and distance to journal center. The engine goes into a machine that measures cam bore diameter and valve tip to cam bore center.
With this information the machine control works out the ideal tappet thickness for each valve.
An operator takes a fixture with 16 holes in it and places it on a slide in front of the tappet storage rack. Lights on the rack then guide the operator to select the correct tappet for each valve and place it in the fixture.
Once the fixture is full its then taken to another machine which measures the thickness of each tappet to ensure the correct tappet has been selected.
Next the cam caps are removed then the fixture with the tappets is placed on top of the head locating in two reamed holes. The tappets are then pushed through the fixture and into the tappet bores.
Next the two cams are fitted, then the caps are fitted using 20 electric spindles.
Then each position is checked manualy by an electronic gauge which works by measuring the distance between two balls which locate on the face of the tappet and the base circle of the cam.
Any out of limit are replaced manualy.
Its not an exact science and there is always a "fudge factor" built in to get the correct result.
The machine cost 1.3 million Euros 15 years ago.
I also did the conrod weight grading, piston, and main and big end bearing liner selection equipment.


Edited by Yuxi on Monday 31st May 08:03
Beautiful. Exactly the information I was looking for, thank you Yuxi.

stevieturbo

15,502 posts

215 months

Monday 31st May
quotequote all
I think many simply do not get the level of equipment the OEM have when building engines.

It's is light years beyond what even good workshops or machine shops would ever have.

There are various videos on Youtube etc of them building engines etc which is very interesting to watch. ( some of the videos of huge engines for boats etc are equally fascinating. )

https://www.youtube.com/watch?v=w4uMX5mWAF4

Obviously it doesn't go into all detail...but still cool

https://www.youtube.com/watch?v=s4sEzlbeVMw

Edited by stevieturbo on Monday 31st May 18:00

colin_p

3,338 posts

180 months

Monday 31st May
quotequote all
I would have thought in this day and age most (non racing or specialist) engines would have hydraulic tappets which negate the need for shimming.

I'd be interested to know what doesn't and i'd also be interested to know if pushrod ohv engines are still being made? I'm fairly certain some Amercian V8's still are?

Boosted LS1

20,077 posts

228 months

Monday 31st May
quotequote all
^ Chevrolet LS series and now LT.

DVandrews

1,190 posts

251 months

Monday 31st May
quotequote all
colin_p said:
I would have thought in this day and age most (non racing or specialist) engines would have hydraulic tappets which negate the need for shimming.

I'd be interested to know what doesn't and i'd also be interested to know if pushrod ohv engines are still being made? I'm fairly certain some Amercian V8's still are?
The Ford/Mazda Duratec has solid lifters.

Hydraulic lifters are the answer to a maidens prayer but can only handle a certain amount of valve acceleration , more extreme profiles pump them up or out.

Don’t think I can make the sort of hardware investment outlined above, prefer the more labour intensive but lower capital spend method and ultimately it is without compromise.

Dave

Penelope Stopit

8,854 posts

77 months

Tuesday 1st June
quotequote all
Off topic

Is there such a thing as a cheap shim grinder ?

Megaflow

Original Poster:

7,643 posts

193 months

Tuesday 1st June
quotequote all
colin_p said:
I would have thought in this day and age most (non racing or specialist) engines would have hydraulic tappets which negate the need for shimming.

I'd be interested to know what doesn't and i'd also be interested to know if pushrod ohv engines are still being made? I'm fairly certain some Amercian V8's still are?
Lots of industrial off highway diesels are still OHV & pushrod.

RizzoTheRat

21,054 posts

160 months

Tuesday 1st June
quotequote all
Penelope Stopit said:
Off topic

Is there such a thing as a cheap shim grinder ?
I thought shims were case hardened so you shouldn't grind them?

DVandrews

1,190 posts

251 months

Tuesday 1st June
quotequote all
..

Edited by DVandrews on Tuesday 1st June 15:58