Valve to Piston Clearances

[dlbarnes1]

Hi All,
I need to check valve to piston clearances using modeling clay or whatever. I haven't done this before, so I'm interested in any suggestions, hints or details of the procedure. Thanks
David 72 Sprint DHC

[types26/36]

--- In ***@***.***, "David Barnes" <dande@s...> wrote:

suggestions, hints or details of the procedure.

David,
Take the clay and press it into the piston cutouts, about 5mm thick.
Grease the valves heads (this is to stop the clay sticking to the
valve)
Do a dummy build on the engine with an old head gasket.
Turn the engine over two full turns.
Remove the head, take a knife and cut the clay in half and measure
the
thickness of the clay, this is = to the clearance.
All the books I have read recommend a minium clearance of 60 thou
(1.5mm)
Brian.
64Elan/72Sprint/J.P.S.Europa/Birkin T.C.Seven

[dlbarnes1]

Brian,
Thanks. This is the info I was looking for.
David 72 Sprint DHC
----- Original Message -----
From: Brian Goodison
To: ***@***.***
Sent: Friday, May 13, 2005 12:25 AM
Subject: [LotusElan.net] Re: Valve to Piston Clearances


--- In ***@***.***, "David Barnes" <dande@s...> wrote:

suggestions, hints or details of the procedure.

David,
Take the clay and press it into the piston cutouts, about 5mm thick.
Grease the valves heads (this is to stop the clay sticking to the
valve)
Do a dummy build on the engine with an old head gasket.
Turn the engine over two full turns.
Remove the head, take a knife and cut the clay in half and measure
the
thickness of the clay, this is = to the clearance.
All the books I have read recommend a minium clearance of 60 thou
(1.5mm)
Brian.
64Elan/72Sprint/J.P.S.Europa/Birkin T.C.Seven















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***@***.***

[elj221c]

Dave,

Seems a lot of unnessary hassle unless you are using wild cams, very
heavily skimmed head or block ( both?) or funny piston/rod combination.
Using normal of all the above you only need a dial gauge and protractor
to set the cams along with a set of offset dowels.

The procedure I am sure has been detailed before.

Roy
'65S2

[Fred Talmadge]

I'd agree that it is unecessary for stock configurations, but it's really
not that difficult or time consuming. And it gives you a chance to
practice installing the head and cams. And the peace of mind it brings is
priceless.

What Roy describes is "dialing in the cams" is a worthwhile investment of
time. Compared to just lining up the dots on the sprockets it is probably
worth a few extra horsepower to get it exactly right. They also make an
adjustable sprocket that can save some time.

Fred

At 07:33 PM 5/15/2005 +0000, elj221c wrote:

[dlbarnes1]

Thanks for the comments. I've been using cams with 0.385" lift and in my current rebuild I'm figuring to mill 0.040" off the head. The pistons I'm using are Hepolite +0.030". I wasn't sure if the valve pockets in the pistons would accomodate the milled head. I may also want to experiment with advancing the intake valve timing. I've completed the valve to piston clearance check and it looks like the clearance is adequate for what I'm planning. Like Fred says "peace of mind".
David 72 Sprint DHC
----- Original Message -----
From: Fred Talmadge
To: ***@***.*** ; ***@***.***
Sent: Sunday, May 15, 2005 1:11 PM
Subject: Re: [LotusElan.net] Re: Valve to Piston Clearances


I'd agree that it is unecessary for stock configurations, but it's really
not that difficult or time consuming. And it gives you a chance to
practice installing the head and cams. And the peace of mind it brings is
priceless.

What Roy describes is "dialing in the cams" is a worthwhile investment of
time. Compared to just lining up the dots on the sprockets it is probably
worth a few extra horsepower to get it exactly right. They also make an
adjustable sprocket that can save some time.

Fred

At 07:33 PM 5/15/2005 +0000, elj221c wrote:














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***@***.***

[Guest]

David

20 years from now you will regret milling the head when there is no more left to mill and you cannot (afford to) get a new one, I did.

Rod

Rodney Stevens
CSIRO Minerals
http://www.minerals.csiro.au

Ph. 61 2 97106701
Fax 61 2 97106789

Personal Home Page
http://mywebpage.netscape.com/rodjohnst ... mepage.htm


-----Original Message-----
From: ***@***.***lto:***@***.***
Behalf Of David Barnes
Sent: Tuesday, 17 May 2005 1:39 PM
To: ***@***.***
Subject: Re: [LotusElan.net] Re: Valve to Piston Clearances


Thanks for the comments. I've been using cams with 0.385" lift and in my current rebuild I'm figuring to mill 0.040" off the head. The pistons I'm using are Hepolite +0.030". I wasn't sure if the valve pockets in the pistons would accomodate the milled head. I may also want to experiment with advancing the intake valve timing. I've completed the valve to piston clearance check and it looks like the clearance is adequate for what I'm planning. Like Fred says "peace of mind".

[rgh0]

--- In ***@***.***, "David Barnes" <dande@s...> wrote:

pistons I'm using are Hepolite +0.030".


David

I would not mill the head unless I had to in order to get it flat
again. They are just to expensive and hard to keep long term without
taking metal off unecessarily.

Your sprint engine with a standard head gasket has a 10.3 compression
ratio already if the head is standrd thickness which it is probably
not as almost all heads have already been milled in previous
rebuilds. With todays fuels you will struggle to run above about
10.5 in normal road use.

If you want a higher compression ratio because your planning to use a
fancy racing fuel or equivalent then better ways to get it than by
milling the head.

Rohan

[Elan45]

You are sooo right. If you want higher CR, buy pistons w/ taller pop-ups.



20 years from now you will regret milling the head when there is no more left to mill and you cannot (afford to) get a new one, I did.

Rod

Rodney Stevens
CSIRO Minerals
http://www.minerals.csiro.au

Ph. 61 2 97106701
Fax 61 2 97106789

Personal Home Page
http://mywebpage.netscape.com/rodjohnst ... mepage.htm


-----Original Message-----
From: ***@***.***lto:***@***.***
Behalf Of David Barnes
Sent: Tuesday, 17 May 2005 1:39 PM
To: ***@***.***
Subject: Re: [LotusElan.net] Re: Valve to Piston Clearances


Thanks for the comments. I've been using cams with 0.385" lift and in my current rebuild I'm figuring to mill 0.040" off the head. The pistons I'm using are Hepolite +0.030". I wasn't sure if the valve pockets in the pistons would accomodate the milled head. I may also want to experiment with advancing the intake valve timing. I've completed the valve to piston clearance check and it looks like the clearance is adequate for what I'm planning. Like Fred says "peace of mind".





















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[Fred Talmadge]

Unfortunately the heads do warp and they need to be flat. I explained
to my machinist how expensive a new head was and he understood and took
off as little as possible. You can also have a solid copper head gasket
made to make up the thickness lost. Might be expensive but probably
less than a new head.

Fred

[types26/36]

--- In ***@***.***, "Fred Talmadge" <FTalmadge@f...>
wrote:



I agree about taking off as little as possible and only as a last
resort,what is easy to remove is not as easy to put back.
I have heard that there is a process whereby a warped head can be
bolted to a solid steel block,heat treated and left to cool which
will "true up" the head, anyone had it done?
Also heard that if some heads are skimmed (not Lotus)when they are
refitted the alignment for the camshafts becomes distorted and it can
break the camshaft.
Brian.
64Elan/72Sprint/J.P.S.Europa/Birkin T.C.Seven

[saarhus]

I seem to recall that one of the upgrades to Sprint spec. was a .040" mill of the head? Am I remembering correctly?

Stan


pistons I'm using are Hepolite +0.030".


David

I would not mill the head unless I had to in order to get it flat
again. They are just to expensive and hard to keep long term without
taking metal off unecessarily.

Your sprint engine with a standard head gasket has a 10.3 compression
ratio already if the head is standrd thickness which it is probably
not as almost all heads have already been milled in previous
rebuilds. With todays fuels you will struggle to run above about
10.5 in normal road use.

If you want a higher compression ratio because your planning to use a
fancy racing fuel or equivalent then better ways to get it than by
milling the head.

Rohan















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***@***.***

[Rob_LaMoreaux]

I seem to recall that the US Spec Sprint motors were not milled to the 10.3
compression, so he might just be taking the head to European sprint spec.

Then again my memory may be gone....

Rob LaMoreaux

MTS Systems Corp.
Powertrain technology Division
4622 Runway Blvd.
Ann Arbor, MI 48108
734-822-9696
Fax 734-973-1103
Main Desk 734-973-1111
www.mtspt.com
Work email: ***@***.***
Home email: ***@***.***

[Esprit2]

From: "Robert D. LaMoreaux" <***@***.***>


Rob,

Your memory is good. There's something like a 0.040" difference in the
thickness between the 9.5 and 10.3 compression heads.

Later,
Tim

[dlbarnes1]

This is consistent with my understanding. The Federal Sprint has the same head thickness, 4.64", as the earlier engines for a CR of 9.5:1. The European Sprint has a head thickness of 4.60" for a CR of 10.3:1. Consequently, itseems to be common to reduce the thickness of the head (mill) to bring theCR up to the European Sprint spec. If the head has not been previously resurfaced (mine hasn't), this would be a mill of 0.040".
However, the comments recommending not milling unless necessary make a lot of sense. I plan to investigate higher compression pistons.
David 72 Sprint DHC

----- Original Message -----
From: Tim Engel
To: ***@***.***
Sent: Tuesday, May 17, 2005 3:51 PM
Subject: Re: [LotusElan.net] Valve to Piston Clearances


From: "Robert D. LaMoreaux" <***@***.***>


Rob,

Your memory is good. There's something like a 0.040" difference in the
thickness between the 9.5 and 10.3 compression heads.

Later,
Tim














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