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From: Dave Baker
Subject: Re: Engine rebuild questions
Date: 07 Sep 1999 21:19:55 GMT

>From: "Keith or M.A. Carlson"
>A couple of questions regarding a rebuild. Appreciate any help with
>I've had people recommend brass frost plugs for the block.  What's the
>advantage?  There a little on the rare side for a Ford 2.9V6 (appears to
>me), and I had the auto parts guy ask why I wanted brass instead of

Just use standard ones

>During this rebuild, I have been planning to replace the main bearing
>cap bolts.  This engine is being built with performance parts to bring
>power from the stock 140hp up to approx. 200hp.  Thinking back to my
>engineering classes, I know bolts go through many, many stress cycles in
>use, and I figured it would be good insurance.  Again, at the parts
>counter I'm told I don't need to replace them; they're reuseable.
>So, is this overkill to replace the main cap bolts?  (The rod bolts and
>cyl. head bolts will be replaced; no question there).

Yes - it's overkill for a road engine - in fact for most race engines too.

>If I have a machine shop resurface the block deck, how *little* can they
>remove and get a clean-up surface?  I have some scratches on the
>surface, (hard to tell how deep they are; my guess .010 or less) and I
>want to make sure I have an absolutely solid seal around the cylinders.
>Taking off too much would bump the CR up higher than I want.

I'd be more concerned about getting both sides of the block machined parallel
to the crank centreline and to the same deck height. You might be surprised how
far out the standard machining is, both end to end and for deck height. How can
we say how deep your scratches are - we haven't seen your block? Most cast iron
gasket faces clean up with 5 thou or less though.

Make sure the machine shop uses a proper jig referenced off the crank journal
housings and clocked to the bore sides to ensure the deck faces are at 90
degrees to the bore centrelines. Then rebore the engine if needed true to the
deck faces. When I do an engine like this I measure both deck heights, skim the
lowest first and then clean up the other side to the same height.

Then measure the chamber volumes and machine the heads to balance these too and
remove any material necessary to get the CR right.

Dave Baker at Puma Race Engines (London - England)  - specialist cylinder head
work, flow development and engine blueprinting. Web page at

From: Dave Baker
Subject: Re: Tercel head gasket won't hold seal - help!
Date: 22 Jan 2000 22:49:41 GMT

>From: ralph lindenfeld
>My 1989 Toyota Tercel (3E-carb engine) burnt a valve a while back.  I
>had the head rebuilt and have attempted to reinstall it twice.  Twice I
>got leaks.  First one that only showed up once the engine heated up.
>The second time it leaked radiator fluid when I was filling the block.
>The leaks were in different areas.
>I've checked the head / block for warpage, cracks.  Each time I replace
>the head gasket and all head bolts ($$)
>The whole time I've been doing this I've gotten more worried about the
>torque values.  Book says to work up to 36 ftlbs, then 1/4 turn more.
>Well, I finally did the final 1/4 turn with a torque wrench instead of a
>breaker bar, and it seems that each time I put on a head, a few bolts
>don't tighten, but rather 'stretch'.
>Here's what happens:
>Once I get the head to 36 ftlbs all around I go back and do the 1/4
>turn.  Most of the bolts read about 60 lbs when I get done with the
>torquing, but the stretchy ones never seem toget above 40 -45 lbs.
>Continued torquing doesn't raise the values. These bolts aren't in the
>same position as the last ones that 'stretched'.
>Head holes are clean, chased, bolts and washers are lightly oiled (just
>like the manual says).
>Right now I'm on the 3d installation.  The final torque values
>discouraged me from hooking up the mainfolds etc and wasting more time.
>I'm considering getting a few more bolts and replacing (seperately) the
>bolts that seem stretchy.  Is this possibly going to work?
>Does anyone have experience with problematic head gaskets?  Should I be
>looking into high performance non-stretchy head bolts? Is there such a thing?
>I'm losing my mind (and my wife's good will, whose car it is) .  I
>haven't had a car to a mechanic in 13 years...

To answer on here and also to your email - this is not an unusual result with
stretch bolts which are designed in the last part of the turn to go past their
elastic limit. Such a wide variation is a bit odd though but I doubt if it is
the cause of your leaks.

I suggest first you check your torque wrench against another one just to be
sure. However, the vast majority of leaks are due to faults in the head/block
surface finish. A straightedge won't show up low spots easily unless you are
extraordinarily careful in checking every inch of the surfaces. If a valve has
burnt out then chances are there is a distortion somwhere which you will only
solve by getting the head and maybe also the block skimmed.

I'll bet you that if I had your parts in my shop I could run a light skim on at
least one of the two components and find a spot that the cutter was missing on
the first pass.

Get a good flat block (planed wood or similar) - wrap 240 grit round it and
give both head and block a light rub to remove any crap on there. Then check
with a piece of float glass and engineers blue for low spots. Or just take the
lot to a good machinist and have them checked and surfaced. Make sure the
quality of machining is top notch with smooth surfaces. I use a single point
carbide flycutter at 550 rpm on aluminium and 180 rpm on iron. No more than 3
to 4 thou feed per rev for a good finish.

I've had loads of so called problem engines brought to me over the years and
never found one that didn't have an easily found mechanical problem that was
causing the gasket failures.

Dave Baker at Puma Race Engines (London - England)  - specialist cylinder head
work, flow development and engine blueprinting. Web page at

From: Dave Baker
Subject: Re: Renault Clio White smoking
Date: 11 Feb 1999

>From: (Lesley)
>We have a J reg Clio 1.4 that was losing water and white smoking.
>On removing the head ,the gasket looked to have been the cause.
>So we had the head skimmed and replaced it with a new gasket.
>Still the same...
>So we then had the head pressure tested.....nothing showed up.
>Replaced it with another new gasket and new head bolts.
>Still the same....
>On removing the exhaust manifold bolts,each time water has poured out.
>Is this right. Do these bolts go into a water jacket? Or is something
>wrong here?
>The next step is going to have to be replacing the liners,but this is
>going to be rather costly and if it doesn't solve the problem  we're
>going to be ill!
>Can we try anything else first?
>Advice much appreciated. Thanks.

I know nothing about this particular engine but if it is wet liner like the
Peugot 205. Renault V6 etc then you need to check the liner protrusion above
the block face. Normally this is in the 4 to 5 thou range but I once had in a
Renault V6 where the liners were dead flush due to a manufacturing fault.
Caused the owner much fun and grief until we checked it out properly and
rebuilt the engine for him. Some engines have shims under the liners to set the
height and others just rely on the block and liners being made exactly to size
which is a bit of a bugger if they are made wrong.

If you are in our neck of the woods I can machine blocks to very exact
tolerances to save the cost of new liners if you want or need this done.
Trouble is they often have dowels in the block face which can be murder to get
out and back in.

I'd also make sure that when you had the head skimmed it was to the correct
surface finish. You can't believe the "ploughed field" finishes that some so
called engine reconditioners create when they skim heads and blocks. The
smoother the better (except you don't want any polish) and don't get fobbed off
with "they need a bit of roughness to bite the gasket mate" and other similar
bollocks that you hear.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: How to convert um to rms (used to measure cylinder head & 
	block finishes)
Date: 17 Dec 1998

>From: (Peter Howard)
>Can anyone out there tell me how to convert the unit um (the u should be
>the Greek letter mu, a u with a tail) to rms?  I had machinist tell me
>that the only unit of measure to define the smoothness of a finish on a
>cylinder head or block (or any metal surface) that he has heard of is
>I have been told by many performance shops and head gasket manufacturers
>to get a surface finish of 0.6 um (for Al heads) That is good to know,
>but useless if you cannot convert that into rms.  We have speculated that
>um is %2522micro meter%2522 , but even so we do not know how many micro
>meters are in 1 rms.
>The only other place I have heard of RMS is from Performance Friction
>(manu- facturers of high performance brake pads).  The require a finish
>of 125rms to be put on the rotors before use.  This confims to me that
>rms is used in the industry, and it is a measure of smoothness.
>Can anyone shed light on this for me?  I am sure someone knows a machine
>shop or someone that has the answer.
>Please send all responses to me directly at
>Thanks a lot!

Firstly there are many different ways of measuring surface finish including Ra,
Rt and Rz. The differences relate to the way in which the average depth of the
peaks and troughs is calculated.

Secondly you are very unlikely to find an average machine shop, automotive or
otherwise, that has surface finish measuring equipment. Now should you expect
to. Surface finish is normally only controllable to any degree of precision by
grinding, honing or polishing. A good engineer knows what finish to put on a
cylinder head face without thousands of pounds worth of arty farty, laser beam
operated, computer controlled, robot designed, moron operated surface profiling

You want a good smooth flycut finish without obvious tracks or tool marks. The
average machine shop will put a damn sight better finish on than the factory
did when they were trying to cut machining times to the nth degree.

As for "µ" it is the greek letter mu and means one millionth. µm is one
millionth of a metre otherwise known as one micron. One metre = 39.37 inches so
one micron = 39.37 millionths of an inch.

Alternatively there are 25.4 millimetres to the inch so there are also 25.4
microns to the thou.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Astra cylinder head
Date: 07 Oct 1998

>From: Andy Garman <>
>	Wisely or not, I whipped the cylinder head off my (1.4 1991 MkII)
>astra at the weekend. I wasn't trying to cure a particular problem, just
>throwing it in with the bi-ennual coolant/timing belt change on a 97K
>engine. I've never seen the underside of a real live cylinder head before,
>so I've got a couple of questions:
>1. The cylinder head mating face carries minor stains (poss corrosion)
>particularly around the water jackets which the gasket remover won't
>budge. It's barely sensible to the finger, but will it effect how the new
>gasket seals? Should the head be skimmed? How much could I expect that to
>cost, and will it effect the compression, and hence timing or whatever?

Normal. Check the head face for truth with a good straight edge and only skim
if warped. If flat, lightly go over it with 400 grit wet and dry wrapped round
a flat block and plenty of paraffin just to remove any traces of gasket or
crud. £20 to skim if needed.

>2. The exhaust valves all carried dry carbon deposits above and below the
>seat-face, which could be easily removed. However all four inlet valves
>carry a thick layer of burnt, blistering, rust-like carbon (I think) which
>nothing I dare try will shift. The stem and the cylinder face of
>each valve is fine; the crud starts abruptly where the stem flares out and
>ends at the seat-face. The inlet ports are spotless, except for a single,
>tidy  streak of carbon in each. The valves are only slightly pitted, and
>the general build-up of carbon doesn't seem excessive for the mileage.
>Should I just ignore it and carry on, or does it signify something

Put the valves in a lathe or drill and remove carbon with a metal scraper, old
chisel etc, and polish with 120 grit paper. Don't touch the valve stems or
seating face. You sure you haven't got the valves mixed up. The exhausts should
have light brown hard carbon deposits and the inlets dark black softer easily
removable stuff?

>3. One of the cylinders (#2) is rather more carbonised than the others.
>Worrisome, or just one of those things?

One of those things.

These heads respond well to porting while you have it removed and if it is the
33mm inlet valve head some bigger inlets make them fly.

Lap the valves in with fine grinding paste before re-assembly but if you don't
get a nice even contact patch on the seat within a few seconds then it's better
to recut than go mad lapping. A nice 3 angle valve and seat job is worth 5 bhp
on it's own.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work.

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