02GF74
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| posted on 14/1/08 at 03:43 PM |
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when head porting goes tragically wrong...
.... so can a cast iron head be welded at reasonable cost?? (broken into the bolt hole from exhaust port  ).
anyone had this done and idea of cost before I start to ring round.
will the heating up of the head distort it?
.... the alternative would be to bore out the bolt hole and sleeve it, like what is done with liners - would avoid any heating?
[Edited on 14/1/08 by 02GF74]
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nitram38
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| posted on 14/1/08 at 03:45 PM |
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It can be welded but not by your mig!
You will also need a skim afterwards as I doubt it will be straight after.
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Paul TigerB6
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| posted on 14/1/08 at 03:45 PM |
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What head is it?? Gotta be asked is it really worth it as its surely got to be a nightmare to weld up and then gas flow again. If another head isnt
too dear then i'd treat the knackered head as something to practice on.
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Confused but excited.
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| posted on 14/1/08 at 03:47 PM |
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Start again. Crossflow heads can be picked up for buttons. Certainly less than the cost of repairing the existing one.
Tell them about the bent treacle edges!
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andyharding
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| posted on 14/1/08 at 04:03 PM |
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New head
Are you a Mac user or a retard?
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bonzoronnie
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| posted on 14/1/08 at 04:07 PM |
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Cast welding
The welding of cast iron is a very specialised field
This often icludes preheating in a kiln prior to welding. Then a carefully controlled cooling process
This is likely to be very expensive work to have done.
Speaking from personal experience, it would be wise to steer clear of general fabricators who claim it will be no problem. Been there done that
It realy is quite technical 
Yes a head skim would normaly follow.
Yes probably cheapr to replace the head if its a X-flow one
A picture would be handy. You sleve idea may not be impractical.
Ronnie
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paulf
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| posted on 14/1/08 at 04:17 PM |
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Its not generally worth welding a cast head especailly in the ports as it is timeconsuming and not always sucessfull.
If it has just broken into the stud hole i would just try and tap the stud a couple of threads deeper and refit it if possible.
Alterantively I have a crossflow head with rockers etc that you can have for £20 but it will need to be picked up.
Paul.
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davew823
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| posted on 14/1/08 at 04:42 PM |
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head repair
Some times you can repair the head without welding, by enlarging the head bolt hole and pressing in a thin wall tube.
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02GF74
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| posted on 14/1/08 at 04:45 PM |
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quote:
Originally posted by davew823
Some times you can repair the head without welding, by enlarging the head bolt hole and pressing in a thin wall tube.
that is what I'm thinking. the bolt hole seems to be larger than it needs to be.
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Phil.J
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| posted on 14/1/08 at 04:50 PM |
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Sleeve the stud hole. Shouldn't be a problem.
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Memphis Twin
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| posted on 14/1/08 at 04:56 PM |
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Lots of "tuners" break through into the exhaust ports bolt hole (I bet it's the centre two) on the X-Flow with no adverse effects
whatsoever.
Don't worry- just leave it. Not a big deal.
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02GF74
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| posted on 14/1/08 at 04:58 PM |
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^^^^ yes, it is centre two. So since the bolt head seals off the bolt hole, you are saying this is ok?
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Memphis Twin
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| posted on 14/1/08 at 05:05 PM |
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Perfectly OK. I've seen it lots of times...
I must say though, that removing metal from the outer end of the exhaust port really doesn't do a lot. X-Flow ports need LOTS of metal removal
further down the port and in the valve throat area, particularly on the inlet. The actual port entry from the outside ia actually already big enough
(if it's a 1300 or 1600 casting).
If you haven't already got one, I suggest getting a copy of Peter Burgess' excellent book on cylinder head porting (SpeedPro series). He
goes into great detail including stage by stage photos of a cross-sectioned X-Flow exhaust port.
Better still, take it to him!
[Edited on 14/1/08 by Memphis Twin]
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thunderace
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| posted on 14/1/08 at 05:09 PM |
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porting is not really a diy thing i have seen loads of cars that have less bhp after diy porting.(a genral clean up and polish will be better then
grinding the hell out of it)
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Memphis Twin
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| posted on 14/1/08 at 05:13 PM |
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quote:
Originally posted by thunderace
porting is not really a diy thing i have seen loads of cars that have less bhp after diy porting.(a genral clean up and polish will be better then
grinding the hell out of it)
I absolutely agree! Unless you know exactly what you're doing, and have the correct tools to do it.
Unfortunately, a general clean up and polish will achieve F***-all on a crossflow.
[Edited on 14/1/08 by Memphis Twin]
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MikeRJ
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| posted on 14/1/08 at 05:29 PM |
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quote:
Originally posted by thunderace
(a genral clean up and polish will be better then grinding the hell out of it)
Polishing is generally a waste of time. Flow comes from size and shape, not shiny finishes.
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thunderace
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| posted on 14/1/08 at 05:53 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by thunderace
(a genral clean up and polish will be better then grinding the hell out of it)
Polishing is generally a waste of time. Flow comes from size and shape, not shiny finishes.
NOT TRUE WHY DO PEOPLE USE SMOTH BORES ON MOTORBIKE THEN???
AND I HAVE NEVER SEEN A PORT ON A RACE OR RALLY CAR ENGINE THAT HAD NOT BEEN POLISHED .
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jrevillug
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| posted on 14/1/08 at 06:40 PM |
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The World-Famous engine tuner Dave Vizard doean't like polishing the ports- smoothing, yes, but leaving them with a rought finish.
'parrantly it aids the buildup of fuel on the surface though what the benefit is I don't know.
EDIt- Please don't shout.
[Edited on 14/1/08 by jrevillug]
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iank
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| posted on 14/1/08 at 07:02 PM |
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quote:
Originally posted by jrevillug
The World-Famous engine tuner Dave Vizard doean't like polishing the ports- smoothing, yes, but leaving them with a rought finish.
'parrantly it aids the buildup of fuel on the surface though what the benefit is I don't know.
EDIt- Please don't shout.
[Edited on 14/1/08 by jrevillug]
It's the opposite. Both Vizard and Keith Calver refuse to polish ports on any of the A-series heads they do as a completely smooth port lets
fuel drop out (especially where the ports have been enlarged and gas velocity is lower). They also don't bother with the combustion chamber as
that gets covered by carbon in a couple of miles anyway. Their opinion seems to be that a lot of tuners only do it because joe public will pay more
for a shiny head (ooer)
Here is Calver's own words on the matter
http://www.calverst.com/articles/ch-cylinder_head-about_mintec_heads.htm
quote:
Smoothed finish in ports - not mirror-finish polished - to minimise drag. Yes it does. Fuel can stick to smooth shiny surfaces, reducing fuel
efficiency and economy - particularly where overly large ports are used which reduce gas speed within the port. On a racer that is driven flat out
everywhere perhaps this isn't such a problem. And highly polished ports will slightly increase airflow in certain instances. So on a racer where
port velocity is being driven hard, fuel fall-out is less likely. On the street however, you certainly don't want fuel pooling in the intake
ports and dribbling into the chambers when tottering about at low speed. If nothing else the excess fuel will do it's damnedest to extinguish
the spark in the combustion chamber, drastically reducing torque. Let alone increased bore wear caused by bore-washing and horrendous fuel consumption
figures. The smoothed finish is easier and quicker to achieve than the highly polished item. It also gives a better over-all port surface finish -
i.e. reduced lumps and bumps that polishing simply won't remove as the polishing agent isn't resilient enough.
Now whether that logic works on Bike engines/more modern heads is open to debate, but blindly assuming that because some engine tuners do it makes it
correct is risky logic.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Confused but excited.
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| posted on 14/1/08 at 07:38 PM |
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Highly polished surfaces inside a tube actually create drag. If the inside is smoothed but left with fine lines tangential to the flow (such as left
by a strip of emery cloth on a stick in an electric drill), then the ridges of these lines generate micro-vortices that act like tiny roller bearing
for the fuel/air mixture and thus give increased flow over a polished port of the same diameter. IIRC.
Tell them about the bent treacle edges!
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Andy S
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| posted on 14/1/08 at 11:05 PM |
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Only show heads are polished to attract the eye. Just like show totty.
True race engines are left carbide rough. Exhaust ports and combustion chambers can be polished to prevent carbon build up but never the inlets.
For your bolt issue - have it sleeved
Oh and on your X-Flow unless you have gone big valve the stock port size is more than adequate and is best left alone with only a smooth off of the
casting marks to a stone finish. Any enlargement will loose power.
Hence why the stock engine responds so well to a cam change and an increase in compression with the 1300 pistons
Andrew
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MikeRJ
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| posted on 15/1/08 at 10:52 AM |
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quote:
Originally posted by Andy S
Only show heads are polished to attract the eye. Just like show totty.
Exactly. Time spent polishing is better spent optimising the shape of the port and valves seats etc.
It's very true that "shiny sells" though.
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Memphis Twin
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| posted on 15/1/08 at 10:59 AM |
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Oh and on your X-Flow unless you have gone big valve the stock port size is more than adequate and is best left alone with only a smooth off of the
casting marks to a stone finish. Any enlargement will loose power.
Andrew
Not so I'm afraid Andy.
The standard X-Flow inlet port may look big at the head face, but it constricts to 28mm (or less!) further down the port, and has a ruddy great gob of
iron cunningly disguised as a valve-giude boss restricting flow even further. Even with a standard GT valve of 39.5mm the optimum port size is 35mm.
With a 41mm "big valve" the optimum port size is 36mm.
In reality these port sizes are unacheivable without finding fresh air. The very maximum the port can be safely enlarged to is 33mm, and this requires
an awful lot of difficult metal removal, particularly as any attempt to staighten out the curved port loses power due to the loss of swirl in the
cylinder.
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r1_pete
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| posted on 15/1/08 at 08:47 PM |
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If you can get the head to Weldspek, Ollerton, Nottinghamshire, he'll repair it if it is repairable. Call him on 01623 835555, ex aviation
industry coded welder!
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Andy S
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| posted on 16/1/08 at 12:43 AM |
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Ah.. I had not taken into account that he had already been doing significant work already at the seat, throat and guide etc. I just read it that he
had just been rattling a stone around the port/manifold face.
Cheers
Andrew
quote:
Originally posted by Memphis Twin
Oh and on your X-Flow unless you have gone big valve the stock port size is more than adequate and is best left alone with only a smooth off of the
casting marks to a stone finish. Any enlargement will loose power.
Andrew
Not so I'm afraid Andy.
The standard X-Flow inlet port may look big at the head face, but it constricts to 28mm (or less!) further down the port, and has a ruddy great gob of
iron cunningly disguised as a valve-giude boss restricting flow even further. Even with a standard GT valve of 39.5mm the optimum port size is 35mm.
With a 41mm "big valve" the optimum port size is 36mm.
In reality these port sizes are unacheivable without finding fresh air. The very maximum the port can be safely enlarged to is 33mm, and this requires
an awful lot of difficult metal removal, particularly as any attempt to staighten out the curved port loses power due to the loss of swirl in the
cylinder.
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