HOMEMADE ENGINE UPDATE, HELP NEEDED

[elioti]

Hi,looking for some help if possible! Did post on here a while ago about a homemade engine my father built, about 40 years ago, and now he`s putting it back together after some modifications. When i posted on here last time, some people wanted to know more about who my father was, but he doesnt want me to say! So although i have not been helpful to you lot, am still hoping for some advice/help if there is a chance! He`s been getting local people to do jobs any they are messing bits up. The latest is to do with a cylinder head ( 4 infact) . my father wanted to add anothe plug hole, so took it to a local business that has milling machines and he said he could drill and tap the holes for the plugs. My father said please say if you cant do it as its a `one off`. he said he could. So my father picked them up today and was shocked to see this guy has messed them up. instead of drilling holes inbetween two valve seats evenly, he has drilled to one side, making the wall between the plug hole and valve seat very thin and likely to crack. he did this to all the heads. I could have done better myself, now my father is about to give up on this as likely needs new heads making, would cost thousands. Is it likely the plug holes could be welded and redone, does anyone know anyone please  who could perhaps do this, someone reputable! Do you think this guy who messed them up should foot the bill to correct them? He`s not any back street garage, he has about 100,000 pound worth of hi tech milling machines, he just says hes not sure what happened. im going to see him tomorrow to tell him my father will not be paying him. My father is too soft so i must deal with it. Would like opinions please, about fixing the problem, and dealing with this guy, we/my father does not have alot of money, and cannot afford to coorect his mistake, and i think the guy should be compensating. As said would be glad of opinions please. Can get pics tomorrow cheers!

[IRacingGreen]

Being quite dispassionate about it (because although it's something very precious and personal to you and your father, you're really just on the receiving end of a poor quality engineering job) it pretty much comes down to one thing. Did your father provide a drawing with a clear positional tolerance for the feature? If yes, you can probably do something.  If not, he can probably claim it is within spec (as there wasn't really a spec defined) and so there is no complaint to answer.
We have had similar (but less catastrophic and more easily replaceable) poor quality work from engineering firms. We do as much as we can ourselves, but where we have to use someone else, we only use companies recommended by fellow racers who know what proper engineering is (and they seem to be getting harder to find!)
Good luck.

[rogerwilko]

What on earth did he want another plug hole for? I presume you aren't going to race them anyway!

[johnnyboy-wonder57]

Hi,
Twin plug set-ups supposedly increase power, a racer friend told me there was heated debates about this feature in Classic racing, with the people who did this upgrade, claimed power increases were not that noticeable & some independent research indicated that a 10bhp advantage in an engines power output could be gained by this modification, over a single plug set-up.

I believe piston-engined aeroplane cylinder heads always used twin-plug set-ups for efficiency and as a ignition failure precaution, if one  of the plugs went duff!

Its all to do with flame fronts, burns rates, thermal efficiency & the speed of combustion, the quicker the combustion takes place, the greater the engines propensity to make more power is realised, of course engine carburation & ignition timing play an important part in this process to allow greater  more efficient rpm.
So in the racing class breakdowns, twin & single plug set-ups  became a point of contention.

Racing engines use a smaller power band- width to create top-end high rpm power for the high speeds needed; the more efficient the process the better the temperature distribution in the cylinder-head, the less danger the exhaust valves & guides will be under possible failure through excessive heat build up.

Not so sure this modification is applicable to tourers except as an emissions aid!

Cheers

JBW

[runesika]

Elioti how can i put it ? you're $%^&&ed !
It's to late now but your father really should have given only the one head to start with before putting all his heads into one basket .

Like you i would not be paying for this work , i walked out with my petrol tank after a poor chrome plating job , i was so pissed off that they knew not to try and make me pay for it .
How about trying the head as it is and then have it welded if it fails at a later date ? as for trying for compensation i would say you have not got a head to stand on .

[elioti]

Hi thanks for the replies, not sure why he wanted twin plugs, but is a racing engine. Cheers for the advice, will just go in and make it clear we wont be paying for the shoddy work. Need to find a solution for the head though as guess welding will warp it, can anyone reccomend anyone to weld this, thanks

[johnnyboy-wonder57]

Elioti
I do not know where you are but this firm is on the Isle of Sheppy, Kent;
www.uk-racing-castings.co.uk/historiclinks.html

There's also
http://www.hillmanimpspecialists.com, Reg Patten, he does Triumph Trident Modifications too!
http://www.castaldini.co.uk/cars.shtm;
http://www.maynardltd.co.uk/
http://www.rodwellmotorsport.com/products_page2a.htm

Most race shops should be able to undertake this kind of work,  there's usually a specialist welder somewhere who can bridge & build up the damaged area, if they have the machines, they can scan the castings , put it through to a CNC machine and earmark the areas to be worked on, or a craftsman could do it the manual way, many race-shops weld up inlet ports and re-engineer profiles of downdraft angles, port bore e.t.c.  so tricky work is often there  specialty.



Best of luck


JBW

[R]

Sorry to say this, but some of us are beginning to wonder if this thing is in good hands ?

[johnnyboy-wonder57]

Sammy Miller likes specials & would probably buy it off you & professionally restore it!

Let him take the strain, he has the contacts!


Cheers


JBW