View Full Version : ARGHHHHHHH.....So close but now so far!

srn4 - n/a
25-Mar-06, 01:57 PM
Ok, so I went to start the engine for the first time with the fan attached and the engine wouldnt start....

Checked everything and then noticed that one of the plugs was loose, so I tightnened it up...and it simply wont tighten...

I guess the thread is stripped...

What on earth do I do? (Apprt from cry and tear my hair out!)

I guess I can get a heli-coil kit from Namrick, but does this mean I have to strip my head off?

Im so dam annoyed with myself now...ARGHHHH!!!


Ian Brooks - n/a
25-Mar-06, 03:05 PM
That's incredibly bad luck. You better get your spanners out, the head needs to come off. It's a pushrod engine (right?) so it shouldn't be too bad a job - no camshaft to fiddle about with. So long as it can be done with the engine in the craft?

Think yourself lucky - I've still got an incomplete hull! (still, it's looking like a hovercraft now, the hull's about 80% there)


srn4 - n/a
25-Mar-06, 03:46 PM
It is a pushrod engine....

Do you recon its worth paying someone to do the rethread or just get the kit and do it myself? (I can think of several places locally who could proberably get it done...just depends how much)

Should I get both heads off at the same time so that the lifters are all adjusted at the same time and the heads/valves inspected or does it not really matter?

Do I need new gaskets?

To be honest with you Ian, I just want to get hovering now, I have been working on the hover for over a year now and its getting on my tits http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif Even if I am going to miss the challenges when its done http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif


jar2 - n/a
25-Mar-06, 07:22 PM
Bad luck Dunc,

First the bad news - one stripped plug won't stop this engine starting (I've had one of mine run OK on just two cylinders - idle a bit rough tho!). These engines are pretty good starters - if you have fuel and a spark they will run.

If you are desperate to avoid stripping the head to fix the plug thread then you could try bonding a new plug in using bearing retainer (green coloured Loctite). It will be very difficult/impossible to remove the plug again but you should get at least 2-3 years out of it.

Suggestion #2 - fill the cylinder with expanding PU foam then tap and re-thread the plug hole. Vacuum out big aluminium particles from the plug hole then break up the foam using a bit of wire and it will all be burnt and ejected out the exhaust port (complete with any remaining bits of metal).

If you do remove the head then you will need a new head gasket and a probably a valve cover gasket. It may also be worth replacing the valve stem oil seals while you are in there. You don't need to touch the other head.

Mart366 - n/a
25-Mar-06, 08:10 PM
Are you sure its a pushrod engine???

I thought they were ohc, i know mine is..

if you have access to the engine, you should be able to fit a helicoil yourself, the tang that you break off, will be retained in the pliers jaws,,

another alternate method if your going to go head off, is to just get a replacement head from a sc**ppy, might be cheaper in the long run


lazza - n/a
25-Mar-06, 09:38 PM
You don't need to remove the head to fit a heli coil, I used to do them at work on engines back when we had a apprentise http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif and that was the benefit of using heli coils, to do them in place. Just got to pay attention to making sure you don't get metal filings left in the bore. Putting a smear of grease on the tap etc will help to grab excess filings and prevent them from making their way into places they shouldn't.

Mart - Duncans EA81 is the pushrod engine with the blue rocker covers , my EA82 is the OHC motor with the alu covers and cambelt.

ugglas - n/a
25-Mar-06, 10:04 PM
I have a suggestion..

If you go with the idea of making the helicoil with the head still in place you could try to blow compressed air through the exhaust port on the head while the exhaust valve is open.

This would probably blow most of the metal pieces out of the plug hole while you drill and make the threads for the helicoil.


tonybroad - n/a
26-Mar-06, 09:18 AM
Off with it's head i say !! http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

you can blow as much compressed air through the exh port and smear as much grease on the tap as you like but you'll rue the day you did not take the head off when the lot lets go http://hovercraft.org.uk/images/icons/smiley_icons/icon_redface.gif

i never thought i'd ever quote my dad but here goes

"cleanliness IS godliness when it comes to engines"

"don't spoil the ship for a ha'peth of tar"

good luck - you're not the first and you'll certainly not be the last or else why was the helicoil invented ?


srn4 - n/a
26-Mar-06, 09:37 AM
If I can keep the heads on then its going to save me a small fortune in gasket costs.

My reasoning is that the small particles of aluminium will not be able to scratch the bore or the piston rings as they are much harder and will most likley get forced out of the exhaust port....

A couple of people who are mechanics have told me to do it with the head on, so I might as well give it a try.


Ian Brooks - n/a
26-Mar-06, 08:17 PM
I agree... Off with her head!!

Get a gasket and you'll have it done next Saturday.

Seriously, you might get away with doing it in-situ, but you won't know until you are bobbing around in the Severn with no power, heading for the Shoots and wondering if SARA can launch before you go in!


srn4 - n/a
26-Mar-06, 10:03 PM
Logic tells me to take the head off and do a proper job, but my bank balance says otherwise!

I will give the local engine rebuild company (Malvern rebore) a ring tommorow and have a chat with them as they are most likley to do any work that has to be done.

If I do remove the heads do I need to get the thing skimmed?


lazza - n/a
27-Mar-06, 05:19 AM

Nick Long - n/a
27-Mar-06, 05:33 AM
What? I don't know this particular engine but I've never heard of a head that needs skimming just because its been taken off.

Dunc, there's some holier than thou attitudes being bandied around here and you need to do your own risk/reward or cost/benefit assessment.

The risk from bits going into the cylinder is low; probably down in the noise compared to other reliability issues on a hovercraft. On the other hand, taking the head off enables you to see the problem better and do a better job of fixing it. Then there's the risk of creating another problem in the process - one risk from working in situ and a different risk in taking the head off and putting it back.

If head off is 10 minutes and 10, take it off. If it is two hours and 50, then try an in situ repair first.


lazza - n/a
27-Mar-06, 07:05 AM
Well i say "yep" because as a fully qualified mechanic for over 17 years i would not and will not re fit a alu cylinder head without skimming it first or at the very least placing a proper flat edge over the surface and testing it. But then again i'm talking from a professional point of view, as a backyard repair goes its certainly achievable to refit a car cylinder head without skimming it and achieve success but in my experiance the potential for a good success rate drops largely. It comes down to do you want the job "done" or "done right" ? http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Nick Long - n/a
27-Mar-06, 09:37 AM
or at the very least placing a proper flat edge over the surface and testing it

Well, I'd agree with that, but that's very different from automatically skimming it.


srn4 - n/a
27-Mar-06, 01:49 PM
Just spoke to my local autoparts shop and they want to charge 45 for the tools and gear to do the job...Cant find anything cheaper on the web..

Alternativley I can get the guy from Malvern rebore to actualy come to my garage and do the job for me for 40....

Its not cheap, but I think its worth paying a greace monkey to do the job for me!!!


Sean Atterbury - n/a
28-Mar-06, 05:24 AM
Hang in there boy and do it right. http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif

Craft is looking good, can't wait to see it going, but please round off the fanguard, all that hard detailed work and then you chuck on that blocked off piece of mesh, maybe take a piece of 4mm round bar and tack it to the end bits, make it nice and round and finish off the craft, the way it should. http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif

Well done, hope that you get the blades set perfect first time.

Good luck.

srn4 - n/a
28-Mar-06, 09:19 AM
I was tempted to do something like that with the fan guard but im not sure that I can weld to galvanised steel...: :-s


Sean Atterbury - n/a
28-Mar-06, 11:06 AM
I'm not shure on that one either http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

jon_curtis - n/a
28-Mar-06, 11:51 AM
not sure about much i recon!

you can weld to galv steel but the fumes which come off are not nice at all! infact very very bad for you! the galv burns off when you ark ergo nasty fumes!

so yeh you can weld some rod around the outside but do it in extremly well vented area, like outside and don't breathin the fumes! NASTY

i'm surprised you have already galved mesh! if you buy weld mesh from a steel supplier it can have a copper plating on it, but unless you buy galv you dont get it if you state WELD MESH. you

could have got away with larger mesh too. (someones not been reading the specs lol)

also just out of interest how far is the leading edge of your fan from the frame and guard?

1/ there is a min distance, so you cant touch the fan with your fingures, which is one reason why a fan guard is domed, (also to fit over drive systems etc. you may have to set it off the duct, to get this distance

2/ it might just be the angle of your pics, but it looks awfull close, you know a fan blade can come forward 2inches or more under full load? rapid deceleration and ecceleration can cause the blades to wip further! the leading edge of the blade should be sat back nicely within the straight portion of the duct! worth checking!

srn4 - n/a
28-Mar-06, 12:17 PM
The fan is about 140mm from the guard which is why I chose small mesh to make it harder to get fingers through it.

I will have to see what I can do to make the edges neater...I do agree that it looks pants...But function wins over beauty...I just want to get this thing moving!

Nick Long - n/a
28-Mar-06, 12:30 PM
The fan is about 140mm from the guard which is why I chose small mesh to make it harder to get fingers through it.


Dangerman is right. Go and read the regs, especially if your blade to guard spacing is "about 140 mm". I think the latest cruising construction regs are 2002 and the paragraph you need is 3.3.1.B.

AFAIK the gist of this is not changing in the as yet unpublished update.


Sean Atterbury - n/a
28-Mar-06, 12:38 PM
You going the same route I did, do whatever it takes to get it off the ground....


Do it propper, you going to mess it all up now if you rush this last bit, like Don implies, I rushed the last bit and sent a brand new set of blades to heaven. http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

Just a thaught, not that I ever thing according to some people ( Hint Hint Dangerman )

PS: Lets not start up again Danger, might get in some serious trouble this time. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

jar2 - n/a
28-Mar-06, 12:47 PM
I have to chime is here with some more comments Dunc!

You also don't appear to have a guard over the top pulley and bearing. This is classified as a "rotating assembly" and, AFAIK, and must be guarded.

You should use as large a mesh and as small a wire size as allowed by the regs. The restriction effect of too fine a mesh is significant (for example, a 25mm square 3mm wire mesh covers about 24% of the intake area). If you do space the guard away from the duct make sure there isn't a gap (from memory the regs specify 15mm to prevent fingers getting in). And lastly, don't attach the guard to the duct lip and spoil the nice airflow around the lip - attach it to the outside surface of the duct ideally.

As was said above, you can weld galvanised steel OK if you are reasonably careful (if you are worried then wear an organic mask). Try to do small spot type welds to prevent the zinc igniting - the extra energy can burn through thin plate. I recently welded galvanised mesh (every two inches) between two 6.5ft diameter galvanised conduit rings to make a prop guard with no problems (or ill effects!)

srn4 - n/a
28-Mar-06, 12:48 PM
I only have the construction regs for light hovercraft from the hovercraft club of america because getting hold of the HCGB regs is tricky! (Incidentaly, where do you get them from...they are not available anywhere on the club site)

My guard complies to the ruling in that...just http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_cry.gif

Im not intending to rush anything and make a mistake, I like to think that I take safety very seriously....I will have to take a look at the guard and see exactly how far from the fan it is and what can be done to adjust it...

Ho hum..


srn4 - n/a
28-Mar-06, 03:33 PM
Some good news that makes me feel good http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Fred from malvern rebore came up and hey presto the engine runs again http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif It has a bit of a misfire but he assures me this will stop after a little while.

So now I can get back to testing the drive system and fan http://hovercraft.org.uk/images/icons/smiley_icons/icon_cool.gif


jon_curtis - n/a
28-Mar-06, 09:47 PM
"Just a thaught, not that I ever thing according to some people ( Hint Hint Dangerman )

PS: Lets not start up again Danger, might get in some serious trouble this time."

yeh you will!

how about you post a pic of your hovercraft!

we will see who knows what he is talking about then!

Sean Atterbury - n/a
29-Mar-06, 04:56 AM
Want to go out this weekend, will take a pic of it going and post that. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif