How much ally around the top of the liners??

mgbv8 · Post by **mgbv8** » Sun Mar 07, 2010 6:58 pm

Does anyone know the depth of the ally in the block around the top of the standard 4.6 liners??

I blew a head gasket in a big way today and the escaping gasses have chewed some of the block away

Post by **Coops** » Sun Mar 07, 2010 7:34 pm

OH ouch!!!!!!
WTF happened mate???
to much gas???

mgbv8 · Post by **mgbv8** » Sun Mar 07, 2010 8:02 pm

Can you ever have too much gas

I was only running 60hp more gas than usual. And I retarded 2 more degree's to compensate.

I've just found my BIG FAT SPARK from the MSD and Blaster coil is not as it should be. In fact, its not as strong spark at all. If I crank with the coil lead off it normally jumps nearly 3" from the coil to the bodywork. Now it dont?? I could just about get 3/4" when I tested. And using a spark tester at 30 thou gap it was still a silly little spindly spark rather than the thick fat spark I normally get.
Time to rework the ign system as well I reckon

The loss of metal around the liner at its deepest point is about 2.5mm. I'm hoping I can get away with filling this with ally or liquid metal and then hand smooth it. I'm not keen on using heat to flow some ally this close to the liner. Which is why I'll probably opt for the chemical metal option. I dont have time to pull the block and get it reworked. And I hope a comp gasket may take up the odd thou of eneven surface on the block. My thought is that the repair should not be under any undue heat or pressure on the outside of the liner.
Are the heads made of stronger ally?? Because there is no damage to the face of the head at all? Just a slight layer of ally spatter??

I may of course be completely wrong. But I'll have a go anyway.
If it all goes badly wrong, I'll have a year or so to rebuild and maybe transplant the running gear into the next project car. A rear wheel drive 4.6 V8 MG ZR. Or maybe the MK3 Escort 2 door shell we have laying around??

If anyone is sure that having this area filled with low temp ally filler or even having it tigged is ok I'll do that instead.

Advice please guys...

Pel

Eliot · Post by **Eliot** » Sun Mar 07, 2010 8:35 pm

mgbv8 wrote:A rear wheel drive 4.6 V8 MG ZR. Or maybe the MK3 Escort 2 door shell we have laying around??

There a bit slow in std from chap.

Post by **Coops** » Sun Mar 07, 2010 8:42 pm

you aint the only one with a dead car this weekend mate,
my ecu has farted poop and died yet again

im getting soo close to saying f**k the fuel injection and going back to a carb...

mgbv8 · Post by **mgbv8** » Sun Mar 07, 2010 9:02 pm

I'm not getting into the "Carb vs EFI" debate mate.

I'm happy to have been able to hit the goals I have so far with my carb and dissy. But I would also like the option of being able to log AFR's / rpm / fuel pressure etc. Which I can do if I save up some more eh?

I'm also wishing I had not sold my old carb and manifiold. But I needed the wedge to go towards the new carb and manifold.

I'm now thinking I would like to try a weber 500 on the new manifold.
My old manifold would not house the 8 point nitrous injection plate. So I had to convert from dual plane to single plane in order to fit the spider plate. This single plane mani does not develop enough vacuum to pull the carb in until around 3500rpm. So I have to compensate by increrasing the size and volume of the accelerator pumps and jets. And I'm almost there with this setup. But it still bogs a bit from idle to WOT with the gas off.?

Tricky · Post by **Tricky** » Mon Mar 08, 2010 9:54 am

Perry
Thats what we call in the motor trade FOOKED

Still its made me think of a name for the MGB BLOWJOB

Eliot · Post by **Eliot** » Mon Mar 08, 2010 12:10 pm

mgbv8 wrote:I'm not getting into the "Carb vs EFI" debate mate.

On a drag car - a carb will work fine, EFI delivers benefits for road cars in terms of startup, mid/part-throttle - and of course making changes is easier.

As you note, the ability to log whats going on is handy with efi. You could always install a megasquirt with all the sensors and leave your beloved carb and dizzy in place - then you get a great datalogging system.

Tricky · Post by **Tricky** » Mon Mar 08, 2010 12:17 pm

Perry
As far a drag racing goes you need a bucket to get the fuel in
IE a 600 dp

Carbs on old school motors rule for me mine works great

mgbv8 · Post by **mgbv8** » Mon Mar 08, 2010 12:33 pm

I agree with all the above!
Does anyone know how much ally will be under the melted bit in the picture??

bigaldart · Post by **bigaldart** » Mon Mar 08, 2010 12:37 pm

Perry,

Been there and done that, had similar damage but took the head out as well. Could poke a pencil through from the valley to the chamber.
As to repairing it, we did plastic metal one to make a show for static fire ups and that held up ok. But we wouldn't risk it under load. To weld it you will need to pull the liner, tried it without but no chance of getting close to good liner support. At one time we used to mill the block about 40 thou and the deck starts to get unstable and move around, I reckon there isn't a lot of material there. Look on British V8 at the 4.020 bore thread, one picture shows most of the deck machined away and you can see how little material there is in that area. If I was you I would just get another block and transfer everything over. While doing that get it machined for O'rings and switch to copper head gaskets. Your cylinder pressures will probably be higher than ours and we need O'rings for a consistent seal. You can probably get away with only missing one meeting.
Do it right and everything will be happy days. Did it block a fuel jet or something? Can't see a weak spark being the cause of the meltdown. Good luck mate, keep pushing the envelope.

Alan

mgbv8 · Post by **mgbv8** » Mon Mar 08, 2010 4:22 pm

Thanks Al
I'm checking the fuel delivery over this week to make sure all is well. The other plugs on that bank looked good. And that bank is fed from one fuel solenoid.

kiwicar · Post by **kiwicar** » Mon Mar 08, 2010 4:27 pm

Hi Perry
try asking Gelmonkey about epoxy resins, the stuff he got me is excellent for filling and sticks like the proverbial to a blanket, he can probably get a high temperature resin/ hardner combination that would last well, then you just add ally powder until you get the consistancy you want I think you will need a top hat liner to get it to seal properly, so it seals onto the liner, not the block, having said that I think a replacment block will be simpler in the long run.
Best regards
Mike

Post by **katanaman** » Mon Mar 08, 2010 5:23 pm

Personally I dont see any epoxy that will repair that. Part of the damage is on the inside of the fire ring on the gasket (you can see the circle) so any repair is going to see the full pressure and heat of the combustion chamber. Top hat is the only way I can see to repair that block I am afraid.

bigaldart · Post by **bigaldart** » Mon Mar 08, 2010 7:39 pm

Perry,
Look at it this way, get packed up, tow to the track, it leaks first pass and this time toasts the head. Tow home and unpack. The time you just spent you could have pulled the motor, put everything in another block and be ready to go for next weekend. Just doesn't make sense to risk it. Be safe whatever you decide.

Alan