Head Gasket / Unleaded Advice

[pridaux]

Hi Guys wonder if you could help here

I decided to do a compression test on the vixen today as I thought there was something not quite right and had a reading of 1/190 2/190/ 3/170/ 4/70 so I stripped down the engine to see what was happening what I found was the bores are all great and did a petrol test on them with all mid bore and although level went down very slowly they all went down at the same rate ie the 190s and the 70 so I feel happy that all the problem is in the engine head , Yes I know another oil change .

The Head gasket was blowing between number 2 and 3 bore and the valve in number 4 is suspect so I have sent the head off tonight to get that all dealt with.

The Engine spec is as follows

Bore 83.271mm
Stroke 77.62
capacity 1690cc
compression Ratio 10.6:1
Camshaft Kent 244
Crank Balanced Ground 20/20
Flywheel Lightened and Balanced

First Question

When ordering a head Gasket what one do I order the emergency one I had in the cupboard does not match what has come off and is there a different gasket for a crossflow that has been taken out to 1690cc ?? obviously I want the best gasket I can get but the right one for the job.
In the picture the top one is the old one?

Second Question is there any way of having the heads done to unleaded there are large valves stage 3 I believe so would that make it a problem converting to unleaded or should I not bother.

It was to late to ring Burtons by the time I finished so I will ring them in the morning but thought I would check here as I know some of you other petrol heads like solving problems from your armchairs

Will do my best to get her all back together for the pre 80s seems a repeat of Spa Classic Gear box out 2 days before I went so whats 10 days we should be able to build another ??? LOL

[Monkeythree]

Yes you can get head gaskets to suit crossflows with non-standard bore sizes. Burtons stock various sizes. I use Ajusa and find them to be reliable.
Your new spare gasket looks the same as your old one to me. Just turn it over to make it match the old one!
Yes you can fit unleaded inserts in a big valve head. Any engine machine shop should be able to do this for you. FWIW, i would recommend a cnc head from Ric Wood over anybody elses "stage 3" or whatever they want to call them. Not cheap but worth every penny in my opinion. And you can get them in unleaded.
Tom

[pridaux]

Monkeythree said:

Yes you can get head gaskets to suit crossflows with non-standard bore sizes. Burtons stock various sizes. I use Ajusa and find them to be reliable.
Your new spare gasket looks the same as your old one to me. Just turn it over to make it match the old one!
Yes you can fit unleaded inserts in a big valve head. Any engine machine shop should be able to do this for you. FWIW, i would recommend a cnc head from Ric Wood over anybody elses "stage 3" or whatever they want to call them. Not cheap but worth every penny in my opinion. And you can get them in unleaded.
Tom

Thanks Tom
There is a fair difference between the two and there are holes in the old one that are not in the new one also some holes are smaller and yes I know that is often the case to restrict flow rate but I want to make sure the gasket is correct for the engine spec the Engine was built by John Noble engines so I will try and speak to them but all I got was an answer machine today.
Just looked at burtons and they have the Ajusta so will order in the morning just hope the Engineering company can turn the head around for me fairly Quick as long as I get in by Friday evening I can get it back together Friday evening as we are joining the wedge return trip up to the Hot rod Café and a run to Blackheath on our way up Saturday fingers crossed.
A

Edited by pridaux on Thursday 29th August 23:15

Edited by pridaux on Thursday 29th August 23:17

[gmw9666]

nothing quite like a bit of pressure hey Andrew

clock is ticking for the pre 80's :-)

[pridaux]

gmw9666 said:

nothing quite like a bit of pressure hey Andrew

clock is ticking for the pre 80's :-)

Well we will see how things go ordered up the correct head gasket from Burton this morning not cheap but sounds the right one had a look at it on there e bay listing picture and it looks spot on just waiting for a call from the engineering company on what needs doing and time scale as i said as long as i have it next Friday then we are good to go only a couple of hours work max to put it back together a far cry from the 3000S as it took me half a day to just get the exhaust back on and lined up the memory still haunts me LOL
A

[tomtrout]

As you are running twin 40's, did you do the compression test with the throttle wide open? If not it might account for the low compression on 3&4. Don't ask me why but it makes a big difference!

[pridaux]

tomtrout said:

As you are running twin 40's, did you do the compression test with the throttle wide open? If not it might account for the low compression on 3&4. Don't ask me why but it makes a big difference!

Thanks for that
Yes peddle to the floor it does need full air flow.
Fuel pump off and distributer HT lead off.
Still not heard back from the engineers hopefully will hear later.
A

[Moto]

pridaux said:

The Head gasket was blowing between number 2 and 3 bore and the valve in number 4 is suspect so I have sent the head off tonight to get that all dealt with.

Andy, take this with a degree of scepticism as it's a long time since I did any engine work but if as you say it's not the cylinder bore / piston leaking and it is the head, surely it would be either a broken valve, broken spring or cracked head which would all be visible. If not then the valve & seat should just need a bit of grinding paste to ensure the valve is seating properly.

[pridaux]

Moto said:

Andy, take this with a degree of scepticism as it's a long time since I did any engine work but if as you say it's not the cylinder bore / piston leaking and it is the head, surely it would be either a broken valve, broken spring or cracked head which would all be visible. If not then the valve & seat should just need a bit of grinding paste to ensure the valve is seating properly.

Hi Steve
You may well be right but but as all stripped down we want to check will wait and see what the engineer says however i had thought of putting unleaded seats in at some point so as all apart may as well do it now
Thanks
Andrew

[Monkeythree]

It is very common for crossflow heads to crack between the valve seats, especially on big valve heads where the bridge narrows to a ridge. Not always obvious to the naked eye so have it crack tested before spending any money on it.
Tom

[pridaux]

Monkeythree said:

It is very common for crossflow heads to crack between the valve seats, especially on big valve heads where the bridge narrows to a ridge. Not always obvious to the naked eye so have it crack tested before spending any money on it.
Tom

Thanks Tom will do.
A

[ATE399J]

I hope it wasn't me driving it that did for it?

[pridaux]

ATE399J said:

I hope it wasn't me driving it that did for it?

More than likely LOL hope we will see you at the Barbecue Tomorrow
A

[pridaux]

Well it was a late night and a busy Saturday but managed to get a lot done it was far easier to not mess around and pop the spare engine in that I had lying around managed to scratch the wheel arches as not easy to do single handed and the wife let it slip so a quick rub down and a rattle can of black and all sorted had to move a few things around as it seems a little larger than the other one seems a bit louder than the other one?



A

[thegamekeeper]

pridaux said:

Well it was a late night and a busy Saturday but managed to get a lot done it was far easier to not mess around and pop the spare engine in that I had lying around managed to scratch the wheel arches as not easy to do single handed and the wife let it slip so a quick rub down and a rattle can of black and all sorted had to move a few things around as it seems a little larger than the other one seems a bit louder than the other one?



A

Your wife seems to have done a reasonable job on her own, looks to be at a strange angle but the big air filter disguises it. Bit sexist to make a big deal about the "rattle can" but thats what women do! If its louder maybe she hasn,t done the exhaust gaskets properly. What I dont like, in fact hate, are those blue hose, why do women do that?

[pridaux]

thegamekeeper said:

Your wife seems to have done a reasonable job on her own, looks to be at a strange angle but the big air filter disguises it. Bit sexist to make a big deal about the "rattle can" but thats what women do! If its louder maybe she hasn,t done the exhaust gaskets properly. What I dont like, in fact hate, are those blue hose, why do women do that?

No Idea but she had them done to match her Dress for Goodwood Revival I can always get some Spray Chrome Rattle cans instead after Goodwood and chrome them
Ps I did help a little someone had to keep the cups of tea coming it was thirsty work
A

[thegamekeeper]

pridaux said:

No Idea but she had them done to match her Dress for Goodwood Revival I can always get some Spray Chrome Rattle cans instead after Goodwood and chrome them
Ps I did help a little someone had to keep the cups of tea coming it was thirsty work
A

I can get you some spray cans, no need to wait for Goodwood. Chrome or tea bags not required.

[pridaux]

Well back to the real engine,Engineering Firm have tested the head worn valve guides so changing plus while at it changing over to unleaded so should be all systems go for the weekend shame that engine was not really mine double the cylinders would be nice but we can always dream
A