Block to gearbox gaskets
Turbo Mini Forums

Was having a look over the car today and noticed that the block to gearbox gasket has started to creep out the front of the joint! The car is a N/A 1293 that revs to 8,000rpm and I can only think this is caused by one of two things. 1. The poor quality of gaskets that are supplied now or 2. At high revs the block and gearbox are flexing apart allowing the gasket to move? It is the standard 1/4" UNF bolts that I'm using.

Has anybody else experienced this and what do people think of the copper shim gaskets you can get now? I also did a search and found that Sprocket was running with just a bead of sealant, how did you get on with this?

Cheers, Keith.

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

I'm using one of the copper gaskets, seems quite good, I heated mine before fitting to make it soft.

i have a dipstick spring in the exact same place lol

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

oh, i just use a bit of fernox ls1 stuff (basically like silicone sealant)

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I have had no issue with just the sealant, but do remember I checked the transfer gear mesh clearancies before I decided to go that route, as obviously the primary gear to idler clearnace had opened up roughly 3 thou due to the main bearing line bore.

I believe the copper gaskets are a solution to the very problem you have, however, I personaly would try and fix the problem rather than the symptom, and the problem looks like it could well be flex of the block and gearbox, xo there may well be something in it after all by upgrading to M8 or 5/16th gearbox to block bolts, and that was also one reason I chose a 4 bolt main cap.

I also think that a thin smear of Loctite RTV on both sides of the gasket would help prevent this. I am not talking about smothering the gasket and mating faces with the stuff, just a smear so that the RTV is opaque.

Cheers for the replies, well spotted Joey, drilling the clamp seemed the easiest way to mount a spring for the dipstick.

Sprocket, I suspected that it may be flex in the block, but thought I would get a few opinions from on here. I've only got a centre main strap fitted just now, so it would probably make sense to upgrade to the 4 bolt main cap. I'm sure I remember the debate over the benefits of upgrading to 5/16 bolts, need to do a bit of research on that, don't imagine it can do any harm though. The gasket was fitted with the lightest smear of sealant.

Maybe I should just get a rev-limiter, but then it makes peak power around 7,800rpm.

Keith

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

I have done 6k miles with this engine so far and 3500 of that since crank bearing failure. The engine gets buzzed to 8k nearly every time I am out in the car, but obviously its not at 8k for long.

I am not covinced a seperate piece of metal bolted ontop pf the main cap will do much, and some believe that there is no need for a strap at all. I personaly looked at the leverage and load spreading of the four bolt cap and accepted that there has to be at least some benefit somewhere, whether it was stiffening the block, reducing the load on the mains bolts, and or reducing the flex of the cap itself. It has not been without its problems though.

Cheers for the reply Sprocket.

I read about your woes. I will be pulling the engine for the winter check over so will investigate further and give serious consideration to the 4 bolt centre main and upgrading to 5/16" block/gearbox bolts.

Thanks, Keith

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

have you enough breathers keith ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I was going to mention that,

also have you done a leak down latly?

Edited by Keith Timpson on 23rd Nov, 2009.

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

Like twin SUs yum!
Compression test means jack I'm afraid! Leak test is where it is at.

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

I doubd you would have any problems with excessive crankase pressure with those breathers, and even if there was excessive pressure, a gasket blowing out like that says to me one of two things, either the mating faces are not flat and clamping the gasket, or, 'flex' (i still need convincing fully) of either block and or gearbox casing is allowing the gasket to creap.

I have always found excessive crankase pressure will blow oil out the dipstic, and I don't mean the normal wet patch around the dipstick hole, but, seeing as the age old dipstick rocket fix has been applied, its not going to give you any indaication of excessice crankcase pressure.

When you change the gasket, use the same theory as head studs, tighten the middle ones first and work outwards. A drop of sealant wouldn't hurt either.

Could have a burr also? That might prevent proper mating?

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

or a thread pulling,

iv'e never had any probs with gaskets working there way out loike that Kieth,
i use a very thin bead of silicone on both sides of the standard gasket, but i run it on the outside of the bolts so it squeezes outwards and not into the engine, i make sure i run a thinners cloth over the surfaces to make sure they are oil free so the silicone cures correctly and sticks,


carl

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

I have seen this befour on race engines which are still using the standard gearbox to engine bolts any of the race engines with the bigger M8 or 5/16 inchemeters bolts, seem to keep the gasket in place.

I have been omitting that gasket for probably 3 years now and just using sealer I find it greatly reduces wear on Straight cut drop gears I can only put in down to better tooth engagement.
regards,
Paul.

P.s. as Colin said above its not just a matter of just leaving out the gasket it is important to check clearances with the gasket out, I got a recommended backlash figure from MED which you check with a DTI gauge.

Thanks for all the input guys.

The gasket was fitted with a smear of sealant but the faces would probably of had traces of oil on them, so may have defeated the purpose. I'll try and get a leak down test done before I pull the engine out. With regards to the dipstick issue, I always found, regardless of engine specification, on the A plus it would rattle about and oil would find its way out there, so as a matter of course I fit a spring to hold it tight. I'll try running it without the spring and see how much oil appears. The last time the engine was out (the specification hasn't changed) there was zero oil in the clutch housing, so I'm doubtful it's a crank case pressure issue, but won't rule anything out.

Maybe I should just not pull 8k in 4th......

Thanks again for all the suggestions and apologies if this post is nonsense, I've just finished an 11 hour nightshift!

14.914 sec 1/4 mile @ 91.38mph, NA 1293cc on 1.1/2" SU's (all steel and glass shell)

AlexF

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=296964

I checked mine the crude way using some plastigauge on one tooth of the primary and the input gear, assembled everything and turned the gears, pulled it appart and measured the plastigauge. It revield 7thou on the input gear to idler and 4 thou from primary to idler. Take out of the equasion the line bore, that would be 1thou primary to idler, plus 9 thou gasket results in 10 thou assembled clearance with gaskets on an un line bored block.

This is a simplified theory but I think its good enough to determine whether it will work or not.