846 replies to this topic

[timmy850]

So an update on the double head gasket experiment:

For most of the time I've been struggling to get the timing under control I was having pinging at around 3000rpm. It was only at part throttle, the plugs were changed to cooler ones, the timing was reduced to 15 degrees, the fuel was on the rich side, I used 98 octane fuel and octane booster, removed the vacuum advance etc but it never cured the problem. I ended up with a strange inverted timing curve. (The base timing was set at 10 degrees, so all the advance numbers here have 10 extra on top)


Now I've got a proper shaped timing curve and the vacuum advance is hooked up too. At 3000rpm the advance is set to 25 degrees and it's been running really well. Idle is smoother than before, starting is good, no run-on, no pinging. In terms of performance it seems much the same, so possibly the extra timing has offset the lower compression


I've been out for a couple of drives to work and the carb tune is much the same as before. The needle still isn't perfect, the main issue is that it goes a bit rich under full throttle. It idles and cruises at a good mixture


I had moments where I thought I'd cured the coolant leak


However it's still leaking from the bottom hose! I've tried tightening the clamp when hot and that didn't help either


Overall the double head gasket has been a huge success, it's not a long term solution but it's given me an idea of how to get it running better in the future. I will need to investigate the best way forward:
Dish the pistons and/or open up the head to lower compression
Go to a longer duration camshaft to reduce effective compression
Change to a different head like a 12G295 which has bigger chambers
Drop back to a 998 crank

[sonscar]

I was taught to fit hose clamps close to the end of the pipe,you may be clamping too near the flare.Just my thoughts,Steve,

[timmy850]

Perhaps from the photo it's a bit hard to tell, but the hose goes on the radiator a fair distance, so the clamp is still away from the flare. I'd removed the radiator a few weeks ago, cleaned the radiator end (back to bare brass) and inside the hose and tightened the clamp up while it was out of the car. 

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[PoolGuy]

How tight is the hose on the radiator? I always like them to be a real bastard to fit, I've had some rubbish in the past that my 7 year old could push on. 

[KTS]

..is it a new hose ?  if the old one didn't leak then it's worth a close look at the inside of the hose to see if there's anything untoward going on

[timmy850]

How tight is the hose on the radiator? I always like them to be a real bastard to fit, I've had some rubbish in the past that my 7 year old could push on. 

 

 

..is it a new hose ?  if the old one didn't leak then it's worth a close look at the inside of the hose to see if there's anything untoward going on

 

The radiator is a C-ARA4442 Minispares "super 2 core" https://www.minispar.../C-ARA4442.aspx

The lower hose is a GRH240KEVLAR from here https://minisport.co...h-heater-outlet

I assume (as per most of their parts) that the Kevlar hose comes direct from Minispares. 

 

So up till August I was using my old radiator hose that never leaked. It's been on for maybe 8 years and the ends were starting to get a bit torn up from being on and off a few times. When I had the radiator out to check on the crank pulley I thought it would be a good idea to put in new radiator hoses. My normal supplier didn't have any in stock so I got this one from Minisport Australia (not connected to Minisport UK)

 

I installed the new hose the first time with the radiator out (after I cleaned the radiator outlet). I removed the radiator and hose and cleaned it again a second time with the same results. I did get the coolant leaks out of all 3 ends of the radiator hose, so I don’t know if this 1275 “Kevlar” hose is just a bit long for my setup, or maybe it’s a bit too stiff and not fitting the water pump and radiator ends properly. I’m still yet to decide what to do next. I might just get another hose or maybe take the radiator and hoses to a radiator shop and get them to pressure test it with the hoses on.

 

I found out much later that they sold Australian made hoses for small bore engines which are a bit shorter. However I couldn't find it the first time I was ordering as they didn't think to use the word "radiator" in their description of a radiator hose!

https://minisport.co...h-heater-outlet

[timmy850]

One thing I did when the head was off was I swapped the LH tappet cover. It used to have one with a breather canister on it, but when working on that side of the engine (getting the exhaust manifold on or off, getting to the radiator hose, getting to the fuel hose etc) it was a bit inconvenient to work around and a pain to line up and get the bolt in. Now it's got a plain one like the other side


Now it just has a single breather port on the flywheel housing & it's connected to the port on the carb. It has a decent suction from the carb which means all the crankcase vapours are burnt and stops the smell. I've also done an oil change and checked the tappet clearances and after a few more drives it appears the coolant leak has subsided for now. One slightly annoying thing was the clutch master cylinder extension sleeve started leaking from the O-ring and it's ruined the paint on the bulkhead already. I've now drained all the extra fluid with a syringe and removed the extension sleeve so I'll need to clean up and sort out the paint. The brake fluid also soaked up into the bulkhead insulation blanket and held it against the paint, so that needs a good clean out before I can use it again


On the weekend we had a small turnout for the MITG run to Thirlmere. We did about 200km and the new slightly lower compression hasn't harmed the performance at all, in fact I think the extra timing at lower RPM has improved it


My uncle let me know one of their neighbours was getting rid of some imperial sized tools, so I scooped these all up before they went to the tip.