Dragster from New Zealand

jseng1

jseng1

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Had to post a photo of Alex'sincredible drag bike. Quite an engineering accomplishment.
JS3 cam (D+), Long rods and domed pistons, beehive springs etc.
Dragster from New Zealand
 
I wonder if that actually is an X-pipe exhaust (the Red one) or merely welded together at that joint.
 
Here's the class info he ran in New Zealand.

Was run under 2 classifications.

2 IHRA NZ

And last year as a modified bike which is open class dial your own and came second for the season against all comers.
 
jseng1 said:
jseng1 said:
Had to post a photo of Alex'sincredible drag bike. Quite an engineering accomplishment.
JS3 cam (D+), Long rods and domed pistons, beehive springs etc.
Dragster from New Zealand
Click to expand...
Click to expand...

jseng1 said:
Here's the class info he ran in New Zealand.

Was run under 2 classifications.

2 IHRA NZ

And last year as a modified bike which is open class dial your own and came second for the season against all comers.
Click to expand...
A bite late but thanks for posting a picture of our bike.
I was going to do a write up of the engine build and assembly issues mating English and American parts together.
Things like having to grind clearance in the Molnar cases for the JS rod bolts to spin round and boring the cam tunnel to clear the fat JS3 cam, among a bunch of minor fettling. Unfortunately all photos and notes on a previous laptop are just digital memory somewhere now, after some overheating.

I'm hoping someone is reading this and might offer some advice on an issue that annoyed us for much of the last season.
I will give bit more of an update first to the information already here.
Built a new Engine with more compression after 2nd placing in our class for the season 24/25. More power obviously required. Upped compression from 9.8 to 11.8 and changed from AvGas to C12 fuel. Had also had an issue with oil in cylinders lowering effective octane and had seen evidence of minor detonation even at 9.8:1, so fitted seals to the inlet valves. Few other tweaks as one does. Had a bad start to the 25/26 season with a blown big end before racing started (whole 'notha story) so missed points meetings and effectively stopped our chances of chasing a better result than previous year. We did however set and then break the NZ for our class of racing in IHRA NZ once we got the new parts from USA and UK landed and fitted. Season best and PB of about 11.6 @ 118 MPH, sorry don't have paperwork for that handy and the laptop excuse of course. Happy enough with that, but also battling some carburettor issues hindering our launch, so more to come.

So, to the annoying issue.
We are running Molnar cases and aluminium barrel with iron liners. these are standard bore 828cc. I could see in one very small area where the boring for the liners has just penetrated the barrel between the fins - no cause for alarm. I noticed that after a few runs that we had a small witness of oil leaching out this area, again not concerned. By the end of the season we were having issues with oil in the cylinders again. On stripping the engine I found oil was migrating under the head gasket from around the tophat of the liner and from one of the through bolts into the cylinders, more on the timing side. I use a copper head gasket and a copper gasket spray to seal the head, but could see tracks where the leaching occured. We did not have a leaking head gasket to atmosphere top or bottom side. I also checked leaking by blocking off all crankcase outlets and pressurising the cases with compressed air. I could witness bubbling around the tophat and one of the through bolts.

So, the questions, is this crankcase pressure or vacuum from the pistons bringing the oil up the liners? The crankcase has a one way sump valve. Obviously the next question is how to resolve this issue. Happy to consider any relevant thoughts thanks, Alex.
 
Last edited:
Schwany said:
I wonder if that actually is an X-pipe exhaust (the Red one) or merely welded together at that joint.
Click to expand...
Hi Schwany, deceived by the photo angle. They are two individual pipes, bit of a gap between them but bent like that to achieve a desired length before the megaphone. Not a lot of room with 50mm ground clearance.
 
CUin11.2sec said:
A bite late but thanks for posting a picture of our bike.
I was going to do a write up of the engine build and assembly issues mating English and American parts together.
Things like having to grind clearance in the Molnar cases for the JS rod bolts to spin round and boring the cam tunnel to clear the fat JS3 cam, among a bunch of minor fettling. Unfortunately all photos and notes on a previous laptop are just digital memory somewhere now, after some overheating.

I'm hoping someone is reading this and might offer some advice on an issue that annoyed us for much of the last season.
I will give bit more of an update first to the information already here.
Built a new Engine with more compression after 2nd placing in our class for the season 24/25. More power obviously required. Upped compression from 9.8 to 11.8 and changed from AvGas to C12 fuel. Had also had an issue with oil in cylinders lowering effective octane and had seen evidence of minor detonation even at 9.8:1, so fitted seals to the inlet valves. Few other tweaks as one does. Had a bad start to the 25/26 season with a blown big end before racing started (whole 'notha story) so missed points meetings and effectively stopped our chances of chasing a better result than previous year. We did however set and then break the NZ for our class of racing in IHRA NZ once we got the new parts from USA and UK landed and fitted. Season best and PB of about 11.6 @ 118 MPH, sorry don't have paperwork for that handy and the laptop excuse of course. Happy enough with that, but also battling some carburettor issues hindering our launch, so more to come.

So, to the annoying issue.
We are running Molnar cases and aluminium barrel with iron liners. these are standard bore 828cc. I could see in one very small area where the boring for the liners has just penetrated the barrel between the fins - no cause for alarm. I noticed that after a few runs that we had a small witness of oil leaching out this area, again not concerned. By the end of the season we were having issues with oil in the cylinders again. On stripping the engine I found oil was migrating under the head gasket from around the tophat of the liner and from one of the through bolts into the cylinders, more on the timing side. I use a copper head gasket and a copper gasket spray to seal the head, but could see tracks where the leaching occured. We did not have a leaking head gasket to atmosphere top or bottom side. I also checked leaking by blocking off all crankcase outlets and pressurising the cases with compressed air. I could witness bubbling around the tophat and one of the through bolts.

So, the questions, is this crankcase pressure or vacuum from the pistons bringing the oil up the liners? The crankcase has a one way sump valve. Obviously the next question is how to resolve this issue. Happy to consider any relevant thoughts thanks, Alex.
Click to expand...
Awesome bike Alex!

The JS rod clearance issue is due to Molnar (and Maney) intentionally having ‘just enough’ clearance in order to leave the cases as thick as possible. The longer rods different angularity puts the rod bolt heads in a different place as the crank rotates, necessitating material removal.

Is the top hat of the liner protruding a little too much perhaps, and preventing the gasket from clamping firmly enough to the head and barrel flanges and therefore not sealing around the through bolt holes correctly? I’m not sure but IIRC Maney used 4 thou protrusion.

I know someone who siliconed over the Allen heads of the through bolts for a similar reason, that was also with an alloy barrel kit (Norvil). @ludwig makes plugs to cover them, for slightly different reasons, but maybe there’s an idea there somewhere?

Are you still using the stock oil drain hole in the barrels? If so that is also a classic point whereby oil could leach into the combustion chamber.

What porting has been done? Aggressive porting can break into the oil drain in the head, thus sucking oil in. This is why Maney heads use an external oil drain connecting the head (from between the ports) to the cases.

FWIW I do not believe that piston suction alone would cause this, surely the path of least resistance would obviously be to suck in charge via the WOT ?!

Are you using the NYC Norton version of sump breather? I use these on my 920 and 1007 and they comfortably handle the task even on track where they are really at the high end of the rpm range for prolonged periods. I do know that some other brands seem to use stiffer reed valve springs, but I don’t know if this effects their performance.

Very surprised to hear you have issues where the liner is visible, I have a set of 1007 Molnar barrels on the shelf with no sign of this, and the OD of the liner is much bigger ( for the 83mm bore).

It does sound to me (total layman) that perhaps your liner to barrel interference fit is not ideal? If oil really is being forced up between the liner and barrel, maybe some wicking loctite applied around the base (and where it breaks through) might help @lcrken used to do this when machining stock barrels out to take 920 liners.

Other thoughts are, slightly oval bores. Oil being sucked down the OD of the guides. Rocker spindles fitted in the wrong way around causing over oiling of the head. Leaching from the pushrod tunnels to the combustion chambers.

For some more context, what rpm are you using? And what weight oil?
 
I would use pliobond contact glue rather than the copper spray to seal the head gasket. Apply it to each surface.
 
Fast Eddie said:
Awesome bike Alex!

The JS rod clearance issue is due to Molnar (and Maney) intentionally having ‘just enough’ clearance in order to leave the cases as thick as possible. The longer rods different angularity puts the rod bolt heads in a different place as the crank rotates, necessitating material removal.

Is the top hat of the liner protruding a little too much perhaps, and preventing the gasket from clamping firmly enough to the head and barrel flanges and therefore not sealing around the through bolt holes correctly? I’m not sure but IIRC Maney used 4 thou protrusion.

I know someone who siliconed over the Allen heads of the through bolts for a similar reason, that was also with an alloy barrel kit (Norvil). @ludwig makes plugs to cover them, for slightly different reasons, but maybe there’s an idea there somewhere?

Are you still using the stock oil drain hole in the barrels? If so that is also a classic point whereby oil could leach into the combustion chamber.

What porting has been done? Aggressive porting can break into the oil drain in the head, thus sucking oil in. This is why Maney heads use an external oil drain connecting the head (from between the ports) to the cases.

FWIW I do not believe that piston suction alone would cause this, surely the path of least resistance would obviously be to suck in charge via the WOT ?!

Are you using the NYC Norton version of sump breather? I use these on my 920 and 1007 and they comfortably handle the task even on track where they are really at the high end of the rpm range for prolonged periods. I do know that some other brands seem to use stiffer reed valve springs, but I don’t know if this effects their performance.

Very surprised to hear you have issues where the liner is visible, I have a set of 1007 Molnar barrels on the shelf with no sign of this, and the OD of the liner is much bigger ( for the 83mm bore).

It does sound to me (total layman) that perhaps your liner to barrel interference fit is not ideal? If oil really is being forced up between the liner and barrel, maybe some wicking loctite applied around the base (and where it breaks through) might help @lcrken used to do this when machining stock barrels out to take 920 liners.

Other thoughts are, slightly oval bores. Oil being sucked down the OD of the guides. Rocker spindles fitted in the wrong way around causing over oiling of the head. Leaching from the pushrod tunnels to the combustion chambers.

For some more context, what rpm are you using? And what weight oil?
Click to expand...
Thanks Fast Eddie
I appreciate that grinding the cases for clearance is due to maximising case thickness and just part of building a new engine. I haven't checked if the tophat is proud of the barrel face, I think unlikely as I have run the head and barrel over wet and dry on a surface table and don't recall seeing any witness on the iron part. Will check.
I have a stage II Maney head which maintains the original oil return, nil obvious leakage but will observe more closely as the timing side has more evidence of oil in cylinder. Similar with the pushrod tunnels, nothing obvious. I use a JS motorsport sump breather, appears to work as expected, leaving very little oil in the cases after a run. I am getting probably too much oil to the head (rocker spindles fitted correctly) as the exhaust rocker covers weep at times after a couple of hot runs. Engine runs 6400 to 7600 rev/min for duration of the run. Use Lucas 30 weight straight break-In oil with additional TB Zinc plus.
To be honest I have been a bit disappointed with the products from Molnar, feel like I got the lower spec parts sent out as too costly to return them. Had issues with the crank output taper and drive pulley offset, crank journal burr with nil relief on oil hole, swarf in crank, timing side idler sprocket shaft bore needing re reaming, few other poor finishing items, and now suspect fitting of liners.

For the liner issue I am considering using Loctite 290. A wicking type threadlock.
Is oil getting sucked down the outside of the guide (valve guides I assume) a thing ? Anyway of determining this? I guess if in doubt 290 could be used there also.
I only questioned the piston vacuum sucking the oil as another issue we had was on launch when the engine first came under load the Lectron carb slide would flutter, closing against the return spring. This took some diagnosing I can tell you! Seems like it was getting a wrong signal from induction tuning, hopefully we have overcome this by extending the taper on the inlet manifold.
Thanks for your input.
 
jseng1 said:
I would use pliobond contact glue rather than the copper spray to seal the head gasket. Apply it to each surface.
Click to expand...
Hi Jim, yes I used Pliobond on a previous motor which was excellent. Unfortunately it was very difficult to get apart again, sticking too well. Considered not worth the aggravation as usually I have not had issues with sealing.
 
CUin11.2sec said:
Thanks Fast Eddie
I appreciate that grinding the cases for clearance is due to maximising case thickness and just part of building a new engine. I haven't checked if the tophat is proud of the barrel face, I think unlikely as I have run the head and barrel over wet and dry on a surface table and don't recall seeing any witness on the iron part. Will check.
Click to expand...
Seem like this might be the issue. See https://www.accessnorton.com/NortonCommando/head-gasket-leak.21177/

Pay special attn to Comnoz's comments. He is the goat.

(No offence in intended @jseng1 !)
 
Last edited:
CUin11.2sec said:
Thanks Fast Eddie
I appreciate that grinding the cases for clearance is due to maximising case thickness and just part of building a new engine. I haven't checked if the tophat is proud of the barrel face, I think unlikely as I have run the head and barrel over wet and dry on a surface table and don't recall seeing any witness on the iron part. Will check.
I have a stage II Maney head which maintains the original oil return, nil obvious leakage but will observe more closely as the timing side has more evidence of oil in cylinder. Similar with the pushrod tunnels, nothing obvious. I use a JS motorsport sump breather, appears to work as expected, leaving very little oil in the cases after a run. I am getting probably too much oil to the head (rocker spindles fitted correctly) as the exhaust rocker covers weep at times after a couple of hot runs. Engine runs 6400 to 7600 rev/min for duration of the run. Use Lucas 30 weight straight break-In oil with additional TB Zinc plus.
To be honest I have been a bit disappointed with the products from Molnar, feel like I got the lower spec parts sent out as too costly to return them. Had issues with the crank output taper and drive pulley offset, crank journal burr with nil relief on oil hole, swarf in crank, timing side idler sprocket shaft bore needing re reaming, few other poor finishing items, and now suspect fitting of liners.

For the liner issue I am considering using Loctite 290. A wicking type threadlock.
Is oil getting sucked down the outside of the guide (valve guides I assume) a thing ? Anyway of determining this? I guess if in doubt 290 could be used there also.
I only questioned the piston vacuum sucking the oil as another issue we had was on launch when the engine first came under load the Lectron carb slide would flutter, closing against the return spring. This took some diagnosing I can tell you! Seems like it was getting a wrong signal from induction tuning, hopefully we have overcome this by extending the taper on the inlet manifold.
Thanks for your input.
Click to expand...
Oil past the guides is a thing if badly fitted etc, certainly won’t be a thing on your Maney head !

Surprised you’re running 30wt break in oil in such arduous situations, what’s your reasoning there if I may ask?

Very surprised and saddened to hear about your issues with Molnar parts.

It’s looking like the wicking loctite is you favoured next step.

What rimgs are you using? Might be worth trying gapless total seal jobs if you’re not already.
 

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