Cyl heads for 1098

Side valve, 803, 948, 1098., 1275 and Vizard mods

Re: Cyl heads for 1098

Postby austin » Mon Jan 20, 2014 1:57 pm

A couple of comments....

point 7. Your point regarding fitting a 1275 is not straightforward due to the different flywheels. True but it's not difficult either. Easiest is a 1275 Midget engine complete with it's flywheel. Or minor flywheel needs holes accurately drilling. Putting this Midget flywheel onto a Marina engine needs a bit of machining, or putting Minor flywheel onto Marina needs just the drilling only.

point1. Yes these heads are a useful improvement on a 1098, but mainly (only?) at higher revs. If you want more power in the 4 to 5 thousand revs area then these heads will give you more. But if you drive around 2,500 to 3,000 revs the 1275 will give more power than any 1098. How often do you actually go over 4,000 revs?
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Re: Cyl heads for 1098

Postby woodywoodchipper » Mon Jan 20, 2014 2:56 pm

minor to marina, flywheel £50 exchange esm and fitted for needle roller spigot,

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Re: Cyl heads for 1098

Postby bmcecosse » Mon Jan 20, 2014 5:36 pm

Mine pulls really well at the lower revs with the 1275 head - and it was fitted to replace a very good 295 head - the difference was very obvious. Hence it is able to pull the 3.7 final drive really well.
 









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Re: Cyl heads for 1098

Postby joshhicky » Wed May 28, 2014 9:02 am

Just to bring this thread back alive, I am fitting a 12g940 head onto a 1098 block, i have read all about this is about the clearances needed and such like, this means sinking the valves as you all know. People on here say the best way is to use a countersink and a vertical drill press/miller now i can do this in my own garage if i could find a counter sink big enough.. Can anyone help me with this?

Also while am here any advice from people who have done it before, any needs to knows?

Thanks josh
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Re: Cyl heads for 1098

Postby bmcecosse » Wed May 28, 2014 6:56 pm

Measure first! You may not need to do anything. You need 320 thou (8mm) - although actually you could 'get away with' only 300 thou -but this is the absolute minimum clearance between the exhaust valve head face - and the head surface. Yes - a simple pillar drill running slowly and a good big 45 degree countersink. The one we used is generally used for de-burring the edge of holes after machining. We put a small piece of emery paper in between the tool and the seat to prevent chatter. The tool was simply lowered to the seat and allowed to find it's own centre, then gently moved down the 40 thou required. I had decided to go for the full 40 thou in case I later opted to use a different cam with perhaps a slightly higher lift. Other matters - you will need to file a small amount off the top of the water pump, use a 1275 head gasket and a set of 1275 sintered rockers (or re-align the 1098 rockers so they act DIRECTLY on each valve stem tip). You need to put thin packers (washers..) under the springs on the valves where you have done the 'sinking. Washer thickness = the amount you sunk the valve. Use 15 thou exhaust valve gaps - and either change the thermostat cover or use a top hose with a bend in it....a section cut from an old bottom hose works well. You may find the heater valve rubs on the battery tray - so a little 'adjustment' may be required...... Good luck with it!
 









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Re: Cyl heads for 1098

Postby joshhicky » Fri May 30, 2014 8:01 am

Nice one thanks for that, i did some rough messuments last night just to get and idea and from the looks of it i have just over 8mm clearence so am right in thinking i will be okay, if so thats saved a whole load of pain. also thanks for letting me know about the other bits i didnt know you had to modify the water pump cheers ! also one last question might be a stupid one but why do people choose the 1275 gasket ?

thanks josh
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Re: Cyl heads for 1098

Postby bmcecosse » Fri May 30, 2014 8:29 am

Measure carefully - not just roughly! But yes - if you have 8mm it's fine. You must use 1275 gasket (get copper/copper if you can - and I advise carrying a spare) to match the head chamber shape. You just file a bit off the top edge of the water pump where it sits on the engine - no need to remove it ! And if you don't mind the exhaust valves 'bouncing' at 6000 rpm rather than (say) 6,200 - then don't bother shimming (washer) under the springs.
 









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Re: Cyl heads for 1098

Postby joshhicky » Fri May 30, 2014 11:29 am

yea i will messure using my depth mics and such like i was just look for a rough messurement to see how close i was, and right yea the 12g940 has a diffrent shape hence the gasket (makes sence now) thanks for all of the advice i will let you know how i get one this weekend.

Cheers josh
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Re: Cyl heads for 1098

Postby Deant94 » Tue Jul 15, 2014 10:11 pm

I've heard in a number of that a 12g940 head can be placed dirctely onto the 1098 block. Only if you have 320 thousands of clearance on the exhaust valve. Seamly if you have a standard rocker setup and standard cam it can be done. But also the 1098 blocks water ways are in a different position to the 1275 so I've heard you can modify either the 1275 gasket or the 1098 not sure can't remember fully sorry. I have definitly read it before and it can be done. Also sorry if I have Ritter anything anyone els has already.
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Re: Cyl heads for 1098

Postby bmcecosse » Thu Jul 17, 2014 4:02 pm

No need to alter the 1275 gasket in any way.
 









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Re: Cyl heads for 1098

Postby FrankM83 » Tue Aug 05, 2014 8:41 pm

not sure if I missed this somewhere but can an unleaded head from a late A series 998cc be fitted to a 1098 or a 948? Thanks
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Re: Cyl heads for 1098

Postby MM » Wed Aug 06, 2014 12:05 pm

Yes, it will fit the 1098cc, which has the same bore size (64.58 mm), however, the 948cc engine has a 62.9mm bore size, so you may find the valves hit the side of the cylinders...
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Re: Cyl heads for 1098

Postby FrankM83 » Wed Aug 06, 2014 12:07 pm

Thanks will there be mich decrease in power u think?
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Re: Cyl heads for 1098

Postby bmcecosse » Wed Aug 06, 2014 12:12 pm

No cylinder hitting worries. The inlet valves are smaller, and the porting is not as good. However the chamber is slightly smaller so the CR will go up slightly. It will lose a little power - but may gain economy!
 









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Re: Cyl heads for 1098

Postby Caz » Wed Aug 20, 2014 9:20 pm

Would this be a cam4810? I'm looking for a cheap unleaded head for a 1098 to improve fuel economy. Cash strapped student you see :) Would this be a simple bolt on job with the 1098 rockers?
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