I have an 1100 bored to 1210 with a mild cam of unknown quantity. the engine has quite high compression around 200psi per cylinder and the cylinder head is modifyed and ported etc. I am running an single 1 1/2 SU.

6 months ago i removed the old side entry 25D dizzy and replaced it with the pulsar dizzy, but i am not quite convinced it is setup correctly and/or suitable for my particular engine combination.

I am sure with the correct mods this can work with this engine but i really am sick of playing the then thing every few days for 6 months now. Recently i commented i thought i had the right spring/advance combo in the dizzy but i think i may have been a little optimistic there.

basically i have decided i might change the dizzy with one that is a bolt in that is designed for a A series engine.

i had my eye on this
http://www.minisport.com.au/prod1593.htm

What do you guys think of this dizzy? looks like good value to me. I dont have deep pockets so wanted to keep the cost under $200 if i could. if i retore my old 25D and convert it to electronic it would end up being more than $200 with a new cap, condensor, points etc etc.

Would this dizzy be suitable do you think or would i still need to have it modded to suit the engine?

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'66 BRG Morris Mini Deluxe 60HP ATW

Once you change the cam you really need to modify the dizzy curve to match.

I would send the Pulsar dizzy to Russell Engineering for advance curve mods.
Or, check the Pulsar dizzy thread at top of the Mini Mods forum. It explains what's needed to make it work in a modded A series.

You could go buy a new Lucas style dizzy, but it's a lottery whether the advance curve is near correct for YOUR engine.
I bought an electronic one and it wasn't, my modified Pulsar killed it for low speed and midrange torque.
Pretty much any stock dizzy will be in the same boat, and need the curve modified.

You really need to dyno the motor, whilst fiddling with the dizzy to get a curve approximation for max torque at various revs (ie make an advance curve spec), then get the dizzy recurved to those specs by someone who has a dizzy machine.

The expensive 123 dizzy might have 16 curves in it, but they won't be perfect for your particular modified engine either.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have tried a few different advance settings with the pulsar dizzy. a few different spring setups and different static timing aswell.

How soon should the timing advance? i am finding the engine pings badly around 2500-3000 if i run 5-7 degrees static at idle and the 10 degrees distributor advance. it seems like the advance is advancing to early and the engine pings. according to my timing light with these settings it is only getting around 15 degrees at 2500-3000rpm. max advance comes in around 4000rpm. but as i said its pinging at these settings. i have tried making the springs stronger and this does help but it still has light pinging at this rev range with this static setting.

i do run only BP ultimate 98 octane and the carb is on quite a rich setting with a slightly rich needle for the engine.

will a modded engine require the advance to come in a lot later? i find if i run 2 degrees of static at idle and 10 degrees of advance in the dizzy the engine does not ping anywhere and has strong midrange but does lag a little as this is quite retarded.

maybe i just forget trying to get the setting even somewhat close and just send the dizzy to graham?

as i said i am abit over it now. i have three pulsar dizzys. three modded plates with different settings and about 6 different springs that i have tried. i just cant seem to get a good balance of idle/low end performance for every day driving, and mid to high performance without pinging at the settings suggested.

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'66 BRG Morris Mini Deluxe 60HP ATW

Ok heres a question for everyone.

Can anyone suggest a tuner in Brisbane who has a dyno that can mod pulsar distributors and is good with SU tuning and mini's with a dizzy machine?

Any idea on what this may cost? just a guess.

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'66 BRG Morris Mini Deluxe 60HP ATW

Generally engines with modified cams need the advance to come in sooner. You can do this because cylinder filling at low rpm is lower, so effective C/R then is lower, it will stand more advance.
If you don't advance it, low and midrange torque (and HP) suffer.

example only: (note this motor has a radical chamber shape, so needs more advance than most).
1360cc, C/R 10.7:1, RE282 cam, 1.5 rockers, race head, 45DHLA Dellorto , Maniflow LCB

Pulsar D4R85 dizzy, no vac advance. GT40-R coil, Bosch leads.
9° cam plate, 1 light spring removed.
static advance = 20°
max advance = 38°

It pulls from 1800rpm, gets on cam around 2500, revs to 7500+.

NO it doesn't ping on 98 fuel.
Are you really sure yours is??

<edit> perhaps it's just that your C/R is too high. If it's a 1220 it has flat top pistons, the head may well need the chambers opened out more.
10.5:1 is about the limit for use with (say) a 270° cam.
I would pull the head and measure the chambers. Enlarge if needed.
There is another C/R checking method used on bikes, can be done with head on.
PM me for details.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Maybe that is the whole problem. Maybe the enigne has to higher compression for everyday use.

I am finding i have to run the timing very retarded to stop the pinging.

I am not 100% sure if it is high for a mini engine, but the techs here at work suggest 200psi is very high compression.

Judging from my experience with the mods by the previous owner i would say htis may be the case and the compression is to high.

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'66 BRG Morris Mini Deluxe 60HP ATW

If you know the CV (clearance volume) of the whole combustion chamber you can accurately calculate the C/R.

Here's how to do it with the head on:
1. Park the car facing slightly uphill or put the front on ramps.
2. With motor COLD, remove all spark plugs, and distributor cap.
3. Turn motor over in neutral until rotor is pointing at #1 plug lead position.
4. Check timing marks- align with TDC 1/4 mark on flywheel, or the TDC mark on the timing cover if it has one.
5. Fill a horse syringe, burette or measuring cylinder with ATF. You could use water but ATF won't cause rust.
6. Fill through #1 plug hole until it is just above the bottom of hole. Rock engine slightly to maximise the level. Top up to 1/2 way up the plug hole.
7. Note the total quantity that you poured in. This is CV.

C/R = (cylinder displacement + CV)/CV

example for a 1220 motor:
displacement = 1220/4 = 305cc

for a CV of 32cc,
C/R = (305+32)/32
= 10.53:1 which is in the ball park.

for a CV of 31cc,
C/R = (305+31)/31
=10.84:1.
I would not go higher unless you have a race cam in it.

To get the ATF out put some rags on the front of the motor and crank it over. There's only 32cc or so in there, wash it off afterwards.

<edit> If you find the CV is less than above, subtract it from my figure, that is how much you need to increase size of each combustion chamber by grinding out.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

excellent drmini. thank you for that information. i will perform this test on the weekend and see what the result is.

I will post the result on this post. i have suspected this to be the case for some time, but being an amatuer i was hoping the carb and dizzy were the cause. it still may be yet.

thanks again.

Jason

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'66 BRG Morris Mini Deluxe 60HP ATW

Bought a syringe today and will measure the CV tonight if i have the chance.

Quick question though. If it is to high can i use a thicker head gasket or spacer shim or something to lower the compression instead of grinding the head?

A few people have noticed the fact that the head is sitting hard on the top of the water pump and the engine number has been machined away and replaced by a department of transport engine number.

i would say the head and block are machined to their limits, therefore my thoughts that it is quite high in compression.

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'66 BRG Morris Mini Deluxe 60HP ATW

You could probably get away with using two ACL Monotorque composition head gaskets on a smallbore.
I was once running over 11:1 on my 1310 with flat top pistons, so I fitted 2x BK450 (1275) gaskets and ran it like that for 2 years, no problem.
The gaskets and sealing were fine when I finally took them off and opened up the chambers.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I measured the capacity of the cylinder at 29cc.

if the engine is in fact a 1210cc as the previous owner tells me it is, the compression ratio would be about 11.5:1 if my calculations are correct.

is this the correct calculation?

as i said i compression tested the engine at 200psi. thats pretty high.

is this to high for pump 98 octane fuel in a daily driven road car?

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'66 BRG Morris Mini Deluxe 60HP ATW

GR reckons you can run up to 11:1 on a smallbore motor, with his cams.

Hang on, I have a calcs sheet here from the last 1220 I built.

[edit] this one was 29cc chambers (head only)
add:
ring land volume 0.6cc
valve cutouts 1.0cc
deck height volume 1.81cc
1098 gasket volume 2.7cc
-------------------------------
total volume 35.11cc.

C/R worked out to 9.68:1.

If you have 29cc TOTAL,
your C/R is indeed 11.51:1

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

yep,,, waaaaayyyy to high

I try to keep them all under 10:1 as best i can,,, that "always" leave room for hot days or poor fuel &/or poor tuning etc (ok my 1510 is on 10.3:1 but i can get away with more if i wanted cause the donk is so big in capacity),,, the bigger the capacity the more comp you can get away with ---> to a point !!!!!!!!!

However ... there`s not much point trying to get away with hi comp ratios on a "Road" engine (in my books) when there`s always that chance of the 'silent" pings starting to eat away at your head gasket &/or pistons

Our "ReadSpeed" delivery vans (all 5 of them) ran 3x std 1275 Tam1251 head gaskets for about 15 years,,, no dramas,,, just make sure you have everything very clean & re-torque them (maybe even a couple of times)

If/when-ever we wanted/needed a race donk we`d rip the head gaskets off ... swap out the std-ish cam for a race cam ,,,& stick one head gasket back in,,, hey presto, quick & easy race donk ready to go

Otherwise you can always try to find someone good with a die-grinder & open the chamnbers up

Probably only need about 5 ccs (sorry havn`y worked it out acuratly, just guessing) taken out of each

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Make the head chambers themselves 28 or 29cc and you will be near the money, see my figures above.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.