I wouldn't be interested in spending big bucks and i'd be quite happy for the rev limit to be much lower than 7500 so all good .

Can anyone confirm/deny what he says about the pistons?
I looked up some 18R pistons just to get a ballpark figure on them pricewise and it was like $90 a set for new old stock ones .

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Going to throw my 2 cents in, limited though my experience is... I am using L28 +040 pistons in my ute, gives you 2mm extra on std L20 ones and i have a feeling you can get a flat top in that as well... but don't quote me on that

I used to run Hepolite flat tops in that size.

Yep, you can get flat top L28 pistons - I'm running a set of 86.5mm ones in my car at the moment.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

How much are these L28 flat tops? I presume you can buy them in lots of four and not just six? How much power are you making roughly Dave?

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I got them from Datsport (as a set of 4). I can't remember how much they were though (around $200 ??) You can get them very cheap off US eBay, but I was wary of going that route in case I ended up with dished pistons due to possible differences in spec between US and Aussie cars.

Stewart Wilkins also has them, but at the time didn't have them in the size I wanted.

My engine is nothing fancy - an L18, A87 head ported and polished by me, 44mm and 35mm valves, 72 degree cam, flat top pistons and 1 3/4" british SU's on a ported Datsun factory manifold. Apart from that, its just been carefully assembled (balancing, paying attention to the best clearances for performance, cam timing and valve train geometry spot on, etc).

Ended up costing around $1000 for parts, machining, pretty much everything.

I had it dyno'd at John Collins a month or so back - 102hp. Not a huge amount, but plenty for a bit of good, cheap fun

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

Cool, this is the engine in the 1600 I saw with the polished ram tubes on the SUs?
What's your comp ratio with flat tops? A few posts back up it was suggested that with the A87 head it'd be too high with flat tops.

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a l20b with an a87 (41cc chambers) and 1mm over flat tops comes out to around 11.2:1 which is too much for a street engine. Mine wont run on ultimate 98

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Circuit Race 1600 in the build

Mine works out at 10.4:1 or thereabouts. Its an L18 though, so compression is lower than an equivalent L20.

Runs fine on 98.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

people say that alot but have you actually tride that set up?

mine runs fine on 98 no pinging and more toque than i know what to do with.

yes i have got that exact setup at them moment and i can only get 6 degrees static advance with a standard distributor on ultimate 98 with limited power. Put race fuel in the tank and i can crank it up to 15 degrees with a recurved dizzy and it makes great power.

10.7:1 is widely considered the highest comp you want to run on pump fuel

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Circuit Race 1600 in the build

by standed do you mean points? i have a s2 dizzy 32deg at 4000k on 98 no pinging, it's my daily driver and F#%kn love it

the first question should be;

how did you come up with that compression ratio?

did you "cc" the chambers with the valves that you wanted to use, after they were fitted/seated, after all grinding/polishing, after surface grinding & with the plug you inteded to use?
did you then either "cc" or calculate the cylinder "cc" once compressed, including allowing for the little bit of clearance around the outside of the piston to the top ring, the compressed gasket thickness & the deck hieght (if its not zero decked)?

many people quote CR figures, yet have not actually measured everything required to complete the calculation. Many don't even have the equipment to measure it.

Although the chamber/piston shape & plug location have alot to do with the end result, I have seen some cars (EFI Falcons) be pushed to 11-11.5:1 CR and run on Pump 98. However, they can't run more than 28deg of total timing before detonation & consequent blown head gaskets become a problem. I have seen other engines (SBC V8s) not be able to run reliably over 10.5:1CR on the same fuel, yet I have seen hemispherical chamber (Mitsubishi 4G54) motors run over 11.5:1 and still be able to run 36deg total ignition advance on Pump 98. Many modern motor bike motors have close to 14:1 CR and still be able to pull up at the bowser.
Remembering that camshaft overlap (lobe centre seperation) also plays into this, due to the "swept" CR calculation. the more that both intake & exhaust are open at the same time, the more static CR you can get away with as some of it is being lost down the exhaust.
Generally, from experience, you end up with a more reliable and more responsive engine if you run a little less compression, so you can still run good ignition advance. It may not make quite as much power on a dyno, but who really cares about that anyway - its all about how it actually performs.

FWIW, I calculated mine after cc'ing all the combustion chambers and measuring the head gasket crush and deck height. I looked up my calculations and it worked out at 10.38. Assuming everything is the same except for the larger capacity, by my quick calculations this would indeed be around 11.2 on an L20B.

I run 17 degrees static advance in a regraphed bluebird electronic dizzy (I've forgotten what the total advance was and it isn't shown on the dyno sheet ). As mentioned, hp is 102 @ 6000rpm and torque is 102 ftlb @ 4700 rpm.

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

I cc'ed my chambers at 41.6,41.9.42.1,42.1
i have a 72 degree works cam retarded 4 camshaft degrees to try to stop the pinging problem.

dynamic compression ratio can be dependant on a lot of factors
Volumetric efficiency of the ports
Cam timing
combustion chamber shape

Most if not all of this is not measurable
Around 10.7 static seems to be the general concensus from all the older style 2 valve engines
I have proof that 11.2 does not work

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Circuit Race 1600 in the build