Rolling Road Figures

In answer to Albrechts questions,

Early 71 US spec. with compression ratio of 9:1
Standard unmodified L24 block and head ( notes state stock cam and flywheel )
Documented low miles 36k with oil and filter change every 3k miles from new

Where are extra horses over standard factory Z ?
Pertronix ignition ( oops, I forgot about that ), Magnecor HT leads, 2.25 inch free flow exhaust / manifold, ITG filters/no box. Guess 10-15hp overall ?

My mechanical knowledge is pretty basic but assume on the road the limited slip diff will assist torque, not sure what effect if any that would have in rolling road situation although difference between torque at 4400rpm ( factory max ) and 5000rpm is very small.

I'm not competing in the willy waving contest going on here ( obviously ) and used the rolling road test just to re-inforce my feeling of confidence about how good the engine felt, check the Hitachi SUs were in perfect balance and record any potential power gains after any tweeking ( not needed in the event ).

Without going into then accuracy of rolling roads in general, I'm really happy with the outcome and agree on reflection it should not be used as any kind of arbiter for power output on a factory standard 40 odd year old car. Sounds like one of Rob's cars is much more standard spec. than mine, maybe his can be the guinea or patsy.
 
Blimey,im scared to put my figures on here,no one would believe it,but like skids said ,at least he botherd to put them up,personally i cant be arsed like skids said,Its wot it does on the road that counts and if chrisvega is happy then that is all that counts,as usual there is allways some one on here to pick holes with wot people have to say albreight has a point and so do some of the others,thats why a lot of people that came on here in the past cant be arsed any more,
 
chrisvega said:
Early 71 US spec. with compression ratio of 9:1
Standard unmodified L24 block and head ( notes state stock cam and flywheel )
Documented low miles 36k with oil and filter change every 3k miles from new

Where are extra horses over standard factory Z ?
Pertronix ignition ( oops, I forgot about that ), Magnecor HT leads, 2.25 inch free flow exhaust / manifold, ITG filters/no box. Guess 10-15hp overall ?
Click to expand...

Thanks, but I was kind of hinting that there's a bigger story here; There were a lot of variations and market-specific differences in the L24 engines that were fitted to S30-series Zs between 1969 and 1973. That's why I think it's important to pinpoint the date of the engine, the original spec of the car, the sub model / market variant (EG: Californian emissions compliant model) and anything else that might be relevant. The term 'L24' doesn't mean just one thing any more than the term '240Z' means just one thing.

Generally speaking, the north American market models used different distributors than other market models. That's why I asked what dizzy your car has. There's a difference in advance curves there. I wouldn't be surprised if your dizzy has been modified to give a different advance curve. Is the car still fitted with Federal emissions-reducing devices, or have they been removed / disconnected? Still on the original E31 head? It's all relevant.

chrisvega said:
My mechanical knowledge is pretty basic but assume on the road the limited slip diff will assist torque, not sure what effect if any that would have in rolling road situation although difference between torque at 4400rpm ( factory max ) and 5000rpm is very small.
Click to expand...

There's a basic misapprehension there. An LSD won't have any bearing on the torque your engine produces (which is one of the main things the rolling road dyno is actually trying to measure), and it is simply a device that is downstream of the engine's power, involved in making use of that power but not able to alter what is producing that power.

Of course, rolling road dynos usually seem to give somewhat optimistic figures (has anyone ever noted an overly pessimistic rolling road...?) but I have a hunch that your engine has had a little bit more of a tweak than you realise.
 
Albrecht,

Whilst I think I have every invoice and receipt on this car from new, I am not that former owner of 30 odd years, so I suppose it is possible that something has been done to the engine that is not documented but unlikely. Out of interest I will see if I can make contact with the old boy and get the full story. In meantime, I know you are a stickler for detail and you did ask, so here you go ;).

Car was built in April 1971 and sold new in Florida in June 1971. Attached original warranty registration card for interest. Engine number as listed L24-029341. Owner moved to Tennessee when car 6 months old. No restrictive federal smog eqt on car now ( if ever ? ) and not CA market car.

Factory distributor was changed in mid 70s to Mallory Dual Points unit but when car re-commissioned ten years ago was swapped for 22100-E4603RE standard Datsun reconditioned unit from Bill Gatton Nissan, Bristol, TN and fitted with Petronix electronic ignition, matched to uprated coil and Magnecor 8mm HT leads.

As stated before, standard block and head is original unmolested E31.

 
chrisvega said:
Car was built in April 1971 and sold new in Florida in June 1971. Attached original warranty registration card for interest. Engine number as listed L24-029341. Owner moved to Tennessee when car 6 months old. No restrictive federal smog eqt on car now ( if ever ? ) and not CA market car.
Click to expand...

Florida a very humid state. Is the car fitted with air conditioning (factory stock or aftermarket) and - if so - was the drive belt attached when the car was on the rolling road?

chrisvega said:
Factory distributor was changed in mid 70s to Mallory Dual Points unit but when car re-commissioned ten years ago was swapped for 22100-E4603RE standard Datsun reconditioned unit from Bill Gatton Nissan, Bristol, TN and fitted with Petronix electronic ignition, matched to uprated coil and Magnecor 8mm HT leads.
Click to expand...

Interesting that it used to have a Mallory. The E4603RE is a remanufactured Hitachi D612-52, and my guess is that it's been re-curved or played with a little. Unusual for an E31 head never to have been off the block, too.




I'm not - contrary to what some people on here seem to believe - trying to pick fault with your car or anything to do with it. It's just that the figures seem to me to be higher than what might normally be expected for a stock or relatively stock early L24, especially as the factory figures are generally misunderstood and a bone stock car driven off the showroom floor and onto a calibrated and certified rolling road would not get anywhere near them....
 
Probably not of immediate relevance to the 240z thread but have just unearthed the rolling road figures for my (manufactured late '73) 260z genuine UK import (southern England). Everything is original other than a carb change to 240z type and a multi-branch exhaust manifold. On mechanical points and early coil. The figures (from a respected motorsport specialist in the Midlands) give a peak torque of 141 lb ft @ 5057 rpm and a peak power of 145 bhp @ 5882 rpm. Is this pretty average? :unsure:
 
Albrecht said:
Florida a very humid state. Is the car fitted with air conditioning (factory stock or aftermarket) and - if so - was the drive belt attached when the car was on the rolling road?

Interesting that it used to have a Mallory. The E4603RE is a remanufactured Hitachi D612-52, and my guess is that it's been re-curved or played with a little.

Unusual for an E31 head never to have been off the block, too.

I'm not - contrary to what some people on here seem to believe - trying to pick fault with your car or anything to do with it. It's just that the figures seem to me to be higher than what might normally be expected for a stock or relatively stock early L24, especially as the factory figures are generally misunderstood and a bone stock car driven off the showroom floor and onto a calibrated and certified rolling road would not get anywhere near them....
Click to expand...

No, I understand that and have no problem with your questions and dis-belief. I am as intrigued as you are as to why/where the figures come from and the more I delve, the more I realise the car is not as stock as I originally thought so your scepticism probably well founded.

You make a great detective ;)
Car is indeed fitted with factory ac and belt attached for RR test :eek:
Quite possible dizzie curve been altered
E31 head - car had only done 34.5k miles when taken off road in 1978 ( still working perfectly ) and only done 36.5k now so very little used engine

In 1975 car was modded per hand written list verbatim:
1.Competition sway bars front and rear
2.Competition shocks
3.Competition springs ( shortened )
4.Headers
5.Free flow exhaust
6.Momo Prototipo Steering Wheel
7.Roll Bar
8.Headlight covers
9.Front and rear spoilers
11.Pearl paint
12.Fire extinguisher
13.Upgraded air filters
14.Carb mods
15.Hella Z beams
16.LSD 3.90

So it seems like the guy planned on doing some pretty serious driving to say the least ? Does mention carb mods too :eek:

Anyway, I'm not a bad detective myself and traced the old guy who owned the car for all those years and commissioned the mods back in 1975. Have emailed him ( well his wife on Facebook actually :lol: ) asking for his memories of the car - he must be well into his 80s now so let's hope he has a good tale to tell if he does ever reply and we will know for sure if that head was ever off.
 
Last edited by a moderator:
You must log in or register to reply here.
Back
Top