How to calc highest revs?

[StewRat]

Second question of the day before going racing on Sunday.

StewRat has only really been down the strip once for testing and I had a low rev limit on the tach light and the MSD box.

I'm not about to crank it up to "11" in one go, but as I add say 500 rpm per pass to the limits - how do I work out what my max should be?

We're talking 82x94, CB case and heads
35.5 x 40 valves
2 x DRLA 40 carbs
Engle W130 cam
SCAT forged crank and lightened flywheel
Balanced rotating assembly

... and a standard gearbox

How do I know what max revs should be ? (apart from when things go pop that was too many)

Maybe I should add I'm as much interested in longevity of components as much as getting the last X% out of the engine.

Thanks
Stewart

[Fastbrit]

What rods/bolts are you running?

Your engine will start to run out of puff at 6500rpm due to cam/valves/carbs, but will breathe to 7000rpm quite happily. Won't be making too much more power at those revs, though.

[StewRat]

What rods/bolts are you running?

Your engine will start to run out of puff at 6500rpm due to cam/valves/carbs, but will breathe to 7000rpm quite happily. Won't be making too much more power at those revs, though.

Thanks - that's useful.
CB Unitech 5.4" rods and - erm - whatever bolts came with them.

[andy198712]

And what valve springs.

I guess a dyno would show where the power tails off too

[StewRat]

And what valve springs.

I guess a dyno would show where the power tails off too

Springs are what came with the CB 044 Supermag heads - singles, though it seems they are shipped with dual springs these days.
I do have a set of of dual springs not fitted.

At this early stage I'm not so concerned about wringing the last ounce of power from it, but trying to set shift lights/MSD limits appropriately so I don't get carried away and do damage by overrevving. But without throwing away too much potential

Thanks

Stewart

[leec]

Single springs with an engle 130, I always thought a 110 was the most you could run with single springs. My 1776cc with engle 120 is dual spring

[StewRat]

Single springs with an engle 130, I always thought a 110 was the most you could run with single springs. My 1776cc with engle 120 is dual spring

Sounds like I should probly get those dual springs on then.

[leec]

Sounds like a good idea. The heads will probably need machining for dual springs

[Iryanu]

You could maybe use the stateside single springs, I run them on a fairly "peaky" camshaft. Check below to see if they'll be ok?

http://www.statesidetuning.co.uk/newproducts.html

This is not an ordinary uprated valve spring, the material used SWOSC-V, is the best available in today’s manufacturing industry and the same wire quality as used in the Japan motorcycle industry.

Using modern day manufacturing processes we have been able to achieve a valve spring that gives huge travel before coil bind and will not distort or loose poundage rates common with the typical import springs. From the installed height this spring gives good progression in poundage rates. The high quality wire used is 4.3mm on the outer spring and 3.1mm on the inner spring, the manufacturing process includes and heat treatment two times to safe guard against fatigue.

These will fit all Type 1 cylinder heads and Type 4 with minor guide boss machining.

Single spring set £39.00 + vat
Dual spring set £59.00 + vat

Full range of base shim sizes available to suit T1 and T4 cylinder heads


In House Testing
Using light weight valve train parts we have thoroughly tested these springs on Type 4 engines running 86B Web camshafts with just the single valve spring. We have also tested them on type 1 engines with Web 86A & 86B camshafts with 1.4 ratio rocker arms on just the single valve spring.

Checking pressures using Longacre digital spring testing equipment:

Single spring
In a single spring form measured at installed 1.50" – 111lbs
0.400 – 219lbs 0.450 – 234lbs 0.500 – 247lbs 0.550 – 263lbs

Duel spring
In dual spring form installed at 1.53" – 149lbs
0.400 – 297lbs 0.450 – 342lbs 0.500 – 367lbs 0.550 – 391lbs 0.600 – 415lbs
Coil bind at 0.712”

Give them a ring maybe! Could be an out there without the need for machining?

[andy198712]

I run them on an 86b at the installed hieght he told me to set them at and all is good, normally Rev limit is 6 k but sometimes 6.5k

[StewRat]

Give them a ring maybe! Could be an out there without the need for machining?

Absolutely - at those prices, it feels like the cost and hassle of machining would be much more. Will check - thanks!

[DaveN]

If it was my engine I would fit CB 650 springs.  I would have thought the cylinder heads would have been already set up to run dual springs, check anyway.

[leec]

Another thumbs up for the 650 spring. Good value as well

Lee