Stroking a Harry Barlow stage 4 top end

[johnny rotten]

Would there be any benefit to putting a 60mm crank on one of these set ups?
Has it been done?
Would it just mean fitting an extra 1.5mm packer plate at the base of the barrel?

Cheers

John

[ArmandTanzarian]

Short answer, "yes".

In my experience, it makes it more torquey. Not any faster but pulls better up hill and into the wind.

Hopefully, a grown up will be along shortly to explain the technical side.

[Jack221]

The answer is more like "yes but". Depending on where you put the extra stroke makes a big differance. Going from 57 to 60 you have 3mm to play with. A handy program to calculate port timing takes out the guess work. For those who can't be bothered with all the geeky calculations, a 1.5mm packer on the base will make a barrel rev much higher or a 1.5mm head gasket will rev slightly more but make more torque. And if you can't decide put 0.75mm on both head and base

[johnny rotten]

Where do you place your packer plate(s) jack?..I spoke to HB about it n he mentioned removing the packer from the base of the barrel where it currently is with the 57mm crank set up n getting the head machined to suit.

[Jack221]

HB is suggesting the "keep the same rpm but with more torque method". Great for cruising to a rally.

Putting in a long stroke crank is a favorite way to play with the porting without ruining anything. Where and how big the packing plates are depends on what you want. The first of which is what do you want to use it for? Or in other words; how many rpm do you want it to make in 4th gear ? From this point any tuner will always try to suit the power and torque to your purpose, without losing too many mpg out of the exhaust

I plan to be bored at work all week, so I have time to run some calcs to give you my idea of what is possible. Let me know how many rpm you want in 4th and I'll need a little info about the barrel and head as well. Like how many mm from the top of the barrel to the exhaust port and to the main transfers. And exact distance the piston stops from the top of the barrel with a 57 crank. And what is the current head and squish clearance?

[johnny rotten]

Thanks for the offer jack...I spoke to HB again n he said that raising the stage 4 207 barrel wouldn't work with a long stroke crank as it would just throw all the port timings out of sinc n just kill off the bottom end so looks like the lowered barrel n modified head is the only option

[sean brady scooters]

just asking ,but what is the squish clearance on the "HB" head ,and volume ?

[johnny rotten]

I'm not sure Sean I'll try n find out for you

[Jack221]

It would still be interesting to calculate why he said that. Next time you have the barrel off take a picture, measure the ports and we'll see what HB thinks is too adventurous!
How thick is the packer you have on now?

[johnny rotten]

Ive no plans for taking the barrel off at the moment Jack as i was just enquiring about what possible options where available for long stroking that setup if i remember on next time i take it off i'll drop you a line however i do know that the packer is 1.5mm thick