24 replies to this topic

[supermotolee]

any thoughts on the best place to have a head built for my 1380 re build? i have flat top pistons and some other trick bits in this engine and dont want the head to let it down but fitting a standard one

i know blue mini does some but never been able to get hold of him and how much should i expect to pay for big valve and mild port work to the correct compression ratio?
thanks lee

[Sprocket]

Flat tops in a 1380????

What CR are you running?

[Puddings]

MED road comp like mine Look

this is sat on top of my 1380 but still being bult pick it up on friday

[The Matt]

I am gonna be getting mine from Bill Richards Racing. There are plenty of people that would sell one, but it's budget dependent.

if you want to get the compression ratio right though, you are gonna need some seriously big chambers in there!

[Puddings]

1380 i have flat top pistons

ive got 11cc dish omegas and 20.5 in the head

[supermotolee]

i dont know thats why i need a head to suit and someone with experiance to make it...

the block has not been decked to the pistons so i thought i could have a head made to suit...

can it be done?

thanks lee

[Puddings]

give MED a ring they can make any head to any needs or any other engering company

[The Matt]

i dont know thats why i need a head to suit and someone with experiance to make it... can it be done?

Yep, according to Vizards 'bible' 26cc was max in the head, but people have gone up to 31cc on turbo ones (IIRC). It also depends on the piston fitted. It may have a slightly lower crown height. The best thing to do is set the pistons up at TDC and measure the capacity of the block (the piston could be sitting lightly lower in the block than standard ones do).

Seriously though, it can be done. It's worth trying to get an ID off the pistons and talking to some engine builders like Morspeed or Bill Richards etc.

[supermotolee]

i've got morspeeds number was gonna try them tomorrow but i'l try med too to compare prices they wont need the block will they just bore and swept volume ?

lee

[The Matt]

i've got morspeeds number was gonna try them tomorrow but i'l try med too to compare prices they wont need the block will they just bore and swept volume ?

lee

yeah, like I said, if you measure the block CC or give them a piston ID it should be enough for a quote. Also, measure the height from the block face to the piston crown (when at TDC), it's easy enough to calculate an approximate block volume from that with flat tops.

[Puddings]

they should be able to do it for you just give them as much info as poss
or wait for one of the tech's to poast on here

[The Matt]

I've made a few assumptions with piston crown level. But I reckon you are gonna need to have about 27cc in the head to get an approximate CR of 10:1.

But really need more info to be more sure.

[supermotolee]

thanks alot mini mad me i will get some quotes tomorrow is 10:1 about right for fast road? what sort of power should i be expecting with kent 286 twin carbs and 1.5 roller rockers? will it get close to that magic 100bhp mark?

this is the picture of the piston, i have not removed them as i dont have the ring compression tool i cannot see any markings on them from the top they sit pretty close to the top of the block at tdc i'l measure them later i'd say 2mm max probably not even that far with my veriers i checked the bore and i got 73.5mm is that about right could be dodgy measuring though i dont have a bore mic

thanks for all your help i'l get back to you with quotes to see what you think

Attached Files

•  piston.jpg   24.73K   9 downloads

[Sprocket]

Pistons may be flat top due to them being machined?????, I think?????. Looks like the top ring land to crown is a little short????? so CR may be fine. Like MMM said though, acurately measure the piston to block distance as best you can. 2mm roughly gives 8cc

[Guess-Works.com]

Same thought as MS... the ring to crown looks a little short which suggests they have been machined flat, this could also weaken the piston... maybe worth getting someone to have a look at it..

As for 100hp, possible at the fly, but don't expect it at the wheels..