Stafford Show 19/20th September.

[Maverick440]

My Engines Knakerd.........................LOL

[petercoll]

My Engines Knakerd.........................LOL

Really ?

[Maverick440]

Its a good excuse to spend some money on her................
To get the best out of the cam thats fitted she really needs the valves upgrding from 38mm to at least 45mm, and a bit more work on the ports and combustion chamber shape.

My cam gives 13mm of lift so for optimum flow the valve should be four times larger than the lift, but you cant get 49mm valves in a pinto head.....

im now looking for somone who can mod the head with new valve guides and bigger valves, and then i can start to alter the shape of the combustion chamber.....

[Timbo]

I had mine done by autosprint, he fitted new bronze guides and stainless valves,was about £130 all in
Are you doing it to an injection head? As theses are already suitable for unleaded they have the harder valve seats. Problem is the inserts can let go when they are machined/re cut, with the potential to scrap the head. it would be better to do the chambers and ports before you get the valves done if you are doing a home brew chamber. Unless you are CNC machining it you WILL hit the guides and seats with your die grinder! Make sure you can accurately measure the CC in the combustion chamber in order to balance them, (it could get very lumpy if not!)

Whilst i'm on this thread, a quick thanks to Pete and Jams for the scrummy burgers on Sunday. it was good to catch up, and to give the car a run before the winter lay up. (even though i've just got it back!)

Tim.

[Maverick440]

Cheers Timbo.

Just going to use a standard unleded head and load of adative, the good nes is ive finaly got round to borrowing my mates puca Snap-on compression tester and i now need to rethink what im going to do (better still spend the money on)
Shes actualy pumping out 225psi so im a happy camper as the bottom end is OK (bar needing a new rear main oil seal) my dilema now is what is the compression ratio? do i need to skim the head or not? do i do a home brew port job or get it dome properly?

I know my current head is limiiting it performance due to only running stock valves,

[Timbo]

You measure compression ratio by working out the volume of the cylinder, (area of piston top x stroke) plus head gasket, (typically 2cc) plus volume in the combustion chamber. divide this by the volume in the cylinder at the top of the stroke + gasket + chamber, this gives your CR

EG, cylinder volume at BDC 480cc, gasket 2cc, combustion chamber 40cc, total volume 522 cc
Cylinder volume at TDC 10cc, gasket 2cc, combustion chamber 40cc, total volume 52 cc

522/52= 10/1 compression ratio (roughly!)

if you are not sure of the history of the head the only way is to measure it. Turn the head upside down on the bench, make sure it's dead level. Put the valves in place in the head (seal with a bit of grease) and place a piece of perspex over the chamber.Again, Seal it with a VERY thin smear of grease. The perspex should have a hole in the centre large enough to put the end of a syringe through. Using the syringe inject some paraffin (baby oil works quite well too)into the hole, letting the air vent back through the hole. Continue filling until you have filled the camber to the bottom of the hole. Hey presto, the amount gone out of the syringe is the CC of the combustion chamber. Be careful skimming the head, and do it AFTER you do the chambers, I did mine first and had to carve a bit more than i wanted to from the chambers in order to get my CR back down to a reasonable level. I can only run on 98ron or above, and it will still pink occasionally! It does have some grunt though!

There is a very good book out there by Des Hamill, it's in the speed pro series, "how to modify and power tune the Pinto".
It's full of advice about how to do it.