Race Engine Forum UK

Hi Guy and everyone,

First of all please forgive me as i may ask some really silly questions, but as they say "you must learn somehow"

The Ford crossflow engine is very old and some would say that it has been modified about as far as needed but from talking to a few people in the classic Ford tuning circles there are a few flaws in the design that not many people have even bothered trying to combat and as i have a mk1 escort mexico, i would like to keep with the original engine albeit modified

The flaws i am talking about is the combustion chamber as a whole, its a bowl in piston design and that because of this it first of all needs alot of ignition advance to produce any power and the burn rate is very slow, so at high RPM it produces very little torque and this is because the BIP design has no squish, or so i have been told??? please look at the pictures below and let me know what you think on that front

when i looked at the pistons i would say that the edge around the piston, on the crown would be the squish area??? please correct me if i am wrong

here is a pic of a typicle forged x-flow piston have a look and tell me what you think



To make life difficult the head is totally flat so you cannot do much with that to help the burn rate

a pic of the head to help



these engines are very good and 150BHP out of a 1600cc is not uncommon and in fact there are some 190 BHP 1800cc versions going around

what my questions are is what would be the best way to modify the combustion chamber to improve the burn rate an to try and gain some torque/performance???

these engine have been known to rev to 10K but the torque drops off very rapidly after about 8000 RPM, i would like to make use of the extra RPM

Any advice would be appreciated

thanks

Ricky

In my experience you are correct. The flat head engine design means the chamber is part in the bore and part in the piston. There are 3 ways to tackle it.

1- Use a good forged piston for the job and a flat head.
+ simplicity
- Heavy piston

2- Use a flat type piston and leave it down the bore.
+ Very light piston
- Poor chamber design meaning lots of advance.

3- Use a flat piston and create a chambered head.
+ Very light piston
- Chambered head means sinking the valve into the head, sorting the rocker geometry and the short turn in the head is now not as nice..limiting top end power.

I have only tried 1 and 3. Number one produced best power, number 3 best low down torque but fell away sharply. It also needed 6 deg less ignition timing.

Steven

Thanks for the reply,

There is a chambered head available but the valve size is slightly limited, i am going to look into this though and see how much of a negative it will be.

Thanks again.

Ricky