Race Engine Forum UK

Hi.

a short report on a lower compression 5 porter head, i will try and add photos and text as the project slowly moves along.

I was asked if i could have a go at converting a head for a supercharger conversion.

A kit sold by several companies uses a decompression plate ( and two headgaskets) to lower the compression ratio.
The owner found this idea not too enticing and asked if i could try and lower the compression of a head as well has make it breathe a bit better.

GOALS:
1# lower compression as much as possible while staying well within the limits of the casting (including core shifts).
2# improve breathing by reworking the ports.

Method:
1# lower floor, cut out beak region, cut back chamber walls.

Result:
1# increased volume from 23 to 28 cc with minimal deepening of the chamber ( which is bad for the approach of the port to the seat)
2# work in progress

I have done several heads around that chamber volume when we were running a couple of clients in the Group A metro turbos in 90s... over 200bhp was attainable but the drop gears never lasted very long!

good luck with the project.

the head is very much in developement stages and need tons of work. I have finished the one intake port and that has to be copied to the other siamese port. i'm allways suprised how hard it is to copy the shape and the dimensions along a port to a new port



it has since moved on quite a bit and i hope to get this one done as well as a new, more elaborate version of the 12g202 i did. After that i finally get to build something for myself..a new short block for my new project (modified 1380 cc A+ with a 16v bmw bike head. projected power 125-130 bhp at a leasurely 7800, torque about 130 to 140 NM).

you're S.Gault are you not? I would like to pick your brain about a few things..

I am indeed Steven Gault.

Guys site is great isnt it!

Good luck with the new project. Should find that hp easily