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pinto head staging question
omega0684 - 11/4/09 at 09:38 PM

i have been reading through dave vizzards book about modifying sohc engines and he references stage 1,stage 2 and stage 3 heads along with big valve heads etc,

can someone please explain to me the processes involved in modifying a std head to stage 1, stage 2 and stage 3?

cheers

clairetoo - 11/4/09 at 10:12 PM

As I understand it ....
Stage 1 - ported / polished
Stage 2 - ported / polished / slightly oversize valves
Stage 3 - ported / polished / big valves / double springs (the full monty)

omega0684 - 11/4/09 at 10:20 PM

according to the burton catalog

stage 1 inlet 42.0mm, ex 36.0mm
stage 2 inlet 44.5mm, ex 36.0mm
stage 3 inlet 44.5mm, ex 38.1mm
full race inlet 45.5mm, ex 38.1mm

apart from that is that about it,

reading the book further it says that there is no point polishing the cylinders as is doesn't cause sufficient gains in air flow into the cylinders.

britishtrident - 12/4/09 at 07:24 AM

Stage 1 anchors small boat.
Stage 2 anchors cargo ship
Stage 2 very large crude oil tanker.

omega0684 - 12/4/09 at 07:52 AM

quote:
Originally posted by britishtrident
Stage 1 anchors small boat.
Stage 2 anchors cargo ship
Stage 2 very large crude oil tanker.


Y I ORDA......!!!!

ncoll - 12/4/09 at 09:51 AM

Stage 1,2,3 etc only means something to the person or firm who modified it. To another firm it may mean something totally different. It might be better for everyone if those peple who owned flowbenches put their increases in percentages, people would be able to understand what they were getting and could compare one from the other. A pinto injection head with a 44.5 mil inlet valve fitted, three angled valve seats, the ports only modded no further than an inch from the valve seat, a small mod to the combustion chamber will produce a 35% increase in flow, the rest of the port and chamber is standard. I wonder what stage Burton and others would call that? As far as a pinto engine been a boat anchor, it may not produce the out and out break horse power of the modern 16 valve engines, but a well modified one will equal them on torque anyday.

neil

austin man - 12/4/09 at 11:16 AM

doesn't stage 2 and 3 also look at the changing of camshaft, little point in doing all the work and not changing the cam to allow a valve to open for longer etc

MikeRJ - 12/4/09 at 05:15 PM

quote:
Originally posted by ncoll
Stage 1,2,3 etc only means something to the person or firm who modified it. To another firm it may mean something totally different.


Spot on. Referring to a tuned head as particular "stage" is completely meaningless, unless you know which tuning company modified it. You can't compare heads between manufacturers by simply comparing the "stage" number it's advertised at, because there is absolutely no standardisation.

snapper - 13/4/09 at 06:38 AM

quote:

doesn't stage 2 and 3 also look at the changing of camshaft,


No just the work done on the head.
I agree that the numbers are almost meaningless but do roughly equate to standard valves, bigger inlet, big inlet and exhaust.

If you study Vizards book hard and start to look beyond the full bore drag race engines, most of the early gains are in the clever head and valve work, Vizard starts to qoute big bhp but by then the compression ratio is very high as are the revs.

The issue of cams and valves is brought more into focus by the technical guides in the Burton cataloge with the formula X = 1/4 of Y when valve lift at the seat is X and the valve diameter is Y. If X is bigger the 1/4 Y no more extra flow is produced, solution a cam with more lift.
Conversly if you have a high lift cam and your valves are to small flow will be reduced.

You can pretty much throw a few bits together with a Pinto and get 130 bhp, a bit of selective matching of parts and a good set up should give 150 bhp the big numbers after this need carefull matching of parts and if got wrong could give you an engine that does not give its potential or one that does indeed achieve big bhp numbers but is in practice undrivable.

I came across a car on the rollers that had been very heavily home modified with a race cam and a huge turbo, the engine came on cam at almost the same time as the turbo overcam massive lag to produce huge power, this car produced amasing bhp and torque figures but could not put the power down, if it was driven on the street it just ejected itself from the road, on the drag strip it sat there in a pool of smoke.

[Edited on 13/4/09 by snapper]