was that question for the rod for birch or danger.
i don't think birch would have a clue.
maybe he wants to A. phone a friend. B palm it of with some idol chit chat.C. alittle from column A and a little from column B
down sharon.
😂
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
i take it you like that one hah.
down sharon.
cracker
68AutoBug wrote:where was the bonnet pull knob on a 1968 beetle?
(((Under the dash)))
where was the bonnet pull knob on a 1969 beetle?
(((in the glove box)))
what did a 1969 beetle have that no others had?
hint: something to do with the heaters...
(((Little lever in the front 1/4 panel carpit both left & right)))
why are 1968 beetle wiper arms different from any other model beetles?
(((You got me there, are you talking Aussie/nz assembled beetles here?)))
(((Note, I didnt have to look any of this up its straight off the top of my head so if I'm wrong thats ok, if I'm correct, thats sad😂)))
got one for you what is said to be the best ratio of valve to port measurement ratio? another, stoich for methanol?
EVERLAST CONCRETE TANKS
1800 552 123
Hi Mac,
the smallest point of the ports in relation to the valve size is said to be between 85% and 91%
depending on valve angle and chamber wall shape.
Normally I aim for about 90 and then hand finish the high speed area, so the throat is actually an egg shape.
This time I will start with 88% intake and 85% exhaust before hand finishing.
From mem stoich is 6.4 but max power figure varies, I think mine is at 5.0 at the moment but would have to check my logger.
I would phone a friend but I have none,
just blokes I know.
Brennden, 24mm.
Matt, fu*#ed if I know,
cut, cut cut is my answer for that delema, but dont raise it more than 32mm,
that way you can use a bus nose cone and keep the shift rod in the tunnel.
Rod length is a whole book in its self.
By simple answer is to keep it as short as possible for easy fitment.
This way your pushrods are nice and short, and clearancing and barrel spacers are easy.
In theory wear would be less,
but even from one extreme to another,
say stock stroke with 6" rod,
to say, 86 stroke with 5.352" is only 2 degrees different angle at half stroke.
So wear difference would be minimal, and not even measurable with a change of 0.1" for example.
The general consensis is longer rods move the torque and power peaks up in the range,
but nothing measurable if cams are optimised
to the point where piston speed is maximum.
One degree of lobe centre or duration would cover the extreme that I gave for the example above.
You would gain more from the shortest rod you can fit due to the shorter pushrods giving better valve train stability,
and being able to use shelf cams instead of custom grinds.
That is the short version as I see it at this point in time.
Views and opinions change over time.
westi wrote:That's mad Alan.
hey dave i need a definitive answer pls..
if it takes a week to walk a fortnight, how long is a piece of string?
🤓
fractal geometry; the inner most limits of mind altering abuse
Fantasy
http://seventhchronicle.com
Z = Z2 + C1/r = 1/0 = infinity
Barrels
www.barrelman.com.au
VW Workshop - aircooledgarage.com.au
allcooled.com.au
h wrote:hey dave i need a definitive answer pls..
if it takes a week to walk a fortnight, how long is a piece of string?
🤓
Medium I would say.
🤓westi wrote:That's mad Alan.
Ive gone one...
What is considered to be safe maximum pistons speeds assuming you are using a CP forged piston?
For that matter, what piston speeds does the your pauter engine achieve at 8000 rpm too?
Cheers,
Ian
The rod bolt will be the limit with your 88 stroke.
I would have to look n my black book for the formula that takes rod length into consideration,
but with my 90 stroke and 5.7 rod I set the limit to 7750 so it remained within acceptable limits.
My current 82.5 stroke is not an issue, but the limit is currently 8400.
Piston mass,
combined with the accelleration give resulting FORCE,
that is so critical to that failure point that you want to stay clear of.
Remember from school,Force=Mass x Accelleration?
westi wrote:That's mad Alan.
2443TT wrote:What is considered to be safe maximum pistons speeds assuming you are using a CP forged piston?
For that matter, what piston speeds does the your pauter engine achieve at 8000 rpm too?
Cheers,
Ian
Just to clarify, it is not the SPEED that is a problem,
but the ACCELLERATION.
The maths for mean piston speed is stroke x rpm divided by 6.
This gives the piton speed in Feet per minute.
Anything over 4000 is high, but as i said above speed is not problem.
it is the sudden stop that will do the damage.
(actually it is the change in direction at TDC that is so tough on parts, bt you get the annalogy)
I have the accelleration formula in front of me but need to be able to type in, in forum version so you can understand it.
westi wrote:That's mad Alan.
OK.
practical limit of 100 000 to 150 000 feet per second per second,
is what the book says.
I would say 100 000 with stock parts and 150 000 with the best quality rod bolts , rods, and pistons.
[(rpm x rpm x stroke in inches) divided by2189]
multiply this by
[(half stroke divided by rod length) + 1]
SO,
8000x8000x3.465" divided by 2189
=101 293.9
x (1.732" divided by 5.7") +1 (=1.3039)
answer 132 078 ft per min
westi wrote:That's mad Alan.
That was the maths for 8000 rpm,
88 stroke(3.465 inches)
And 5.7 inch rod.
westi wrote:That's mad Alan.
please explain reversion?
EVERLAST CONCRETE TANKS
1800 552 123
Okay... I've got one! Right out of my phantasy (deliberate lacking the F, considering how quickly things go downhill around here) scenario book 😂
*cracks typing knuckles*
Planning a road trip hunting out the best roads & tracks in Europe, mainly around Germany. Got my 'dub sorted except for engine & box...
Want 400HP that I can be ON more than off during the trip, 250KPH top speed and being delivered from a pushrod, flat 4 derived motor.
What would you recommend from the specials board? 😁
dont want much do ya!!!!
EVERLAST CONCRETE TANKS
1800 552 123
Westi started it dude 😀
😵💫 haha
fractal geometry; the inner most limits of mind altering abuse
Fantasy
http://seventhchronicle.com
Z = Z2 + C1/r = 1/0 = infinity
Barrels
www.barrelman.com.au
VW Workshop - aircooledgarage.com.au
allcooled.com.au
dave the muffin man.
what head torque for 14 to 1.
i have an issue with leakage
down sharon.
"i have an issue with leakage"
I hope this is still related to the head torque and not just a personal problem..😀
mactaylor wrote:please explain reversion?
That is the acid like substance you get after a big meal?
I use VW 10mm head studs currently,
torqued to 35 lbs with moly lube or anti-seize.
My blown engines also used Raceware studs in 10mm.
But also VW studs were OK if the tune-up was not lean.
I have used 8mm studs in Genuine VW and they worked OK to a point,
as long as the washers were thick and had lube on the thread and face of nut during tensioning.
westi wrote:That's mad Alan.
lol
down sharon.
have you tried copper barrel spacers / gaskets there nice n soft and will bite into the barrel n head
Whats the engine case alloy with savers or a magnesium old type
Dave, how accurate is a flow bench at "calculating" hp?
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
i quess it depends on the bench.
and how well everything is working together i guess.
my heads flow quite well ,i think so anyway.
my heads flowed 170 cfm @ 600' lift @ 10 inches of water and it did 198hp at 5850rpm,but i don't know the calc's for cfm to horsepower.
it would be interesting to see what you have to say on this one dave.get technical.i love technical.
down sharon.
Thanks Westi.
Get Tech Dave
My heads came back today,
flowed 104 cfm @ 10" / .600", but they calc should be good for 178.8hp
We shall see.
Main thing is, before valve job, was 96.3 cfm/168 hp.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
Mos people agree that the flow figure at 25"
CAN POSSIBLY make the same number in engine HP.
But this is all theory.
Most engines make less(mine heaps less), but some, particularly small port engines, can make more.
25 divided by 10 and sqaure root your answer
is the multiplier for converting 10" figures.
Mine flows 170
@10" at .650" lift(but keeps flowing right up to coil bind).
=268.8...I'm making 247, so perhaps with some optimising and tuning?
Matt 104= 164.4 engine power
As westi said it depends on the flow bench...still stumped as to why yours is not standard Westi,
but remembring it is a tool, you can use it to find real gains.
westi wrote:That's mad Alan.
stop calling me a tool
down sharon.
Swift y did the valve job and by the test data sheet, says 104cfm = 178.88hp.
I wonder if he has possibly optimised his bench with the number of race engines he's built.
Can only hope we can get somewhere close, this engine in Col's car ran a computed [1/8 mile/mph/wieght] hp of 135hp and going by swifty's figures of 141 hp @ .500"lift, before the valve job, seems pretty close.
Hell 178.88 hp from nonwelded 42x37.5 vw heads sounds fine by me, fingers crossed.😀
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
