I know a lot of people are critical of mag cases. What is it exactly that kills them? Revs? Power? Overmachining for big pistons and stoker cranks?
Lack of case savers?
Be interested to hear peoples experiences (not theories) with mag cases and their weaknesses.
Heat
yep HEAT or the number of times the engine has been used at excessive temperatures
Also corrosion if there standing around for a long time
case savers or lack of them as well
ok, so is the whole external oil cooler thing important on high rev/hp motors?
it helps, but no oil cooler can wash away excessive head temperartures .................from say too much compression, improportionate valve sizes,
restrictive exhausts, incorrect jetting......these are the things causing the oil temps
mag cases get hard/brittle through the heating cooling cycles (over many years tho)the difference when i practiced spot facing an old one compared to
the newie was plain to see
can be weakened if the spiggot hole at number three cylinder is run in unessecarily deep....and crack
mags suffer from case "shuffle" at high revs
do crack along the top of 3 & 4...........through the rear mounting flange and forward to the oil light switch..........
do stuff up behind number three........mainly when your rear main is shite.........but can live here if everything is o.k
mags only have say around five degrees difference in temperature tollerence between survival and loosing 70% of their strength........around 120'c ^
they're stuffed, loosing ridgidity
mags do get holes in the roof when your crank breaks in half.......which can be hard to fix
How much compression is too much?
How high is "high revs"? 6k, 7k, 8k?
What's the benefit in swapping over to an alloy case with these dramas? Will the alloy case support the high revs better?
good read on compression here....
http://www.shoptalkforums.com/viewtopic.php?t=107320
whats high revs? dunno really, all depends on the balance and importantly RIDGIDITY of your crank. even with great cranks combined with high revs, the
case still gets flogged out.they're a "wearing" part after all..........anything above 4500rpm is more than what they were intended for (taking
into account more for the over engineering built in from the factory:thumb)..........Mr Torrens had no trouble reving his to oblivion, how often did
he replace/reco the case tho? Stan didn't offer warranty till the ally cases came thru, there must be something in them he likes
alli cases solve problems?...........dunno that either, broke a few mags tho....now i play with complete packages to avoid the known problems, rather
than what i can get my grubby 'lil mitts on and to hell with the consequences........some peple have been known to make 300hp successfully with the
mag cases, discarding them when due.........
yeah Pete, just yaking here really, realize you prolly know most of this..........it's just sooo quiet
heres a techo link with heaps of info, not sure if you go the shoptalk..........don't bother reading the very fist link there, it's garbage!
http://www.shoptalkforums.com/viewtopic.php?t=107350
[ Edited on 24-6-07 by dumone ]
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| Originally
posted by dumone ..Mr Torrens had no trouble reving his to oblivion, how often did he replace/reco the case tho? Stan didn't offer warranty till the ally cases came thru, there must be something in them he likes |
The one I bought off Stan 8 years ago came with a waranty....:thumb
cool Craig, i didn't think you'd ever had case worries, ooopsy if that came accross the wrong way, i actually intended it to be a good
example........good crank and machining from the man:thumb as we all know.......didn't realize Stan had warranty earlier, realize now it was probably
the warranty offer with the steroids motor i was thinking of.........did that only come about a couple of years ago with the aluminium cases, i just
recall some sort of thread about it a while back???
are you now using the ally case?
[ Edited on 24-6-07 by dumone ]
So Craig, your saying an emphasis on impecable balancing can save the case in high rev applications?
Reason is, I want to build a pretty serious PRC style 1302/03 rally car for my kids to race in the future. My 3yo daughter has already picked the
color. :P The motor will be a 1599cc with the works as I want to stay in away from the datto brigade with all the L20s and such in the 1600-2000cc
class. I'm trying to figure out whether to keep the late Type 3 mag case I have or go ally instead. Keeping in mind, I want to be able to really rev
it and have a high comp ratio.
BTW, Miss 3yo told me today she wants a 5 speed gearbox!:duh
Asking Craig about engines is like asking a Panel Beater about gardening, thats why he pays the man to work everything out 4 him..
Or asking a Writer about brakes what a joke.
make sure you read the regs for PRC first, iam pretty sure you can't change block material (well iam pretty sure its not stated that engine block is
free)....... And the new engine swap rules only allow you to swap an engine with the same block material to.... so you need to use a mag case if you
want to run PRC. If you wish to run RRR (eg rally car other) you can run what you want.
I went through this with my new engine in case it ever got put in a PRC car...., hence is a mag case......
[ Edited on 24-6-2007 by BiX ]
If it's intended application is for the "kids in the future" then factor AGE of the materials used as well.You would either need to use a new Ally
case or new Mag case...as it would be quiet a few years before it got "used" unless you keep it running for them. I'd go the Ally case
myself,they're just better,stronger and made of a more stable compound...
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| Quote: |
| Originally
posted by jakjones Asking Craig about engines is like asking a Panel Beater about gardening, thats why he pays the man to work everything out 4 him.. Or asking a Writer about brakes what a joke. |
I'll start looking into whether I need a mag case for PRC I think. I guess could be that by the time we are ready to race, you can only by ally cases
too, which could make it interesting. Hopefully CAMS would be flexible for that sort of thing.
Bix, how does the RRR class work?
Ima not sure about the RRR thing. It also depends on the event. Eg the car i was in for KCF (Rx7) ran RRR as it had wheel arch flares which are not
PRC compliant....
Probably best to go and talk to a cams scruit, or a rally focus club. Just reading through my regs, and block material must remain the same. I used a
mag case (brand new) but as one person told me, there are probably so few scruitineers that actually know that if should be a mag case and can pick
it....
If you jsut want a car for the kids to muck about it, most clubs will allow it to run at club level as long as it has all the safety gear.
| Quote: |
| Originally
posted by jakjones Asking Craig about engines is like asking a Panel Beater about gardening, thats why he pays the man to work everything out 4 him.. Or asking a Writer about brakes what a joke. |
ally or mag suffer from fattigue?
| Quote: |
| Originally
posted by jakjones Asking Craig about engines is like asking a Panel Beater about gardening, thats why he pays the man to work everything out 4 him.. Or asking a Writer about brakes what a joke. |
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Your "mood" explains it all........
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Originally
posted by VWCOOL
Yeah, or asking JJ about ANYTHING The MAG cases suffer from fatigue (simply too many hundred of millions of cycles) and crook machining and balancing. Loose heads add to the 'hammer' effect... Heat also adds to the workload... [ Edited on 25-6-2007 by VWCOOL ] |
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I just a had a good look at the PRC rules and I'd be running as a historic (should be hysteric) rally car in practice.
http://www.camsmanual.com.au/road.asp
Cars pre-86 are not TRUE PRC cars now. I'm not wanting to run state championship being that my job as a minister means sundays are pretty well out
for me. So I guess rally sprints, khanacrosses/motorkhanas and small rally events will be the sort I'll enter. Probably a good thing too coz I'd
prefer EFI and rear discs and both of these are a no no in PRC for a beetle. Stupid really where the brakes are concerned. I'd have thought brakes
would be classes as a safety feature and therefore be unlimited...but no.
As far as the mag vs ally debate goes. There's nothing in the rules to suggest that case material would be an issue unless you made it one I
think.
"The original type of cylinder block and crankcase must be employed."
What does type mean. I guess that means a pauter or a subaru is out. But a VW block is a VW block not matter what the material is I'd reckon. And you
could argue type 4 blocks are ally so why not have a type 1 case in ally too, but as bix said before, most people wouldn't even notice...until they
tried to set it on fire that is :P
Group 3c-PRC rally cars. Point 3.1 "Only the Following modificaions are allowed to PRC rally cars"......
If all you want to do is run club events not a problem, but if you want to run state events or bigger.....
3.7 Braking system: The complete braking system is free, subject to any replacement components complying with the relevant registration requirements
and any modifications to bodywork being restricted to the drilling of holes for the fitting and/or operation of components.
A circular flexible pipe to channel air to each brake assembly is permitted, but its interior diameter must not exceed 10cm. These air cooling pipes
must not protrude beyond the front of the car, as seen from above.
Teh regs are allot of details to get your head around....
I love Volksy mag cases.
The reality though is the aluminium ones will last longer under the same conditions.
Now a days you can buy a pre clearanced, bored, tapped and case-savered case cheaper than modifying a new mag case.
I used three different mag cases when I started racing
and the last one is still OK.
They never got hot, but when I ran it lean, it did suffer and detonation eventually caused cracks.
Poor tuning (in my case) or overheating,
or poor balance will damage any case (yes even Pauter),
but the mag case will last well if you treat it kindly.
Being that I do my own machine work,
I would prefer mag, but this is false economy for the masses these days.
It is good advice to deburr all the rough, loose casting flash from inside those sand-cast aluminium cases.
The weight saving may be important to some by using mag cases.
[ Edited on 26-6-2007 by dangerous ]
wow bix, you know the regs better than me. thanx
dave, I was hoping you comment at some stage. One question, are ally cases available for 85.5-87 mm bore size or do they start larger than that?
Your induction system is also free, so you can run efi/webbers/etc if you are running prc. If you are going to run historic rallies the rules are little stricter and you have to comply with the homoglation of the vehicle at the time. Classic rallies are differnt again.
mmm, I just had another look at those regs. They are a lot more open than I first thought. TOPS!!! :bounce