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 mkII_baja
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 posted on September 27th, 2012 at 08:03 PM |
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Advice sought on building a quality 1641 for my trike
Hi
I'm looking for some engine build advice for the 1641cc that I'm building for my trike.
I already have a new set of Mahle pistons and barrels.
I have an AS21 case that will be full flowed
I have a 45mm weber to use and I will tig up a stainless mandrel exhuast
I was considering buying a 4340 moly counterweighted crank,
moly Hbeam rods and a lightened moly flywheel then balance the whole rotating assembly
I am not sure about the other components such as cam, lifters heads etc.
I would like to get at least 120 to 130 hp from it
I realise that the 4340 moly gear might be a bit of overkill for 130hp but I would like to make a strong bottom end that will rev to somewhere between
6 and 7 thousand rpm comfortably
Am I on the right track? or am I barking up the wrong tree with the chrome moly gear
What valves and rocker gear should I use etc etc etc
cheers Jade
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hellbugged
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| posted on September 28th, 2012 at 06:35 AM |
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Hp figures are a tad high to expect from a 1641........but yes if you really want to rev the $@#! out of it balancing is totally necessary
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bajachris88
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| posted on September 28th, 2012 at 06:50 AM |
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put in a 74mm crank (no machining required to fit this one) and you bring it to 1760cc with the oversized pistons. Buy decent rods though particularly
with the desired rev range. if you can get 5.3 inch rods, you don't need head spacers for the heads either.
Oh, and HD springs to keep valve float at bay (again at that rev range)
Ratio rockers might also be ideal with the greater displacements. Heard it can 'simulate' the same performance as a bigger valve in a head in some
senarios. Given the extra work to move the spring/valves with this, you'd want decent pushrods, then lifters, and cam. Chain reaction 
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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Stanley
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| posted on September 28th, 2012 at 09:06 AM |
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| Quote: | Originally
posted by hellbugged
Hp figures are a tad high to expect from a 1641........but yes if you really want to rev the $@#! out of it balancing is totally necessary
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Agreed....also depends on what your using it for. If you want longevity think about a bigger displacenent and lower the revs.
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vwo60
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| posted on September 28th, 2012 at 10:01 AM |
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If you are concidering putting a chrome moly crank, go as big as you can ,82MM, big increase in torque. if you run the single weber it's hard to tune
then well, a set of dual 36MM IDF webers would be a worth while addition.
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Craig Torrens
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| posted on September 28th, 2012 at 11:51 AM |
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1640 with a top rev range of 7000rpm will give you around 75-80hp atw.......dont get fooled by all the HP figures floating around on forums.
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1303Steve
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| posted on September 28th, 2012 at 01:13 PM |
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Hi
The 87 mm barrels and pistons are not really ideal. The top of the barrels is very thin and are prone to leaking, better of with 90.5 or 94, although
these do need machining of the case and heads.
Steve
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mkII_baja
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| posted on September 28th, 2012 at 01:21 PM |
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Thanks guys
I appreciate the input. I have never owned a vw with a vw engine in it always had conversions
The rev range that I mentioned was a bit of a pie in the sky figure by the looks,
However I would like for it to rev comfortably when necessary
If around the 100 engine hp is a more realistic figure then that's still going to be pretty pokey considering the trike should come in
around the 450kg
Are 5.3" rods readily available from vw performance parts suppliers?
Are there any other mods necessary other than crank and rods to stroke using a 74mm crank?
I was planning on using chr mly pushrods,case studs etc and a decent set of valve springs to handle the revs is an ob vious must
I've read that factory DP heads can be good for up to 100hp is this correct
I've heard that thye castings of the factory heads are much better thatn most aftermarket heads has anybody found this to be true.
I am willing to spend up to about $1000 on the heads if need be.
Thanks again Jade
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bajachris88
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| posted on September 28th, 2012 at 08:27 PM |
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Hi Jade,
This is an awesome read and explains about performance engine internal mods with no machining:
http://www.aircooled.net/1800cc-vw-engine-no-machine-combo/
5.325 inch rods to be specific and aircooled.net and cip1 sell them. However, because it is a size used for porsche, it has the porsche label and thus
the price. I bought cylinder spacers which are a heap cheaper with 5.4 inch H beam forged rods from cip1. Fairly affordable.
rods from air cooled: http://vwparts.aircooled.net/5-325-H-Beam-Connecting-Rods-Type-1-Journals-p/5...
For the same price or only a little bit more on counter weighted forged cranks you can get larger strokes up to 84mm, but then comes the need to
upgrade heads to allow for the new required larger air flow, and then you got comp ratio to deal with, and you can only space the head so far. It also
makes the engine wider, making tinwear fitting and some exhausts fun to fit too. For large stroke cranks you don't just have to clearance the case,
but also have to clearance the cam. After market cams (well the scat one i purchased) appears to be clearanced already but stock you'd have to grind
out.
haha, as said the 'vicious' cycle. Change one part, and there goes the entire system 
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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mkII_baja
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| posted on September 30th, 2012 at 11:24 PM |
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Hi Chris,
Thanks for the link, I have studied it over the last couple of days along with many other links and reading material suggested by aircooled.net.
At this stage I think I have decided to sell the mahle P&C's that I have and go with a non machine stroker.
I have a bit more reserch to do yet when I recieve a couple of books I ordered but think I will go with the 88mm thick wall slip in's, , a 74mm
crank, 5.325" rods,
CB Performance 044 heads (not 100% sure on this yet), Engle w110 cam and then all of th other bits and pieces to go with.
I think the fact that the trike is half the weight of a vw sedan, negates the need for higher revs and with the extra torque of a stroker and fully
ballanced internals
The desired rev range should come back down to a max of about 5500rpm, well under the tolerance of the parts just listed.
Hopefully this then will provide for a longer more reliabe engine life.
Have many people had dealings with Aircooled.net as a parts supplier? what are their freight charges like etc?
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hellbugged
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| posted on October 1st, 2012 at 08:23 AM |
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Sounds like you're getting the idea of it now... Careful selection of parts all aiming for the same level of performance
Go bigger in the cam if you get the 044's
Not sure if those heads are made with less than 90.5 bore?
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mkII_baja
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| posted on October 1st, 2012 at 08:45 AM |
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From what I have read, if I get the 88mm thick wall cylinders they require the larger bores in the head but the std case bores.
As Far as the cam goes, I have never had much to do with cams or cam selection, would either of the engle w120 or scat c45 cams work? or would I be
better off
stepping down a notch in head size? are the 044's excessive??
This may also be a silly thought but I was thinking about using a 45mm DCOE sidedraft webber that I have in the cupboard.
I would need to fab my own manifold, other than that It looks like I would have to spend another $ 700 to 800 to put duals on.
Just a thought at this stage
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