stretch
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| posted on 21/10/09 at 08:39 AM |
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building a 1700 crosslfow
what 84mm pistons do i use?
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irvined
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| posted on 21/10/09 at 10:23 AM |
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I built a 1660 crossflow and used 1300 pistons, these have a higher compression ratio than the stock 1600. This then meant that with the valve
cutouts compression stayed pretty good.
These were standard cast pistons from Burton power. I think part number: 20552/030.
I used ARP con rod and flywheel bolts, standard end caps, and standard con rods.
All where fully balanced before assembly. With a Piper 285 cam, twin webers its putting out 122hp@6200rpm and still rising (rev limit is 6800, but we
didn't run it that fast on the dyno (yet.))
More is easily possible, I need to change the emulsion tubes, and rejet which is going to be quite expensive, so I'm holding out for fuel
injection.
- Hijack -
Incidentally, what cam are you going for? I've just ordered a Kent 234 cam, but I'm debating if its going to be an improvement or not.
The piper cam is pretty good, but i'd like a bit more power, its got plenty low down, and good torque and im prepared to sacrifice a bit of that
for some more top end still.
http://irvined.blogspot.com
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prawnabie
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| posted on 21/10/09 at 10:30 AM |
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I used 18647 pistons from a 1300 in my 1700 build. You will need to get them modded if you intend on a high lift cam.
I built mine on my own apart from the bottom end which burton did for me. With a 234 cam and a modified mexico head I had it rolling roaded at 136
bhp.
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stretch
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| posted on 21/10/09 at 10:35 AM |
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currently
what i've got is, 1300 pistons in 711m 1600 block at 40 thou oversize - circlip came out and the gudgion pin made a nice indentation on the bore
kent BCF3 cam, with double chain cam gear. head ported and max oversize valves with double valve springs.
one option is to try and get 90thou oversize and just use existing setup
the other option is using another 84mm piston thats alot lighter with a lower compression hight, then cutting down 5-7mm off the top of the block to
get the correct compression ratio, also need to cut down pushrods with the same amount.
comments?
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Marcus
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| posted on 21/10/09 at 11:21 AM |
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I'd go the +90 route and see if it gets rid of the scratches in the bores, if not it's a new block. My winter build will be a fresh rebore
to +90, a set of 1300 pistons, kent 244 cam with duplex gear. I'm keeping my current head and prob going either bike carbs or TBs.
Marcus
Because kits are for girls!!
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irvined
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| posted on 21/10/09 at 11:30 AM |
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Marcus,
Why the 244 cam? People keep telling me its too hot for the road, what do you have in now?
http://irvined.blogspot.com
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stretch
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| posted on 21/10/09 at 11:40 AM |
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quote:
Originally posted by Marcus
I'd go the +90 route and see if it gets rid of the scratches in the bores, if not it's a new block. My winter build will be a fresh rebore
to +90, a set of 1300 pistons, kent 244 cam with duplex gear. I'm keeping my current head and prob going either bike carbs or TBs.
cant find +90 in SA so i'm going to sleeve the damages cylinder and reuse the +40
i'm using twin 40 dellorto's AND i just put on a hayabusa bike can, with most of the innerthings taken out - sounds amazing! prob too loud
for you guys - it wont pass MOT
[Edited on 21/10/09 by stretch]
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02GF74
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| posted on 21/10/09 at 02:20 PM |
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quote:
Originally posted by stretch
then cutting down 5-7mm off the top of the block to get the correct compression ratio, also need to cut down pushrods with the same amount.
comments?
yeahm you are right to shorten the push rods to keep the valve train geometry the same but how do you plan to do that?
cut the rods then weld up or fit a sleeve and weld?
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Memphis Twin
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| posted on 21/10/09 at 05:01 PM |
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Crossflow pushrods are solid steel. You just ground down to the correct length and reshape the end.
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clairetoo
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| posted on 21/10/09 at 06:39 PM |
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quote:
Originally posted by irvined
Marcus,
Why the 244 cam? People keep telling me its too hot for the road, what do you have in now?
I used a 244 cam in my 1700 Xflow , along with the biggest valves I could find and a decked block - it was a bit of a pig on delorto's and made
135bhp - so I went for injection , and it bumped it up to 165bhp at 8000 , and was as docile as a production car around town 
Its cuz I is blond , innit
Claire xx
Will weld for food......
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Marcus
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| posted on 21/10/09 at 07:08 PM |
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What Claire said  I was advised by Mr Kent (at the retro motorsports show) that this was the best in my application, ie light car reasonable torque
and bike carbs / injection. I believe the 244 is the one Caterham used in the 1700 Super Sprint.
Marcus
Because kits are for girls!!
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thunderace
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| posted on 22/10/09 at 09:18 AM |
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84mm pistons are they + 90 if so you use 1300cc ones +90 and a big valve head 41.3mm inlet an 34mm exhaust thats the max you can go
(can you not get a 2Lxflow engine in south africa,im sure you can)
kent BCF3 cam and aldon dizzy and twin 40 webers.
here is mine
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Memphis Twin
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| posted on 23/10/09 at 09:46 AM |
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That's a nice looking head Thunderace, and looks to be well ported. Who did it?
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