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Location:
Rocklea qld
Registered:
February 2003
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determaning what 18rg parts are from what engine..how???
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Sun, 14 November 2004 03:27
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ive done some searching and it says that the 9.7-1 compression pistons have huge domes like 15mm high. is this correct or is there other ways to tell?
which head was the best..ive read some conflicting infomation..one says 88230 is the best but the other says 88270 is the best..what would be better for a good hp NA engine
which cams work the best with the best above head. i read that the 88231 cams ran the best due to the size..would that be right??
basically i have a 88230 engine 2 x 88250 engines and a 88270 engine. I want to blend the best part together to make a good hp NA engine. ive done searching and it says some stuff about them but not about which actual parts will run better together to get good compression
all help is appreciated
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Location:
Hobart
Registered:
June 2002
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Re: determaning what 18rg parts are from what engine..how???
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Mon, 15 November 2004 02:05
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ok, heres goes. My take on the whole thing:
As far as complete engines go:
18R-G:
140/145 Hp
twin solexs
9.7:1 Pistons (pretty big dome, and fly cuts for valves)
88210 or 88230 Head/cams
The cams in this engine are desirable, with highest lift and duration.
18R-GU:
130? Hp
twin solexes
8.3 or 8.7 pistons?
88250 or 88253 head and cams
Less agressive cams
18R-GEU:
EFI
8.3 pistons?
88270 head and cams
Apparently better head than early models, larger valves/ports.
Cams same as 18r-gu?
So people that say 88230 is best, are usually refering to the complete engine in standard trim. People that say 88270 head is best are refering to the bigger valves and ports in teh head. So if you aren't going to touch one (mix'n'match) then early one is best.
Or as people have mentioned you can mix'n'match so that you get 88270 head, 88230 (or maybe 88210) cams, 9.7:1 pistons and put the efi gear on if you want nice economy and drivability.
The only thing i would be concerned about is the larger valves having clearance issues when used with the high compression pistons and the higher lift cams.
My engine is a mix of old and new. I have and early 18R-G, with head number 88210 and 9.7:1 pistons. Someone has replaced cams with 88250 items. And i have replaced carbies with EFI. I'm on the look out for a pair of early cams.
Sorry, long post!
Cheers
Chris
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Location:
Adelaide
Registered:
June 2003
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Re: determaning what 18rg parts are from what engine..how???
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Mon, 15 November 2004 02:48
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Ok, here's the deal,
I've haad a close up look at many of these parts as we have them at home.
Head:
88230 head - small valves, may have recession issues with ULP.
- smaller ports
88250 head - has mixture of the small valves and the large
valves if I remember rightly. I can't remember
whether it was the intake or exhaust valves that
are of the larger variety.
88253 head - has large valves and good ports, but head design is
not as strong as 88270 engine.
88270 head - large valves, large ports (good for port job)well
reinforced head
Pistons:
88230 - I have not seen these, but have seen 88252 pistons
88252 - note: piston part number, not engine art number
9.7:1 CR dome height is 7mm, vlave releifs clear
large valves (we've used these with late model
heads)
88250 - Not too surte about these, depends on model, some
were 18rgr, some were 18rg and I tink some were
18rgu. Who knows what you've got? I can help!
18rgu - 8.7:1 CR has a dome height of 4mm. Valve reliefs
suit large size valves.
88270 - dome lower that 18RGU pistons. Valve reliefs suit
large valves.
Cams:
88231 - These have a larger lift and generally broader lobe
than all later models
- requires slightly thicker shims than later models.
- 11mm lift intake (accounting for .23mm clearance)
88251 - These are almost identical with 88270 cams.
- 9.7mm lift exhaust (accounting or .3mm clearance)
- 10.3mm lift intake (as above)
88270 - almost identical with 88251 but .5mm less lift at
max. overlap
88231 - as far as I know these cams were never made, all
18rgu motors used 88251 cams.
carbies:
Read what it says on the large venturi (restrictor 1/2 way down throat.
The bigger it is, the older the carbies are
31mm are newer carbies.
32mm were in the 88220 model 2tg carbies and possibly in the 88230 18rg carbies.
We have as set off of a 88210 manifold and they have 32mm venturis and are from before adjustable floats.
Feel free to mix and match.
We are using
- late model block (18rgu due to dip stick,88270 era)
- 88252 pistons (.5mm OS)
- 88210 timing case
- 88270 head
- 88231 intake cam
- 88251 exhaust cam
- 18r dizzy modified for electronic ignition (21RC)
This set up runs fine, the main reason for the odd cams is that we wanted to profile the 88231 exhaust cam, as we haven't got a graph of that one yet.
We have made graphs of all the cam profiles that we've got (88231, 88251, 88270, 30/70 regrind (280 degree)
If you want a copy of these, PM me and I'll send it through.
If you are building an engine up, you could look in Sydney for .5mm OS 9.7:1 CR pistons, there may still be 2 sets over there 13103 - 88252 part number)
Good luck with the build up, if you have any question, PM me and I should be able to find out for you.
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