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Location:
Nelson NZ
Registered:
August 2003
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which pistons to use in 18rgeu
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Thu, 20 May 2004 19:37
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I am at the stage of rebuilding my 18rgeu i am purchasing new pistons and have priced up over sized pistons. What im wondering is if i can put 18rgu pistons in as they have a larger dome raising compression. Has any one done this conversion is it worth it and what is the best sized piston to go with for reasonble powered na engine
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Location:
Brisbane
Registered:
October 2002
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Re: which pistons to use in 18rgeu
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Fri, 21 May 2004 09:33
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any piston will fit, the 9.7:1 out of the first 18RG may have cam clearance issues with the RGEU cams, u will have 8.2:1 and 18RGU is 8.7, RGR is 9.2 and RG is 9.7
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Sat, 22 May 2004 02:04
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dohc
I'm about to go down this road. I'v bought the 9.7.1 pistons to put in a 18rgu with efi gear. I have the geu cams and the rg cams. Are you saying that the geu cam profile will be to big and the valves will come in contact with the pistons. As the rg cam have a higher profile that mean they would be impossible to fit unless you re- shim them????
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Location:
Brisbane
Registered:
October 2002
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Re: which pistons to use in 18rgeu
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Sat, 22 May 2004 04:22
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as i have been lead to beleive {by multiple reliable sources} as the engines got newer the cams got wilder, but i know for a fact that the comp ratio went down, as did the power unfortunately,
i dont know for a fact that the cams will hit, the best way to find out is {if u already have the engine apart}, put some blutack/playdoh ect on the top of the piston, put the head back on {remember to use a HG, but use the old one or else the new one will be fucked} line up the cam timing correctly, remove the plugs for easier spinning and slowly turn the engine over, if it spins freely then its fine, if there is a bit of resistance when one of the postons come to TDC then the valves are hitting the blutack, turn it over a few times to make sure its all good, pull the head off and measure how deep the playdoh is to work out the clearance.
I have no idea what the acceptable limit is.
btw, dont forget to lube the playdoh so it doesnt stick to the valves and lift off the piston
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Sat, 22 May 2004 05:52
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Thanks for the reply. Pity nothing is a yes or no answer.
I'll go through the proceedure and take it from there. cheers.
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Location:
Brisbane
Registered:
October 2002
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Tue, 25 May 2004 07:43
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Just a quick question. Providing both cams spin freely, which would be the better cams to run. I'm not keen on testing both, but will if I have too.
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Location:
Brisbane
Registered:
October 2002
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Re: which pistons to use in 18rgeu
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Tue, 25 May 2004 09:34
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the later the better, if u can find some 88270 cams that'd be best, or some 88253 ones, or just get yours ground,it'
ll cost u like $200
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Location:
adelaide
Registered:
May 2002
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 02:15
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I have considered this many times also, and something i have been told is if you have the early domed pistons with high CR they will most likely hit the valves with 88270 cams.
my 8.2:1 pistons have quite a low clearance with the 270 cams, so a bigger dome would probably touch if you didnt adjust shims, lower cam lift, etc.
i have also been told not to try and raise the compression/modify cams with stock EFI gear because the ECU/injectors wont accept, or adapt to, the change in fuel patterns and cam overlap.
In summing up, dont make a hi-comp motor with racey cams if you are going to use the old factory computer. get an aftermarket system happening, and maybe ditch the Air flow metre...
or go for webers.
this is why my motor is still basically standard, because it will be too expensive to upgrade everything properly for the gains in kW/reliability.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 06:26
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why is it that the later cams create interference problems?
Are you sure its not just the later model heads with the bigger VALVES?
Considering that the:
88230 head had 43/35mm valves,
88250 had 45/37m and
88270 had 45/39mm
I mean, i always believed that the cams on the 88230 were the most aggresive, with longest duration and biggest lift, which progressively went down with each model 18R-G*.
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 09:30
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Back to the piston sizes. I'v just read a performance book and it states that the 18rg has 97.0mm bore the 18rgr has a 92.0 bore 18rgu a 87.0 bore and 18rgeu has a 83.0 bore. Didn't you guys say they would all be the same size???? I'v just bought 97.1.1 comp to replace my 18rgu pistons 87.1.1 comp, though I have not taken it apart yet to measure.
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Location:
Brisbane
Registered:
October 2002
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 11:07
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| omegaman wrote on Wed, 26 May 2004 19:30 |
Back to the piston sizes. I'v just read a performance book and it states that the 18rg has 97.0mm bore the 18rgr has a 92.0 bore 18rgu a 87.0 bore and 18rgeu has a 83.0 bore. Didn't you guys say they would all be the same size???? I'v just bought 97.1.1 comp to replace my 18rgu pistons 87.1.1 comp, though I have not taken it apart yet to measure.
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they are all the same {unless its been bored out}, max piston size for a 18RG is 92mm {which takes it to a 2.2L, and i think they have a 87/88mm std.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 12:17
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89.0mm stnd bore
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Wed, 26 May 2004 21:46
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so has anyone yet figured out what this 18R-GEU 9.7:1 piston interference is yet?
Personally, i still believe its the fact that the valves in the late model heads are that much bigger than the earlier models (4mm is a big difference)
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Location:
SYDNEY
Registered:
August 2003
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Location:
Brisbane
Registered:
October 2002
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Re: which pistons to use in 18rgeu
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Thu, 27 May 2004 10:21
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if anyone in brissy wants to lend me a complete 88270 head i can work it out as i will have my head off soon.
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Fri, 28 May 2004 08:20
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Pity, your in Qld, I have a spare 88270 head complete as i'm using the 88250 head on my car. But I'm in sydney.
Is there a rule of thumb calculation I can use to work it out.
I've also got a spare block with the 8.2.1 comp pistons in it.
This might help if I had a calc or do I go back to the blu tac idea and change 1 piston to 9.7.1 and try that.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Fri, 28 May 2004 09:10
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i have both the 88250 and 88253 heads (88253 is same as 270 with the 250 cams)
ill find out some differences when i pull the two apart, hopefully soon.
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: which pistons to use in 18rgeu
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Fri, 28 May 2004 10:20
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use the 9.7 to 1 pistons and the earliest cams you have 1s with verniers and pins not bolts dont use the 18rgeu head not as good as the early 1s flow wise the higher comp will be better also the 18rg had the most power and not much in the way of pollution devices charcoal canister and solidnoid valve that bolts to the rocker cover to stop over run ,and std bore is 88.5mm
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Fri, 28 May 2004 10:59
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By earliest cams, you mean the later ones ie. 88270 with adjustible verniers. As to me the early ones are the 18rg
145hp ones the 88231 cams which I have.
Shouldn't the 88231 cams which give max power at @ 6400rpm at 131ft.lb if the 9.7.1 pistons were in it. Therefore wouldn't they be a better choice. 88253 head, 9.7.1 pistons & 88231 cams that would be a more powerful combo than the 88270 cams????????
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Sat, 29 May 2004 00:17
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from all accounts i had heard that the late model heads were better flow wise (and valve wise), what is it that makes the early small port small valve heads better?
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: which pistons to use in 18rgeu
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Sat, 29 May 2004 02:55
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the 18 rg were made up till 84 some countries or islands still ran the 9.7to 1pistons with no pollution at all ,also some rg had vernier and some didnt the cam profile were 10mm lift until the efi motor came out also the 18rgr ran on regular fuel hence the lower comp of 9 to 1 but still had the same cams ,the efi head had smaller ports for the lower comp not sure of the valves still have the GROUP C homalagtion papers that tells you what you could run and valve sizes and diff ratios etc
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Location:
SYDNEY
Registered:
August 2003
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Re: which pistons to use in 18rgeu
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Sat, 29 May 2004 03:05
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Witzl, i agree the later heads are better flow, I'm not sure you missunderstood my post. I meant that the earlier cams should have been a better option that the efi later cams, still using the later heads eg. efi 88270 or the 88253
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: which pistons to use in 18rgeu
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Sat, 29 May 2004 07:00
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omega - i was talking more to mr RA45 here. I agree that the best combo is the 88253/88270 heads with the 88230 cams are the best.
RA45 - i beg to differ on the port sizes. I have compared side by side an 88230, 88250 and 88253 (the latter two i still own) and the 88253 by FAR had the biggest ports and biggest valves (45mm IN, 39mm EXH).
When i pull the two motors apart ill get some pics up and demonstrate (or stand very corrected  )
Can you please specify the the engine model number when referring to parts? When i looked at the cams or any other part, they show 11111-882**-****** as their part number. This is a little more acurate so that we dont get confused here.
I am interested then in the cam lift and duration profiles for the following motors:
88230 = 18R-G
88250 = 18R-GU
88270 = 18R-GEU
basically i want to find out if they got bigger or smaller over time, since i only have the 11111-8825*-***** cams to go by (two sets of em too!)
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Location:
nth ringwood, Victoria
Registered:
August 2002
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Re: which pistons to use in 18rgeu
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Sat, 29 May 2004 11:15
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18rg 10.1mm of lift 18rgu has 9.5mm 18rgeu has 10mm lift
btdc16 btdc34 btdc12
abdc60 abdc90 abdc56
bbdc56 bbdc66 bbdc52
atdc20 atdc42 atdc16
comp 9.7 8.3 8.3
allhad the same valves 45mm inlet and 39mm exhaust the group C guys used all the heads you speak of except the pollution heads 18rg u with the exhaust recirclation and air pump and the efi head
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