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Engine basics => Engine set up tips => Topic started by: Air Ministry . on May 04, 2018, 11:20:14 PM
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Anyone let the cat out of the bag ,
pictures or drg of head / chamber .
Any Timing Mods .
Ive Found .312 for the venturie , and ' free flow ' 1/2 in outlet for muffler , for 6 Oz fuel burn - to cool , & provide decent 4-2 switch .
Other than that , We have to assumes it Hand finishing/ fettling . S?P
Pictures Pictures Pictures , please . H^^
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So no one has any pictures of the Big Jim's Hemi heads? It would be a shame if we lose this technology.
Best, DennisT
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Hurumph .
Contrary to popular belief ?? ??? The Double Star , and to a degree , Stalker - are said to pirate their ' specs ' ,
Particularly the DS 60 . Ive a pic of a DS 40 chamber somewhere - essentially ' a bowl ' .
The DS 60 Lite might be said to be a derivitive of the earlier ST 45/51/56 Plain Bearing 'V ' engine .
V Early 'V' 60 I have , dual ring - short rod - has open chamber ( No Squish Band -or minimal ) head .
Im presumeing maybe the Hemi is rather similar .Will recheck the timing on this ,
The Merco 49 ran steady and strong on the ( Original ) ' Stalker ' 130/110 sleeve timing .But little round shaft port .
Might try setting a pdp 60 at the 130/110 timing - for steady four stroke run , :-\ perhaps .
Im sure the ' Big Jim ' motors are out there , he mustve done a ton . Wonder if theres any destinguishing marking / engraving
or somesuch .
R%%%% R%%%% H^^
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Hi all!!
Just for the record, all Mercos (29,30,35,40,49 and 61) are Hemi head.
Kind regards from Spain.
Manuel.
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So no one has any pictures of the Big Jim's Hemi heads? It would be a shame if we lose this technology.
Best, DennisT
The de-compressed BJ Hemi heads run very much just like the first ST 60 Low Comp heads I call the Bell head, it is hemi and looks like the under side of a Bell, no squish band, That said the very latest hemi Squish high compression head with the scalloped top was/is the BEST head for the ST 60, if you have the rest of the engine setup correctly, ie venturi size, head shims, exhaust outlet size etc. You need a larger venturi with the hemi low comp head, smaller venturi with the stock high comp squish/hemi head
I built over 600 of these for people, and a few that were 65s and a couple of 71s and 74s
Randy
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Hurumph .
Contrary to popular belief ?? ??? The Double Star , and to a degree , Stalker - are said to pirate their ' specs ' ,
Particularly the DS 60 . Ive a pic of a DS 40 chamber somewhere - essentially ' a bowl ' .
The DS 60 Lite might be said to be a derivitive of the earlier ST 45/51/56 Plain Bearing 'V ' engine .
V Early 'V' 60 I have , dual ring - short rod - has open chamber ( No Squish Band -or minimal ) head .
Im presumeing maybe the Hemi is rather similar .Will recheck the timing on this ,
The Merco 49 ran steady and strong on the ( Original ) ' Stalker ' 130/110 sleeve timing .But little round shaft port .
Might try setting a pdp 60 at the 130/110 timing - for steady four stroke run , :-\ perhaps .
Im sure the ' Big Jim ' motors are out there , he mustve done a ton . Wonder if theres any destinguishing marking / engraving
or somesuch .
R%%%% R%%%% H^^
Many of the motors Jm did had either BJ or LJ carved nto them, and some had a number like 150 160 130 wrote on the head . He measured the psi on what they read
Randy
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Here are pics of a Genuine Big Jim Hemi Red Head.
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Thanks. H^^
Not B J but T L .
(http://forum.rcdesign.ru/attachment.php?attachmentid=1272438&d=1479566726)
The cuts reduce the buckling of the piston and, from the part, help to wash the bottom of the piston behind the deflector. Useful for non-rectilinear deflectors.
(http://forum.rcdesign.ru/attachment.php?attachmentid=1281936&d=1482586882)
The depth of the cutting is 1.6 mm. 1.7 mm, the angle at the top is 60 degrees.
From the exhaust side a chamfer is removed from the top of the cut to the bottom of the piston. See the photo from the blowdown side for a sharp edge.
(http://forum.rcdesign.ru/attachment.php?attachmentid=1281937&d=1482586931)
(http://forum.rcdesign.ru/attachment.php?attachmentid=1281938&d=1482586975)
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Matt,
Very interesting shots of the piston baffle can you post some shots of the head? It would be interesting to know what Tom was trying to get from the baffle slits. Interesting to try to record this technology for the ST 60.
Best, DennisT
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can you post some shots of the head
In a WORD ; NO . :-\
abducted Info from Russian Site . IF I find said picture there , sure will .
Last knight , dithering with Spitfire & injuns , Found the Earlier Prop Diver 60 has longer nose by maybe a quarter inch , Due To the Earlier Deeper Prop Driver .
So the a amenity to alter fit / spinner posn through that .
Ive got the Timing for the First Hemi 60 written down , will measure PDP & post them & Engine Test of another year also .
Can Do Pictures of Above Heads , Early is Big chamber . Also in time one Herb is opening up to Hemi - narrow squish band . But That is a individual one .
Curtosey SKIP . B J on left .
(https://stunthanger.com/smf/engine-set-up-tips/attn-matt-spencer-re-st-head-pics/?action=dlattach;attach=286132;image)
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In a WORD ; NO . :-\
abducted Info from Russian Site . IF I find said picture there , sure will .
This guy owns this engine. He did and pictures.
https://stunthanger.com/smf/profile/?u=34752