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Can anyone suggest a good compression ratio for a dedicated LPG motor, & the best way of acheiving it in a 186 (flat pistons, 179 head etc...) What kind of compression would you get with a 161 head & a set of flat-tops? I've heard diesels run LPG fine & they have massive compression. If I have high compression do the rods etc need to be changed to cope? Ta heaps!
The Beige Hornet.
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I have just been running a 208 with 161 head (pulled it apart today...208 block died) so that puts the compression up around 10.5:1
I had no detonation problems.
186 already has flat tops as standard...if you use a 179/186/202 open chamber head you
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You're a wealth of info FastEH! I reckon good YT heads are getting hard to find (read expensive). If I get a 161 head, it will probably need a rebuild anyway, so if I get it ported that should make it similar to a YT head (there goes the budget anyway...)
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I used to use hardened seats and stainless valves..but the bloody head cracked.
I get around it by using a pcv hooked to under the base of the mixer...it breathes all the oily air into the manifold...and so far its worked for about 30000 km.
"they"
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If you use an early head,149 or 161, then you will have adjustable rockers and don't have to worry about shimming them if you get the head planed.
Thats a good idea using your pcv for lubrication, as long as it breathes a bit.
You can also get upper cyl
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Cool -So my shopping list is a 161 head with hardened seats & valves & fairly heavily ported (& maybe a bit of a shave?). A re-graphed blue dizzy, LPG friendly cam & LPG engine oil. I've got a Cain 4bb manifold that I was going to use, I assume Holley is
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Just curious - how would a 10:1 motor run on premium unleaded?
The Beige Hornet.
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P.S. are YT heads cast any differently or can you get the same result with a 161 head at a machine shop....?
The Beige Hornet.
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re - detonation with lpg.... I've been playing with the timing on the 186, advanced it to 50+ degrees wot - could not get it to detonate on LPG ???????? still ran ok but with no guts. got me stuffed.
I'm guessing lpg is good for a fair bit more compress
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LPG is also 104 octane for those who didnt know-cheap power if its set up right
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