If it was low fuel pressure or volume causing the problems then surely the lamda sensor on the dyno would have shown the mixture leaning out as the rpm/load increased? From holmsens description it does sound like its getting restricted higher up Someone allready mentioned the exhaust maybe not flowing enough and the carbs have been swapped for a known good set Which led me to think of the valves not opening far enough Its all just guesswork though
theres some excellent quality materials gone into this build, some aircraft spec too! Aluminium Alloy A356 - T6 is a silicone based alloy with a hint of magnesium, solution annealed heat treated with a 320'F aging process.. You have 7075 grade aluminium alloy pushrods, this is a typical aerospace grade alloy due to its strength & light weight..a good one The 4340 you refer to is 4340 low alloy steel with a composition of nickel, chrome and molybdenum, typically used on aircraft landing gear components (as well as oil and gas) - you tend to heat treat it (through hardening) to suit the application
last on this matter. Engine is now apart,,the Stuska ( brake bench) owner, suspects that the cam lobes are slightly misplaced .
Is that the Cam you "won"? Maybe it was a duffer and they gambled nobody would actually use it, or is that too cynical?
it's a blody nightmare. It's now back together, checked ok. Same mysterious problem,,dies just before 6 k.. 161-165bhp. Starts to run fat at the same time, fuelfumes coming up the carbs. I'm thinking it's something wrong with the cam, even if they say it checked out ok.
Ok,,last on this matter. cam is being sent back to JPM for a check up. He'll send it back if ok,,otherwise he'll send back a new one
This to me is normally an indicator that it's either under-fueling, or the inlet valves aren't shutting properly/fast enough Kinda harks of bad cam or bad/binding valve springs... Bit hard to call without seeing it in the flesh!!
The boys are still banging their heads on this. last time they had it apart they found wear on rod bearings and that the piston rings had way to small gaps. Other than that all checked out ok. Now all cleaned up, new rings and bearings,(with the better oil lubrication trick) and on its way back together. New dyno day this week,,Wish em luck
