Xj8 pistons
#1
Xj8 pistons
I have bought a 2005 4,2l sub assembly to put into my 1999 XJ8, the supplier has put in flat top pistons, but I have only seen this engine with slots for valves clearances, they say they are correct, can someone confirm this before I assemble and install, I have bought the 2005 heads and cams as well and believe the valve timing is higher than the 1999 cams, so I am totally confused.
#2
EDITED
As far as I know the naturally aspirated pistons in the 4.0L are flat tops, the supercharged pistons are the dished ones to reduce the compression ratio, not for valve clearance.
I cannot find any pictures of a 4,2L N/A piston, only the 3.5L and the 4.2L Supercharged. Both of these are actually dished/shaped, not flat tops.
Also check the 4.0L to 4.2L swap thread at the top of this subforum regarding the camshafts, the VVT is different.
As far as I know the naturally aspirated pistons in the 4.0L are flat tops, the supercharged pistons are the dished ones to reduce the compression ratio, not for valve clearance.
I cannot find any pictures of a 4,2L N/A piston, only the 3.5L and the 4.2L Supercharged. Both of these are actually dished/shaped, not flat tops.
Also check the 4.0L to 4.2L swap thread at the top of this subforum regarding the camshafts, the VVT is different.
Last edited by Cambo; 04-16-2015 at 03:17 AM.
#3
many thanks for your info; I based my idea of using the 4,2 on the same thread you mention and it sounded a good idea, but with little info on the 4,2 piston tops I am not sure I should use the sub I bought, but find a complete engine to fit.
I did find info on the VVT's the 4,0 has 30 deg advance and the 4,2 has up to 48 so valve clearance will be a problem, also the 4,2 has inverted tooth main chains which I would like to use.
I did find info on the VVT's the 4,0 has 30 deg advance and the 4,2 has up to 48 so valve clearance will be a problem, also the 4,2 has inverted tooth main chains which I would like to use.
#4
#5
I have looked on the JTIS, and have found data on the pistons, the data given is that the 4.0 has relief for the valves, and shows a diagram, but on the 2004 (the highest year on JTIS) the piston is flat topped, also with a diagram!!!!!!!!!!!!!!!!!!!
As you suggest the pistons can only be P&A as I have found no supplier of a A/M version after hours of trawling on the internet.
I think I will put the heads on using an old gasket, and turn the engine over by hand allowing for the VVT lead on the timing, and see where that leads.
As you suggest the pistons can only be P&A as I have found no supplier of a A/M version after hours of trawling on the internet.
I think I will put the heads on using an old gasket, and turn the engine over by hand allowing for the VVT lead on the timing, and see where that leads.
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