Chimeara Big valves on a 4.5?!!
Discussion
My father owns a 4.5 Chimeara 1998 recently put a new head gasket on and stripped it down for a general look around and measured the valves to find they were big as in the 5.0. Also cross hatching on the pistons yet the piston stroke is a 4.5 spec so it has been breathed on.
Any one know the reason for this or has experience just anequiry really. Cheers
Any one know the reason for this or has experience just anequiry really. Cheers
v8 racing said:
The big valves were quite often found on the 4.5 beleive it or not! the problem was that is all they did!! the ports are still standard s too is the valve throats! still flow much more that standard heads though so a bonus for people thathave got them!
Sounds like maybe they hadn't paid for a few suppliers that month then :cheekymonkey:
Dave
...or several months.... etc...
v8 racing said:
The big valves were quite often found on the 4.5 beleive it or not! the problem was that is all they did!! the ports are still standard s too is the valve throats! still flow much more that standard heads though so a bonus for people thathave got them!
When i stripped my '99 450 last year to start a major rebuild and mods i found what V8 Developments refer to as "ultra big valve heads" 43mm inlets and 37mm exhausts but the seats and throats WERE quite significantly worked although not the rest of the port (they are now!
). I suspect these were very similar, or the same as 500 heads. chrispitman said:
Dose anyone know if the pistons fitted to the 4.5 were all the same type ie pocketed (cutouts for the valves)
AFAIK the pocketed pistons are a modification and are not fitted to any standard LR engine. Whether all the TVR 4.6 engines in 450's have pocketed pistons I dont know, it would be essential if the engine runs BV heads though. Equally the standard LR engines all use standard heads with standard size valves. If you look at a bog standard head you will see a big difference in the throats compared with a BV head.
Judging from my engine TVR seem to have done quite a bit of work on these (albeit only in the throat area and the valve seat) and then fitted the big valves necessitating reaming out the guides, as the stems are larger, and fitting them at a lower installed height to allow for greater valve lift (mine in fact had 17mm clearance between oil seal and underside of cap!! - compared with around 12mm as standard). In addition the bottom end has been dynamically balanced including the crank, damper, flywheel and cover plate - all stamped with matching ID numbers (together presumably with the rods and pistons - but i havent disturbed these (only 25000 miles). The cam was a TVR350RM. So clearly in theis case there is no question of TVR taking production LR items and just plonking them in.
Edited by Tahiti450 on Tuesday 24th April 12:25
Tahiti450 said:
chrispitman said:
Dose anyone know if the pistons fitted to the 4.5 were all the same type ie pocketed (cutouts for the valves)
AFAIK the pocketed pistons are a modification and are not fitted to any standard LR engine. Whether all the TVR 4.6 engines in 450's have pocketed pistons I dont know, it would be essential if the engine runs BV heads though. Equally the standard LR engines all use standard heads with standard size valves. If you look at a bog standard head you will see a big difference in the throats compared with a BV head.
Judging from my engine TVR seem to have done quite a bit of work on these (albeit only in the throat area and the valve seat) and then fitted the big valves necessitating reaming out the guides, as the stems are larger, and fitting them at a lower installed height to allow for greater valve lift (mine in fact had 17mm clearance between oil seal and underside of cap!! - compared with around 12mm as standard). In addition the bottom end has been dynamically balanced including the crank, damper, flywheel and cover plate - all stamped with matching ID numbers (together presumably with the rods and pistons - but i havent disturbed these (only 25000 miles). The cam was a TVR350RM. So clearly in theis case there is no question of TVR taking production LR items and just plonking them in.
Edited by Tahiti450 on Tuesday 24th April 12:25
That is a very wierd engine you have (or rare i should say!) never even seen a tvr350 cam? all the 450's i have stripped (which is too many!) either have tvr 51's or if its an hc tvr 435, and as i said the throats on the ig valve 4.5' are more or less as per land rover, the valve stem sizes are definetly the same so they cant be rec valves you have? out of interest have you had your car on the rollers as it may (sounds a bit spiecial to me?)
v8 racing said:
The big valves were quite often found on the 4.5 beleive it or not! the problem was that is all they did!! the ports are still standard s too is the valve throats! still flow much more that standard heads though so a bonus for people thathave got them!
Got BV on mine and i`ll have worked ports etc by the end of the week (come on Jamie you promised)
v8 racing said:
[ That is a very wierd engine you have (or rare i should say!) never even seen a tvr350 cam? all the 450's i have stripped (which is too many!) either have tvr 51's or if its an hc tvr 435, and as i said the throats on the ig valve 4.5' are more or less as per land rover, the valve stem sizes are definetly the same so they cant be rec valves you have? out of interest have you had your car on the rollers as it may (sounds a bit spiecial to me?)
Sorry for the delay in getting back to this thread (been to busy getting the engine back in the car!). I have mislead you a bit as the cam is the TVR435 I dont know where the 350 came from! All the other details are correct tho. Th valves I think are the same spec as used by JE motors on their big valve heads and I thought that TVR used a similar item.
I havent had the car on a dyno (I plan to once finishing the current project) but it certainly raised some eyebrows a couple of years ago when i was putting in very competitive times (with standard suspension etc) on a sprint against modified 5.0l Griffiths and Chimaeras. The car has always felt fast but to be fair thats pretty meaningless and the best 0-60 time Ive managed has been 5.0s dead on T1R's - again lots of unquantified variables.
Edited by Tahiti450 on Friday 27th April 12:04
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