RV8 Compression ratio increase.
Discussion
I bought a spare Rover V8 3.5 lump a little while ago, so I could swap the heads onto the one in the TVR (worn valve guides).
The thing is, that the engine in the TVR is actually from a Range Rover and is the 8.25:1 compression ratio variant,
the spare engine is 8.13:1 cr.
My question is whether it will be worth all the agro of swapping all of the pistons between engines? How much in terms of a power increase will I expect to see (maybe at the expense of some torque?). I am not going to consider putting the whole engine in, as the next time I remove an engine from that car it will be to fit a 3.9!
I don't mind doing the work, but only if I am actually go to achieve something.
Any thoughts?
Thanks
James
The thing is, that the engine in the TVR is actually from a Range Rover and is the 8.25:1 compression ratio variant,
the spare engine is 8.13:1 cr.
My question is whether it will be worth all the agro of swapping all of the pistons between engines? How much in terms of a power increase will I expect to see (maybe at the expense of some torque?). I am not going to consider putting the whole engine in, as the next time I remove an engine from that car it will be to fit a 3.9!
I don't mind doing the work, but only if I am actually go to achieve something.
Any thoughts?
Thanks
James
spend said:
Its not easy for the casual observer to note the differences in TVR heads, the ones on your profile look better than std LR heads to me. Be very careful you are not taking a retrograde step 
I know what you mean, but both of my RV8s are sourced from Range Rovers and have never been near Blackpool The only difference between the two engines is the piston crowns (one deeper than the other).
tr7v8 said:
My TR7 had a low comp Defender lump, 1mm (40 thou) off the heads bought the compression up to 9:1. Sharpened the throttle response up & had no downside.
From what I have heard, this is the benefit of H/C, although my L/C is quite happy to rev it would be nice to add a bit more urgency!
peaktorque said:
eliot said:
I wouldn't waste my time with any sort of low compression 3.5 engine. Slugs-Ville usa.
Thanks, just the answer I was looking for.I was going to give a long technical answer - but didn't have time. Correct me if I'm wrong, but it will have dished pistons, small ports on the heads and what ever you do to it - its still a old 3.5.
Find yourself a later 3.9 (or bigger) engine, mild porting job, cam, tidy up the induction etc and you should see a little over 200bhp on it.
There's a chart half way down this page to give you an idea of power expectations:
http://www.mez.co.uk/TuningTheRoverV8-pt4.html
eliot said:
peaktorque said:
eliot said:
I wouldn't waste my time with any sort of low compression 3.5 engine. Slugs-Ville usa.
Thanks, just the answer I was looking for.I was going to give a long technical answer - but didn't have time. Correct me if I'm wrong, but it will have dished pistons, small ports on the heads and what ever you do to it - its still a old 3.5.
Find yourself a later 3.9 (or bigger) engine, mild porting job, cam, tidy up the induction etc and you should see a little over 200bhp on it.
There's a chart half way down this page to give you an idea of power expectations:
http://www.mez.co.uk/TuningTheRoverV8-pt4.html
Thanks, that's more like it!
The pistons are dished as you say, but a lot less so on my spare engine. Although my heads are mildly improved over standard.
In defence of the 'mighty' 3.5, it does pick up well and my brothers M3 EVO doesn't easily shake it off (that's got a proven 340 bhp).
My aim, when I'm in a position to, is to fit a larger RV8.
Just before I stick the spare engine on ebay (the b
d is in the way) I want the make sure that I am not discarding the more powerful/revvy (term to be used loosely ) of the two!Seems that it isn't worth the bother!
Thanks for the info.
James
The fact that 3.5's fetch very little more that the price of scrap on ebay should be a clue.
I sold one for 99p - in fact when he came round to collect it, i didn't even take the money off him. All he did was strip it down and flog the parts to yanks for their mgb v8's - fine if you can be bothered with the mess.
I sold one for 99p - in fact when he came round to collect it, i didn't even take the money off him. All he did was strip it down and flog the parts to yanks for their mgb v8's - fine if you can be bothered with the mess.
Edited by eliot on Tuesday 9th December 20:23
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