Discussion
If you're prepared to take it apart then some head work would help. Otherwise, port matching the manifolds to the heads (these are terrible from the factory) and a remap - though there aren't the sorts of gains to be had as there are on the 4.5
TBH, the best thing is probably just to make sure that it's running as well as it can; check that you can get full throttle, that the cam timing and valve clearances are right and that the air filter is in good condition.
CliveF got 400bhp from the 4.2 that he put in his Griff, I don't know of any others that have made that much. To be fair though, he also had a bespoke exhaust manifold which looked to be a better design than the Cerb one.
TBH, the best thing is probably just to make sure that it's running as well as it can; check that you can get full throttle, that the cam timing and valve clearances are right and that the air filter is in good condition.
CliveF got 400bhp from the 4.2 that he put in his Griff, I don't know of any others that have made that much. To be fair though, he also had a bespoke exhaust manifold which looked to be a better design than the Cerb one.
Hi, I managed to get an extra 25hp out of my 4.2 by having a remap and some porting work on the inlets. The job was definatley worth it, i got more bottom end torque as well as top end thrash! Jools did mine, top job. He's now at Raceproved in Sheffield i Believe, Speak to him he'll give you an idea of what you can realisticaly expect to get. Mines running 375bhp at the mo, but have been thinking of those ACT manifolds.... Steve.
Edited by assynt road on Tuesday 21st September 11:36
Given that when you lift the head off you find a fair proportion of 4.2s are actually 4.5s I think there may be quite a lot of potential in some of them! I have a factory 4.2 on the bench now that's stamped as a 4200 and came out of low mileage factory original 4.2 car, but it's not a 4.2 at all. I hear it's pretty common as TVR saw the 4.2 and 4.5 more as model designations than engine sizes towards the end. Or to rephrase that they used what they had and what was the point in buying in 2 different sizes of cylinder liner and piston.
382 out of mine at last test, but it has Joo's inlet work and mapping plus ACT exhaust and manifolds.
To be honest I don't really notice the extra 10% as it was quick before. What I do notice is the drivability as the torque curve kicks in at 2k revs now rather than 3k. It's really pleasant and easy to drive now in all traffic.
To be honest I don't really notice the extra 10% as it was quick before. What I do notice is the drivability as the torque curve kicks in at 2k revs now rather than 3k. It's really pleasant and easy to drive now in all traffic.
Mine is an 02 "4.2". I had Joolz (formerly TCS now RaceProved) remap, some very mild inlet polishing, lightweight RaceProved flywheel (allows to rev quicker), new CATS, sports back box - now punts out 393bhp on RaceProved dyno. Last year punted out 392bhp on same dyno - so fairly consistent results.
As previously posted, when I initially got the car it was only about 270bhp = gained another 30bhp simply by changing the air filter. Then had the new CATS and remap and took it up to 371bhp (at TCS - but that's the same dyno now at RP). After the mild head work got up to 393.5bhp.
As previously posted, when I initially got the car it was only about 270bhp = gained another 30bhp simply by changing the air filter. Then had the new CATS and remap and took it up to 371bhp (at TCS - but that's the same dyno now at RP). After the mild head work got up to 393.5bhp.
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