later 4.2 s use the 4.5 block?

[WISHY]

????

Does the later 4.2 ajp v8 use the block from the 4.5 but have the head from the 4.2? if so is this the best of both worlds? or have i got it completely wrong? (probably!)

Thanks

[alinton]

I think you're right. I was looking at a 2004 car a few weeks ago in Hexham Horseless Carriages, it was a 4.5 but had the 4.2 style inlets.

Andy.

[TT Tim]

I'm pretty certain that John Wilson has this set up on his Cerb, and he's doing rather well in the Tuscan Challenge, so it must work.

Tim

Edited by TT Tim on Thursday 16th August 10:07

[PetrolTed]

Yep, I was told this many years ago.

[touching cloth]

I believe Wilder is running one of these late "4.2" models so could ask him for more info - but yes there is a current thinking from both APM on JohnnyW's and Austec on HarryW's (are they brothers ) that using the 4.2 on 4.5 can be an advantage due to better design, in standard form some say it is slightly restrictive in overall flow but HarryW is currently running 335 on a standard 4.2 inlet(he will be going to a modified 4.2 inlet once they get it running properly) but even on the standard he was getting 335 on the RR so seems to work nicely up to that sort of power.

[longbow]

I think there is some confusion here - the 4.2 and the 4.5 block are virtually identical - it's the liners/pistons that are key to the 4.2 or 4.5 displacement. The 4.2 and 4.5 have the same stroke and therefore same crank throw, but the journals are thicker and therefore stronger on the 4.5 (The 'early' 4.2 cranks were therefore smaller in diameter. As far as I can tell, the only physical difference between a 4.2 and 4.5 block is the 'deeper' machining for the bigger crank main bearing journals.

For example, my car has a 4.5 crank and a refurbished 4.2 block (done late 03 at TVR Factory) but it is definitely a 4.2 as I measured the bore at 88mm. The 4.5 liners are 91mm across.

[touching cloth]

But maybe what they really mean is that the later ones were in fact displacing the same as a 4.5, i.e really are 4.5 complete bottom ends, just with the 4.2 induction - not unbelievable as would have been a bit easier for them to work with just one standard set of sizes as the order numbers sloped off. Looking at Wilder's times from FT his is pretty much a match for yours, not conclusive either way because we know yours is a 4.2, but he either has a factory 4.2 aquitting itself very admirably or a 4.5 displacement giving him an extra hand. Be interesting to see one of these on the rollers and see the torque figures as that would be a good indicator.

[longbow]

Yep, agree, and the only way to know for sure is to pull the heads off and look at the liners. But I do get the impression that people are talking themsleves into believing they have a 4.5 just because it is a late 4.2 when I think what happened is TVR dropped the smaller early 4.2 crank and used the more robust 4.5 item. If you look at the TVR Power AJP 4.2 - 4.5 upgrade chart - http://www.tvrpower.co.uk/ajp.engine.only.php - the only two machining actions are 'LINE BORE LARGE MAINS' (to take the thicker 4.5 crank) and 'BORE BLOCK' (to take the wider liners). As a result, the two blocks are identical, except the 4.5 has more metal removed i.e. the initial AJP block is the same.

Also, my engine had the 4.5 crank fitted during its previous rebuild and the owner was told it was a 4.5 block, yet when stripped it had the 4.2 liners. I would be interested to see Wilder's car on a dyno though, as that might be simpler than pulling the heads off

Edited by longbow on Thursday 16th August 13:51

[Wilder]

longbow said:

I think there is some confusion here - the 4.2 and the 4.5 block are virtually identical - it's the liners/pistons that are key to the 4.2 or 4.5 displacement. The 4.2 and 4.5 have the same stroke and therefore same crank throw, but the journals are thicker and therefore stronger on the 4.5 (The 'early' 4.2 cranks were therefore smaller in diameter. As far as I can tell, the only physical difference between a 4.2 and 4.5 block is the 'deeper' machining for the bigger crank main bearing journals.

For example, my car has a 4.5 crank and a refurbished 4.2 block (done late 03 at TVR Factory) but it is definitely a 4.2 as I measured the bore at 88mm. The 4.5 liners are 91mm across.

Sorry old mate -but there are no liners used in the tvr AJP engines. They changed the engines to 4.5 capacity ONLY AFTER 2000.
Paul Forrest and Heath Briggs at TVR confirmed to me that the 4.2 I have is actually a 4.5 capacity engine. They just put the 4.2 induction system on it anjd called it a 4.2.

[Wilder]

WHat I mean by no liners, is that TVR did not reduce the 4.5 capacity to 4.2 in the post 2000 engines by the use of liners or anything else. They just left them at 4500cc.

[Wilder]

touching cloth said:

But maybe what they really mean is that the later ones were in fact displacing the same as a 4.5, i.e really are 4.5 complete bottom ends, just with the 4.2 induction - not unbelievable as would have been a bit easier for them to work with just one standard set of sizes as the order numbers sloped off. Looking at Wilder's times from FT his is pretty much a match for yours, not conclusive either way because we know yours is a 4.2, but he either has a factory 4.2 aquitting itself very admirably or a 4.5 displacement giving him an extra hand. Be interesting to see one of these on the rollers and see the torque figures as that would be a good indicator.

Thats exactly what Heath / Paul and also Dave at Automedon told me, so its likely to be true.
In TVR tradition, they didnt want to continue the last years of Cerbera production buying two different engines, so to save money they bought the bigger one only, and fitted it to both models -problem sorted !

[Wilder]

BTW I was going very easy at FT . I just wanted to have some fun without blasting the car at all.
Had I have tried & lit the tyres up, AND unblocked the induction duct (Paul Forrest spotted that and is sorting that for me now). He reckons it cost me 5 mph on the top end as I had to change up at 6400rpm as it just wouldnt pull beyond that because the air wasnt being fed through top the engine as it should have been, so yes I can believe that 1/2 sec would have easily been taken from my time without too much trouble.

[trackcar]

That's interesting .. i wonder what your insurance company would have to say about that if you mowed down a bus queue ?

[Wilder]

Nothing seeing as they go by the manufacturers figures for all cars they produce,whether accurate or not

[APMAUTO]

Wilder said:

longbow said:

I think there is some confusion here - the 4.2 and the 4.5 block are virtually identical - it's the liners/pistons that are key to the 4.2 or 4.5 displacement. The 4.2 and 4.5 have the same stroke and therefore same crank throw, but the journals are thicker and therefore stronger on the 4.5 (The 'early' 4.2 cranks were therefore smaller in diameter. As far as I can tell, the only physical difference between a 4.2 and 4.5 block is the 'deeper' machining for the bigger crank main bearing journals.

For example, my car has a 4.5 crank and a refurbished 4.2 block (done late 03 at TVR Factory) but it is definitely a 4.2 as I measured the bore at 88mm. The 4.5 liners are 91mm across.

Sorry old mate -but there are no liners used in the tvr AJP engines. They changed the engines to 4.5 capacity ONLY AFTER 2000.
Paul Forrest and Heath Briggs at TVR confirmed to me that the 4.2 I have is actually a 4.5 capacity engine. They just put the 4.2 induction system on it anjd called it a 4.2.

ajp8's were originally 4.5's as per tuscan challenge a lot of early cerb 4.2s were in fact 4.5s as i have found on several stripdowns i believe it was down to lack of the new 4.2 pistons/liners being available at the time. the crank journal size change came about when landrover changed theirs nothing to do with 4.2/4.5 as many tuscan challenge engines still run small journal cranks in billet steel form,it was only early cast road cranks that were weak later ones were ok.i think with late 4.2s it was a case of what engine parts were on the shelf due to most orders being for 4.5 cerberas

[longbow]

I'm sure there is a lot of strength to the 'whatever parts were available' argument. However, this is an interesting topic, and if I had Wilder's car, I would want to know for sure, so..............

Firstly, a dyno run might prove it, as anywhere north of 340lbft would strongly hint at 4.5 litres.

Secondly, if it is a 4.5 then it must use a 4.5 ECU chip then - and they were all labelled were they not? I know my chip has 4.2 written on it in black pen.

Oh, and Jon, the AJP is ALL about liners!! It uses wet liners that sit in the coolant within the block - you don't bore them out like you would on steel blocked engines. So what I'm saying is that the block casting for all AJP's was the same, except perhaps for the Tuscan race engines that use dry sump lubrication. If TVR only had the 4.5 pistons, then yes, I'm sure they would put them in, but I doubt they would do this for all engines, else the 4.2 would probably be quicker than the 4.5 (due to the 'better' 4.2 setup) which would have made TVR look a bit silly.

Edited by longbow on Thursday 16th August 22:20

Edited by longbow on Thursday 16th August 22:22

[jeremyc]

longbow said:

Secondly, if it is a 4.5 then it must use a 4.5 ECU chip then - and they were all labelled were they not? I know my chip has 4.2 written on it in black pen.

Buys black pen.

Offers 4.2 to 4.5 upgrade service.

Only £500!

[Wilder]

The business of stating no liners in my car came from the guys who built it. They said that the 4.5 in mine was straight 4.5 with no liners fitted to reduce it to 4.2 capacity.
I take it as TVR engineers,that they know whats what, and we all know TVR has some quirky ways.
Paul & Heath service my cars, and Pauls had a good look at it several times.
Im a mechanical ignoramus, but they do know their stuff.

[RetroWheels]

Wilder said:

touching cloth said:

But maybe what they really mean is that the later ones were in fact displacing the same as a 4.5, i.e really are 4.5 complete bottom ends, just with the 4.2 induction - not unbelievable as would have been a bit easier for them to work with just one standard set of sizes as the order numbers sloped off. Looking at Wilder's times from FT his is pretty much a match for yours, not conclusive either way because we know yours is a 4.2, but he either has a factory 4.2 aquitting itself very admirably or a 4.5 displacement giving him an extra hand. Be interesting to see one of these on the rollers and see the torque figures as that would be a good indicator.

Thats exactly what Heath / Paul and also Dave at Automedon told me, so its likely to be true.
In TVR tradition, they didnt want to continue the last years of Cerbera production buying two different engines, so to save money they bought the bigger one only, and fitted it to both models -problem sorted !

This is what i was told by a senior ex TVR engineer.
4.5 bottom end with 4.2 induction.
Reputed to be a very sweet combination.

Edited by RetroWheels on Thursday 16th August 22:31

Edited by RetroWheels on Thursday 16th August 22:36

[longbow]

Trust me Jon, I've rebuilt my own engine - I've had it to pieces and it 100% absolutely definitely uses wet liners. I've also seen pictures of the 4.5 block, as I have the TVR AJP8 rebuild manual and know the difference in size and shape between the 4.2 and 4.5 liners. If you look at my rebuild pics on webshots and look at the block, you can see the liners clearly.

The 4.2 and 4.5 liners are different - you don't modify one to make the other.