4.0 V 4.0HC....difference? worth it?

[theironduke]

As above really, i know the HC is more powerful but how much of a difference is it?

I've got two cars shortlisted, both the same money really, one is a HC and would be a couple of hundred quid more, all things being equal it it worth it?

[4Lmike]

http://www.chimaerapages.com/chimaera.php Half way down the page you will see the answer.

[darkcat]

Well having not driven a "normal" 400, i cant comment. but my HC is better.

Im considering selling, if your shopping....

[theironduke]

darkcat said:

Well having not driven a "normal" 400, i cant comment. but my HC is better.

Im considering selling, if your shopping....

I think your car will be out of my budget chap. Feel free to be PM though.

[Hades42]

On the same note is there a 4.3 none HC? I noticed on that like that it said all 5.0 were HC but only listed a 4.3.

>Sorry that really doesn't read right but I can't think of a better way to write it. Ihope you understand what I'm asking.

[Chimpafrolic]

Hades42 said:

On the same note is there a 4.3 none HC? I noticed on that like that it said all 5.0 were HC but only listed a 4.3.

>Sorry that really doesn't read right but I can't think of a better way to write it. Ihope you understand what I'm asking.

Its really quite simple, HC just indicates "High Lift Cam".

All the 5.0 litre cars have this high lift cam as standard so they are all HC spec.

Back in the day, if you chose a 4.0 litre car but wanted a bit more performance you could tick the HC box on your order.

The best way to describe it is, for an extra £1000.00 you got the high lift cam and a few other tweaks to get the best from the cam.

The change in valve timing the HC cam delivers necessitates the figment of special pistons with valve reliefs cut in the crowns.

This avoids the otherwise highly likely situation of the valves meeting the piston at high RPMs with obvious dramatic consequences.

To get the best from the high lift cam a vernier adjustable cam sprocket was fitted so the valve timing could be precisely adjusted, a stronger duplex timing chain was also used.

Because of the characteristics of the cam the HC cars were expected to be taken to higher revs, so to alleviate valve bounce, double valve springs were fitted.

The heads certainly needed additional machining to accept these double valve springs but its debatable if the HC cars ever received any extra porting work.

Finally the fuelling was altered to match the HC specification by loading a different map on the ECU chip, an HC chip will be clearly marked as such.

All this sounds like the 4.0HC should be a real flyer, but the truth is there are lots of other variables involved.

The lack of consistency in TVR RV8 power figures is well documented.

So lets say you decided to save the £1000.00 and went for a standard 4.0 litre car, you may just have got lucky and received a really nicely built standard 4.0 litre engine that made almost as much power as an average HC spec car.

The other thing to consider here is that these days our cars are getting on a bit.

A standard 4.0 litre car with a healthy cam in rude health will certainly produce a lot more power than a poorly maintained 4.0HC with a worn cam.

So the trick is to drive a few cars and compare them, I wouldn't get too hung up on the whole HC or standard 4.0 litre thing.

However you could argue that an HC spec car does represent a much better starting point if you are looking to tune the car further.

Edited by Chimpafrolic on Thursday 3rd February 08:22

[JR]

Chimpafrolic said:

Hades42 said:

On the same note is there a 4.3 none HC? I noticed on that like that it said all 5.0 were HC but only listed a 4.3.

>Sorry that really doesn't read right but I can't think of a better way to write it. Ihope you understand what I'm asking.

Its really quite simple, HC just indicates "High Lift Cam".

All the 5.0 litre cars have this high lift cam as standard so they are all HC spec ... I wouldn't get too hung up on the whole HC or standard 4.0 litre thing.

Yes, the whole HC thing is a bit of a footnote really. TVR offered the 4.0 and the 4.3. To try to ratinalise production they only ever really offered two sizes of an engine so when they introduced the 5.0 they dropped the 4.3. This left a big gap in bhp from 240 to 340, the 4.3 was 280, so the 4.0HC was introduced at 275. As chimp says there are other elements inc higher cam wear due to the double springs. The 5.0 were all HC and ported etc. Why High Lift Cam is HC and not HLC no-one knows ... or is there a story there? Had they run out of 'L's?

[Ribol]

I

Would

Go

Entirely

On

The

Condition

Of

The

Cars

And

Not

Worry

Too

Much

About

The

Extra

Letters

By

Now

Very

Few

Are

As

They

Left

The

Factory

Anyway

HTH

[spend]

To answer your question ALL 430's & 500's are built for high lift cams (pocketed pistons, double valve springs, valve guides machined for lift...), not all 400's & 450's have these features. Outside of the 400's (which never had them) are the availability of BV heads, again only fitted 100% on 500's although not rare on 430's & 450's, yet it seems the 45mm trumpet base and enlarged inlet manifold are very specifically limited to the 500?

Mainly 400 owners will keep telling you that they are good enough, but many buyers soon seem to be asking for more shortly into their ownership.... If you are asking about power already you are probably better getting a developed car with dyno sheet provenance right from the start - it will save you shed loads of money in the long run

[Hades42]

Thanks Chimpafrolic, JR and Spend, just the answers I was looking for and very well written.

[spend]

Chimpafrolic said:

To get the best from the high lift cam a vernier adjustable cam sprocket was fitted so the valve timing could be precisely adjusted

FYI thats not entirely true BTW, there have been enough examples discovered of 4.0HC and basic 430's with basic timing gear to suggest they weren't anomalies.

[K4TRV]

spend said:

Snippity......To answer your question ALL 430's & 500's are built for high lift cams (pocketed pistons, double valve springs, valve guides machined for lift...), not all 400's & 450's have these features. Outside of the 400's (which never had them) are................Snip

Pedant at work again................Recent cam change on my previously unmodified early (Apr 93) 400 showed it has Double Valve Springs (No indication of HC on documents/ECU etc and heads not removed to view pistons etc).

As has been explained many times, go drive and "see" how each car feels.

I've had my 400 for 8+ years, TVR Speed Championship participant and a trophy winner with a good std (mechanically) 400 who's times are not very far away from the 450/500s. It's all in the eye-of-the-beholder!!

HTH

Trev

[Ribol]

K4TRV said:

Recent cam change on my previously unmodified early (Apr 93) 400 showed it has Double Valve Springs (No indication of HC on documents/ECU etc and heads not removed to view pistons etc).

Dom would have the definitive answer to this one, they still have records of engine builds going back to the early days. The only thing that isn't open to debate is that if a valve lifts high enough it will hit a flat piston if it is close enough

The down side of forums such as these is that if readers read the same wrong "facts" time and time again and people who actually know better are not around to correct them they assume what is posted is correct

[spend]

K4TRV said:

spend said:

Snippity......To answer your question ALL 430's & 500's are built for high lift cams (pocketed pistons, double valve springs, valve guides machined for lift...), not all 400's & 450's have these features. Outside of the 400's (which never had them) are................Snip

Pedant at work again................Recent cam change on my previously unmodified early (Apr 93) 400 showed it has Double Valve Springs (No indication of HC on documents/ECU etc and heads not removed to view pistons etc).

As has been explained many times, go drive and "see" how each car feels.

I've had my 400 for 8+ years, TVR Speed Championship participant and a trophy winner with a good std (mechanically) 400 who's times are not very far away from the 450/500s. It's all in the eye-of-the-beholder!!

HTH

Trev

Pretty bad quoting chap, I may not have written it well enough, but the highlighted comment was referring to BV heads, if that is what you are moaning about? The rest is pretty much a you may/may not have anything in a particular build as original never mind if it's been up/downgraded at servicing...

[drak ula]

that's an interesting thread. i had assumed the HC stood for high compression! so from what you guys have said above, chimpafrolic, jr and spend, the HC is more like the earlier nck 390/400 se engine in the wedge, double valve springs, pocketed pistons etc possibly ported (the 390se is, 400se seems not to be) high lift cam, but what of compression?
can any of you tell me what the compression is of the 400 and 400hc. the compression of the 390se wedge is 10.5:1
also what about ignition timing? is that set the same for 400 and 400hc? can you tell me what you guys set your ignitions to at idle and 'all in'? do they have different advance curves in the lucas dizzies? cheers

[Brithunter]

Thank you for this thread as this has been most useful and enlightening. I too thought the HC was for High Compression .............. Now I know better and just a little more about the TVR's.

[ianwayne]

This thread is from 2011, and as long ago as 2004, it was explained on here that HC means high lift cam:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Also, that all 500s are HC due to the camshaft and some buyers have been 'persuaded' that they have a special 500 it being an 'HC' one:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[trev4]

If you have a car with 70,000 on the clock you will be due a new cam which is the road I have just been down, so I would see the HC as an advantage as you could go for a sportier cam with the pocketed pistons.

[Skyedriver]

I had an HC as my first Chimaera, current one is an non HC
Both previous owners would agree with me that mine is just a well put together engine and a real flyer

[drak ula]

am more confused than ever now. surely whether hc means high compression or high (lift) cam , it should not be a matter of opinion or anecdote, what is the compression ratio of a 400 and what is the compression ratio of a 400hc? are they the same? if so i may be correct that hc means high cam (bizarrely), and the compression ratio is not a matter of opinion either, it is a measurable quantity. they are the same or they are different. fact. i would like to know what the compression ratio if for each. also if there are other differences as stated above, to cam timing, porting, cam lift, chip, timing chain, double valve springs, pocketed pistons etc. this is either fact or not and an 'ordinary 400 and hc with those real tuning mods, in similar condition (not one 400 in lovely condition and one 400hc in knackered condition) should have real measurable performance differences or what is the point of tuning? can we not get into 'mine is bigger than yours' argument or my dad is harder than your dad. just fact, what are the differences in spec and in performance. and yes i know there is some variation between all tvrs, and there is an issue with whatever was available on the day, but there must also be some 'norm' whereby the majority of 400s were x and the majority of 400hcs were y, and maybe at some year z, 400s became the same as 400hcs? yes or no?

Edited by drak ula on Friday 20th January 20:27