Extractor Manifolds

[JohnC]

I'm hoping for some further advice on what my next step should be in getting the best out of my car. In particular, whether to ditch the (Triumphtune?) 6:2 manifold in favour of the original cast iron one. Perhaps a Racetorations 6:2 or a Phoenix 6:3:1 is somewhere in the car's future, but for now it's the choices mentioned.

 

It struck me when reading Andy Thompson's reply in this post that my car may be suffering exactly the symptoms he describes:

The system I posted a photo of is an old Mike Randall system (Mike the Pipe) which was effectively a race system (hence slip joints) and made back in the eighties when Gareth Thomas and co. were spouting the virtues of the configuration whilst the mainstream suppliers (Moss/ Triumphtune) all sold versions of what was originally the SAH 6-2-1.

 

John C.. if your 6-2-1 has the collector into 1 then back into twin it will be giving better top end power than a standard manifold thanks to a less restricted exhaust port but unfortunately the interference issue in the midrange doesn't help torque.. this issue gets worse as the cam duration increases so modified engines can really suffer in the 3000 -4500 band..

 

The works had a lot of problems particularly tuning the rally 2000's because they stuck with a cast iron 6-2-2 set up and found they lost a lot of torque with long duration cams... if you study some early SAH cam profiles they are all lift and bugger all duration....if only they knew.... The 6-3-1 manifold really helps torque with a long duration cam

 

I helped build the engine in Jimmy Elliotts (CSCC) Mk1 2.5 PI before I knew some of these secrets. It has a 357 SAH cam and the 6-2-1 and the hole of torque feels like "turbo lag" until it "comes on cam" at about 4300 revs

 

This surge of torque and hence steep rise in BHP at these revs make you think it has a really wild cam but infact running 6-3-1 manifold in an otherwise similar spec car gives a lovely smooth progressive increase in power... the idle is still a little lumpy but you have no real gaps in the torque curve..It can actually 'feel' slower but is in fact far more flexible and suited to the torque characteristics of the long stroke 2.5

It never ceases to amaze me what depth of experience is in our forum! Anyway, I bought the manifold from Triumphtune in about 1989, so that fits with Andy's description. Just to clarify, it's a 6:2 with the first collectors roughly at the level of the starter motor. There are then twin pipes curving down and back under the car, ending beside the bellhousing. At this point they enter a 'Y' piece connecting to a 2.5" single system. The cam is (I gather) fairly hot with inlet valve opening at 43 and closing at 79; exhaust 75/40. Don't ask how I ended up with this...

 

Attached (hopefully) is a pic of some torque & power curves from my car. The blue one is the latest, and as you can see this has a steep increase in torque at 4000-4300 rpm.

 

So my question to Andy (and anyone else who has had experience playing with these alternatives):

Is the mid-range 'hole' likely to be a symptom of the hot cam plus TT 6:2 manifold? Am I likely to improve or worsen the situation by going back to the cast iron manifold?

 

A second question - is the torque peak at 2500rpm-ish part of the same story? Or is something else happening here?

 

Thanks

John

[Guest andythompson]

John,

 

Thanks for showing that graph, I think it shows fairly conclusively that the engine is struggling work efficiently from about 2700 to 4200... the fact that the mixture is rich here too indicates that the combustion process is probably fairly incomplete..

 

I have not ventured to far into the science of why a 6-2-1 doesn't work well in this range but I believe it is due to exhaust pulses mucking up adjacent ports trying to "exhaust" with flow reversion... in effect the extractor does the exact opposite of what it is meant to... hence standard is better in this part of the rev band.... over 4300 revs it starts to work better or at least cancel out negative effects... probably due to better initial shape of the exhaust after the port.. a cast iron failing (which has almost a 90 degree turn)

 

The decent torque at 2500 revs is probably due to the manifold design being almost irrelevant at such low revs... the 2.5 is inherently torquey low down due to its long stroke. The factory 2.5 PI sedan was quoted with a max of 153lb/ft @ 2000 revs. Now this was not a din figure but the torque was definitely excellent at the bottom end with only a single exit cast iron manifold.

 

I guess in theory you could set up the MU to give a better mixture in this band but due to the limitations of the Lucas unit you will possibly lose top end power

 

I have not seen a power/torque curve of the engine that I built which is obviously similar to your but the "seat of the pants" feeling match your more quantitive measurements perfectly.

 

Really I should go and get my engine dynoed ... I will see if I can get it done in the next month or so... it would be really interesting to compare curves.. I haven't done so so far because the plugs indicate that full load is OK (maybe slightly rich ie safe) and the power and economy are fine (about 25-27mpg on a run and about 155-160rwhp calculated from several 1/4 mile times )

 

I think that your best option is probably to stick with what you have as it is fairly well set up (unless you really like changing manifolds for comparison purposes) . I would think that the standard manifold would give better mid range torque (factory max torque is quoted a 3500revs) at the expense of a bit of top end "zing".

 

The real difference would be to fit a good 6-3-1... maybe a few graphs from such specced engines would help you part with the necessary cash

Edited May 28, 2006 by andythompson

[Andy Moltu]

Some of it can be put down to the limitations of the Lucas PI system which, with tuned cars tends to overfuel in the mid range.

Not all 6:2:1 systems are the same although the alternate pulse 6:3:1 probably outdo them although the performance of the "bunch of bananas" manifolds was pretty impressive.

I doubt that reverting to your cast iron original manifold would be a forward step.

[john.r.davies]

John, All,

I have what is basicly a TR6 engine in my Vitesse.

Raised compression (10.5), ported, Lucas Pi.

And a TT 6-3-1 exhaust manifold.

 

Here's the rolling road report.

I've adjusted the vertical and horizontal scales so they match those in JohnC's

 

Apart from a small dip just above, the power curve is almost flat from 2000rpm.

IMHO, an improvement on JohnC's, though a comparision between two engines will not have the power (!) of one tested with both systems.

 

John

Edited May 28, 2006 by john.r.davies

[JohnC]

Thanks for your replies here, and for Alec's in the other "which is best" thread:

Andy is, in my view, quite right to suggest that the old 6-2-1 can give improved top-end power BUT at the expense of midrange torque. That's what it was intended to do. Which may or may not be what you want !

 

Certainly the midrange performance was lacking compared to the top-end, but then you couldn't have the cake AND the halfpenny ! Since those days, knowledge and technology has moved on. Nevertheless, if a standard manifold improves your situation, either there was something drastically wrong with the comparative testing of 25-30 years ago, or perhaps fuel formulation has changed even more drastically than we've realised. In either case, I'd be very surprised, and if I was looking for top-end grunt I'd be sticking with the manifold I'd got - and playing with tweaking other elements.

All this makes sense and is consistent with what I'm experiencing. Since the last dyno test, I've backed off the max fuel setting a little, and I'm now getting an AFR of ~13.5:1 at 5000rpm, estimated from the EGO sensor I've fitted. Even so, I still see a very rich mixture (~11:1) between 2500 and 4000rpm. I have also fitted a Pertronix contactless ignition. Compared with the way the car used to drive, it goes like the proverbial bat. Happy with that

 

Still, I don't race or sprint my car, so where I most need grunt is in the mid range, not at the top end. I have no intention either of revving the engine above 5500rpm. All you gurus seem to agree that the TT manifold I have is a compromise at best in the mid range. I hear what you say Alec, and I'm sure you're right that I'll lose top end power by going back to the cast iron manifold. Even so, I'm now sorely tempted to try swapping back, just to see what happens. If I do, I'll do before & after dyno tests and I'll report back here.

 

The saga continues...

John

 

PS Andy T:

The real difference would be to fit a good 6-3-1... maybe a few graphs from such specced engines would help you part with the necessary cash

I was afraid you might say that

[Roger H]

John - I would seriously look at putting back the original cast-iron manifold and down pipes.

 

There appears to be a few to many unknowns in your setup and starting with a 'known' exhaust system is a solid start to sorting things out. I don't think the original was really that bad, it really can only be improved on if everything else is up to, or better than original specs.

 

I suggest getting the mixture, advance curve and electronics right - then think about the manifold. My guess is a maximum of 5% increase in power and torque is what should be hoped for - any more and you may be dissappointed. The original manifold has a pretty flat torque curve (albeit tapering off as revs increase) and was aimed at making the car driveable around town. A good interference type manifold should bump the torque curve up from the factory line between 3500 and 5000 revs and increase the 'pulling' power. It will improve torque more than overall power.

 

I would also be a little careful of tuning using a A/F readout. Unburnt oxygen is present with many 'fast' cams which stuff up the readings. Additional fuel is only really needed if you have increased cylinder volume (bored out or smaller head mazda pistons). I seem to remember that you have access to a calibration bench (and guru!). My advice would be to get the MU setup by him to factory specs and have another MU 'castle' set a little richer - THAT is the on that you play with. The maximum fuel setting should not change and you can always revert to the factory set 'castle'. A rich mixture only costs you money in petrol - if you are only above 5000rpm for a few seconds at a time, a 'leaned off' mix should not be an issue.

 

I'd certainly be interested in any follow up in due course....

[Andy Moltu]

Top end fueling can be an issue - many hot cams do need more fuel than delivered by the standard metering unit can deliver. Simply screwing the A1 ring in & out on the castle at the top of the metering unit will richen or weaken the mixture thoughout the throttle/rev range within the limitations of the maximum fuel settings . In terms of fuel delivered it will not increase the maximum delivered by the metering unit at full throttle - to do this you'll need to increase the maximum fuel settings. This can be crudely achieved by pulling the choke out fractionally (The choke on the PI cars isn't a choke in the way that we have on a carbed car) it moves a cam which allows the maximum fuel aparatus to move away from its normal position)

 

You can see more about this on Egil Kvalberg's Lucas PI pages.

 

A ball park figure for the gap in the max fuel settings for a hot cam engine with head & exhaust mods is around 63 thou" - you do this with the little screw (the one with a locknut) under the choke assembly. After that you'll then need (ideally) a rolling road session to tinker with the A1 - A3 rings to optimise fueling.

 

However providing that you accurately note down the existing max fuel settings before you increase them and mark the exact positions of the A rings with tipex or paint you should be able to revert to your existing set-up if you find it worse.

Edited May 30, 2006 by andymoltu

[JohnC]

Roger,

Thanks for your suggestions. Your point about 'too many unknowns' is the main reason behind my thoughts of swapping back. On the subject of AFR, the situation was a little more complex than I've described so far. Just to clarify:

1. Did dyno test in 2005. Very lean AFR at 5000 rpm, plus dramatic drop in torque from about 3500 rpm (see chart). I wonder if this was 'real' or an artefact of the hot cam as per your observation?

2. Retimed cam (it was very late ). Test drive (subjective) showed torque increasing after 4000-ish rpm, quickly followed by misfire as the revs continued to rise. Uninformed (i.e., my) diagnosis of lean mixture.

3. Increased max fuel by ~4cc/1000 injections. Test drive showed misfire had gone. Joy! Decreased fuel back to original. Misfire back. Vindication! Increased fuel again.

4. Fitted 2.5" single system from bellhousing back to tailpipe. Noise changed, wallet lighter.

5. Dyno test - Feb 2006 line on chart above. Indicated rich mixture at full load throughout the rev range, but particularly bad below 4000 rpm. OTOH, very lean mixture on over-run, including nasty crackling/popping.

6. Intermittent and minor misfire under load. Suspected points. Decided to fit Pertronix contactless breaker setup (always wanted to). Misfire gone.

7. Fitted EGO sensor upstream of silencer; used it to monitor small leaner adjustment of max fuel to an EGO voltage of 810mA = 13.5-ish AFR.

 

I have noticed that the mixture appears to lean out dramatically at near-idle rpm. I've ascribed this to large cam overlap allowing intake mixture to dilute the exhaust with unburnt intake charge. Is that what you're describing? Or is there another effect at all rpm?

 

You're right, I do know a very helpful guru. Two in fact. I hope Justin and Peter aren't reading this, or they'd probably roll their eyes in despair - I think I'm their nightmare of a customer: Tinkers, and then spends ages on the phone asking advice! Thing is, I really like to know what makes the beast tick, so I enjoy the voyage of discovery. It just wouldn't be the same if I gave the car to somebody and they fixed it. Plus I probably couldn't afford it! Anyway, I want to get the setup as close as I can without touching the datum track or 'castle'. Max fuel is easy enough to do in a controlled way, but not the others. Once I'm satisfied, I'll take the car to Justin & Peter with a load of dyno data (full & part load AFR at various rpm), and put myself at their mercy.

 

I haven't considered your idea of swapping 'castles'. I do have two MUs, so I guess it's possible. I'll have to have a close look, as one is an early TR5 (I believe) MU with a PRV port on the top (my pressure gauge is plumbed in there); the other is the original CP-series unit. The springs are probably the same, although I know the MU (not CU) diaphragms are different. Still, before that point, it's important to get exhaust choice sorted, get the max fuel adjusted to suit, and set the datum track to get the idle close.

 

All good fun

 

Cheers,

John

[JohnC]

Hi Andy,

Sorry, you must have posted while I was replying to Roger. Thanks for the info on adjusting the MU. In fact the max fuel screw is how I increased the fuel by 4cc/1000 injections (to 47.5cc). From memory (don't have notes to hand) that was half a turn on the screw. I have since backed off half of that. Your 67 thou equates to 45.24cc/1000 injections. I'm now at 45.5...

 

One amendment I'd make to your notes is that I'd first make sure the datum track is set right before moving on to the A1-A3 adjustments. It is a bit iterative, but the A1 & A2 screws control where the kinks in the delivery curve occur (A3 is simply a minimum fuel stop), whereas the datum track controls the slope (in combination with the spring ratios, which are fixed unless you have a source of alternatives). Obviously the datum track and A1/A2 settings work in concert, hence the iteration. Anyway, if the datum track is set to give the same fuel delivery at idle vacuum as is required by the standard cam, with the A1-A3 unchanged from standard, then you'll be pretty close. A little tweaking on A1 & A2 and Bob's your proverbial.

 

That's my plan, anyway. But before I get the datum track adjusted, I need to settle on which manifold to use. I'm going to be in the UK in August - perhaps I should see if a Phoenix 6:3:1 would be cheaper there than here. Only problem is sneaking it back without it being detected by Marital Customs & Excise. The manifold I may be able to afford. The resultant clothes shopping probably not...

 

As always, many thanks for the advice.

Cheers,

John

Edited May 30, 2006 by JohnC

[john.r.davies]

JohnC,

 

Am I invisible?

I offer you a comparision with a TR6 engine with a 6-3-1

I copy my RR report for you, even manipulating it in PhotoDraw to equalize the scales, so you can compare

And you ignore it?

Go paddle your own canoe.

 

John

Edited May 30, 2006 by john.r.davies

[Guest Wyn]

JohnC,

 

Am I invisible?

I offer you a comparision with a TR6 engine with a 6-3-1

I copy my RR report for you, even manipulating it in PhotoDraw to equalize the scales, so you can compare

And you ignore it?

Go paddle your own canoe.

 

John

Based on recent postings, I never want to cross John!

 

Wyn

[Andy Moltu]

JohnC,

 

Am I invisible?

I offer you a comparision with a TR6 engine with a 6-3-1

I copy my RR report for you, even manipulating it in PhotoDraw to equalize the scales, so you can compare

And you ignore it?

Go paddle your own canoe.

 

John

 

The comparison is only valid if all other things are the same. The effect on a standard tune 6 may be wildly different to a tuned one. Really you need to compare manifolds on the same engine with identical fueling, timing etc.

[marvmul]

John C., may I ask what cam and cylinderhead is fitted? IMHO the hole in the midrange is a cam question in the first place (too long duration). The difference between the blue and red curves can be explained by the ignition advance curve : more advance in the blue curve. If the inlet valve is closing very late, a better extraction manifold won't help things a lot. Perhaps a camshaft with a somewhat shorter duration, and higher lift, and if possible better flowing inlet tract (airfilter, inlet ports...) will improve the midrange torque.

[JohnC]

JohnC,

 

Am I invisible?

I offer you a comparision with a TR6 engine with a 6-3-1

I copy my RR report for you, even manipulating it in PhotoDraw to equalize the scales, so you can compare

And you ignore it?

Go paddle your own canoe.

 

John

Sorry John,

I didn't reply to your post specifically because I don't honestly have a response. You have a 6:3:1 manifold, your engine is ported, and your CR raised. As I don't plan to do/get these for quite a while, I find it hard to make a comparison or draw any conclusions other than that you're getting more out of your engine than I am from mine.

 

I do appreciate the effort you went to. You may have missed my starting remark immediately after your post:

Thanks for your replies here, and for Alec's in the other "which is best" thread

Anyway, thanks again. If you're still willing to lend a paddle, it would be useful to know if you have any intermediate RR reports to show what impact each change had...

 

Gratefully,

John

 

PS Andy - Thanks for your post which I haven't read yet...

[Tom Fremont]

Exemplary, JohnC!

[john.r.davies]

JohnC,

Suitably mollified.

But a simple thanks in the first place would have sufficed.

 

I can't offer any further comparisions.

That was my first RR trip - thoroughly worth the money, IMHO, for the benefit it did bring, nevertheless.

 

May your paddles always be double ended.

 

John the D

[JohnC]

Hi marvmul,

You're really opening a can of worms here...

 

First the easy stuff. I think you misread my earlier posting - it was the camshaft timing that I advanced by 8deg between the red & blue dyno runs; ignition timing was unchanged. I had set the cam too late when I installed it during the rebuild

 

Now the wriggly stuff. The head is unmodified. My goal was simply to rebuilld a standard engine with the benefits of balancing the rotating/reciprocating bits and a slightly improved cam. What I asked for and was promised was a cam which gave slightly improved mid-range torque and top end, driven largely by modern (i.e., asymmetric) cam lobe profiles rather than wild overlap etc.. What I believe I got was this:

Some caveats:

1. The engine idles better than before the rebuild. Probably because the pistons no longer pump oil into the chambers with each stroke, but then I'd expect a wild cam like this to give a very lumpy idle.

2. I have not degreed the cam, so I have not personally verified the data

3. The cam sheet wasn't provided with the cam, only a few months later when I requested it. It's possible therefore that the cam shop got its records mixed up.

 

So now I'm trying to make a silk purse out of a sow's ear. I'm sure that eventually I shall get the cam reground again, get the head worked over, fit a 6:3:1 manifold, etc.. In the meantime I'm using the opportunity to learn as much as I can about what effect each bit has on the overall package. Right now I'm focusing on the manifold. And in particular, might swapping back to the cast iron manifold at least make the pig oink less loudly?

 

Incidentally, if I do have the cam on the sheet, let's just assume it was my fault for not getting a copy of the data sheet before the work was done, shall we?

 

Cheers,

John

[marvmul]

John, if the cam was timed too late and you advanced it by 8 degrees, one would expect that the midrange torque would improve most, wich is not the case. Changing the ignition timing has much influence on the torque : when advancing the ignition, it's at high rev's that torque can improve. If the ignition is already advanced a lot, further advance will have a bad influence on the mid range torque without improving the torque at high revs.

The blue curve seems typical for a hot cam (at least a sprint cam/290°) , maybe with too much advance.

More valve clearance will shorten the duration and the overlap a bit, don't know by how much degrees, but it can have some influence on the midrange torque (always assumed that the accellerator is fully to the floor).

[JohnC]

marvmul,

Thanks, that provides food for thought. I'll make sure that I err on the late side when setting up the ignition timing before the next dyno session. As you'll see from the charts, I did increase the valve clearances for exactly the reason you suggest. I may try increasing again to 18thou, but I really don't want to risk too much shock loading on the valve gear.

 

There are two things I found odd about the blue & red torque curves, considering the changes I had made:

1. Torque increased at high and low rpm, but not in the middle

2. The mid range torque has the same distinctive wiggle in both lines.

 

My working hypotheses are:

1. High torque rpm was choked in the early (red) test because of a very lean mixture. Increasing the max fuel fixed this. Not sure what effect the cam timing had here. Could have improved things, could have made them worse (if advanced too much).

2. Mid range torque is being limited by the manifold, as Andy explained early in this thread. Advancing the cam should have helped here, but didn't (at least not by much). The 'wiggle' occurring at exactly the same rpm is also characteristic of the kind of harmonics set up by tuned pipes (e.g. manifold).

3. Low range torque was dramatically improved by the cam being advanced 8 degrees

 

These are the reasons why I'm focusing on the manifold at present. As I said earlier, I also think I have too many unknowns with the current setup, so going 'back' a step may not be such a bad idea.

 

Oh, the joys of theoretical tuning

John

 

PS Dyno session booked for next weekend. The 'before I do anything else' session...

[JohnC]

In case anyone is interested, I've now completed my 'before & after' comparisons of the OE (Cast Iron) manifold and the Triumphtune TT1200 6:2 manifold which has been on my car for the past 15+ years. Basically, everybody is correct

1. The guys at the store (is Cox & Buckles still around in Kingston or thereabouts?) told me I'd get 5-10hp increase by swapping to the TT1200. That's true, although misses the point, which is:

2. All the gurus in the thread above told me the TT manifold would be better at the top end, but probably at the expense of mid-range torque. True. With bells on!

Here's a printout of the comparison:

 

So it looks like (of the two choices) the OE manifold is by far the best solution on my car as it's currently configured. It may be that a properly gas-flowed head would allow the engine to breathe better at high rpm, getting far more out of the TT1200. I may find out one day. A Phoenix-style 6:3:1 could well get more out of the cam I have. Again, I may find out one day. I am curious to find out what going back to the original cam will do, and I have a new cam to test just that. I don't know why the engine is running out of puff a bit early, but it may be a combination if mismatched cam/head/manifold/exhaust (!). Any ideas on that one? I'd also love to know why the torque fluctuates. All the torque curves I've seen are lovely smooth lines, not wiggly like mine. And the shape of the wiggle is replicated exactly between multiple runs.

 

I'm amazed at how well the car runs with the abomination of a cam it has, and I put it down to how flexible the PI system is. I've got it almost right, running an AFR of ~13:1 at full chat and 14:1 at cruising throttle and 2500rpm. The mixture does get too rich at mid-rpm and manifold vacuum between 2"Hg and idle (getting richer as the vacuum increases), so the datum track probably needs a little tweak, but overall I'm pretty happy. I got 28mg on a recent club run of ~200 miles including some pretty decent up & downy twisty bits, and I'm getting a bit better than 20mpg in stop-start short trips. I used to get 24 at best, and as poor as 15 on short trips.

 

Oddly, the car doesn't feel as fast with the OE manifold. I used to feel a surge when I first put my foot down, and then again when passing through the 4-4.5k rpm band. Now the second surge is gone. Of course that's because the torque is there from the beginning, but the smoother power delivery actually feels less exciting!

 

A few notes:

1. I've cropped the TT1200 graph (which is from the dyno run shown earlier in this thread) to exclude low rpm as it showed a torque spike which was an artefact of the way the mechanic operated the dyno in the earlier run.
   
2. My car isn't totally standard, so it's possible the TT1200 manifold would perform entirely differently on such a car. Differences from standard:
   • Wild cam: 43/79/75/40 with durations of 302/295, all taken at seat. Valve clearances are set to 0.016"/0.018" (I/E) to tame the cam a little. This improves torque by about 5% compared with the cam supplier's recommendation of 12/14.
     
   • Single 2.5" pipe exhaust (from 2:1 at end of standard downpipes or after TT1200 manifold, depending on which manifold was fitted)
     
   • Pertronix Ignitor contactless ignition
     
   • Balanced
     
   • Hardened valve seats, but head is otherwise standard
     

 

[*]FWIW, max torque & power at the wheels are now 128 lb.ft @2900rpm and 110bhp @5300rpm, which converts to around 158 lb.ft / 136bhp at the flywheel. Supposedly normalised for atmospheric stuff, but who knows. Important thing is that both tests were done on the same dyno, with the same operator.

[*]I found that I can set the static timing to 14degBTDC without pinking (I used a knock sensor attached to the engine). That's running 98 octane BP Ultimate here in Sydney. More advance gives no more power, and retarding a couple of degrees loses about 5bhp at the top end.

 

I reckon that getting & fitting a Phoenix 6:3:1 would cost me about the same as having the head gas flowed. Any thoughts on which would be the best alternative, if I only do one?

 

Cheers,

John

Edited August 30, 2007 by JohnC

[Tom Fremont]

Hi John,

 

Obviously it's a lot less work to swap out an exhaust manifold!

 

Since headwork is wildly variable maybe the exhaust system is a better bet if you must choose. I've bought (2) stage #@%&!! heads outright for 3-4 times what an entire exhaust system cost, but I got a well-matched system of valves, springs and precision machining/polishing to fit the cam selected in each case - a very delicate matter considering the frequent failures of shopping-cart attempts.

 

When cost is secondary to result some choose to entrust the entire engine plus fuel delivery/ exhaust system to a specialist. I've gotten away with farming out the short block to one supplier, the head/cam/followers/exhaust to another and took care of the fuel delivery myself. This has been plenty large an undertaking for me.

 

One UK specialist told me the other day that a customer in Houston, Texas decided to ship his entire TR3 over to him. I guess that represents the far end of the spectrum! Seems each of us finds his own little zone in the process

[JohnC]

Thanks Tom,

As you'll have gathered, cost is certainly an issue, so sadly the 'turn-key' solution is not one I can use. I thought I'd do the head or manifold when I pull off the head to swap back to the standard cam, so the amount of work is pretty much the same either way. I take your point about 'shopping cart' head improvements. I wonder if I'll have a better chance of a good result by sticking with the standard cam and manifold?

 

It seems a little strange - here I am pondering whether or not to 'improve' my car by returning to standard spec

 

Cheers,

John

[Tom Fremont]

Hi again John,

 

Since you're removing the head anyway I would urge having it done over by a well-qualified specialist prior to refitting, and spend your money there. Later you can add a performance manifold with comparatively little trouble.

 

Nothing wrong with the stock cam; just be sure you get a new one and use competition followers to be safe. With an improved head you should see an appreciable improvement over stock which you can augment with the manifold later. A single bore exhaust, too is recommended for optimum performance.

 

150 BHP ( actual ) is a fine amount for the displacement given the period. This can be made to last 100,000+ miles with today's available components