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1500 build for 100HP-reliable for street

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Patrick B Avatar
Patrick B patrick bennett
Gainesville, GA, USA   USA
1976 Triumph Spitfire 1500 "Gloria"
Think I'm going to locate me a good motor and start building it on the side.... This way I will stil enjoy driving (when I get to that point) the car. So for a 1500 I can start with any year and get the higher compression of the 76 model with flat top pistons alone? Just want to give myself a baseline starting point for this.

Thanks!

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bluecrab Avatar
bluecrab tom broring
Maryland, USA   USA
Patrick, picking up another project motor while you still drive the car is a good idea. All the 1500s have the same block and crank. Most of the later heads have EGR ports and most early do not. Assuming you do not need emmisions parts for your state, I would pick an earlier head without the ports. Also different years seem to have different head thickness to lower the compression for emissions. I do not know how to tell from numbers, but you will be milling the head anyway. You can also look for MG Midget 1500s which are the same engine as the Spit but I think have a different serial number prefix.

AJ6mod6 Avatar
AJ6mod6 Gareth T
Disabled Account, Antarctica   ATA
1989 Jaguar XJ40 "Animal2"
In reply to # 844853 by oldag98 This thread is for those who have built a reliable performance 1500.

Looking for about 100 streetable HP, but something that is not going to grenade the engine. How do I do this? What machining operations are required/recommended? What parts are the best for this, crank, rods, pistons, valves, cam, rockers?

So far I have a stock engine with LCB headers (TriumphTune- called LCB/Long Center Branch), dual HS4's with heat shield.
Any good engine builders with experience doing this?
No problem to do this.
You will get AT LEAST 100bhp doing this and loads of torque.

You need a properly flowed 1300 head from the limited large valve 21814x series, (see photos) I have modified the TKC1155 heads with the slightly smaller 35mm inlet valves too, but they are not quite so good.

As you can see, even my 1147cc 6 port head ports come up pretty darn good & run to 85bhp, despite it only having the tiny valves in the photo compared back to back with the 1500 valves.
Look how the original ports look compared with the flowed ones.
That is how I get 45% more flow out of them, and lots more power without having to rev the blazes out of them.

Additionally:-
you need a decent camshaft
(a Mk3 spitfire or a TR6 Pi profile will do fine).
keep your USA dished pistons.
(contrary to what people say here).

I could supply all those bits if you really want, but I don't usually ship to the USA any more, because people don't want to pay the transport.

It is essential to nitride the crankshaft (plasma nitride or tufftride will do).

You need to balance the crank with an original Unipart clutch, & use original Stanpart gaskets, or deck the block flat and get rid of the recesses to use a Mk3 Spitfire gasket.

This way you can get rid of any block distortion and fill in the factory guide hole next to number 4 cylinder, which often makes the cheap repro gaskets blow.
Buy a set of APT head fasteners, balance the conrods properly.

Fit a set of Vandervell or trimetal bearings (nothing else will do),and get someone to make you up a proper oil pump.

There is no such thing as a LCB for a Spitfire.
They don't have those wimpy A or B series MG heads from Abingdon.
They have proper heads with 8 ports.

The "LCB" for Abingdon MOWOG cars is because they have one deficient centre exhaust port that has to share the output of 2 cylinders.
A well done Triumph engine will easily outperform any MGB or A series motor.

For years I supplied exactly the spec you are asking for, to loads of people in France.
I have 3 more to deliver before christmas, one to Finland.

In the last 2 years I supplied one which must be the LAST brand new 1500 engine left in the world.
Exceptionally, this was not a complete short engine, but one made entirely from new parts.
We know this engine fitted in a road car is delivering 125bhp, totally reliably, and can run 6000rpm all day long.

You need a full width early type radiator, not the wimpy thing that originally came with the 1500.

Take a look at our Jaguar engine developments some day.
I'm more into 24 valve engines these days, but I still spend a lot of time flowing Triumph cast iron heads, despite the filthy work.

There is nothing as satisfying as showing how you can turn what other people term a "low powered or fragile" engine into a world beater, just by using a bit of applied brains, and buying your parts from the right places.

Lastly, ignore any daft comments about me here.
I only post this to help you, as I have plenty of work.

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208vkjet Avatar
208vkjet Walter Baroni
Skokie ILL, USA   USA
Thanks for the Pics. Where does one get F.I. TR-6 cam grind for a Spitfire?
I've looked at all the suppliers that I can find. Mk 3 Spit yes.
What are the specs for the F.I. cam?

AJ6mod6 Avatar
AJ6mod6 Gareth T
Disabled Account, Antarctica   ATA
1989 Jaguar XJ40 "Animal2"
I do them from time to time for the 1500, but I don't do the USA.

I'm sure if you ask around the UK, you'll find someone prepared to grind one for you.

The TR cam is 280 degrees, 35 - 65 timing, and has 0.360@lift.
So more lift and duration than the Spitfire 111, which was used in all the early 2.5pi saloons & the UK GT6 Mk2, so it's a bit more lumpy at idle, and a bit more powerful.

If you sort out the carbs/needles, put on a decent manifold & sort out the advance curve, it'll give you 90bhp, and a lot of torque low down.

Be aware the 1500 head doesn't have the largest valves (for what it's worth).
I'm flow testing a tweaked one* on Tuesday, to see if IN FACT you can get it do deliver more than the larger valve one, as well as the little 1147cc thing.

If you like I'll post the results of all 4 tweaked heads.

1/ 1147cc enlarged valve(from Mk1>Mk3) nice ported one with raised CR (had to lop off 3mm to get it up from 8.5:1)

2/ 1300 large valve (36.5mm) tweaked one (STD brand new valves back cut). Ported.
chopped off 1.6mm)

3/ 1300 largest valve one, 37.4mm was originally from Triumphtune, but needed masses more work. Ported properly. (Chopped off 4mm!)

4/ 1500 STD size valve head*, back cut (35mm). Ported properly etc.
(Chopped off 2mm.)

My bet is on the 1147cc head with the 32mm valves 1/ coming up better than 4/

208vkjet Avatar
208vkjet Walter Baroni
Skokie ILL, USA   USA
Thanks for the info. From my small corner of the universe it's predominatly 1500's
Also used in the last Midgets, so alot. 1300 mostly end up in SCCA/Midwest council etc.
I like to see actual photos of ported heads. Describing in words how to port a
head is kinda like describing how to create a marble statue!

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
GT is speccing a great engine above, which will live at high revs and will produce well in excess of 100HP- at a cost.
The original brief was for reliable, inexpensive, street engine, that would make 100 HP

A list of cam suppliers.

http://www.mintylamb.co.uk/?page=camcompare.htm

The specs are all there, and as GT said, armed with this info, you will be able to get a cam ground to whatever you want.
The TR profile has 10 deg more (35/65) than the mk3 spitfire (25/65) which is useful at the top end, but the idle and low speed will suffer a little, and may get annoying, if you spend much time in traffic.

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AJ6mod6 Avatar
AJ6mod6 Gareth T
Disabled Account, Antarctica   ATA
1989 Jaguar XJ40 "Animal2"
In reply to # 853703 by claytoncnc GT is speccing a great engine above, which will live at high revs and will produce well in excess of 100HP The TR profile has 10 deg more (35/65) than the mk3 spitfire (25/65) which is useful at the top end, but the idle and low speed will suffer a little, and may get annoying, if you spend much time in traffic.
Not at all.

For a start you will NOT get more than 100bhp from 2 SU carbs however hard you try.
(Reasons I won't go into)
The 1500 runs even better on this Pi cam than the 1300. (Because it's bigger)
Larger engines make warmer cams milder. (This is an established fact).

I have seen loads of these conversions about, as it became quite popular in the UK.
I have never seen one of these that had to be revved hard, and the power delivery was absolutely superb with no loss of low speed torque whatsoever.
This is also owing to the heavy flywheel, clutch & crank fitted on the 1500.

Of course the majority of people don't have any head work done, and this is the other limiting factor on the power output.
The original heads struggle to make even close to 100cfm at the inlet valve, which is only about 60-65cfm at 10", which translates to about 23bhp at the cylinder MAX. (93bhp)

I blueprinted one of these EU spec engines 2-3 years ago to see what you could get.
This had the UK spec head & pistons.

This is the torque curve.
As you can see it's pretty darn good, giving peak at 2700rpm.
As you can see we also got about 8bhp more over the book figure, by cleaning a few things up.

If you up the cam spec, it will give almost the same curves, as this engine had the original UK spec cast iron manifold, (just the torque curve will extend up another 500-800rpm at the top, giving you the extra 10-12bhp over the mild original cam).

That gives it much superior low down torque compared with a tubular 4-2-1 manifold, but most people don't realise how good that OEM system is.


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claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
That is a nice torque curve. I am assuming that is with the stock 18/58 cam.

I am pleased to hear the PI cam gives a good idle, as I have not tried this spec. My favourite 30/70 cam works well, and idle is acceptable for a sports car, running on SUs.
It is a couple of years since I last built an Spit engine, and I look forward to trying a PI cam on the dyno.


Can you explain why 1.5 in SUs cannot support 100HP?

My experience with other engines (Not Triumph) has been that each 1.5 SU can support 55/60 HP, with air filter/ ram tube.

My 100+ HP spit motors have been Webered 1300s.

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AJ6mod6 Avatar
AJ6mod6 Gareth T
Disabled Account, Antarctica   ATA
1989 Jaguar XJ40 "Animal2"
In reply to # 854005 by claytoncnc That is a nice torque curve. I am assuming that is with the stock 18/58 cam.

Can you explain why 1.5 in SUs cannot support 100HP?

My experience with other engines (Not Triumph) has been that each 1.5 SU can support 55/60 HP, with air filter/ ram tube.

SU carbs will never ever give you decent high rpm performance, despite claims to the contrary.
As the venturi opens wider and wider with the air flow, the droplet size goes absolutely HAYWIRE.
It's funny I constantly hear claims of high powers from SUs, but I have never ever seen one that runs above 5500-6000rpm (cos they can't!)
All you get is crap-filthy emissions, and the torque drops off through the floor.
Hence the limit of about 90-100bhp on a pair of SUs.

Those carbs may "theoretically" be able to run a certain airflow, but that's not everything, and on top of that, the pumping losses go up exponentially as soon as you try to get them to run any revs.
If you increase the damping factor you can make some improvements (ie, why the A series Mini is so incredibly sensitive to inlet manifold length and shape).

If you try to use any of the Triumph spitfire manifolds, you might be able to see right through them but the performance is just crap, because they are the wrong design.

The only decent designed SU manifolds for Triumph were the late TR6 "S" long branch carb manifold (once it's been modified properly), and the Dolomite 16V engine, because it has such a stupidly long inlet port in the first place.

oldag98 Avatar
oldag98 Jeff and Brittany Brackenridge
Choctaw, Choctaw, Oklahoma, USA   USA
1969 MG Midget MkIII
1975 MG Midget Conversion
1976 MG Midget 1500 "Yellow One"
1977 MG Midget 1500 "Dunkirk"    & more
For the 100+ HP engines, has anyone tried an intake gasket that has a mesh screen over the head port holes? This would be like the Torque Plus gaskets used in Ford and Chevy engines. The mesh helps to re-atomize the fuel as it enters the combustion chamber. This might cure the fuel atomization/drop size issue experienced with SU's at 3/4 piston lift to WOT.

britsnspits Avatar
britsnspits Michael Stoliker
Bethlehem, PA, USA   USA
1976 Triumph Spitfire 1500 "The Phoenix"
1978 Triumph Spitfire 1500 "Lucky"
*cough*Gimmick*cough*

spurs1canada Avatar
spurs1canada Silver Member Barry Hotspur
Winnipeg, Manitoba, Canada   CAN
1972 Triumph GT6 MkIII "Mellow Yellow"
1976 Triumph Spitfire 1500 "Li'l Red"
We only get 91 octane here so i assume when i rebuild the spare engine there is not much i should do?

AJ6mod6 Avatar
AJ6mod6 Gareth T
Disabled Account, Antarctica   ATA
1989 Jaguar XJ40 "Animal2"
In reply to # 859611 by spurs1canada We only get 91 octane here so i assume when i rebuild the spare engine there is not much i should do?

91 CKI is the equivalent of 95-96 RON (EU).

I have no difficulty making these kind of engines produce good power at 10.25-10.5:1 CR using this kind of of fuel quality with one of my modified heads.

The fact is, if you leave the original chamber shape it will pink at anything over 9.5:1.

I spent a lot of time investigating the various options modifying the swirl coefficient.
I have road engines now running as high as 11:1 with only traces of pinking under extreme conditions but using computer controlled & optimised advance curves.

(forget old fashioned springs and bob weights in worn out distributors)

POLLYMARKA Avatar
POLLYMARKA MARK ALLEN
San Marcos, TX, USA   USA
Are there any porting templates available for the 1500 heads?

Preshaped to use as guides in porting?

I have seen them for rotary engines.

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