Guess about BHP and Torque

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moggiegeek
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Guess about BHP and Torque

Postby moggiegeek » Thu Feb 14, 2019 7:19 pm

Hi, I'm having a clutch built up by Larkspeed ( gulp). They're asking what HP and Torque my engine might produce.
It's a 1275 marina engine, 12G940 head, HIF44, K and Nair filter, Maniflow inlet and exhaust manifolds - straight through exhaust.
It will have Kent 600 cam, duplex, Vernier adjustment, electronic ignition. New dizzy etc. It's a good engine, well running, good compression etc.
Larkspeed have asked re HP and Torque I might be expecting to build up the right clutch.
In addition I wonder what needle to start off with?

oliver90owner
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Re: Guess about BHP and Torque

Postby oliver90owner » Thu Feb 14, 2019 11:03 pm

Torque and maximum operating speed would, I think, be better design parameters. Cluthes are really rated on torque, not power.

panky
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Re: Guess about BHP and Torque

Postby panky » Thu Feb 14, 2019 11:03 pm

You can get a good idea by down loading WinSU and entering your engine details. It will give a calculated list of what your engine could be capable of, not sure how accurate but better than a guess. Pay the registration fee (£10) and it will also give you suggested needles to try.
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philthehill
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Re: Guess about BHP and Torque

Postby philthehill » Thu Feb 14, 2019 11:05 pm

Here in a summery:-

The standard 1275cc Morris Marina/Ital (which is fitted with a 940 head and 1.5" SU carb as standard) puts out 60bhp and 94N-m @ 2450rpm.

With the modifications specified above I would guesstimate the power to be 75 - 80 bhp and 110N-m @ 2800rpm.

I would request a clutch able to cope with 90 bhp and 120N-m at 3000rpm.

Your modifications have upped the rev range but have not seriously increased the available torque.

Whilst these figures are only a guestimate of engine output they will put you on the right side of the equation.

Larkspeed should be able to suggest and supply a suitable starter needle against the information supplied above - but only on a engine dyno-meter or rolling road can the maximum power output of the engine and correct carb needle be fully determined.

Phil


IslipMinor
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Re: Guess about BHP and Torque

Postby IslipMinor » Fri Feb 15, 2019 10:21 am

Making lots of assumptions, and using as a base spec:

Small valve 12G 940 head, NOT flowed
Compression ratio not known, so assume ~9.0:1
Kent 600 cam is similar to Kent 276 (Win SU does not have Kent 600)
Inlet manifold NOT flowed
Twin box exhaust system - straight-through Maniflow or similar

Using Win SU with the above spec gives a similar projected power output of 80 bhp @ 6000 rpm, but a slightly higher torque of 85 lbf. ft. (119 Nm) @ 3000 rpm.

I suppose the question is if the engine builder fitted a Kent 600 cam, which is very similar to the 276, it is not the obvious choice for a standard(ish) engine spec, so what else may have been done?

The Kent 600 cam is good for 100+ bhp, so if the engine has been modified, such as bored more than standard, flowed head, bigger valves, higher CR, flowed inlet manifold, high ratio rockers, etc., Win SU projects that both power and torque could increase anywhere up to 100+ bhp and 105+ lbf. ft. (147 Nm) torque, which are borne out in actual rolling road results.

Do you have any more details about the engine spec?

As far as a suitable needle for the HIF44, a BDL often seems to be a common starting point, but needs a rolling road session to make sure that engine and carb are set up properly.

On our 1380 engine, we have a standard Midget 1275 diaphragm pressure plate, and an AP Racing 6.5" hybrid driven plate to suit the 1275 pressure plate and Toyota T50 gearbox splines. It handles the power very well, including track days, but we do not do over-enthusiastic starts as a norm. If we did, I am sure that the clutch would object quite violently!
Richard



moggiegeek
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Re: Guess about BHP and Torque

Postby moggiegeek » Fri Feb 15, 2019 11:10 am

Many thanks for this. It also gives a really good idea about areas of development but I'll see what this combination turns out to be like. At this point its still just sourcing the components. I'll pass on what Larkspeed say.

IslipMinor
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Re: Guess about BHP and Torque

Postby IslipMinor » Fri Feb 15, 2019 4:20 pm

If you haven't already got the 600 cam, I would suggest something slightly tamer, unless the head is well modified, flowed and has the bigger inlet valves. The Kent spec for the 600 suggests that it is less tractable than other suppliers', and Kent's own, 276 cams, and more like a 286! Anything with a '276' type timing, or longer, is slightly peaky, lumpy idle, and needs 3500/4000+ rpm to work really well, even in a 1275 engine.

There are some common 'milder road' choices:

Kent MD246 - high lift, fairly mild timing (252°). Not sure if the Swift came first and Kent following, or the other way round?
Kent MD266 - 260° In/270° Ex timing. This was the first cam in our 1380, and produced exactly 100 bhp @5700rpm on Aldon's rolling road, with >100 lbf. ft. torque all the way from 2500 to 5200rpm. Very tractable, and an excellent road cam.
Swift SW5-07 - mild timing (242°) with lots of valve lift. No first hand experience, but have heard good things said about it for the road.
Richard



moggiegeek
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Re: Guess about BHP and Torque

Postby moggiegeek » Sat Feb 16, 2019 8:59 pm

Hi, thanks for the figures and advice. Haven't bought the cam and on basis of what people are saying the Kent 266 seems a good choice. Given that I'm building a warmed up 1275 and have to be economical financially what additional mod might I want to do that would pay dividends?
Would it be work of 12g940 head and if so what work or something else on the proposed spec above?

philthehill
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Re: Guess about BHP and Torque

Postby philthehill » Sun Feb 17, 2019 7:46 am

I would recommend that you obtain Vizards book Tuning The 'A' Series Engine - it has everything that you will need to know.

https://www.ebay.co.uk/itm/Tuning-The-A ... :rk:1:pf:0


ndevans
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Re: Guess about BHP and Torque

Postby ndevans » Sun Feb 17, 2019 8:25 am

So what would a 1275 big valve head, HIF44, Maniflow exhaust with standard can be good for? 80+bhp?

Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Guess about BHP and Torque

Postby philthehill » Sun Feb 17, 2019 10:00 am

Empty pockets :wink:


IslipMinor
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Re: Guess about BHP and Torque

Postby IslipMinor » Sun Feb 17, 2019 10:10 am

Empty pockets
True, but enjoyable!

A standard cam would completely strangle the engine spec described - something like a 266 would be required, and with a properly flowed head I would think ~90bhp would be likely.
Richard



ndevans
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Re: Guess about BHP and Torque

Postby ndevans » Sun Feb 17, 2019 10:25 am

It goes well with a HIF38, but lacks high rev power. Stacks of torque lower down though, and climbing Haldon Hill on the A38 went from 50mph at best at the summit to easily sustaining 60.
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Guess about BHP and Torque

Postby philthehill » Sun Feb 17, 2019 12:35 pm

It is always a problem trying to balance the revs and the torque.

Unfortunately revs does not always equate to torque.

My own 1380cc in original spec from Manx Racing with a Kent Cams STR930M camshaft would easily rev to 10,000 plus rpm but there was nothing below 5000 rpm.

I replaced the above camshaft with a BMC special Tuning 649 and now I have torque but the engine is not so free revving above 7500 rpm.

I have a new Kent camshaft MD296SP X/D Blank to try and meet halfway between the two cams above.

As I said above you cannot always have it both ways.

Phil


ndevans
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Re: Guess about BHP and Torque

Postby ndevans » Sun Feb 17, 2019 6:32 pm

IslipMinor wrote:
Sun Feb 17, 2019 10:10 am
Empty pockets
True, but enjoyable!

A standard cam would completely strangle the engine spec described - something like a 266 would be required, and with a properly flowed head I would think ~90bhp would be likely.
Ok, thanks. I may fit a 266 at some point, but for now I'll stick with the standard cam.

I plan on putting the HIF44 on when I get the engine back from being rebored. It's got a big valve head & Maniflow exhaust, but I am using the pancake filter off a Mini-I don't want too much induction noise. I don't race, it's just a road car. The 1098 clutch and box are still fitted, along with the 4.22:1 diff, although I have a 3.9 to go on. I already have hardened half shafts.

The standard clutch & gearbox should be ok as long as it isn't abused, as I understand it.

cheers N
cheers N
'69 Traveller, 1275, discs.

dalebrignall
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Re: Guess about BHP and Torque

Postby dalebrignall » Mon Jun 17, 2019 4:29 pm

just been looking at this thread can anyone give me a rough idea on what bhp my engine might produce its 1098 block with 1275 head hif 38 carb ramair air filter mainflow manifold and exhaust many thanks dale .
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