948 Engine/5 speed box combos

[CLIPPERBLU]

I have a 4 door saloon with a really good 948 in it. I'm considering fitting a 12g 295 head plus better manifold and carburettor to improve the performance with a view to upgrading to a 5 speed box. Has anyone actually done anything similar to this and/or know if the 948( mildly tuned) will have enough guts to drive a 5 speed box or not?. My aim is less stressed cruising without fitting a bigger engine. All thoughts and advice gratefully accepted.

[Peetee]

A 948 with 12G295, water heated manifold, 1.5 carb and K&N is more than capable of pulling a higher gear. My 4 door would easily hold 70 on a hill (with throttle to spare) and would do 0-60 in 18 seconds on a standard 4.55 diff.

[CLIPPERBLU]

Many thanks for your response. I feel suitably encouraged to continue now. Happy New Year.

[bmcecosse]

Peetees car goes ok on a standard high ratio diff he says - but as soon as you load it up with a lower ratio - even the 4.22 of the 1098 it will be killed. The 948 unless extensively modified will just not have the guts for a 5 speed box. You will be constantly changing down - to keep the speed up. Better to go for a 1098 engine - and with decent mods (295 + HIF38 carb etc ) to about 60 bhp it goes very well on the 4.22 diff. Further mods (940 modified head) and it goes exceptionally well. Of course you may wish to go all the way to a 1275 engine - now you are getting into 5 speed box territory !!

[Peetee]

Got to disagree with you there BMC. I don't dispute that your options will have the advantage over my setup but as I said, my car would hold 70 uphill with throttle to spare. That would give it more than enough urge to cope with a higher ratio top. I don't know what the 5th equates to in final drive terms but I would estimate my car could have pulled a 3.9 diff on a Motorway. Bumbling along in traffic a standard 1098 would have the edge in drivability but above, say 2000 rpm, the modded 948 was ahead.

[bmcecosse]

But it only goes well because of the high diff ratio - which is allowing the 948 engine to rev and develop the power. With a lower ratio (or an overdrive 5th speed) it will just not have the revs and therefore not the power. Lower ratio needs the power at lower revs - best done by bigger capacity engine. Holding 70 uphill (how steep !!!????) is not usually difficult. The standard 1098 car is hardly any better than a 948 - because they choked it back with the 4.2 diff. stick a 4.5 in it and it comes alive. But a modified 1098 can pull the 4.2 diff very nicely - and maintain 'high' speeds uphill too. better not say how high -but enough to get me chased by a cop car last year!! He pulled alongside and gave me a severe finger wagging - followed by a thumbs up !!

[Peetee]

BMC, the original question related specifically to a 948 and a 5 speed. assuming the 5 speed Ford box keeps near to the original ratios and adds another on top then I would still argue that a modded 948 would cope. 5th gear is usually only suitable for gentle gradient, motorway use even on modern cars.

[Kevin]

My aim is less stressed cruising without fitting a bigger engine.

I am not sure if I have seen a 5 speed fitted behind a 948cc, but if you are improving the performance but want to make the car quieter when cruising a different diff from a later car will keep the revs down down but will also knock down the performance, but will cost much less than a 5 speed as the kits are currently around £800 with the box, and even if you went as far as a 3.9 diff (not advisable with a 948cc) they can be had for under a hundred pounds with far less work to fit, so its really you pays your money and takes your choice time.

[Scott]

The 5 spd conversion is quite common out here.
The Celica box is the norm as we don't get the Ford box here.

They're usually fitted behind 1098s & 1275s but I know of a few behind 948s (with a bit of work done & retaining the 4.55 diff) & they drive very nicely on the open road.

[bmcecosse]

Kevin's point is what i was suggesting - much easier and less expensive to fit a lower diff - but it will kill the car's performance.

[pauln]

Agree with previous 2 posts much better to use a higher diff ratio and see how you go. The type9 box has a very low first of 3.65/1 and a 5th of 0.87/1 (0.82/1 on 6 cyl boxes)

[CLIPPERBLU]

Thanks for all the responses. I guess to be on the safe side, I'll go for the uprated 1098 option and see how we go. Cheers.

[bmcecosse]

Is that uprated 1098 engine - or just the low ratio 1098 diff ???? I hope it's the engine !