5 replies to this topic

[Noodles]

Hi everyone,

Sorry another cylinder head question. I have used the search thing I promise, but I cant find exactly what im after. Basically iv got a Stage 1 1993 1275cc Sprite and want a new cylinder head to increase performance further because im planning to do a few track days next year (hopefully). I have £400 as an absolute max. I have been looking for stage 3 as I was told stage 2 to is fairly pointless? I have seen the smart performance "Stage 3" heads on ebay for £350 which I thought was a fairly good price + 10% off for TMF . But it has "road quality valves and Steel guides" and the "inlets are 35.7mm and exhaust 31mm. Is this any good? Or is there something better for the money? Also do I need 9 or 11 stud? and can you fit a 11 stud head to 9 stud block?

Oh and one last thing, rockers. Any real performance increase in going for 1.5 rollers?

Sorry for all the questions, but as you can probably tell I have very limited knowledge of cylinder heads so any advice is much appreciated.

thanks,

Dale.

Edited by Noodles, 25 September 2009 - 08:36 PM.

[Cooperman]

Don't take too much notice of this 'Stage....' business. It is fairly meaningless and means different things to different tuners.
The problem with buying a head off ebay is that you don't really know how well the modification has been done. A good gas-flowed head should not only have the right sized valves, and the ones you quoted would be fine, but it needs to have been 'worked' properly and only an initiaql visual inspection can tell. In fact, some will say that a flow-bench is needed to properly test it.
There is nothing wrong with steel valve guides. In fact, at high oil temperatures they are less likely to cause valve sticking than the fancy phos-bronze or whatever is in-vogue these days. Standard road valves should be OK as they are now generally of a good quality.
1.5:1 rockers are not much of an improvement as you won't gain anything noticeable. My 1293 'S' gained 2 bhp at 6000 rpm when I tried a set.
You can modify a 1275 9-stud block to take an 11-stud head, or modify a 9-hole head to taske 11-studs. To modify the block you do really need it out of the car and off the gearbox in order to put it under a pillar drill.
If you want to talk further or come over for a chat I'm also in Cambs, in a village called Earith. Give me a PM if you want to.

Peter

[Noodles]

Hi cooperman, thanks for the offer and the info. The main thing I was worried about was the quality and size of the valves and guides, which as you said are fine.

Has anyone got any experience of smart performance heads? Also does anyone know what sort of BHP increase I should get from this sort of head?

Thanks,

Dale

Edited by Noodles, 25 September 2009 - 09:22 PM.

[Cooperman]

It's difficult, if not impossible, to give an estimated performance increase with just a different head. There are so many factors involved such as: compression ratio, induction system mods, exhaust system mods, distributor advance curve, cam timing accuracy, carburettor size, etc.
On its own a head may not give much improvement unless the fuel/air mixture can get in in increased quantity and with better inwards flow, and trhe exhaust gases get out at the correct speed from the head right to the final point of exhaust.
It is a bit complicated and hard to cover on here in anything like a full way. You can't get much improvement unless you do something to a lot of different parts. The key better to performance is: Cam, Head, Induction and Exhaust as a complete matched package.
On a limited budget you may be better off just cleaning up your existing head a little, putting up the comp ratio, getting a decent exhaust system and a bigger carb on a nice alloy inlet manifold.
I've never worked with a 'Smart' head, so can't comment. I tend to do my own these days as I have experienced some poor-quality high-cost heads including a head on an 'S-Works' 1275 which I thought was very poor for the price charged when new.

[mini7boy]

you don't mention anything about the tires and suspension on your car, but you are likely to reduce your laptimes
more significantly with cornering speed improvements than by improving the engine's straight line performance.

any car which exits corners faster than others gains a performance improvement because its engine won't have to
work as hard to get the car up to speed before the next corner is reached. This won't allow a car with an 850 to smoke
a 1275, but it may well make the difference and provide an edge when comparing similarly tuned and geared 1275s.

to take this point further, if you can also learn to outdrive your competitors, you'll be able to make up for quite a
bit of engine performance deficit by getting through the twisty bits faster than the others.

there's nothing more disappointing than to roar up to a turn, get right on the rear bumper of a guy in front, and then
watch helplessly as he goes through the turn faster and pulls away in spite of your superior power. Power is only
good when it is used. If you have to slow down more than someone else to take a turn, you have just surrendered
part of whatever power advantage you had going into the corner.

Gearing is also a critical factor on track days, but gearing is usually dictated by the Monday through Friday driving needs
for a quiet/comfortable driving experience. If not, a change to a lower final drive(as from 3.44 to 3.7) is like adding power
to the engine because the engine's torque output is multiplied by 3.7 rather than 3.44. This final drive change will
allow the car to accelerate out of each turn in each gear somewhat faster due to this torque multiplication.

And what's more.........gearing is much more reliable than an engine and it doesn't have to constantly be kept in tune, like an engine.

[01smartc]

Hi, glad to see your interested in a head from us... The road quality valves we use are all good quality as are the guides. These are more than adequate for fast road use.

All of our heads are made to order and matched to the engine spec provided by the customer. This ensures the head give the best possible performance on the engine it is bought for.

As it has been said above it is impossible to say exaclty how much more power it will produce. However on other heads we have seen around 40% increase on std. when set up properly and used with a good stage 1 kit.

If you have any more questions just ask

Cheers

Chris @ Smart Performance