-
Hi Guest!
You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
There are some perks with a member upgrade!**Upgrade Now**
(PS: Subscribers don't see this gawd-aweful banner
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
Number one perfermance upgrade.
- Thread starter Tullamore
- Start date
Share this page
Bruce Bowker
Obi Wan
Offline
I imagine there will many opinions here. I like headers and a good flowing exhaust system. Then some very free breathing air cleaners. After that it would get expensive with bigger carbs and cam. Larger pistons and better head but now that gets to be big bucks.
Bruce
Bruce
Offline
The cheapest thing you can do is switch to low restriction air filters like K&N. BUT!! Once you start getting more air into the engine you need to get more out so you need a header and sport exhaust. BUT!! To make the most of this you need a hotter cam, flowed head, larger valves, etc. etc.
Once you start trying for a little more get up an go it becomes a slippery slope into mass expense. Such is the life of a Little British Car nut. Don't ya just love it? /ubbthreads/images/graemlins/laugh.gif
Once you start trying for a little more get up an go it becomes a slippery slope into mass expense. Such is the life of a Little British Car nut. Don't ya just love it? /ubbthreads/images/graemlins/laugh.gif
aeronca65t
Great Pumpkin
Offline
Honestly, the best thing to do isn't really all that fancy.
New plugs and points, rotor,cap, plug-wires, fuel filter and air filters. Be sure that valves are adjusted and igniton timing is correct. Check that carb float bowls are clean and there are no intake manifold leaks.
If you detect any valve leakage (via a leakdown test) a valve job can make a world of difference (and if the head is off anyway, milling about 0.030" off will add a useful bit of power without going crazy compression-wise). If you send the head to a machine shop and do all the on-car work yourself, it's not that expensive.
Headers (especially ordinary "street" headers) don't exactly transform these engines, partly because the center Siamese port is pretty restrictive no matter what else you do.
The Weber carbs are a matter of opinion. Some folks like them and others do not. I think that the much-maligned SUs are actually fine (for newer cars with the Z-S carb, an SU HS4 is a good swap).
Sythentic oil in the trans and rear can help a bit too.
To be honest, one of the best bangs for the buck that I've seen is good tires (with correct pressures) and new shocks. Makes the car better all-around.
New plugs and points, rotor,cap, plug-wires, fuel filter and air filters. Be sure that valves are adjusted and igniton timing is correct. Check that carb float bowls are clean and there are no intake manifold leaks.
If you detect any valve leakage (via a leakdown test) a valve job can make a world of difference (and if the head is off anyway, milling about 0.030" off will add a useful bit of power without going crazy compression-wise). If you send the head to a machine shop and do all the on-car work yourself, it's not that expensive.
Headers (especially ordinary "street" headers) don't exactly transform these engines, partly because the center Siamese port is pretty restrictive no matter what else you do.
The Weber carbs are a matter of opinion. Some folks like them and others do not. I think that the much-maligned SUs are actually fine (for newer cars with the Z-S carb, an SU HS4 is a good swap).
Sythentic oil in the trans and rear can help a bit too.
To be honest, one of the best bangs for the buck that I've seen is good tires (with correct pressures) and new shocks. Makes the car better all-around.
OP
Tullamore
Jedi Warrior
Offline
Thanks for the info, I already got new tires, plug wires, spark plugs, K&N filters, dist. cap and rotor, and new fuel filter. I have yet to check the timing or adjust the carbs.
But the reason for the post is that I am willing to spend $500-700 on one good item that would give me most out of that money towards acceleration.
Does an aluminum flywheel make a great difference? How about a 5 speed conversion?
But the reason for the post is that I am willing to spend $500-700 on one good item that would give me most out of that money towards acceleration.
Does an aluminum flywheel make a great difference? How about a 5 speed conversion?
Trevor Jessie
Yoda
Offline
How about a 4.22 Diff?
aeronca65t
Great Pumpkin
Offline
We have an aluminum flywheel on the 1275 race car. We got it cheap (used) but a new one is $500 USD. Not a great bang-for-the-buck or any real improvement for street use in my view. I'm still running a stock steel flywheel (just slightly lightened) on my 1500 racer and have no intention of switching to aluminum.
An electic fan might help (since you can ditch your stock fan and save 2 or 3 HP). I ran my Bugeye on the street with no fan of any kind...great as long as you don't hit any traffic!
The 4.22 final drive is a good idea (assuming your's has the 3.9) but it makes a Sprite even more buzzy at highway speeds. I have low-profile tires on my 1500 for street use (Sumitomo 175/50-13). They give a similar effect to running a numerically higher final drive (~4000 RPM at 60 MPH).They look sort of cool, though.
The 5 speed setup is neat but I'm not sure you could do it on your budget.
An electic fan might help (since you can ditch your stock fan and save 2 or 3 HP). I ran my Bugeye on the street with no fan of any kind...great as long as you don't hit any traffic!
The 4.22 final drive is a good idea (assuming your's has the 3.9) but it makes a Sprite even more buzzy at highway speeds. I have low-profile tires on my 1500 for street use (Sumitomo 175/50-13). They give a similar effect to running a numerically higher final drive (~4000 RPM at 60 MPH).They look sort of cool, though.
The 5 speed setup is neat but I'm not sure you could do it on your budget.
aeronca65t
Great Pumpkin
Offline
So what aeronca65t is saying is that there really isn't a whole lot you can do to these things to make them a whole bunch better?
In response to your original question, that's correct.
You asked: What is the best single item you can upgrade or add to your car to give it a little more umph in a straight line......I am willing to spend $500-700 on one good item
In my view, there is no single item that will accomplish a useful improvement in acceleration within your budget.
There are lots of ways to spend that money to make a Sprite a better car overall...but there's no easy "one-shot" answer to making a real improvement in useful acceleration.
For the record, I think $700 might be just enough to get you a valve job, head milling, new pistons (let's say around 9.5 to 1) and a hot street cam. That's for "parts only" and assumes that the engine is in good internal shape and you do all the mechanical tear-down and re-assembly yourself. That doesn't include a crank regrinding, new bearings and cylinder re-boring (probably another $300 and very advisable if you were going to tear down the engine anyway). For about $1000 and a lot of sweat-equity, you might add about 15 HP (very noticable in a Sprite), but this would hardly be considered a "single item".
In response to your original question, that's correct.
You asked: What is the best single item you can upgrade or add to your car to give it a little more umph in a straight line......I am willing to spend $500-700 on one good item
In my view, there is no single item that will accomplish a useful improvement in acceleration within your budget.
There are lots of ways to spend that money to make a Sprite a better car overall...but there's no easy "one-shot" answer to making a real improvement in useful acceleration.
For the record, I think $700 might be just enough to get you a valve job, head milling, new pistons (let's say around 9.5 to 1) and a hot street cam. That's for "parts only" and assumes that the engine is in good internal shape and you do all the mechanical tear-down and re-assembly yourself. That doesn't include a crank regrinding, new bearings and cylinder re-boring (probably another $300 and very advisable if you were going to tear down the engine anyway). For about $1000 and a lot of sweat-equity, you might add about 15 HP (very noticable in a Sprite), but this would hardly be considered a "single item".
KerryStagmer
Senior Member
Offline
well, i agree and disagree....
SU is a great carb and makes almost equal power with a dgv weber BUT that being said.....
the weber change is by far the most noticable change on the street. first and formost is the accelerator pump giving much better response. where it makes little difference is on the track where the carbs are opened up all the time, the SU works great then.
also the choke on the weber will give you INSTANT starts all winter long, something SU's are not so great at and Z-S are worthless for
That being said, you havent check the timing? wow what a huge difference it can make
just wondering , does the car have an airpump for emissions? that would be the cheapest power you can get, remove that belt, buy good gas and bump the timing (some)
SU is a great carb and makes almost equal power with a dgv weber BUT that being said.....
the weber change is by far the most noticable change on the street. first and formost is the accelerator pump giving much better response. where it makes little difference is on the track where the carbs are opened up all the time, the SU works great then.
also the choke on the weber will give you INSTANT starts all winter long, something SU's are not so great at and Z-S are worthless for
That being said, you havent check the timing? wow what a huge difference it can make
just wondering , does the car have an airpump for emissions? that would be the cheapest power you can get, remove that belt, buy good gas and bump the timing (some)
When I put the aluminum flywheel on my Sprite, I noticed a whole lot more bang for the $400 bucks.
It's not any faster top end, but it sure does wind up a lot quicker so it's faster off the line.
On the otherhand, I spent serious money on having the head ported and having rim flow valves installed. I saw no "noticable" bang for those 500 bucks.
It's not any faster top end, but it sure does wind up a lot quicker so it's faster off the line.
On the otherhand, I spent serious money on having the head ported and having rim flow valves installed. I saw no "noticable" bang for those 500 bucks.
KerryStagmer
Senior Member
Offline
i'd be willing to beleive that. when i put the tr-6 motor in my spitfire it required the fitting of a gt-6 flywheel and balancer, something like an unbelievable difference of 10lbs. the difference was huge
Tullamore, it's hard to quantify any single item that will give you the results you want, but if it's just "seat of the pants" acceleration you're looking for, the easiest thing to do is swap the diff to a higher number. If you now have a 3.9, a 4.22, or 4.55 will give you a marked increase in acceleration. The down side is that you will be wound up pretty tight at normal highway speeds.
I don't think there is any one quick "bolt on" that is going to accomplish what you want, given the fact that you only have 1275cc's to work with.
I've been messing with these things since 1966, and the only way to make a good, solid, power increase, is to approach the engine as a system, and change things accordingly. Higher compression pistons lead to a ported head, a better intake and carbs, which means a more efficient exhaust, etc...................
Not to sound negative, but when you're dealing with such a small displacement engine, everything is so interrelated that even a minor change to one thing will affect something else.
Jeff
I don't think there is any one quick "bolt on" that is going to accomplish what you want, given the fact that you only have 1275cc's to work with.
I've been messing with these things since 1966, and the only way to make a good, solid, power increase, is to approach the engine as a system, and change things accordingly. Higher compression pistons lead to a ported head, a better intake and carbs, which means a more efficient exhaust, etc...................
Not to sound negative, but when you're dealing with such a small displacement engine, everything is so interrelated that even a minor change to one thing will affect something else.
Jeff