Mazda BP Valve spring Info
#1
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Mazda BP Valve spring Info
Mazda Valve springs
I took some time and checked out some valve springs for the Mazda 1.8 BP engine.
For a base line I checked the SBI catalog.
SBI replacement valve spring
Part # 160-1250
46 lbs @ 1.600
1.831 free length
AERA, Automotive Engine Rebuilders Association
States the spring installed height is 1.555
The spring pressure is 50-57 lbs closed
OnDemand5 lists the spec as
39.5mm/1.550 installed @ 19.9kg/43.87lbs
I started off by checking 8 valve springs from 2 different heads.
All testing was done using a installed height of 1.555/39.5mm
I found they fell in the range of 37-40lbs
When the factory .020 spring seat was used they came up to 40-43 lbs.
So close enough to be put back into use for a stock rebuild.
Next up are SuperTech,(ST) and Brian Crowder (BC)
I know the ST is widely used on this fourm.
I started with the ST Dual springs, that are advertised to be 74lbs @ 33.75mm/1.329
The ST is a bit light, when the math is done, Keep in mind ST supplies a .250 thick spring seat.
So 1.555 - .250 = 1.305 So .025 shorter installed height
So I tested, I found the springs will install 90lbs @ 1.555
This is a bit off still, due to the inner spring not being fully compressed from the Ti retainer not being installed.
Now I pulled the inner spring, so it would be a ST Single spring
On the ST Singles, ST advertised 56lbs @ 34.2mm/1.345
But here again, with the thick seats, the installed height is shorter by .040
When I pulled the single spring with the thick spring seat, I measured 70lbs
At this time, I have not checked the ST Ti retainers against a stock retainer to see if they step up or not.
Now on to the Brian Crower valve springs.
These install 80lbs @ 1.420
If the same .250 thick ST spring seat is used, the seat pressure is a whopping 110 lbs
That is a bit high, so I need to drop some seat pressure.
Now with two .060 thick shims, .120 total
I get 80lbs on the valve seat.
I like this for a boosted application.
The math works out better also
1.555 - .120 = 1.435
If I add a .015 thick shim, I will have 84lbs on the seat.
Since these are a cost effective spring, that does not require a custom spring seat and will work with the stock retainer, I can see this set up going into use on a wide range of builds.
I took some time and checked out some valve springs for the Mazda 1.8 BP engine.
For a base line I checked the SBI catalog.
SBI replacement valve spring
Part # 160-1250
46 lbs @ 1.600
1.831 free length
AERA, Automotive Engine Rebuilders Association
States the spring installed height is 1.555
The spring pressure is 50-57 lbs closed
OnDemand5 lists the spec as
39.5mm/1.550 installed @ 19.9kg/43.87lbs
I started off by checking 8 valve springs from 2 different heads.
All testing was done using a installed height of 1.555/39.5mm
I found they fell in the range of 37-40lbs
When the factory .020 spring seat was used they came up to 40-43 lbs.
So close enough to be put back into use for a stock rebuild.
Next up are SuperTech,(ST) and Brian Crowder (BC)
I know the ST is widely used on this fourm.
I started with the ST Dual springs, that are advertised to be 74lbs @ 33.75mm/1.329
The ST is a bit light, when the math is done, Keep in mind ST supplies a .250 thick spring seat.
So 1.555 - .250 = 1.305 So .025 shorter installed height
So I tested, I found the springs will install 90lbs @ 1.555
This is a bit off still, due to the inner spring not being fully compressed from the Ti retainer not being installed.
Now I pulled the inner spring, so it would be a ST Single spring
On the ST Singles, ST advertised 56lbs @ 34.2mm/1.345
But here again, with the thick seats, the installed height is shorter by .040
When I pulled the single spring with the thick spring seat, I measured 70lbs
At this time, I have not checked the ST Ti retainers against a stock retainer to see if they step up or not.
Now on to the Brian Crower valve springs.
These install 80lbs @ 1.420
If the same .250 thick ST spring seat is used, the seat pressure is a whopping 110 lbs
That is a bit high, so I need to drop some seat pressure.
Now with two .060 thick shims, .120 total
I get 80lbs on the valve seat.
I like this for a boosted application.
The math works out better also
1.555 - .120 = 1.435
If I add a .015 thick shim, I will have 84lbs on the seat.
Since these are a cost effective spring, that does not require a custom spring seat and will work with the stock retainer, I can see this set up going into use on a wide range of builds.
#3
One question and a couple of notes.
So you're basically doubling the seat pressure from stock?
You can look it up in your books, but I had heard that the earlier Miata engines, maybe 1.8 94-97 had slightly stiffer valve springs. I had also heard that volvo b20 engine valve springs were used as a hi-po upgrade.
So you're basically doubling the seat pressure from stock?
You can look it up in your books, but I had heard that the earlier Miata engines, maybe 1.8 94-97 had slightly stiffer valve springs. I had also heard that volvo b20 engine valve springs were used as a hi-po upgrade.
#4
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I use a ton of the BC springs on the 4g heads I build. So I was talking to them one day and wanted to find a budget spring of sorts for the Mazda, so I gave them the spring specs from a used BP spring, and found these.
No as far as price, the ST single kit w/Ti retainers and thick spring seats is around the $325 range, The BC springs with commonly found spring shims along with using the factory used steel retainers will go about $125
I still need to check how the shims and springs fit on the head casting, from all I have checked to this point, it looks to be a solid set up.
No as far as price, the ST single kit w/Ti retainers and thick spring seats is around the $325 range, The BC springs with commonly found spring shims along with using the factory used steel retainers will go about $125
I still need to check how the shims and springs fit on the head casting, from all I have checked to this point, it looks to be a solid set up.
#5
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One question and a couple of notes.
So you're basically doubling the seat pressure from stock?
You can look it up in your books, but I had heard that the earlier Miata engines, maybe 1.8 94-97 had slightly stiffer valve springs. I had also heard that volvo b20 engine valve springs were used as a hi-po upgrade.
So you're basically doubling the seat pressure from stock?
You can look it up in your books, but I had heard that the earlier Miata engines, maybe 1.8 94-97 had slightly stiffer valve springs. I had also heard that volvo b20 engine valve springs were used as a hi-po upgrade.
Keep in mind that when the engine is boosted, the valve spring is given a second job, the spring now has to keep the valve closed against boost pressure.
Figure that there is 1 sq/in of area on the back side of the intake valve, now add 20psi of boost, you loose 20lbs of spring pressure just keeping the valve closed.
Ill check my books and look into the springs you mention.
Last edited by BogusSVO; 01-15-2013 at 07:01 PM.
#6
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Slmhofy
Checking my SBI catalog, the springs 160-1250 are for the 1990-1997
As far as the Volvo B20 spring, SBI does not have a listing for springs, it could be beacuse they are an older engine, B20B and B20E were made from 1969-1978 and is an OHV
Checking my SBI catalog, the springs 160-1250 are for the 1990-1997
As far as the Volvo B20 spring, SBI does not have a listing for springs, it could be beacuse they are an older engine, B20B and B20E were made from 1969-1978 and is an OHV
#9
This is a very informative thread. A+
The question I always wanted to know is how do you calculate the desired seat pressure for valvetrain weight, camshaft specs, and rpm range?
Don't you want to have just the right amount of spring compression for your application? I have seen too many motors with springs way too big for a particular application, throwing horsepower away.
The question I always wanted to know is how do you calculate the desired seat pressure for valvetrain weight, camshaft specs, and rpm range?
Don't you want to have just the right amount of spring compression for your application? I have seen too many motors with springs way too big for a particular application, throwing horsepower away.
#11
I'm wondering the same thing as the 2 posts above:
whats the perfect balance for your average boost setting (10-15) and/or a bit higher (20+)
Something tells me that you don't want to go too stiff, or you'll be putting excessive wear/tear on your valvetrain and/or throwing away power.
Some completely un-educated guessing here: if a stock motor operates at 1 bar and you're running 15+ psi (2 bar) then the double spring rates shouldn't be too bad? Probably doesn't work that way, just guessing
whats the perfect balance for your average boost setting (10-15) and/or a bit higher (20+)
Something tells me that you don't want to go too stiff, or you'll be putting excessive wear/tear on your valvetrain and/or throwing away power.
Some completely un-educated guessing here: if a stock motor operates at 1 bar and you're running 15+ psi (2 bar) then the double spring rates shouldn't be too bad? Probably doesn't work that way, just guessing
#12
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Thats what brought me to this foum in the first place.
"Now you know, and knowing is half the battle!"
I would say I watched GI Joe a bit often growing up
Not at this time, this is a set up that I am working on with BC.
This is a very informative thread. A+
The question I always wanted to know is how do you calculate the desired seat pressure for valvetrain weight, camshaft specs, and rpm range?
Don't you want to have just the right amount of spring compression for your application? I have seen too many motors with springs way too big for a particular application, throwing horsepower away.
The question I always wanted to know is how do you calculate the desired seat pressure for valvetrain weight, camshaft specs, and rpm range?
Don't you want to have just the right amount of spring compression for your application? I have seen too many motors with springs way too big for a particular application, throwing horsepower away.
The springs first job is to keep the valve in contact with the cam, nasty things happen when it fails at that job.
Ramp rates and cam lift, have to be taken into account, along with boost pressure.
Also you have to allow for wear on the spring, after a season of track use,or a year or two of "fun" street use, the seat pressure will be a bit lower than new spring.
I do not know a fourmula for figuring spring pressures, it boils down to the head builders experiances.
But you are correct, they can get too heavy and cost HP, or be too light and cost HP and/or damage.
#14
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18psi...A stock engine is NA, so it operates in a vacuume, springtions do not have to be as much as a Turbo engine.
When you add boost, the spring now has to hold the valve closed against the boost pressure.
With a stock 1.8 intake valve, there is appox 1 sq/in.
So the first thing you do is subtract boost pressure from spring seat pressure.
So with 18psi of boost, and 70lbs on the seat ( ST single if dropped in) leaves 52lbs of spring pressure to keep control of valve motion with the cam.
Factory spring is 43, so you have 9lbs more than stock.
Efini, Once I am happy with the set up, and get back with BC on them. I will let you know.
When you add boost, the spring now has to hold the valve closed against the boost pressure.
With a stock 1.8 intake valve, there is appox 1 sq/in.
So the first thing you do is subtract boost pressure from spring seat pressure.
So with 18psi of boost, and 70lbs on the seat ( ST single if dropped in) leaves 52lbs of spring pressure to keep control of valve motion with the cam.
Factory spring is 43, so you have 9lbs more than stock.
Efini, Once I am happy with the set up, and get back with BC on them. I will let you know.
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Ok. I have been using the Sealed Power ZVS855's. They are about $61 from Summit Racing. At 1.56" installed height they have roughly 66lbs seat pressure and work with the stock retainers and keepers. Just interested if these are a better option.
#18
--Ian