Dual valve spring technical help required - Mazda MX-6 Forum
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post #1 of 22 (permalink) Old 11-1-18, 9:18 Thread Starter
 
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Dual valve spring technical help required

Hey all. 91 f2t rebuild giving me some troubles. Sorry for the novel!!!

I had an engine shop machine and assemble my head. We used the Aussie dual valve spring, also machine work to the valve tops & bottoms, the valve seats, and resurfaced the head. I was told all the valve spring shims were used, and the seat pressure is around 85lbs.

I have removed and reinstalled the rocker assemblies a few times now, but no matter what I do, there seems to be lifter noise as you're letting off the throttle slightly...so basically cruising on a flat road. Once load is applied or removed the noise goes away...I had the same noise before with a collapsed lifter, but I cannot seem to find the culprit!!

I was wondering if maybe there's a chance the rocker arms are knocking? Or if anyone has a suggestion, I'd greatly appreciate it.

I'm under the impression that I'll have to inspect rocker arm geometry, valve lash, and valve travel.

I know how the lifters function, and I've cleaned the oil galleries out thoroughly. I also use a zddp additive to help keep the valvetrain protected from wear.

I read a few people suggesting to use a hammer to close the rocker arm upper relief holes...but that doesn't sit well with me lol, I'd rather a better way to close them off. I really don't want to damage anything in the vise.

Stock cam btw! Also fyi, the short block was decked, deglazed, and had oil clearances spec'd out. I assembled it using Clevite bearings, rings and assembled with an Enginetech Fire Seal head gasket, also OEM Mazda gaskets and seals everywhere else.

In case you are wondering, I torque everything down in sequence using a calibrated torque wrench. Rocker arms are at 16ftlbs (call for 13-20ftlbs iirc) and the head gasket is at 65ftlbs.

Any questions, ask away. I don't have access to bring my engine to the machine shop sadly!! It's my daily driver, and I live in an apartment building, and now doing work is frowned upon ☹️ but I manage some stuff lol.
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post #2 of 22 (permalink) Old 11-1-18, 22:49
 
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Don't knock out the upper rocker arm oil holes, they are not relief holes, they lubricate the valves, cam lobes and rockers.

What shims are you talking about, the factory valve springs use a thin metal seat that keeps the springs from digging in to the aluminum head.

You don't have to inspect rocker arm geometry, valve lash or valve travel. I am sorry but the answer is clear and I think you know it. The dual valve springs are too stiff for the oil pressure under low engine load and the HLA's collapse, you may be able to solve this using a high volume high pressure oil pump if you can find one or make one (by porting the oil hole and shimming the oil pump spring).

You had the block decked and the head shaved, Why? did they need it?
If you want high boost you are going to have to pull timing, the equivalent amount of hp you are making or more from the higher compression you have created by reducing the combustion chamber size, piston distance and quench area. So to match the boost/hp potential of a factory compression block you have to pull timing, the amount of ignition timing you can pull is limited before octane is increased or compression is lowered.

Go buy a junkyard block, pull the pistons and clean the rings, pull the cam off the head and hand sand the combustion chambers until they are smooth (leave the valves in, don't worry about sanding them), use the factory bearings, get valve spring shims, lap the valves. Take the head to a port and polish shop and have them grind the valve seats back to the edge of the lapping marks, valves stay the same size, mouth of the port is larger witch makes the best combo and more flow.

These engines aren't engineered, that means they aren't built for efficiency, that means engineers weren't told to make the most reliable hp out of the engine or to make the engine efficient or to use the least amount of materials. This makes the factory block have low compression pistons, huge strong rods, giant crank and a really strong transmission.
They aren't like other blocks the more the rings wear down the cylinders the more boost the engine can handle and the more overall power can be made.

You have obviously spent money on work and if you don't want to waste it twice get water meth injection for a long term investment, that can be used on any build and increases octane and detonation prevention

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post #3 of 22 (permalink) Old 11-2-18, 20:33 Thread Starter
 
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Thank you for your reply!

The shims I am referring to came with the dual valve springs. I wasn't trying to imply the OEM lowers, I apologize for any confusion!

I honestly just followed advise from this forum, the machine shop, and the valve spring company. I have never used dual valve springs before, let alone aftermarket ones.

What spring seat pressure would you recommend to use?? Or would you just remove the supplied shims, and reinstall the springs?

Thanks!
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post #4 of 22 (permalink) Old 11-2-18, 21:43 Thread Starter
 
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I have spare parts still though, no need to fret! No need to rebuild another engine, not just yet.

But seriously, my car makes maybe 200ftlbs at the wheels, so I am not sure how much of your post pertains to me, but I do appreciate your input.

If we can talk about the valvetrain, that would help me out greatly tho. Thank you
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post #5 of 22 (permalink) Old 11-5-18, 16:14 Thread Starter
 
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Been in contact with the valve spring company, and they advised me nobody else has brought up this issue before with lifters collapsing.

Can anyone chime in on their experiences with their dual valve spring setup? I've been asked if I have a new oil pump and lifters. I do have a new oil pump...but only have used lifters (around 20 of them lol), so I'm not sure how much help I'll get once he advises me to buy new ones.
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post #6 of 22 (permalink) Old 11-5-18, 20:37
 
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Well just replacing the part isnt going to solve the issue so youre probably better off without the springs. You mentioned your car only makes 200 ftlbs. Whats the use for the dual valve springs when it sacrifices your valve train components and looses power. Im going back to stock valve springs. Im tired of the ticking
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post #7 of 22 (permalink) Old 11-6-18, 23:52
 
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I was looking for the correct shim size for these heads and came across some interesting info.

F2/F2T intake valve spring info (for sealed power springs on rock auto) :

Max Outside Diameter 1.31
Wire Diameter 0.17
Total Coils 7.1
Closed Height 1.57
Closed Pressure (Lbs) 58
Open Height 1.17
Open Pressure (Lbs) 157
Type S

The 1992 mx6/626 Factory workshop manual states:

Standard valve spring free length IN- 1.949" EX- 1.984"
Standard setting load/height IN- 45.5-51.5lbs / 1.614" EX- 53.9-60.9lbs / 1.614"

___________________________________________________________________________________________________

B2200 (1991) Sealed power valve springs (intake/exhaust not mentioned):

Outer spring:

Max Outside Diameter 1.417
Wire Diameter 0.156
Total Coils 7.2
Solid Height 1.048
Closed Height 1.45
Closed Pressure (Lbs) 59
Open Height 1.2
Open Pressure (Lbs) 96
Type S

Inner spring:

Max Outside Diameter 0.97
Wire Diameter 0.125
Total Coils 8
Solid Height 1.06
Closed Height 1.35
Closed Pressure (Lbs) 35
Open Height 1.1
Open Pressure (Lbs) 59
Type S

____________________________________________________________________________________________________

Assuming
The solid height would be the spring compressed to it's maximum
Closed height would be on the head with the valve closed (seat pressure)
open height would be with the valve fully opened

How thick are the upper b2200 valve spring seats, the ones that go on top and the keepers sit in.

I find the open closed height of the mx6 spring versus the b2200 outer spring quite different.
mx6- 1.57" closed, 1.17" opened, total travel- 0.40"
B2200- 1.45" closed, 1.2" opened, total travel- 0.25" The inner spring also has 0.25" travel.

MX6 spring pressure closed 58lbs, open 157lbs
B2200 spring pressure closed 94lbs, open 155lbs

Seat pressures:
Sealed power mx6 - 58lbs intake
WSM mx6 - 51.5lbs IN, 60.9lbs EX
Sealed Power b2200 - 94lbs
Mazda Powered Mx6 - 85lbs

The B2200 springs may list the same spring pressure with the valve opened as the Mx6 but that is for 0.25" travel, what is the pressure at 0.40" travel.

This longer travel is why the mx6 spring gains 99lbs over seat pressure when the valve is opened.

It is not easy to calculate accuratly because I don't know if the stiffness increase is linear.
The mx6 spring : 157/ 58 = 2.70689 X seat pressure @ 0.40" or a 270.689 % increase.
If the B2200 springs act the same as the mx6: 94lbs X 2.70689 = 254.44lbs @ 0.40" travel.
If the spring increase is linear: 155 - 94 = 61lbs / 0.25" = 244 X 0.40" = 97.6lbs + 94lbs = 191.6lbs spring pressure with valve opened.

-----------------------------------------------------------------------------------------

If you guys are going back to stock valve springs, I recommend 0.060" thick valve spring shims, you need the inner and outer diameter of the factory valve spring seat (little thin shinny metal seat the valve spring sits on).

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post #8 of 22 (permalink) Old 11-7-18, 0:37
 
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Quote:
Originally Posted by Mazda_Powered View Post
I have spare parts still though, no need to fret! No need to rebuild another engine, not just yet.

But seriously, my car makes maybe 200ftlbs at the wheels, so I am not sure how much of your post pertains to me, but I do appreciate your input.

If we can talk about the valvetrain, that would help me out greatly tho. Thank you


I think you missed my point. Trust me I did the same thing 20years ago when I started with these cars, took a perfectly good working engine to a machine shop, had the block bored 0.050" over (waste of $ and block) had them put in 7.4:1 pistons (pistons were weak, waste of money and block) had the head shaved the minimum needed to make it true (waste of money and head), had the crank machined and used oversized clevite bearings (ruined the durable F2T). Everything I paid them to do lowered the maximum horse power I could make from an F2T and it's durability, looked into 0 decking the block and polished pistons but both had more negatives than positives so I decided against it.

Want to make maximum power: Disassemble the block, clean it, reassemble with new gaskets and seals.
Want to ruin the potential and reliability of the F2T: Send it to a machine shop and give them lots of money to do stuff that should never be done to these blocks.

My post pertains to anyone with an F2T who is looking to make more than 2X factory power.
My post doesn't pertain to someone driving a bone stock F2t at stock boost (what a waste and shame on them) and say the oil pump or head gasket fails and they have the engine rebuilt, heck at factory boost they can use top line N/A 8.6:1 compression pistons, the shitty aftermarket rings and bearings available and have the head shaved. But I feel sorry for the person who buys this piece of junk and tries to throw 25-30 psi at it. The bearings will spin at 18psi and the pistons will crack at 21psi.


If the F2T needed stronger pistons or rods or engine work to make lots of power it would be a lemon like every other engine that needs any of these things done to it. The F2T total cost to make maximum power should be about a 400$, 200$ for the engine and 200$ for all the gaskets and seals.

Therefore there is no need to rebuild any working F2T at all and if yours suffers damage for any reason than 400$ should be your maximum replacement cost and you will have a better engine than the one the machine shop built you.

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post #9 of 22 (permalink) Old 11-7-18, 8:34 Thread Starter
 
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Wow so the seating pressure is ok then if those are in the same range. Just fully opened these aussie ones are 250lbs

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post #10 of 22 (permalink) Old 11-7-18, 9:53 Thread Starter
 
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After reading your post a few times I'm reading these aussie springs are essentially OEM dual valve spring specs?

"If the B2200 springs act the same as the mx6: 94lbs X 2.70689 = 254.44lbs @ 0.40" travel.
If the spring increase is linear: 155 - 94 = 61lbs / 0.25" = 244 X 0.40" = 97.6lbs + 94lbs = 191.6lbs spring pressure with valve opened."
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post #11 of 22 (permalink) Old 11-7-18, 9:59 Thread Starter
 
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Quote:
Originally Posted by juanpac_tupac View Post
Well just replacing the part isnt going to solve the issue so youre probably better off without the springs. You mentioned your car only makes 200 ftlbs. Whats the use for the dual valve springs when it sacrifices your valve train components and looses power. Im going back to stock valve springs. Im tired of the ticking
Sorry I seem to be having issues with seeing posts. It might be my phone, not sure?!

Springs are for higher rpm stability tho, I have everything balanced to 10k. I'd like to be able to rev it to factory redline without worrying about valve spring issues.
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post #12 of 22 (permalink) Old 11-9-18, 10:05
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What's the viscosity of your oil & what are the temperatures of where you live?
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post #13 of 22 (permalink) Old 11-15-18, 18:04 Thread Starter
 
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What's the viscosity of your oil & what are the temperatures of where you live?
Was running 10w30 then tried 15w40 and it was a bit better actually. Recently there was a big temperature drop, also snow now...so the car is parked for the winter lol.
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post #14 of 22 (permalink) Old 12-3-18, 13:17 Thread Starter
 
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Today I spent a few minutes with my car. Friggen cold weather and no time lately.

Really quick I brought all 12 valves to TDC to check lifter movement and preload.

Preload is basically perfect, couldn't get a 0.03" feeler gauge in, and the rocker arms have slight drag when moved side to side.

I found one bad lifter with the engine cold so next time I will go around the block, and check again. I think I will maybe mod a spare valve cover if the issue persists...may help diagnose this.
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Quote:
Originally Posted by Mazda_Powered View Post

Springs are for higher rpm stability tho, I have everything balanced to 10k. I'd like to be able to rev it to factory redline without worrying about valve spring issues.
I am 100% positive what was considered valve bounce by the dual valve spring advocator was actually turbo and boost control related not valve float related. If the intake valves where getting held opened by boost pressure near redline it would make the same tapping noise or worse than you are experiencing now.
I wouldn't really call 6250 rpm higher rpm.
If you are planning anything close to 10 000rpm remember these engines have a longer stroke than bore and unlike 90% of 2l 16v 4 cylinder engines it makes low end power and torque or it breathes well at low rpm, short intake manifolds and short stroke blocks breath better at higher rpm.
Your options for a turbo that will breathe to that high will spool around 6500rpm or would require variable trim housings on the compressor and impeller sides.

The F2T gearbox has pretty tall gears and even then, try shifting 1st, 2nd, 3rd and 4th at redline and note at what RPM you land, I have done the math but im not looking it up right now, it's above 4000rpm so from gear to gear you get about 2200rpm to accelerate with and need to shift. It doesn't matter where in the rpm band that 2200 rpm are (gear ratios are fixed) as long as it pulls the hardest for those 2200rpm it will be it's fastest.
Tall gears take torque to accelerate not horsepower.
Remember with all vehicles the force measured at the wheels by a dino (torque) drops and the mathematical equation (horsepower) climbs.
What moves and accelerates a car force exerted at the wheels or mathematical equations.

Quote:
Originally Posted by Mazda_Powered View Post
Was running 10w30 then tried 15w40 and it was a bit better actually. Recently there was a big temperature drop, also snow now...so the car is parked for the winter lol.
If you only run it in the summer than run 20w50, heck I run it all year long in some of my F2T's.

Quote:
Originally Posted by Mazda_Powered View Post
Today I spent a few minutes with my car. Friggen cold weather and no time lately.

Really quick I brought all 12 valves to TDC to check lifter movement and preload.

Preload is basically perfect, couldn't get a 0.03" feeler gauge in, and the rocker arms have slight drag when moved side to side.

I found one bad lifter with the engine cold so next time I will go around the block, and check again. I think I will maybe mod a spare valve cover if the issue persists...may help diagnose this.
I would be curious to know what the bottom of the cam bearings look like with all that pressure pushing against them. If they start to wear down you will get valve tap all the time.
You have a 91GT so there is no cam lobe for a mechanical fuel pump in the rear head housing, you can confirm this by pulling the distributor and looking in the housing hole it sits in. From what I recall the cam can be pulled by removing the cam gear and housing, the rocker assemblies and loosening the rear cam caps upper housing nut, then slide the cam out toward the cam gear end of the head.



Just how do you plan to modify a spare valve cover?
You do know the rockers squirt oil all over the place, If you made a plexiglass cap and cut opened the valve cover it would be about 2seconds before you cant see anything through the oil, if you just cut the top off you won't be able to get close to the engine bay when idling.
I doubt a collapsed HLA could be diagnosed visually when each rocker moves 6.25 times per second at 750rpm.

Are any of the rockers hitting the valve cover, you should be able to feel it with your hand, a tap on the valve cover that feels strongest where the rocker hits it. Otherwise it's the rocker hitting the cam, it should feel the same anywhere you touch the valve cover.

If a rocker is hitting the PCV baffle in the valve cover you can source a 91 probe GT valve cover, they have more clearance between the baffle and rockers. Or you can take a spare valve cover and sand down the upper level of the aluminum valve covers baffle chambers, this will move the baffle plate away from the rockers. A small palm sander will do the job. A light layer of gasket maker on the valve cover lips will do, use locktite on the screws you don't want them falling into the rockers and cam.

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