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Username Post: 383 valve spring breakage, lunati 00012        (Topic#264621)
Mangus 
Senior Member
Posts: 223

Reg: 12-26-02
06-13-11 11:04 AM - Post#2102939    

Folks, chased my "backfiring out the exhaust issue" to a broken valve spring yesterday. This is the second spring I've broken on these 2.02 fuelie heads in about 10 years. The springs are single coil, "racer brown" springs that were part of the head rebuild in 1988. Heads maybe have 3000 miles on them. Cam is a healthy lunati-00012, int/exh lift 0.515 in.
Question is, do valve springs break with these newer camshaft profiles? Is this set due to be replaced? Again only 3000 miles, tops. Revs are kept under 6000.
Any suggestions for a replacement set?

Thanks
Mangus
My cars:
62 Bel Air, off to work we go, 283, 3 speed on the floor, 17 MPG, black/red...gorgeous.
64 Impala, 383, 11:1, silver blue wild ride!
63 Impala, project.


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 16197
grumpyvette
Age: 66
Loc: FLORIDA USA
Reg: 03-16-01
06-13-11 11:37 AM - Post#2102950    
    In response to Mangus

when valve train parts fail, 99% of the time its a symptom of a clearance or lubrication issue.
a great deal has to do with the CLEARANCES and the springs installed height, if your breaking springs at only 3000 miles theres a very good chance the installed valve spring height and spring bind, or retainer to valve guide clearance was not carefully measured
or the rockers bind on the rocker studs at max lift
guys frequently take the springs that cam with a cam kit out of the package and install them with the stock retainers and never give it a second thought!, the truth is that in 90% of the cases I see where parts break,they never measured clearances.
when a cam manufacturer suggests a certain valve spring be used he also suggests the installed height and minimal clearances, you can,t install the springs without verifying clearances and installed height,and if they suggest new springs its generally because the stock valve train and components and clearances and springs won,t work


READ THRU THE LINKS

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" " IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK !"


Edited by grumpyvette on 06-13-11 12:31 PM. Reason for edit: No reason given.

 
greg_moreira 
Very Senior Member
Posts: 3264

Reg: 10-06-03
06-13-11 11:42 AM - Post#2102952    
    In response to Mangus

Thats actually an older lunati grind. The bracket master grinds arent super aggressive in the lobe profiles, and have been around a while.

Either way...if springs are starting to break....Id replace them.

If it were me, Id get a valve spring that provides 120-125LBS of spring pressure on the seat at your installed height, and between 315-325 lbs open.

That is what you need to make this cam work to its potential.

Definitely look at all the details grumpy mentions to check, because it all matters, but when it comes down to picking a spring....those are the seat and open pressures Id be looking for.

Single springs are not usually my cup of tea, which may be part of the problem.

 
MikeB 
Senior Member
Posts: 9479
MikeB
Loc: Plano, TX
Reg: 08-28-03
06-13-11 03:01 PM - Post#2103019    
    In response to Mangus

For that cam, I see where Lunati recommends their #73943 springs installed at 1.750". The springs are good for .530" lift + .060" safety margin, but if installed too low (such as 1.70"), the retainer may come too close to (or hit) the the valve guide boss at your cam's .515" valve travel.

Using a light testing spring, you can check retainer to guide boss clearance at .515" lift. It should be at least .050", right Greg and Grumpy?

Like Greg, I'm surprised Lunati doesn't recommend a dual spring for that cam, but I'm not sure I like 125 lbs seat pressure on a flat tappet cam. Although, I do tend to err on the conservative side.
Real Hot Rods have a Clutch!

1955 210 2dr: 327, Brodix IK180 heads, Jones cam, M20, Wilwood front brakes

1982 C-10 SWB pickup, 250 six, 3-speed

My car pictures



Edited by MikeB on 06-13-11 03:02 PM. Reason for edit: No reason given.

 
greg_moreira 
Very Senior Member
Posts: 3264

Reg: 10-06-03
06-13-11 04:27 PM - Post#2103049    
    In response to MikeB

lunati has been funky with their spring reccomendations. they are going conservative as is comp and others in fear of trashing cams I suspect.

The majority, from their mildest lobe to wildest lobe hydraulic flat tappet all recommend a spring with 108lbs on the seat.

That cam the op is using is in the mid 240's at .050 and has enough valve lift that it could go every bit of 6500 rpm with the right cylinder head. Problem is...no way, no how will that spring get there safely with 108 on the seat.

120-125ish is what I like for higher performing hydraulic flat tappets. 130 on a healthy solid flat. Keep in mind Id never break em in at those figures. Id be pulling the inners, or pulling shims, or just using a lighter spring for breakin to get the number a good bit lower. I'll even put a few miles on it with the wimpy spring pressures and just keep the rpm down before stepping up to the bigger spring pressure. Plus you gotta figure....if you flatten a cam, it doesnt go flat on the base circle. It goes flat over the nose. 125ish on the base circle is a far cry from what it will see over the nose, which is why I dont worry too much about getting the seat figure up a little. Most valve float issues are caused by the valve bouncing off the seat, so I like to have "plenty" on the seat, and "enough that it wont break things" on the nose.

The biggest factor is making sure the lifters spin in the bores.

.050 is a good figure for retainer to guide clearance that most people like to work with. Some go tighter, but if you start pushing the envelop.....I think its best done under the caution of somebody that has enough experience with the spring package and the weight of the retainers and locks and valves that you really know how its going to react.

Its the kind of thing(going tighter) that I wouldnt want to risk on my own just in case float unexpectedly came into play. Could get ugly if I didnt leave enough room!





 
Mangus 
Senior Member
Posts: 223

Reg: 12-26-02
06-13-11 07:08 PM - Post#2103128    
    In response to greg_moreira

Thanks all. I'll order a set of the lunati recommended springs tomorrow. Anyone know if those springs will fit in a stock 2.02 fuelie-head spring pocket?

These heads were built for a Comp Cams 294S which has even more lift .525 than this lunati stick.

I wonder if I over lashed this valve possibly.
Any other things to check for guys while I'm in there?

Mangus
My cars:
62 Bel Air, off to work we go, 283, 3 speed on the floor, 17 MPG, black/red...gorgeous.
64 Impala, 383, 11:1, silver blue wild ride!
63 Impala, project.


 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 16197
grumpyvette
Age: 66
Loc: FLORIDA USA
Reg: 03-16-01
06-14-11 05:02 AM - Post#2103247    
    In response to Mangus

Ive got a simple cure for your problem
Ill rent you my separate guest house (1200 sq ft) and ill help you get all the issues on your car fixed ,if you supply the parts required, Ill supply some labor on the car, and instruction,FOR FREE!
and over a few months I can bring you up to speed on the skills you need, and you will have supervised access to a lift tools and test equipment
" " IF YOU CAN'T SMOKE THE TIRES FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK !"


Edited by grumpyvette on 06-14-11 05:04 AM. Reason for edit: No reason given.

 
85Camaro 
Senior Member
Posts: 1145

Loc: East TN
Reg: 07-14-01
06-14-11 05:19 AM - Post#2103252    
    In response to grumpyvette

  • grumpyvette Said:
Ive got a simple cure for your problem
Ill rent you my separate guest house (1200 sq ft) and ill help you get all the issues on your car fixed ,if you supply the parts required, Ill supply some labor on the car, and instruction,FOR FREE!
and over a few months I can bring you up to speed on the skills you need, and you will have supervised access to a lift tools and test equipment



Isn't it funny how even with an offer like this you'd get few takers. I've offered to help a lot of guys and none are interested. Like you I have a complete shop with lift and tools.

 
greg_moreira 
Very Senior Member
Posts: 3264

Reg: 10-06-03
06-14-11 06:06 AM - Post#2103270    
    In response to 85Camaro

How I wish I could find a real high performance engine building machine shop locally that would put out that kinda offer.

Machine work, even though I have none of the tools to actually do it....is one thing Id like to know. Id like to hang out in a place that has all the new school CNC equipment just to see how these guys do what they do. The kind of stuff that Carl (CNC blocks) does would be interesting.

Honestly I think some people get intimidated. I try and help out family and friends and such locally. Sometimes when you explain the magnitude of what needs done and how to do it.....people tend to shy away from doing the job full on, even if you offer up the help.

Its the way I personally feel about bodywork! I can do it, but body work is one of those jobs where you cant just do a little. You either do it, or you dont. So sometimes I need a little extra motivation to want to get involved with it.

 
Mangus 
Senior Member
Posts: 223

Reg: 12-26-02
06-14-11 07:00 AM - Post#2103291    
    In response to grumpyvette

Grumpy, last time I checked you are in sunny Florida and I'm in far northwest Montana.
The offer is a great one, but the fuel bill to get there would buy another Saudi Prince a new palace!

I've learned over the years that when a junior at anything, be it mechanic, engineer, carpenter - to simply watch and learn from the guys that have the senior knowledge. Savor and enjoy it, learn from it. No doubt having my beloved 64 in your shop would be such an experience.

Thanks again.
Mangus

My cars:
62 Bel Air, off to work we go, 283, 3 speed on the floor, 17 MPG, black/red...gorgeous.
64 Impala, 383, 11:1, silver blue wild ride!
63 Impala, project.


 
MikeB 
Senior Member
Posts: 9479
MikeB
Loc: Plano, TX
Reg: 08-28-03
06-14-11 01:51 PM - Post#2103438    
    In response to greg_moreira

  • greg_moreira Said:
Plus you gotta figure....if you flatten a cam, it doesnt go flat on the base circle. It goes flat over the nose. 125ish on the base circle is a far cry from what it will see over the nose, which is why I dont worry too much about getting the seat figure up a little. Most valve float issues are caused by the valve bouncing off the seat, so I like to have "plenty" on the seat, and "enough that it wont break things" on the nose.



Good info. I never thought of it that way.
Real Hot Rods have a Clutch!

1955 210 2dr: 327, Brodix IK180 heads, Jones cam, M20, Wilwood front brakes

1982 C-10 SWB pickup, 250 six, 3-speed

My car pictures



 
bobb 
Super Senior Member
Posts: 4928
bobb
Loc: paradise
Reg: 09-05-03
06-15-11 12:31 AM - Post#2103685    
    In response to Mangus

when was the last time you broke a spring? alot of the clearance issues that you may face should not damage a spring but may damage a pushrod or rocker arm. you dont do much driving so it seems that your engine lays dormant for prolonged periods of time. if that is true that may be a problem. whenever you shut down an engine it basicly stops at the same place most of the time. that means the same valves are held wide open with the springs in full compression for long periods of time. that could be bad for a spring. there is also the chance that you got a bad set of springs.
70 L camino 350 all forged,174 baby blower, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
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