New Motor..400 miles BROKE VALVE SPRING

[waterboy1976]

OK heres the scenario (although it really happened)

Cruising the other night...just got the motor done...no more than 450 miles on her since everything was redone.

Engine... 350 4 bolt .40 over Dart Iron Eagle heads (2.02/1.96 180cc runner 64 cc chambers slightly shaved 100thous) Cam...Edelbrock 7102....234/244 @50 lift 488/510......Rockers Comp cams 1.6 rollers....total adjusted lift exhaust side .544 Elgin springs part #rv943x Single damper spring high rpm max lift .550.

Why did my exhaust valve spring on number 1 cyl break?

All clearances are well within specs. No coil bind. Seat pressure good etc.
I called the guy who built myheads and he recommended to go to a .600 lift spring if Im in the pedal a lot. Now wait a minute....when your idling at 900 rpm Im still at .544 lift on the e side or when Im at 5600 rpm Im STILL at .544 lift...it shouldnt change....I would think at TOO high RPM youd have valve float and coil bind NOT a spring breaking.........Help......I have to real good friends who run in the superstock class at our local circle track and both of them tell me it sounds like a bad spring thats all....Any suggestions???

 

[curtis]

Sounds like a bad spring to me. We run the beehive springs from CompCams with just a touch more lift than you have on our race car. Turning 6800 rpm all the time with no problems. If problems continue for you, you might want to check out the beehives .

 

[glen242]

OK heres the scenario (although it really happened)

Cruising the other night...just got the motor done...no more than 450 miles on her since everything was redone.

Engine... 350 4 bolt .40 over Dart Iron Eagle heads (2.02/1.96 180cc runner 64 cc chambers slightly shaved 100thous) Cam...Edelbrock 7102....234/244 @50 lift 488/510......Rockers Comp cams 1.6 rollers....total adjusted lift exhaust side .544 Elgin springs part #rv943x Single damper spring high rpm max lift .550.

Why did my exhaust valve spring on number 1 cyl break?

All clearances are well within specs. No coil bind. Seat pressure good etc.
I called the guy who built myheads and he recommended to go to a .600 lift spring if Im in the pedal a lot. Now wait a minute....when your idling at 900 rpm Im still at .544 lift on the e side or when Im at 5600 rpm Im STILL at .544 lift...it shouldnt change....I would think at TOO high RPM youd have valve float and coil bind NOT a spring breaking.........Help......I have to real good friends who run in the superstock class at our local circle track and both of them tell me it sounds like a bad spring thats all....Any suggestions???

0.100 (100 thousands) is not slightly shaved. Are you sure you got that right?? 0.125=1/8".

 

[Jack]

According to latest Elgin pro stock catalog # EPS-04:

RV-943X: Single w/damper, Max Lift = 0.490", Coil Bind @ 1.160", 110# @ installed height 1.700" (seat).

There is another spring with VERY similar part number (RV-1943X) ... specs: Single w/damper, Max Lift = 0.550", Coil Bind @ 1.160", 125# @ installed height 1.750" (seat). From personal experience, RV-1943X is occasionally installed at 1.800".

Suggest your info on RV-943X spring specs is in error and you have way too much valve lift for RV-943X spring. Possibly someone dropped a digit (1) when choosing/ordering spring. Possibly installer did not get offending spring completely seated into head's spring pocket (it happens) ... that'll make coil bind in a quick hurry. Based solely on Elgin Catalog Specs & the info you provided, I do not think it's a bad spring.

10thous is an average clean-up/straighten shave; 100thous is HUGE.
JACK:gap

OK heres the scenario (although it really happened)

Cruising the other night...just got the motor done...no more than 450 miles on her since everything was redone.

Engine... 350 4 bolt .40 over Dart Iron Eagle heads (2.02/1.96 180cc runner 64 cc chambers slightly shaved 100thous) Cam...Edelbrock 7102....234/244 @50 lift 488/510......Rockers Comp cams 1.6 rollers....total adjusted lift exhaust side .544 Elgin springs part #rv943x Single damper spring high rpm max lift .550.

Why did my exhaust valve spring on number 1 cyl break?

All clearances are well within specs. No coil bind. Seat pressure good etc.
I called the guy who built myheads and he recommended to go to a .600 lift spring if Im in the pedal a lot. Now wait a minute....when your idling at 900 rpm Im still at .544 lift on the e side or when Im at 5600 rpm Im STILL at .544 lift...it shouldnt change....I would think at TOO high RPM youd have valve float and coil bind NOT a spring breaking.........Help......I have to real good friends who run in the superstock class at our local circle track and both of them tell me it sounds like a bad spring thats all....Any suggestions???

 

[wallyknoch]

Jack`s information is correct. The Elgin RV-943X spring has a max lift of .490. not .550. Another Elgin spring that will go .550 lift is the RV-1943X which will probably be a better choice as it has more clearance. A RV-9902X spring will go to .600, but it`s dual and requires a larger spring pocket in the heads by almost .200. However the Dart heads may be correct for this spring.

good luck,

 

[waterboy1976]

Thanks guys for your help.....My head builder keeps telling me the RV943x spring is the .550 lift spring.....I cant find elgin pro stock catalog online...I found ELginind.com website but cant find a catalog..... Oh yeah...it was 10 thous....not 100 whoops.... I think Ill switch springs.......Thanks guys!!!

 

[Jack]

Last time I checked, Elgin did not have an online or downloadable catalog ... I contacted Elgin and requested a catalog ... Elgin mailed a hardcopy to me.

No offense intended, but your head builder is mistaken about max lift on RV943X.

If you install RV1943X with intent to gain more height, you MUST install the spring with an "installed height" greater than 1.700". To do so, you must either: have less shim under spring, or install longer valves, or install taller retainers, or install taller locks, or have heads' valve spring pockets cut deeper or some combination of those 5 factors. The installed height MUST be tall enough that when the valve is fully open at MAX valve lift that there's an additional 0.040"-0.060" valve & spring travel to prevent coil bind. If you install RV1943X at 1.750" and your cam compresses it to 1.206" ... you MUST also be able to compress it another 0.040"-0.060" before it coil binds ... otherwise you have same problem you have now.

BTW ... your current elgin RV943X is essentially the ubiquitous "Z28 spring" ... and has same specs ... it's a good spring ... but it's not made for more than 0.490" valve lift.

If you install taller, you have to check other things too. Check to see that retainers don't hit bottoms of rocker arms (throughout their range). You may have to grind away some on underside of rockers. The rollers must ride on the valve tips properly (throughout their range) ... pushrod length governs this. You may need different length pushrods too.

Simply switching springs won't do a thing but break your heart again ... you have to set them up properly. You MUST set it up for a taller installed height. This is a very basic requirement. Some folks can throw this stuff together without knowing-checking-measuring ... alot of em get lucky ... more than a few don't.
JACK:gap

 

[wallyknoch]

Jack`s Right

Jack, I dont know where you get the patience to sit down and write your answer. If more people would read it there probably would be less camshaft failure or problem threads on this forum that most of the time seem to blame the manufacturer.

 

[Jack]

I may be right ... but that info sure didn't originate with me ... I learned via noting both myself & others do it both right & wrong ... and most importantly ... RTFM ... read the freakin' manual. Most of the popular cam makers have detailed downloadable instruction sheets freely available on their websites that address valve spring install, degreeing-in a cam, rocker arm install, pushrod install, cam install etc.

I'm involved with local/regional asphalt circle track racing ... some of the guys are quite savvy and I've learned some real good chevy motor stuff from a few ... I've also learned that alotta blind/prideful/blissful ignorance exists in racing ... no different than rest of the world. I continue to recommend the novice car buff seek out & learn from local racers (drag, dirt whatever) ... but do recognize that just because one individual is a racer doesn't mean he's always right ... when it comes to basics, you can usually rely on the parts makers' instructions as a solid reference.
JACK:gap

 

[GerryLP]

Waterboy,

One has to remember also that the cam manufacturer usually recommends what spring to use at the installed height and as well as the needed valve seat or lift pressure the spring should have. Once you have the new springs, take them to a competent machine shop and ask them to test each spring at the required installed height and valve lift to ensure that the cam won't sufer too much pressure and flatten a lobe.

Some manufacturers of springs have charts in increments of 0.100" of lift and the average pressure the spring will excert on the cam lobe; however, the best one could do with charts is to interpolate the point in the chart where the gross lift for your cam lies. 3 - 5 lbs of pressure difference is probably close enough.

Some builders recommend adjusting the installed height on all 16 springs to match the one spring with the lowest installed height (i.e. if the spring mic shows a 1.835 height for the valve to close at the seat, and the highest height found was 1.855, then install all the valve springs at the 1.835" install height). The one concern with this is to ensure that the newly adopted installed height (1.835") is tested for the desired seat pressure. I prefer to just reach the recommended installed height and reach it by combining spacers.

GerryLP:cool