[DoneInAMinute]

I started this thread last year:

http://www.chevelles.com/forums/showthread.php?t=237414&highlight=454+is+sick

and the update is that I took it to the shop that built it and they found 2 broken intake springs and 1 broken exhaust spring. they think that it is from over-revving but that sounds shady to me considering i've NEVER revved it over 5500-6k and in my opinion thats well within the limits of about any street motor. they put some much better springs in it (they originally used the ones that came with the rebuild kit) and gave it back to me running very well. my question is...what do you think caused this (besides over-revving)? what common things could they have messed up in the build process? it's pretty close to a stock engine except a weiand intake, headers, holley 750 and harolds cam so i don't think it's an issue with mismatched parts. i wouldn't care since it's now fixed but they charged me to fix what I think might have been their fault AND i'd like to avoid it in the future if it was something I did. Thanks for reading!

James

 

[M.Maner]

James,the springs that you bought in the "Kit" were they the springs that came with the cam you bought from Harold?
Mike

 

[vrooom3440]

I think Mike nailed it...

Valve springs and camshaft have to be a matched set. In general high performance cams have more lift and often faster valve open/closing speeds than OEM cams. So they require stiffer valve springs to control the inertial loads of the valvetrain. Further performance cams are generally designed to operate at higher engine speeds which also increases the demands on valve springs.

Check your camshaft specifications for spring requirements. Then check that your engine builder used matching springs and measured/shimmed them to specification this time. As to responsibility... did your builder know you were using a high performance camshaft? Did you provide them the full specifications? Do they do much work on high performance engines? If you cannot answer YES to each and every one of those questions, then you cannot fully blame them either. I would not expect a basic rebuild to either change valve springs or to measure/shim them to high performance specification.

Just be glad you did not break more valve springs or a valve. I recently broke an outer exhaust valve spring. In the teardown I found that 14 of 16 inner valve springs were broken. I was fortunate that the exhaust valve was not bent/broken. It could have been time for a new crate engine instead of all new valve springs/spring seats/spring shims/retainers/locks/seals.

 

[Guest]

Or call UDHarold here..

(662) 562-4933

and ask him what springs he recommends and go.

And if they aren't the same springs that broke, then nail somebody big-time for selling you the WRONG springs in the kit! And if they get "P/O'd", then just say that Harold told you what springs should have been furnished w/ his cam, BUT WEREN'T!!

pdq67

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[DoneInAMinute]

actually, the builder ordered the cam and all of the parts for the rebuild. I wanted it that way because as far as engine internals go it's my least knowledgeable area on a car. it's a pretty mild grind i wouldn't really call it a "high performance" cam maybe just a little hotter than stock. I just wanted a super-reliable street motor that makes a decent amount of low RPM torque which the displacement alone should do most of. but I will inquire as to exactly how he chose the springs he did. thanks for the info so far guys.

 

[Philip]

Did the builder also assemble the engine?

 

[Tom Mobley]

if he used the springs that came in the engine rebuild kit that's the problem. Those springs are cheap. Get the right springs and install them.

 

[DoneInAMinute]

yes, he assembled the engine as well as acquired the parts. I didn't know that valvesprings were so specific. I spoke with the builder the other day and he has now put on some comp springs that are apparently much better than what came with the rebuild kit. should I be content with this or should I investigate and get some "matched" springs and put them on? thanks.

 

[z15cam]

You can not rev a Moderate Hydraulic Flat Tappet BBC over 5200 rpm with Stock Rockers and Valve Springs without the risk of Breaking Springs, Rockers and possibly the Rocker Stud.

Put a NEW Set of Descent Springs in her like CCA-924-16’s, Descent Roller Rockers and I also recommend ARP Rocker Studs and 7/16" Push Rods - You should be safe to 6000 rpm; other words, just keep spare Valve Train Components in the glove box if you should happen to over rev – been there done it.

 

[vrooom3440]

You will need to get a lot more specific with him than "some comp springs"... Comp Cams sells several different product lines of valve springs. Each product line probably includes a dozen different specification springs for different applications. "Some comp springs" could be any one of a few hundred products.

As I indicated earlier, I got a Special High Intensity Training on just this topic a few months ago. It was very educational because like you I had not really thought much about it nor realized just how critical those darn springs are to mechanical harmony. The rub is that the springs must match up to the cam and the seats and retainers must match up to the springs. Individual parts vary all over the map and mixing parts from different vendors will make it much more difficult (bordering on impossible) to get them all matched up properly. I ended up replacing a lot of parts when it was all done so that I could be certain that it would all work together. And also to do all I could to make sure it never happens again

What I would do in your case is get your cam specifications and recommendations first. Pay particular to spring specifications like fitted load and maximum open load. Next I would get all of the component part numbers being used to put the engine together. This includes springs, seats, and retainers. Then you can do some research and double check everything including: installed height, installed load, minimum open height, load at minimum open height, spring ID versus seat and retainer (need to check both inner and outer if dual spring), and spring OD versus seat and retainer.

I would also ask the builder if they shimmed the valve springs. This would indicate they measured the installed height and adjusted it to match specs. A good thing to do :yes:

 

[DoneInAMinute]

I got the info on the springs. they are comp batch 911-16

seat load: 122 lbs @ 1.9"
open: 309 lbs @ 1.4"
spring rate: 373 lbs/in
coil bind: 1.200

I am waiting to hear back on the cam specs. I thought I had them in the glove box but apparently not. I do know that it is a fairly mild street grind. thanks.

james

 

[Guest]

Please back off CC's springs and call Isky here, imho.....

pdq67

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