Valve stem seals crushed, LS7. More spring?

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72sat
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Re: Valve stem seals crushed, LS7. More spring?

Post by 72sat » Tue Jan 03, 2017 6:35 am

Who recommended the springs. Seems a little lite (seat pressure lite) for a roller. Definitely need to check retainer travel with everything assembled. Should check piston to valve clearance;with clay on top of piston

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Re: Valve stem seals crushed, LS7. More spring?

Post by mdrew » Tue Jan 03, 2017 1:02 pm

I covered all that already.

Anyone have experience with Comp's conical springs? I love the concept, but have zero real word experience.

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Re: Valve stem seals crushed, LS7. More spring?

Post by RW TECH » Tue Jan 03, 2017 6:48 pm

72sat wrote:Who recommended the springs. Seems a little lite (seat pressure lite) for a roller. Definitely need to check retainer travel with everything assembled. Should check piston to valve clearance;with clay on top of piston
How much spring pressure should it have, compared to, say, a NASCAR engine that runs well above 9K RPM with over .800" lift?

The NASCAR engine will have 160 lbs on the seat or less.

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Re: Valve stem seals crushed, LS7. More spring?

Post by wyrmrider » Tue Jan 03, 2017 8:13 pm

well you can ask the camgrinder
but you can also ask the camgrinder who else runs those lobes and ask them but they man not tell who else is having problems
you can go to Spring mfg with valve weights and rev range but that leaves out how radical the lobes are
lots of discussions on duals vs beehives on those LSs
still no discussion on larger or larger- taller valvesprings
used to do it all the time on other engines
NASCAR may be running the lighter exhausts
and is this not an HR?

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Re: Valve stem seals crushed, LS7. More spring?

Post by mdrew » Tue Jan 03, 2017 8:40 pm

This cam is a HR. HUC lobes, which are supposedly a "gentle" profile. Comp suggests I cut the guide down, and these springs are their premium spring to use. I asked about their new conical springs, and was told they won't work, which I think is BS. I don't know I bother calling Comp. They have the 7230 conical that looks like it will work just fine. I like the idea of the lighter spring and retainer, but unsure of the somewhat, unproven round wire conical Comp design. Don't like being a test pilot.

I do not think there is enough room to use BBC springs. I may be incorrect, but it's tight between the springs, as well as the spring to head clearance. I'll take a closer look.

I will most likely limit lift to .650 with the next camshaft anyway. Keep intake duration under 234 at fifty with a 10-15 deg split. The inverse roller has me quite curious, if low lift OL can be reduced over a standard lobe. I have not used one before, however, so I don't know how to guesstimate. Either one of Mr. Jones' cams, or something from CamMotion, maybe EPS. Need to get that figured out pretty soon.

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Re: Valve stem seals crushed, LS7. More spring?

Post by wyrmrider » Tue Jan 03, 2017 10:13 pm

many posters think you have plenty of retainer (locks) to guide and I hate to cut guides down unless I absolutely have to- frequently used longer valves
what about it speedtalkers- anyone use the newer conical springs or larger dia springs

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Re: Valve stem seals crushed, LS7. More spring?

Post by Warp Speed » Wed Jan 04, 2017 5:18 am

wyrmrider wrote:well you can ask the camgrinder
but you can also ask the camgrinder who else runs those lobes and ask them but they man not tell who else is having problems
you can go to Spring mfg with valve weights and rev range but that leaves out how radical the lobes are
lots of discussions on duals vs beehives on those LSs
still no discussion on larger or larger- taller valvesprings
used to do it all the time on other engines
NASCAR may be running the lighter exhausts
and is this not an HR?
Larger diameter springs are NOT the way to go for many reasons. Hell, you got pro stock running 1.500 diameter at 1.150+ lift and 10,500rpm.

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Re: Valve stem seals crushed, LS7. More spring?

Post by Warp Speed » Wed Jan 04, 2017 5:28 am

And looking back through the thread, I would get rid of the heavy exhaust valve! The weight increase here was a bigger hit than the increased moment of inertia from the new rockers. Couple that with a stiffer rocker, and you have exposed a problem.
PSI springs as suggested earlier.

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Re: Valve stem seals crushed, LS7. More spring?

Post by mdrew » Wed Jan 04, 2017 9:22 am

I do have a set of the second rev OEM SI valves I could drop in. Went with these Ferrea's as a compromise between OEM and a solid stemmed valve that would have closer to 100 grams. Friggin Ti valves were another grand or better..... The heads are being fit with Mold Star 90 guides right now. The guy doing the head work, for whatever reason, is not recommending the SI filled valve with the MS90 guides though....

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Re: Valve stem seals crushed, LS7. More spring?

Post by RW TECH » Wed Jan 04, 2017 9:54 am

wyrmrider wrote:well you can ask the camgrinder
but you can also ask the camgrinder who else runs those lobes and ask them but they man not tell who else is having problems
you can go to Spring mfg with valve weights and rev range but that leaves out how radical the lobes are
lots of discussions on duals vs beehives on those LSs
still no discussion on larger or larger- taller valvesprings
used to do it all the time on other engines
NASCAR may be running the lighter exhausts
and is this not an HR?
Or you can put a set of parts into a test rig & find out what they will really do. That's the smart approach. Otherwise you're pretending, guessing, and hoping. Plain & simple.

The next best thing is to get a combination of parts that have already been verified as a system.

Larger = more mass so that's not good. More spring force isn't always good either. Put more spring load on a system that's been dialed in and pretty much it'll be a hot mess once you're done. Not uncommon to see "the fix" involve taking spring force away instead of adding it.

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Re: Valve stem seals crushed, LS7. More spring?

Post by wyrmrider » Wed Jan 04, 2017 12:53 pm

More mass?
depends on the wire diameter and length
longer wire does twist less (per inch of wire)
I do not have the answer for this, just asking
but the exhaust valve weight is too obvious
but I've run heavier
will be interested in what ends up working here

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Re: Valve stem seals crushed, LS7. More spring?

Post by 72sat » Fri Jan 06, 2017 4:38 am

RW TECH wrote:
72sat wrote:Who recommended the springs. Seems a little lite (seat pressure lite) for a roller. Definitely need to check retainer travel with everything assembled. Should check piston to valve clearance;with clay on top of piston
How much spring pressure should it have, compared to, say, a NASCAR engine that runs well above 9K RPM with over .800" lift?

The NASCAR engine will have 160 lbs on the seat or less.
They are not running these heavy ass components. Spring diameter does not dictate spring rate

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Re: Valve stem seals crushed, LS7. More spring?

Post by RW TECH » Fri Jan 06, 2017 7:39 am

72sat wrote:
RW TECH wrote:
72sat wrote:Who recommended the springs. Seems a little lite (seat pressure lite) for a roller. Definitely need to check retainer travel with everything assembled. Should check piston to valve clearance;with clay on top of piston
How much spring pressure should it have, compared to, say, a NASCAR engine that runs well above 9K RPM with over .800" lift?

The NASCAR engine will have 160 lbs on the seat or less.
They are not running these heavy ass components. Spring diameter does not dictate spring rate
In spite of the weight difference they're running about 2K higher RPM with about .200" more valve lift.

BTW, The rocker weight difference would be little to none if he would have kept the stock rockers.

Otherwise, I don't see any mention of spring wire or a correlation of that and spring rate, but already aware of that too.

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Re: Valve stem seals crushed, LS7. More spring?

Post by mdrew » Fri Jan 06, 2017 9:02 am

Here's a pretty good read on the SAM Racing Stock Eliminators LS7 build... http://www.dragzine.com/tech-stories/en ... nator-ls7/

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Re: Valve stem seals crushed, LS7. More spring?

Post by Newold1 » Fri Jan 06, 2017 5:40 pm

It is obvious from the Dragzine article that Samtech did a great job of extracting another 100HP out of a as built COPO LS7 NHRA spec. engine. I think the main things that are represented in the article is that the big increases came from the right camshaft spec., cylinder re-sleeving to stop bore distortion and that special ring package that Total Seal came up with for the ,.043" ring groves of the pistons used and improving windage and oil control.

The information from the article that confuses me is that they give the replacement camshaft specs. twice and they are different each call out. The seem to be saying that they greatly increased intake duration versus exhaust duration, but the printed numbers indicate the opposite. Confusing. It is known that the GM LS7 heads even with added port work have low percentage numbers on the exhaust side and I am not sure in this case whether they were actually adding a lot more exhaust duration to possibly help with that possible issue. In any event if you look at the dyno output numbers you see that even with these fine tuned improvements that a 440 cubic inch LS7 COPO engine has power and torque that is slowing at about 7000 rpms and starts falling at 7400 rpms even with all of the improvements they made. Question here being how much more power up to 7000rpms and at +7400rpms could be made with this engine with a different camshaft spec. that allowed more than .641" valve lift?

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