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I have been having some fun again! We put in the HV oil pump, comp turbo camshaft, new LS7 lifters, head stud kit and heads with good comp springs. It sounded mint when fired up, got it all ready and meet the tuner 3 days before race. Got all the low end fuelling good, went out to tune on the water and only got up to about 4000-4500 rpm, it was just thinking about making boost then it stopped, got it going again and limped back to trailer. Compression tested and found #2 cylinder no compression, pulled head off and found valve has been smacking into piston and bent a bit, pull other head and found #3 cylinder has hit but not as bad. Have found the lifters on the inlet valves on these crook cylinders will not draw out. They can travel up and down in the lifter bore a bit but will not come out! Can shine a torch thru and can see one side of one lifter at the bottom, it looks normal from the small part I can see. So am going to strip the engine and push the stuck lifters all the way thru and out the bottom. Any idea on whats caused this? Cam has 615 lift, can post specs on it shortly if that's a help, lifters are genuine chev LS7. Could they have just not handled the lift and mushroomed?
The springs and retainers came with the cam from compcams, piston to valve clearance was 2.1mm exhaust and 2.5mm intake, standard push rods, not sure if heads had ever been milled- I would say not
Thats alot of lift and duration... Sounds like a PTV clearance issue to me. Was it degree'd?What poundage springs?
IMO if you want the thing to live put a small cam in it. The factory heads do diddly above .550 lift anyway. Run a 212 to 218 duration max at 112 with .565 lift and it will be gentle on the valve train and last. You can make 1000hp with a baby cam like that.
Hey Huff, I'll let this info sink in for a bit. It sounds like you have done all the appropriate steps. A bit of a head scratcher.
A little thinking out loud... Were the heads off of the previous engine? Perhaps some junk ended up in the valve guides or something and hung the valves open. Wouldn't have to be the valve itself. Anything from the lifter to the valve. Now that I think about that a little, was it a valve problem that is causing the lifters to stick in the bores... OR lifters stuck in the bores that caused the valve problem??? There may be something to that.
Are all the pushrods straight as an arrow? Roll them on a flat surface. Any bent ones will become obvious.
While it's not completely input on a solution to the problem (may or may not be)...
I do agree with the above about the cam specs. That's pretty big and aggressive for a build like yours that's intended for long run times at wide open throttle and too much intake duration for your intended max RPM. Not a hideous choice in that respect, just a little more than I'd have gone. Fortunately, power band wise, with a jet most times slight to moderate losses in lower RPM torque/power can go mostly unnoticed and if it never sees peak HP rpm... so what. My biggest concern is valve train reliability and would have chosen more on the conservative side for that reason. Just my two cents. At this point, it is what it is. Let's figure out what happened.
I'd like to see a picture of the pistons and also the lifters when ya get them out.
Thanks so much for the input guys. I would have to find out the spring ratings from the engine builder who got me bits. It was bit of a **** up as I actually requested a different cam, but somehow that never made it in his shipment to NZ and I ended up with this custom grind which I wasn't that happy about as I just wanted an off the shelf cam that I had read a build on and worked well. I wanted a Compcam 281LR HR13, what's the thoughts on that cam? It's been mentioned to me that if the lifters don't have enough clearance in their bores they can nip up, but I wouldn't have thought I could get any movement out of them if that was the case. The push rods on the bad cylinder are very slightly bent, the rest appear fine. The guy who supplied me the engine is an engine builder as well, so he fitted my bits for me. He told me he removed the valves from my heads and checked them as he knew they came from my last engine which had issues, he degreed in the new cam, we didn't have an adjustable double row timing set on hand so he just used the stock single row to get me going as we were running out of time. He told me it went in bang on where it needed to be. This pic is the worst cylinder
If a guy put that together without checking the PTV clearances I'd say that's on him. No way that should have happened.
Originally Posted by Huffa
...piston to valve clearance was 2.1mm exhaust and 2.5mm intake...
Huffa,
After giving it some thought and looking at the pictures I definitely think the issue is related to whatever is going on with the lifters and/or lifter bores.
That's certainly not a light kiss, it's a considerable impact and it's fairly deep. Makes all the sense in the world that the lifter stuck in the bore and hung those valves open. Additionally evidenced by the pushrods being bent on those two valves too.
So, now... Why did the lifters bind in their bores? The answer is currently beyond me. I'll be curious to know what you find.
On the cam, I agree with the statement below. Cam it for 6000 or thereabouts. Soft ramps and whatever lift that gets you is fine.
Originally Posted by Forcefed86
Compcam 281LR HR13 cam is still way too aggressive IMO.
Int Duration @ .050":231
Exh Duration @ .050":239
Valve Lift Int (in.): .617
Valve Lift Exh (in.): .624
IMO you want like a 212 to 224 duration around 112 with .575 or less LIFT on a super mild ramp lobe...
I'm listening about the grind, will put something softer in. My engine builder who is not the guy I got the engine from and fitted the cam and so on says he use to lube lifters up and slap them in, if they dropped in nice then all good until he had a lifter stick in its bore on some dart heads, bending a valve bla bla, so he says now he mics every lifter and makes sure theres .002 clearance, apparently there's a big variance between each lifter, hers a pic of one of the lifters that did come out easily and haven't caused any issues, but is this wear excessive for a half hours running?
I'm listening about the grind, will put something softer in. My engine builder who is not the guy I got the engine from and fitted the cam and so on says he use to lube lifters up and slap them in, if they dropped in nice then all good until he had a lifter stick in its bore on some dart heads, bending a valve bla bla, so he says now he mics every lifter and makes sure theres .002 clearance, apparently there's a big variance between each lifter, hers a pic of one of the lifters that did come out easily and haven't caused any issues, but is this wear excessive for a half hours running?
High end build, yeah... of coarse. But, nearly no one checks lifter clearances, especially on a "junk yard dog" build... and understandably so. It's highly uncommon that they are an issue. And likely not the issue here too.
I wouldn't "expect" to see scoring like that at all.
Is it costly to have a custom grind imported from the US? Easier/cheaper to get an off the shelf grind? What are your cam options there?
The lifter is scored on both sides, but one side is worse than the other. My man who supplied me the engine has kindly sent me some replacement pistons and an LS1 camshaft, I don't know the specs on it but someone said they are the same as LQ4, correct or false? Not sure about cam options here for LS engines, would a stock LS1 or 2 cam be a good option? Any cams possible, but I'm on a shoestring budget as is obvious for trying to boost a stock bottom end, whats happened wasn't supposed to!
Here's the other piston #3 that hit, but no where near as bad
Saturday night... Had a few beverages. Gonna let most of that sink in.
I will say, however... that as far as valve train longevity and reliability goes, you can't get any better than a stock camshaft. Where they might lack is in bottom end torque when compared to other low duration cams... for lack of overlap I presume. Emissions related, I would guess.
And, well... top end power for their lack of intake duration.
HOWEVER... much in the way of intake duration or lack there of, can be made up for when it comes to turbocharging. Low end torque? Not so much, but it doesn't matter too much with a jet.
There are any number of cams out there that will give good results.
But again...the fact there is hard contact on more than one cylinder...I refuse to believe it is a lifter fault. Even more so given it appears to be intake valves each time.
There is a serious PTV issue, and it's either spring or valve/cam timing related. What springs were used and were they installed correctly ?
.100 Exhaust and .080 Intake... are the general acceptable guidelines. Sounds like the OP isn't sure if the heads have been cleaned up/milled either? What about the deck? Running.082 exhaust too tight IMO. And it's darn close on the intake as well at .098. I know guys run closer and get away with it. But throw in a clean up on the deck/heads and I could see it causing issues. Also did that cam have any advance ground into it? How did the builder check PTV clearance. I really don't see anything else causing this. Simplest answer is usually the correct one.
Nothing wrong with an LS1 cam. Guy making 800+hp with them. Personally I think the LS9/ZR1 cam everyone hates on is better for power above 5500. You'll pick up around 100hp above 5k over the truck cam. They are $125 new from summit I believe.
Good little article where they tested a ton of OEM cams on a stock 5.3. LS9 is the biggest bang for your buck.
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A lot of assuming takes place in internet diagnostics. It's very difficult to get every little detail.
Here's my assumptions:
The springs are (actually and factually) as specified and provided by the cam manufacturer
The springs are installed at least reasonably close to their specified installed height
All of the cam lobes are within spec
The piston to valve clearance was, in fact, accurately measured on one cylinder
The block wasn't decked and the heads weren't surfaced after checking piston to valve clearance (Pretty sure you'd know that)
The cam was checked with a degree wheel
The cam was installed straight up, not advanced (or retarded)
The cam was not advanced after checking piston to valve clearance
The engine could easily be turned over manually
The engine cranked over normally
The engine idled smooth
The engine ran fine up to 4300 RPM
The engine didn't exhibit any odd noises prior to it shutting down
Is any of that incorrect?
Here's the curious part. The intake valve is chasing the piston. You can float an intake valve all day long and not contact the piston. So, it was set up wrong, not checked correctly, there were cam lobe variances, or something held the valve open. All but the last would have been relatively evident if the above assumptions are true. Even if the timing chain had wear/streatch and was loose, it would retard the cam giving additional clearance to the intake valve.
12-09-2016, 07:53 PM
