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Poor engine dyno results after Cam/Lifters/Springs/Trunions?
Have an odd situation that has us stumped and I usually have no issues spotting the culprit, so I'm blaming the Crane lifters since they seem a bit noisy.
Put a stock unknown mileage gen 4 5.3 (flat tops, 243 heads) on the engine dyno with a LS6 intake and LS2 cam, and a stock LS3 mechanical water pump.
Tuned with Holley Terminator. ~28 degrees of peak timing on 93. 392 HP, 380 TQ
We switched to E85 to break 400 HP, and a couple of pulls later the drain plug vibrated out of the oil pan and the engine locked up very quickly.
We tore it down, found that a few rod bearings had spun.
My buddy rebuilt the engine. Swapped in a good crank, all new bearings, rings, etc.
The engine is destined for boost and a lot more power, so with the rebuild came:
-Summit Ghost cam (222/233 115+3, .600/.575) and springs
-LS9 gaskets
-Crane 144530 lifters since genuine LS7 are impossible to find for less than $400 right now
-Topped it off with a trunion upgrade on the stock rockers.
Got it on the engine dyno hoping for as close to 450 HP as it could get with the LS6 intake before the Hi Ram gets swapped on (mainly for looks, its a nice truck).
Back on 93, similar tune to what was used last time, but with the fresh engine and cam/springs.
Fresh plugs, everything else was the same as before, including coils/plug wires, etc.
Picked up only 18 HP, similar torque number, so 410 HP, 380 TQ.
Lost torque everywhere below 5800.
Lifters are noisy. Checked lifter preload, it is near the top of Crane .060-.090 spec, but still within spec with the stock pushrods.
Not enough has changed in the setup to create a new variable. LS9 head gaskets have likely dropped compression to ~9.75:1.
Oil pressure is great. About 40 at idle, 80+ at higher RPM, but it seems like the lifters are bleeding down very quickly.
If you stop the engine from firing and give it a couple of cranks, you can see the lifters bleed down some lift almost instantly when you stop cranking.
He went ahead and ordered some Summit lifters yesterday to see if they are any better.
Has anyone used the Crane lifters with such bad results?
I can't remember the numbers off of the top of my head but they were all within spec.
Its back together and running, and the Summit lifters are noticeably quieter.
You know if compression is bleeding down or if it is just that low from the combination of static compression and cam events?
Also, I wonder if the 410 hp is artificially high? Looked like power curve was falling then spiked?
We did 426 HP last year on the same engine with a smaller 222/225 cam with mild lobes and less lift on a 112 LSA. Torque was better throughout the entire pull, even up top.
I expected the Summit cam to do another ~15 HP on top of that, with maybe a few better thanks to the fresh rings.
160 huh? The interesting thing is that torque never moved from the rebuild/upgrade. 392 does seem generous to start as Darth mentioned. When you say springs, what springs?
Lifters made no difference.
Hi ram lost torque everywhere.
Expected on the Hi Ram right? No surprise there.
On the lifters, do you still see the quick bleed down? I've seen that as well. On my own C5, and a customer 2010 Camaro.
Expected on the Hi Ram right? No surprise there.
On the lifters, do you still see the quick bleed down? I've seen that as well. On my own C5, and a customer 2010 Camaro.
It didnt pick up anything anywhere.
Springs are the TFS springs recommended by Sunmit for the cam.
Rechecked cranking compression, 170-180 on every cylinder.
Bleed down on the Cranes was far worse than normal.
Springs are the TFS springs recommended by Sunmit for the cam.
Rechecked cranking compression, 170-180 on every cylinder.
Bleed down on the Cranes was far worse than normal.
That all sounds normal. Good.
I've tuned a few folks who have NA stuff with the Holley Hi Ram, just cause it looks cool. Whatever. Ha!
Nobody notices what you and me have seen with the bleed down.
From there it's just combo. I'd bet a TBSS intake would be fun to try.
I'd expect fast bleed stuff to be more normal at high rpm.
I was thinking more along the lines of higher speeds increase the momentary weight of the valvetrain due to acceleration. So increased load on the lifters. Likely I am stretching. That was my thought though.
I was thinking more along the lines of the old Rhodes lifters which were meant to have high bleed rate. So at slow speeds they tamed a big cam. At high speeds not enough time to bleed, so the cam acted more normal.
Old school stuff. They never really caught on.
Graph looks terrible, springs arent controlling the valves (or dont appear to be) - and will be weaker when you've got positive pressure on the other side working against them when you add boost. I'd look there first - they either need to be shimmed properly or a different package needs to be used. Graph goes to **** at 5400 rpm.
02-14-2020, 09:16 AM
Poor engine dyno results after Cam/Lifters/Springs/Trunions? 
