SCHOOL BUS
DLRA T-O
- Joined
- Jun 27, 2007
- Messages
- 10,513
A customer came to us asking if we would install a set of stiffer valvesprings and heavy duty pushrods in his '05 Cummins. Apparently he had gotten them extremely cheap or free and just wanted them installed even though his application didn't require them. We installed them and he went on his way. Roughly two to three weeks later he came back because he had noticed a funny noise. It sounded like someone bouncing a basketball in the air filter. That typically means pushrod issues or valve seat issues so we pulled the valvecover to inspect. We found the valve lash to be excessive on nearly all the cylinders. We reset the valve lash to proper clearances and sent him on his way. After 700 more miles of commuting he was back complaining of the same problem. We pulled the valvecover again to find the valve lash excessive on most of the cylinders again. This time we knew it wasn't an installation error on our part. Something was wearing down allowing more clearance. The pushrod cups seemed to be slightly the wrong radius so I assumed the pushrods were being formed into the correct shape by the rocker arm ball. To remove that possibility we re-installed the factory pushrods set the valve lash and sent the customer on his way a third time. Well, 700 or so miles later he shows back up to say the issue has come back. This time we knew there was another problem. We profiled about 5-6 of the camshaft lobes and found significant wear. Some of the lobes had lost .015" of lift in just a few thousand miles. The only part left to blame was the freebie valvesprings. Increasing valve spring pressure directly increases the force between the lifter and cam lobe. Our only choice was to remove the super stiff valvesprings and hope the cam would stop wearing down. As a side note, most cams are surface hardened on the lobes and journals to decrease wear. Once you've worn through the hardened outside core, the camshaft will wear very quickly. At this point we had no other choice but to try it since the customer wasn't quite financially ready to pay for a camshaft install.
Well unfortunately, a few weeks later the customer dropped back by to tell us the noise was back and he was going to have to either prepare for a cam swap or park the truck. He talked with Zach from Hamilton cams and they set him up with their new cam 181° .280” intake, 210° .305” exhaust along with a set of their upgraded valvesprings.
I won't bore you with a bunch of pictures of the install. We've documented cam swaps before.
Here's a picture of the tip of one of the lobes of the factory cam. This truck has used Amsoil Synthetic engine oil until this incident. Not sure if it's relevant, but I thought I'd mention it.
We dyno tested the truck before the cam swap in several ways. We dyno'd it with the loose valve lash that it came in with. Then we readjusted the valve lash back to factory specs to see if there was any difference. This was a shocker for me.
There was a little over 13 peak HP gained, but there was 10 HP gained over the entire powerband and it spooled quicker to boot.
The next part of the project was to actually install the cam and valve springs. Here's a quick pic of the cam going in.
Here's a shot during the valvespring swap. The clean springs on the right are the Hamilton springs. The oily ones are stockers.
Here's a pic of the springs as they came in the box.
I've installed quite a few cams from different manufacturers and it's always a good idea to verify the valve lash specs. Sometimes stock lash settings aren't the best for aftermarket lobe profiles. I called Hamilton and talked to Ryan. He told me three times that I could run the exhaust lash a little tighter at .015" instead of .020" but my EGT would be higher. I kept thinking to myself, "Why would I want my EGT to be higher?" I assume he meant it would perform better in some situation, but there would be the side effect of higher EGT.
I decided to break in the cam then dyno test both lash settings. Breakin required 5 minutes at 1500 rpm followed by resetting the valve lash. Then a 50 mile easy cruise followed again by resetting the valve lash. Then it should be ready.
So here's the before and after w/ factory valvelash.
That's 28.7 peak HP gained, but the more important aspect is that from 2500 rpm to 3300 rpm it averaged a 29.7 HP gain throughout. The biggest gain was at 3300 rpm which was 40HP.
Next we tightened the exhaust valve lash down to .015" and redyno'd the truck.
Here's the difference between factory lash (.010" intake, .020" exhaust) and the recommended lash by Ryan (.010" intake, .015" exhaust)
Factory lash in blue, tighter lash in red.
It's within 1 HP peak, but the spoolup was a bit slower. This cam has more valve overlap than stock. More overlap works well when backpressure is less than boost, but hurts performance when backpressure is higher. During spoolup conditions most turbos have higher backpressure numbers until the turbo lights. So typically, increasing overlap will hurt spoolup. By reducing the exhaust lash by .005" we have effectively increased the valve overlap which makes this condition even worse.
For me, I'm impressed. Increasing the entire powerband by 30HP without adding fuel is quite impressive.Relentless Diesel
Site Admin
Well unfortunately, a few weeks later the customer dropped back by to tell us the noise was back and he was going to have to either prepare for a cam swap or park the truck. He talked with Zach from Hamilton cams and they set him up with their new cam 181° .280” intake, 210° .305” exhaust along with a set of their upgraded valvesprings.
I won't bore you with a bunch of pictures of the install. We've documented cam swaps before.
Here's a picture of the tip of one of the lobes of the factory cam. This truck has used Amsoil Synthetic engine oil until this incident. Not sure if it's relevant, but I thought I'd mention it.
We dyno tested the truck before the cam swap in several ways. We dyno'd it with the loose valve lash that it came in with. Then we readjusted the valve lash back to factory specs to see if there was any difference. This was a shocker for me.
There was a little over 13 peak HP gained, but there was 10 HP gained over the entire powerband and it spooled quicker to boot.
The next part of the project was to actually install the cam and valve springs. Here's a quick pic of the cam going in.
Here's a shot during the valvespring swap. The clean springs on the right are the Hamilton springs. The oily ones are stockers.
Here's a pic of the springs as they came in the box.
I've installed quite a few cams from different manufacturers and it's always a good idea to verify the valve lash specs. Sometimes stock lash settings aren't the best for aftermarket lobe profiles. I called Hamilton and talked to Ryan. He told me three times that I could run the exhaust lash a little tighter at .015" instead of .020" but my EGT would be higher. I kept thinking to myself, "Why would I want my EGT to be higher?" I assume he meant it would perform better in some situation, but there would be the side effect of higher EGT.
I decided to break in the cam then dyno test both lash settings. Breakin required 5 minutes at 1500 rpm followed by resetting the valve lash. Then a 50 mile easy cruise followed again by resetting the valve lash. Then it should be ready.
So here's the before and after w/ factory valvelash.
That's 28.7 peak HP gained, but the more important aspect is that from 2500 rpm to 3300 rpm it averaged a 29.7 HP gain throughout. The biggest gain was at 3300 rpm which was 40HP.
Next we tightened the exhaust valve lash down to .015" and redyno'd the truck.
Here's the difference between factory lash (.010" intake, .020" exhaust) and the recommended lash by Ryan (.010" intake, .015" exhaust)
Factory lash in blue, tighter lash in red.
It's within 1 HP peak, but the spoolup was a bit slower. This cam has more valve overlap than stock. More overlap works well when backpressure is less than boost, but hurts performance when backpressure is higher. During spoolup conditions most turbos have higher backpressure numbers until the turbo lights. So typically, increasing overlap will hurt spoolup. By reducing the exhaust lash by .005" we have effectively increased the valve overlap which makes this condition even worse.
For me, I'm impressed. Increasing the entire powerband by 30HP without adding fuel is quite impressive.Relentless Diesel
Site Admin
