Question about lifter spring pressure limit

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matt030305

matt030305

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Hey FABO techs, this is my first time rebuilding a complete top end of an engine and I had a couple of questions on the lifter tolerance I plan on running.

1972 340 block that is being converted to hydraulic roller cam and getting trickflow 190cc heads (TFS-16094-16)


Here are the relevant specs:

They are Morel Hydraulic Roller Lifters
Suggested max spring pressure: 100-180lb seat pressure and 280-380lb open pressure

The preassembled heads I got from trick flow have 1.550” dual springs
138lbs @ 1.950” installed height
430lbs @ 1.250” open
420lb/in rate
.680 max lift

The Cam I purchased has valve spring requirements with my 1.6 ratio Harland sharp rockers of:
145lb @1.800” closed pressure (installed height)
345lb @1.250” open pressure

My questions are:

1. Will my lifters fail due to the specs of my springs and cam? For the lifters, is the max spring pressure based off of the cam specs or the actual valve spring specs?
(I.e. max spring pressure for lifters when valve is open is max 380lbs whereas the valve spring is rated for 430lbs. Cam is rated at 345lbs)
I just don’t want to damage the lifters as that will be an expensive mistake.

2. Will my springs be able to support the camshaft spring pressure?

Can’t thank FABO members enough for the knowledge that you guys have on here.
 
The Cam I purchased has valve spring requirements with my 1.6 ratio Harland sharp rockers of:
145lb @1.800” closed pressure (installed height)
345lb @1.250” open pressure
Click to expand...

The valve lift is .550 with 1.6 rockers?

This will likely add some confusion to the OP, although it’s not the intent.
The TFS-16094 springs are PAC 1294’s in a TF box.
The TF specs don’t exactly agree with the PAC specs([email protected]/[email protected](.550 lift), 428lbs/in).
I’ve tested the 16094 springs, and my results basically agree with the PAC specs.
So, my experience with them is the actual spring loads as installed on the heads is higher than what the paperwork that comes with the heads indicates.
“Ymmv”

And then there’s this:
TF’s own spring chart, which shows the specs for the 16094 to match the PAC specs…….. which doesn’t match the specs in the paperwork that comes with the heads.

https://static.trickflow.com/global/images/chartsguides/t/tfs-16959-16.pdf
 
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Fwiw, imo fundamentally there is no problem running spring loads of 150/400 with a HR cam.
Provided all the components are up to the task……..and for me, that wouldn’t include the Morel street series lifters.
 
PRH said:
Fwiw, imo fundamentally there is no problem running spring loads of 150/400 with a HR cam.
Provided all the components are up to the task……..and for me, that wouldn’t include the Morel street series lifters.
Click to expand...
do you recommend any specific lifters or even springs that could be compatible with my application?

Cam sheet is below:

IMG_8172.jpeg
 
TT5.9mag said:
Short answer, your lifters will be fine at that spring pressure.
Click to expand...
At what point does it become an issue? This is a street motor and probably won’t ever see 6k rpms ever in the setup I have for it now.

I just don’t want the lifters to prematurely wear. Then bam, another $600 has to be thrown into the top end
 
matt030305 said:
At what point does it become an issue? This is a street motor and probably won’t ever see 6k rpms ever in the setup I have for it now.

I just don’t want the lifters to prematurely wear. Then bam, another $600 has to be thrown into the top end
Click to expand...
I’ve never found the limit of a hydraulic roller lifter with regards to spring pressure but I haven’t really tried.
 
If you’re thinking of changing something, then the first step would be to verify what the current spring loads are for your heads.
If by chance they’re within the acceptable range, then you could just use what you have.
If the springs are beyond the specified limit, then I’d start looking for options.

All that said, most people buying those heads are bolting them on ootb……… and reports of problems are few.
 
PRH said:
If you’re thinking of changing something, then the first step would be to verify what the current spring loads are for your heads.
If by chance they’re within the acceptable range, then you could just use what you have.
If the springs are beyond the specified limit, then I’d start looking for options.

All that said, most people buying those heads are bolting them on ootb……… and reports of problems are few.
Click to expand...
Will do, I’ll have them tested with my engine guy on Monday. Thank you for all the help!
 
I'll have to check it tomorrow, but I have a Pac box from Hughes' that they labeled as the 1129 springs that a friend bought along with that same cam grind. It also still has the PAC part number on it.
 
If you don't want to worry about lifter noise or lifter bleed down, use solid lifters. Set the lash to 0.006-8", hot.
 
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