aaronk785
Well-Known Member
Buy new springs. Valve float tears **** up real fast. I have had old ones be 30 lbs. under.
Stock 340 springs vs comp 901-16
- Thread starter 4spdragtop
- Start date
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https://www.oreillyauto.com/detail/...misc--parts-17870/valve-holder/w84003/4614604
This can hold up your valves while you change the springs.
This can hold up your valves while you change the springs.
My dad always said "don't spend a dollar to save a dime".
My point in asking was to see if the different springs were comparable AND to use something I have on hand instead of spending more $$. Springs up here are $100. Then add retainers $90. May as well get new locks too probably $15-20?? I didn' price them out. Not after seeing I was into $190 + the government share.
What i did fail to mention(remembered tonight my bad sorry) is i still have the original 273 springs and retainers.
I will put them back on the 273. Worse case scenario is new locks. Sounds like they should be checked as a few members have had issues with them.
Thanks guys! I will see if I can get the tool up here Lelo.
Cheers
What i did fail to mention(remembered tonight my bad sorry) is i still have the original 273 springs and retainers.
I will put them back on the 273. Worse case scenario is new locks. Sounds like they should be checked as a few members have had issues with them.
Thanks guys! I will see if I can get the tool up here Lelo.
Cheers
Shimming is std. procedure for a valve job, that's all. Every time a seat and stock valve face are cut, the stem moves up in the head and raises the retainer. Shimming will
simply correct the installed height &/or let You tighten up the springs for a little better performance. The maximum recommended lift on the 901's is only .400"....even tho'
they list the load over the nose of a .450" lift @260#. The Red 340HP spring will accommodate .500" lift, and the rate of lift is what will stress the springs out, a set of
valve springs don't have a set "float at" RPM. An aggressive profile with .480" lift can float the same springs @5500 while a smooth profile with .520" lift won't float them
'till 5800-6000RPM , there's no such thing as "X-springs float at Y-RPM's", there are multiple factors that affect effective RPM range.
There is absolutely no reason not to shim them, and usually needed on used springs if You want to set them up for load vs. height. The 340HP's are rated by Mopar at
386#/inch, and are listed as the second choice for the 292/.508" cam! By Comp's own chart, the 901's aren't the "ideal" spring for that cam anyway, & list's the rate at
353#/inch.
This is correct. If you want to know what the spring force is at a length, you have to measure them. Good luck finding better matched springs than OEM HP Mopar. I've measured 340 springs with 100K on them and they were still within spec. Most cam manufacturers will specify an open and closed force. You can shim, but it is only to "hit" a closed force. Then you have to check if the open force is within spec, without coil bind + safety margin. HP 273 valve springs are not High Performance. Do not use them unless you have to.
nm9stheham
Well-Known Member
Where is anyone getting this 'maximum recommended lift' for 901's? Just because they list the spring force at heights of 1.650" and 1.250" does not mean that the difference of .400" is some sort of 'maximum recommended lift' spec.
COMP Cams® - Specialty Valve Springs
BTW, the OP's cam is not a 292/.508 cam. It is 270/.468 (solid)... and will be lower lift once he sets lash and uses the 273 rockers. So he is gonna be around .100" from coil bind with the 901's.
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At no point did I indicate that Steve was going to coil-bind them w/
that cam. With the lash taken out and the rockers probably short-changing Him ~.025" on top of that, He'll be lucky to see .420" lift anyway, comfortably short of the 1.100"
coil-bind Ht............The point is Bro, I wouldn't waste My time removing the 901's for a second with the 340HP's sitting there in good shape, if You're worried at all then the
price for new ones is worth it...........
nm9stheham
Well-Known Member
All good, K6.
I just wanted ask about the 'maximum recommended lift' spec that you spoke of in post #30. I have looked through all listings in the full Comp catalog and in your link (which I do refer to regularly in my searches) and can still find no specifications for 'maximum recommended lift' listed by Comp for the 901.. or for any of their springs for that matter.... just a coil bind height.
As far as I know, nothing changes in the spring in terms of fatigue or spring rate all the way to coil bind height, but I thought maybe you know something on that matter that I don't.
In their list of spring pressure vs. heights in the full catalog, they stop at 1.200" for the 901 but I can't see where that means that this is a maximum compression that they recommend. Heck they list a pressure for at least one spring at a height that is .010" SHORTER than coil bind height... what's up with that !?! So I don't attach any particular meaning to where the pressure values in that chart stop. As far as we know, the spring testing tech had a case of the runs on the day he was testing the 901's and never finished the pressure chart below 1.250" LOL
And understood on the 340 HP's but I am not sure that is what the OP has on there now. I thought the reference to the HP's meant the MP red springs one can buy today .... are those the same as came on the stock 340's?
I just wanted ask about the 'maximum recommended lift' spec that you spoke of in post #30. I have looked through all listings in the full Comp catalog and in your link (which I do refer to regularly in my searches) and can still find no specifications for 'maximum recommended lift' listed by Comp for the 901.. or for any of their springs for that matter.... just a coil bind height.
As far as I know, nothing changes in the spring in terms of fatigue or spring rate all the way to coil bind height, but I thought maybe you know something on that matter that I don't.
In their list of spring pressure vs. heights in the full catalog, they stop at 1.200" for the 901 but I can't see where that means that this is a maximum compression that they recommend. Heck they list a pressure for at least one spring at a height that is .010" SHORTER than coil bind height... what's up with that !?! So I don't attach any particular meaning to where the pressure values in that chart stop. As far as we know, the spring testing tech had a case of the runs on the day he was testing the 901's and never finished the pressure chart below 1.250" LOL
And understood on the 340 HP's but I am not sure that is what the OP has on there now. I thought the reference to the HP's meant the MP red springs one can buy today .... are those the same as came on the stock 340's?
I appreciate the input guys. I am doing some r n r here (reading and research) so keep it coming. Altho I am not 100% committed to the 270s cam yet. But with only 8000 miles or so on it.... also not sure if its an "upgrade" vs the factory cam?
Thanks.
Thanks.
It should run great in a 340 and of course, too big for a 273.
The MP red springs are the same as OEM 340 springs.
Thanks guys. Day "off" tomorrow so I'm gonna check out springs and such on x heads. These were done for me 25 years ago. I don't believe new hardware was installed. Probably hardened seats. Cost $500 at the time. I know how to replace stuff and im mechanical but as I've said before the science behind it is a learning curve for me.
I have various sets of springs available but the best I've got(for 270S cam) would be the 901's or the ones on the xheads (I'm 99% that these are factory 340 ones). I will disassemble and inspect tomorrow in the -30 garage lol. Good idea seeing if machinist will check springs for me.
Thanks all.
I have various sets of springs available but the best I've got(for 270S cam) would be the 901's or the ones on the xheads (I'm 99% that these are factory 340 ones). I will disassemble and inspect tomorrow in the -30 garage lol. Good idea seeing if machinist will check springs for me.
Thanks all.
Well, the catalog I'm looking at may be considered "vintage" by some now, lol! I believe it's an '03 issue, and One can never rule out errors in the data tables so...........
Here is the chart by line in that issue for all the springs w/the specific specs for the 901's;
Installed Ht.- 1.650"
O.D.- 1.494"
I.D.- 1.080"
Max. Rec. Lift- .400"
Spring Rate- 353#/in.
Part No.- 901
# of Springs- Single
Damper- Yes
Spring Height(inches) / Spring Load(lbs.)
2.300 >1.750 -------------
1.700 / 83
1.650 / 101
1.600 / 119
1.550 / 136
1.500 / 154
1.450 / 172
1.400 / 189
1.350 / 207
1.300 / 225
1.250 / 242
1.200 / 260
1.15>.950 -------------
Coil Bind- 1.100"
There is a separate table with a list of spring-sets that shows the 901 outers w/o a damper & lists the coil- bind at 1.160" ?!?!
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Pics of x heads, haven't disassembled yet. Red stripe springs and new frost plugs
I bet the new springs may be cheaper than your machinist cost of checking and shimming the old springs.
OEM 340 Springs
I called machinist yesterday and he said springs in heads are OEM 340.
He also recommended going with 901's as they are recommended for the 270S cam.
Heads had to come apart anyway for the diy port job, and cc'ing chambers.
Thanks
He also recommended going with 901's as they are recommended for the 270S cam.
Heads had to come apart anyway for the diy port job, and cc'ing chambers.
Thanks
nm9stheham
Well-Known Member
Thanks for all the work to answer the question, K6. Hey I still have my old 70's Ford hop-up manuals and so on, so I place a high value on the old stuff. I have looked at all the online Comp info and the term 'Max. Rec. Lift' (or any variant of that) appears nowhere in the current catalog or in the specialty spring chart that they have onlline. So I don't know what to say about that discrepancy.
Here is a link to the Crane valve spring info:
http://www.cranecams.com/userfiles/file/334-343.pdf
They DO list a 'Max Net Lift' for their springs. I have not looked at every line, but for the ones I did, the 'Max Net Lift' is the difference between the coil bind height and the height for the lowest spring pressure (roughly the valve-on-seat spring height), minus approximately .060". So, in other words, the usable spring height range is all the way to approximately .060" short of coil bind per Crane.
Again, I know of no aspect of valve spring operation that starts to change as the height compresses down close to coil bind. It will make more heat in the spring to compress it more, but how that effects things like weakening probably has to be determined per each spring design. The change in a spring's rate with use is in the material itself, down at the molecular level. I suppose the 901 could use some inferior spring wire...??? (That seems unlikely, but that is just my take.)
OP, have fun in the cold! BRRRRR!
Ive spread my brains out on the table here looking thru cam specs, valve spring specs etc, it can be overwhelming LOL. It seems that they all dont have "apples to apples" comparison. Seeing as how these x heads are 69's, I got specs from my 69 FSM. While heads are still assembled im going to cc them. Then also prior to removal, I will get installed spring height etc for the factory mopar springs.
Machinist cant remember exactly what was done to the heads(25 years ago lol) but "may" have put new exhaust valves in. I definitely remember him mentioning(years ago lol) hardened exhaust seats.
69 FSM springs advertised
Free length 1.94"
Seat load installed(valve closed) 80/90 lbs@ 1 11/16" = 1.6875
Valve open load 235/249 lbs @ 1 7/32" = 1.21875"
OD "not listed" ID 1.070-1.090"
Comps 901 advertised
Free length "not listed"
Seat load installed(valve closed) 104@ 1.65, shorter installed height with more load vs factory
Valve open load 236 lbs @1.250" pretty much same as factory load, but slightly taller
OD 1.494 ID 1.080"
Brought heads in the house I am not doing this in the shop lol. -28* C this morning, -43 with wind chill! LORD!!
Machinist cant remember exactly what was done to the heads(25 years ago lol) but "may" have put new exhaust valves in. I definitely remember him mentioning(years ago lol) hardened exhaust seats.
69 FSM springs advertised
Free length 1.94"
Seat load installed(valve closed) 80/90 lbs@ 1 11/16" = 1.6875
Valve open load 235/249 lbs @ 1 7/32" = 1.21875"
OD "not listed" ID 1.070-1.090"
Comps 901 advertised
Free length "not listed"
Seat load installed(valve closed) 104@ 1.65, shorter installed height with more load vs factory
Valve open load 236 lbs @1.250" pretty much same as factory load, but slightly taller
OD 1.494 ID 1.080"
Brought heads in the house I am not doing this in the shop lol. -28* C this morning, -43 with wind chill! LORD!!
When you mention OEM 340 springs (and not the 45+year old used ones) I wonder how those replacements stack up to to the original 340 spring specs.
They are the same. And 45 year old ones are still probably the same. I buy the 45 year old sets whenever I find them.
nm9stheham
Well-Known Member
It's easy to work out the spring rates. Take the height differences for the 2 specs, and the pressure difference. Divide the pressure difference by the height difference.
The 901's are around 353 lbs/in (per the data sheets). Per the OP's data above, the OEM's spring rate works out to 335 lbs/in. Not enough difference for the average Joe's use to worry about IMHO. (Unless there is better quality in the older spring wire that holds its rate up better over the long term.)
The 901's are around 353 lbs/in (per the data sheets). Per the OP's data above, the OEM's spring rate works out to 335 lbs/in. Not enough difference for the average Joe's use to worry about IMHO. (Unless there is better quality in the older spring wire that holds its rate up better over the long term.)
340HP PN 2863439, DC/MP P4120249 Red .206" dia. wire w/damper ;
O.D.- / 1.502"
Coil Bind(solid ht.)- / 1.090"
Load w/retainer- @
1.700"- / 69#
1.200"- / 260#
Calculated Rate- / 386#/in.
Damper- / Yes
The DC/MP Racing manual states there is a possible variation of 15# in these, which they state could be a worst of 372# to 401#/in..................
as per 66fs, I've never seen anything of the kind out of a set.
O.D.- / 1.502"
Coil Bind(solid ht.)- / 1.090"
Load w/retainer- @
1.700"- / 69#
1.200"- / 260#
Calculated Rate- / 386#/in.
Damper- / Yes
The DC/MP Racing manual states there is a possible variation of 15# in these, which they state could be a worst of 372# to 401#/in..................
as per 66fs, I've never seen anything of the kind out of a set.
nm9stheham
Well-Known Member
Tnx. Looks like the MP springs are a bit heavier than the ones listed in the OP's FSM. It just takes a miniscule change in wire diameter or a small outer diameter change to make a 10-20% difference. I had the impression at one time that the standard spring wire stock has changed a bit from back in the day to the present time. So some variation is possibly not surprising. (But I can't recall what lead me to believe for sure why the wire has changed.... it was probably from looking at old spring specs vs. new ones and seeing that the common wire diameters in each era were different.)
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