Dual valve springs stock on 2.02 915 J Heads?

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stumblinhorse

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Picked up a set of 915 2.02 J heads for my 390 stroker build. I was making sure my Hughes adjustable rockers set up properly since I just got some hold downs. The Previous owner said the springs were stock. But wasn’t sure J stock springs were dual. I know my 675 heads were not Dual. And if they are not stock, what is the best way to tell what they are? I know my Hughes rockers are very snug around the springs, they are for up to 1.5” diameter springs. I Didn’t expect that either.

Thanks for the help.
 
Single springs with a damper

Then follow up newby/stupid question. I see new springs say that machining is required in the footnotes, ie comp 995-16. What machining is required to swap Springs? I know some changes I can do myself, but can’t find anything for prepping for higher lift springs.

Any help is appreciated
 
Dual springs require machining the valve spring seat so the inner spring clears.

 
Dual springs require machining the valve spring seat so the inner spring clears.


Sorry last stupid question. The 926-16 comps are single and will support the cam I am putting in. Any issue with saving a little machining and sticking with a single spring?
 
I wouldnt try the single springs with that cam. The fast ramps are going to need the control of the dual spring.
 
Sorry last stupid question. The 926-16 comps are single and will support the cam I am putting in. Any issue with saving a little machining and sticking with a single spring?

As long as the rate, the installed height pressure, open pressure and coil bind are all very similar, they will work.
 
As long as the rate, the installed height pressure, open pressure and coil bind are all very similar, they will work.
926
  • Rate: 415 lbs
  • 1.062'' ID, 1.476'' OD
  • Seat Load: 109 lbs at 1.800''
  • Open Load: 317 lbs at 1.300''
  • Coil Bind Height: 1.140''

995
Dual Valve Springs
  • I.D. of Outer Dia.: 1.073"
  • I.D. of Inner Dia.: .697"
  • Seat load: 115lbs @1.700''
  • Open load: 336lbs @1.150''
  • Coil bind: 1.020''
  • Rate: 402lbs/in

Seems close to me :)
 
The coil bind height is off a good bit. That won't matter as long as you have enough left over for whatever lift your cam is when subtracting coil bind height from seat height.
 
The coil bind height is off a good bit. That won't matter as long as you have enough left over for whatever lift your cam is when subtracting coil bind height from seat height.

Still learning. the coil bind is more on the single then the dual. So let’s see if I understand. Coil bind is how small the coil can be compressed? So smaller number is better?

So if my cam is .525 lift and coil bind is 1.140 and the installed height is 1.7, I am .035 ok. Right?
 
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Still learning. the coil bind is more on the single then the dual. So let’s see if I understand. Coil bind is how small the coil can be compressed? So smaller number is better?

So if my cam is .525 lift and coil bind is 1.140 and the installed height is 1.7, I am .0035 ok. Right?

The seat height on the dual spring is 1.7. The coil bind is 1.020. So, 1.7 minus 1.020 is .680. That means you can run probably about a .650 lift cam and be fine. That's .030 before coil bind.

The seat height on the single spring is 1.8. The coil bind height is 1.140. So 1.8 minus 1.140 is .660. So that means you can run about a .630 lift cam leaving about .030 before coil bind.

But here's the thing. I THINK the small sets up "around" 1.7" on the seat. 1.8" is the big block figure........IF I remember that right. Someone correct me if I am wrong here.

IF that's right, that means those single springs will set up at 1.7, not 1.8 where they are specced to have 109 LBS on the seat. That's only .100" difference, so probably not a concern with spring pressure.

Let's do the math using 1.7 and the single spring.

1.7 minus 1.140 is .560.

Your cam is .525, so that will probably work. I would just double and triple check everything.
 
The spec for the 926 at 1.700, which is more closer to the true installed height, will be 150 lbs, somewhat steep for a seated pressure for this cam idea.
 
the 926 spring is used in our stocker engines. the cam lobe is more like a roller profile, extremely aggresive, those springs have ran 800 runs when retired them. that comp 275 is no where as radical as a stocker cam lobe. use em!
 
You'll be OK for coil bind with the single spring IF you install it at 1.7. But just because the spec sheet for the spring says 1.7, does not mean it will install there. That depends on the retainers and valve. Stock retainers & valves install at around 1.650" IIRC. If that was the case, then the compressed height at max lift would be past coil bind so that does not work. You either change retainers or locks, or deepen the valve spring pocket , or a bit of both.

BTW, IMHO, .035" is a bit close on coil bind. I'd shoot for .060".
 
You'll be OK for coil bind with the single spring IF you install it at 1.7. But just because the spec sheet for the spring says 1.7, does not mean it will install there. That depends on the retainers and valve. Stock retainers & valves install at around 1.650" IIRC. If that was the case, then the compressed height at max lift would be past coil bind so that does not work. You either change retainers or locks, or deepen the valve spring pocket , or a bit of both.

BTW, IMHO, .035" is a bit close on coil bind. I'd shoot for .060".

Should I just get the +.05 Locks? To ensure I have a little breathing room?
 
.060" is kinda the safe norm these days...which is why RRR said to check and re-check. In 'ancient times' LOL, .100" was often recommended.

Do you have your retainers you will use and have you checked the distance between the retainers and the valve spring pocket to see where your installed height will be? You really ought to measure that 1st and see where you are.

Also, be aware that your lift will not actually be .525" but probably around .510-515" when all is said and done, with the losses in the geometry. So you get a bit of margin there. All those things together might get you to .060" or very close.

The +.05" locks would be a good backup option, if they work with your retainers & valves. Easy to buy those at the last minute and use them if needed, once things are assembled and checked. But I wold insure compatibility 1st.
 
I haven't purchased the springs, retainers or locks yet. I am 95% certain of the cam I think will work well in the 390 at 7000ft and 10.5 compression/3.55 and as you know an np435 4 sp. I am still accumulating parts. I don't want to have to buy and re-buy, so taking my time on decisions.

I just don't think if I go thru the trouble of building this motor I will stay under .500 lift. It won't be much over, but the Howards Cam with the footnote(15) and the High lift Comp all seem to want to be over .500 for a SBM.
 
Looks like you are ending up in the low 7's for effective DCR at 7000'. I can see the trade of a lower DCR for more lift.....all depends on where you want the RPM band, and how wide in % terms. 1.6 rockers would help get the lift up with less duration, but sounds like that is settled with the Hughes rockers. I am also not sure how much more the J-heads will flow at .510 vs .475 if they are unported (which the rest of us don't know).
 
The howards cam 711651-10 is a 265/273 with .502/.525 lift. I have that on my short list as well. That probably is a better duration with just a little less lift.
 
use the stock 340 retainers and measure the installed height. mopar said it was 1 11/16" = 1.687, after a valve job figure 1.700. the howards cam is good, a lil more than a 340 cam, a single spring with damper is it, around 110-120 seat and 300 open-what does howards suggest for spring loads?
 
use the stock 340 retainers and measure the installed height. mopar said it was 1 11/16" = 1.687, after a valve job figure 1.700. the howards cam is good, a lil more than a 340 cam, a single spring with damper is it, around 110-120 seat and 300 open-what does howards suggest for spring loads?

Howards has a single and their specs are
  • OD: 1.445 in.
  • ID: 1.040 in.
  • Seat Load: 120 lbs. at 1.680 in.
  • Open Load: 295 lbs. at 1.175 in.
  • Coil Bind Height: 1.100 in.
  • Rate: 350 lbs.
Coil bind looks a bit better with these. Called them and they seem to think the singles would work just fine.
 
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If you have not bought anything i would recommend a custom cam.
Call comp or what ever cam manufacturer you want and tell them about your eng and the elevation that you live at.
They will recommend the cam spring and retainer(if need) to make a much better runner eng, than trying to pick a off the shelf cam.

You really will be Time and Money ahead. Most "off the shelf" cams are designed with near sea level performance.
I had Brian IMM with comp, spec out my cam(live at 6600 feet) I have been way happy with my setup!!!!
 
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