Too much valvespring?

[Orr89rocz]

Can too much valvespring seat and open pressure cause valvetrain instability? I assume yes from increased deflection but do you think this is too much for this application? I like to think i have more pressure than needed but certainly not enough to cause issues

555” BBC. 2.300” stainless intake valve probably 140-146 grams
1.88” inconel exhaust (turbo car) probably 130-133 grams?

Springs are manley nextek 221425 set up at 2.00” so that should be around 340 seat pressure and close to 790-800 open at my lift. Intake is around .076” to bind. Exhaust .123” which maybe a concern?

Cam is 267/272 deg with .440 lobes, comp hi tech family for street stability. Heads are a ported dart 345 cc casting, flow over 425 cfm. 7/16” .160 wall pushrods

Car was nosing over around 6000 when dyno’d all motor. Peaked 5900-6000 then started falling off quicker than expected. I thought maybe because it had a slightly small throttlebody for the setup and running dual 3” exhaust temporarily at the time, figured that killed power and rpm potential. Seems to do the same in boost tho based on the fuel curve. Efi car so my fuel table generally follows the power curve shape and it seems to be falling off after 6000.

I thought it would pull higher to 6400-6500 peak. Talked to one guy who is good with valvetrain says he thinks my exhaust side is unhappy. Possibly unstable, floating or bouncing? Im not sure but could explain the power falling off. Seems to think there could be too much spring on it.

I just not totally convinced. Thoughts?

[panic]

What size pushrod?

[Orr89rocz]

7/16 .160 wall

[Walter R. Malik]

I would surmise that there is not adequate exhaust duration for higher RPM when run in an NA trim.

[Orr89rocz]

I would surmise that there is not adequate exhaust duration for higher RPM when run in an NA trim.

Thats what my other thoughts were. Typically i see cams of 8-12 deg splits and abit tighter lsa than this turbo cam i spec’d. But on the turbo, it still seems to peak early and fall off but i can only tell by my commanded fuel curve. On the dyno since it was unloaded, it spooled late and boost controller spikes beyond peak and tapers off, so the resulting power curve looks like a spike and rapid fall off because not only is engine power falling from ve but also cuz im losing a psi boost time it settles out to target. 1 psi can be 50 whp here so it really throws the curve off

[cv67]

Is this a solid or hydraulic?

[Orr89rocz]

Its a solid roller.

[PRH]

I would “expect” that combo of valvetrain parts to easily go 7500+ without a hitch.
Obviously, it’s possible there is some fuss point in your system, but it’s not something I’d expect.

A couple of the puller guys around here run 8000 with less.
Comp 11-734-9, PAC 1225@1.975, Brodix heads, steel valves, 1.7 Jesel, 3/8 x .135 pushrods.
And they hold it right there for a loooooong time on some of the pulls.

[Orr89rocz]

I have pulled it to 7500 and it revs up so quick and doesnt seem to have any issues or hesitations that i can tell. Just the fuel ve curve drops off faster than expected which makes me believe its falling off in power rapidly like it did na.

I mean its like 475 whp on this dyno at 5900-6000 and by 6700 its 450. I just figured it peak closer to 6300 and hold alittle better up top

[PRH]

I doubt the power curve dropping is the result of a valvetrain stability issue.

It’s one of those situations where it would have been easier to evaulate the combo on an engine dyno.

[CamKing]

Something is way wrong.
We do a lot of Turbo drag race BBC engines, and in a 555, a 269/269@.050", .440"/.440", on a 114 will peak above 7,000rpm.
With that cam, and 1.7 rockers, we run 275-300# seat pressure, and 700-750# at max lift

[Orr89rocz]

Something is way wrong.
We do a lot of Turbo drag race BBC engines, and in a 555, a 269/269@.050", .440"/.440", on a 114 will peak above 7,000rpm.
With that cam, and 1.7 rockers, we run 275-300# seat pressure, and 700-750# at max lift

I mean i can make it peak wherever i want with boost curve shape. The later it spools and the later it hits peak boost thats where the peak power is on the dyno but like i said it seems to fall off faster than expected and seems that the fuel demand on the street pulls shows the engine not needing the fuel to maintain same afr. In my experience that means ve falling off equals power falling off.

So now im curious what to do. I hurt a lifter and need to replace them and the cam so wondering if i should change something or what could possibly be the issue of what its falling off

[mag2555]

I would say that with your cid and the ported heads that forcing the motor to exhaling thru duel 3" Exh was killing 75 hp off the motor easy!

[Orr89rocz]

I would say that with your cid and the ported heads that forcing the motor to exhaling thru duel 3" Exh was killing 75 hp off the motor easy!

I was pretty confident in that myself but im not concerned with the na power. On boost it makes great power for where it actually peaked at, later than what I suspect was peak hp rpm. Just cuz the dyno is not well loaded and it wont spool like it does on the street.

I am curious if the exhaust restrictions killed rpm range on the na dyno. But even if it did it just seems like in boost the fuel curve isnt doing what i thought it should. But its ultimately just speculation until i can get a dyno pull thru the rpm range at a steady boost reading.

[Orr89rocz]

I will add i am using jesel shaft rockers. Aluminum full body. Geometry set by their tool

Hoping to measure deflection with springs and a checker if i can to see the difference