Mild-ish 454 BBC Valve Spring Recommendation

[Ryan Moore]

Newbie Question Time.

I have a Mild-ish 454 in an old Jetboat, we 've had some fun over the last couple seasons.It is time to undo somemore of the neglect though,
and the short asnswer is it needs some new valvesprings.
I have not torn down this engine completely to know all the engine specs as it runs quite well, or so I thought.
It appears to have been last rebuilt around 1986 at a volume engine rebuilder.
Engine specs are, or best guess:

We think this engine started life as a '70 LS-5 "crate" engine from the suffix code.
-454 two bolt main
-stock forged crank
-Con rods appear to just be pedestrian passenger car versions
-Silvolite flat top pistons (dated '85)
-Stock appearing 3917215 heads with likely 2.06" In 1.72" Ex. and 101.6cc chamber volume
-what appears to be a OE or rebuilder's copy of a LS-6 solid flat tappet cam ( 242deg@0.050" , .520" lift 115LSA)
-Old Edelbrock c396QJ dual plane intake with a Holley 750dp on top
-stock 3/8" pushrods
-stamped long slot rockers, 1.7 ratio
-head gaskets are .020" shim style
-I'm guessing deck height at .038" because suffix code is still there.
-And from the deck height I'm estimating a 9.2-1 CR
-Total Ignition timing was set at 34 degrees.
-Ignition is a marine DUI HEI distributor.
-Exhausts through Debbold Log manifolds with over the transom pipes,
running temp was 120-140 deg farenheit hoping to increase that to 140-160 with a thermostat kit.
I run 91 octane pump gas, and our elevation is about 3200 ft.


Right now it has single springs w/damper of unknown origin, and right now they're weak enough that I can unseat, and hold them open, by hand.
Current springs are 1.55" OD
damper ID is 0.985" ID
the heads have .625" OD guide bosses with
intake valve stem seals being positive type at 0.750 OD and
Exhaust valve stem seals are umbrella type, at 0.837" OD
Valve spring pocket is 1.575" ID

The jet pump is a Jacuzzi WJ with likely a "A" impeller, haven't pulled the bowl apart.
The boat will do 55mph at approx. 4600-4700 rpm right now. And it must be limited because of the weak valve springs.

My question is,
Lunati recommends 73815 springs (singles with damper) with there version of the Ls-6 cam ( has 0.530" lift )
but as far as "the big guys" recommendations both Comp and Crane recommend a dual spring for their versions of that cam.
I tend to think the Lunati spring is a little under-sprung for the extended higher RPM I might subject this engine to. Most of the time I cruise at 2500 rpm or so.

I want to be lazy and not cut the valve guide bosses, these heads would be a pain to get off, because this engine has only ever had raw water, open loop cooling, and the headstud threads in thewater jacket are rather rusty.
I am not stuck on any particular brand.

And what would be a good total ignition advance to try out as well?

Recommendations? Comments? Questions.

[Alan Roehrich]

Probably is not 9:1 compression, and it does not have tight enough squish and quench, heads are probably about 5cc above nominal, they usually are, even if they have not had a valve job. That cam is designed for 11:1 or better compression. You may need valve springs, but that is likely not your RPM limiter. Lack of compression ratio and relatively low exhaust flow combined with that cam probably are your limiting factors for RPM. If you want to put springs on it, a decent quality spring with around 130# on the seat should do all you need, the cam isn't likely to be all that aggressive.

[wyrmrider]

I'm near Isky so....
but I like duals like 8005 with height set to get correct pressure what's your spring height? I'll re read your post you most likely said
X2 on what Alan said
but with springs you may get rpm of the big cam but with the compression the low end will be weak and with the exhaust the power up top will be restricted
new Viton seals

[Ryan Moore]

As of right now, on number 1 intake installed height was 1.900" and the exhaust was 1.875" The retainers are mismatched and will get replaced anyway, at least there is shims under the springs.

What is a good spring pocket clearance?
Its mentioned everywhere but nobody seems to have a hard number, or a range.

I was concerned dual springs might be too small on the ID for my current valve stem seals, or the umbrella seals on the exhaust anyway.



The boat seems to run pretty good at lower RPM's , it cruises comfortably at 2500, and actually only uses 5 gal/hr at that cruise speed. Which is about the same as my Dad's 150hp Mercury Outboard.
Maybe due to the fact that Jet drives don't load the engine the same way as a prop drive would.

[Richard Till]

You have closed chamber 1967-69 heads with 100.9 cc`s. 3 angle valve job and mill the heads .030 . If the heads have exhaust spring rotators, chunk em and get the spacers. Every spring sets to the exact same installed height. Don`t exceed .550 lift without checking the retainer to guide and piston to valve clearance. Leave the exhaust valve seals off. It might smoke just a tad at startup but you`ll know the stem is getting oiled and will help with any possible reversion. 115 LSA is too high. Go with 110. Holley 850 DP. The 750 is getting small. Which brand hull do you have? Light, medium or heavy weight? Nozzle angle? You might cut your impeller to an AB or B with tight wear ring clearances. An inducer is snake oil. I`m now predicting at least 5500 @ Wot with a smile on your face and a lighter wallet.

[#84Dave]

Talk to Comp Cams & see if they may recommend their relatively new 'Conical' spring. They're good for frequency suppression. -Dave-

[Ryan Moore]

You have closed chamber 1967-69 heads with 100.9 cc`s. 3 angle valve job and mill the heads .030 . If the heads have exhaust spring rotators, chunk em and get the spacers. Every spring sets to the exact same installed height. Don`t exceed .550 lift without checking the retainer to guide and piston to valve clearance. Leave the exhaust valve seals off. It might smoke just a tad at startup but you`ll know the stem is getting oiled and will help with any possible reversion. 115 LSA is too high. Go with 110. Holley 850 DP. The 750 is getting small. Which brand hull do you have? Light, medium or heavy weight? Nozzle angle? You might cut your impeller to an AB or B with tight wear ring clearances. An inducer is snake oil. I`m now predicting at least 5500 @ Wot with a smile on your face and a lighter wallet.

No Spring Rotators, thankfully. I think once I have new keepers the Installed heights should be a lot closer.

I forgot to mention I do have a 1" open Squarebore to Spreadbore/Quadrajet adapter under that Holley,

I'd say the Hull is light ( Fiberglass, shallow freeboard ) , I would say is 2500lbs wet, at most. Haven't run the boat and trailer across a scale to be sure.

It's a Mastercraft Marine 18 foot "U" Bottom, It's a shallow V hull anyway, Its very similar to Early 70's Rogers and Eliminators. Its probably a copy.
I'm pretty sure my Mastercraft has never had anything to do with the current Mastercraft Ski and Wake boats.

My Nozzle is fixed trim right now, no Diverter. I can't remember what I measured the nozzle angle at, I think it 2-4 Degrees bow down trim. Set-up for Sking, perhaps.

I'll be really happy (for now) if I can get 60-65 Mph out of it.

Anything wrong with Comp 911's installed at 1.875" for about 130lbs on the seat? which should give me close to 325lbs at .520" lift
Once again, It'll be a miracle if I even get to 5000rpm.
5500rpm should be my redline with stock 3/8" rod bolt, should it not?

Quick squirt vid from 2013: http://youtu.be/QosUNqZur48

[ProPower engines]

I'm near Isky so....
but I like duals like 8005 with height set to get correct pressure what's your spring height? I'll re read your post you most likely said
X2 on what Alan said
but with springs you may get rpm of the big cam but with the compression the low end will be weak and with the exhaust the power up top will be restricted
new Viton seals

X3 on the ISKY springs .Their 8005-A will work fine with a 1.900 installed height. I use the 8005- SP or the 8005-SP Plus in some marine hyd. roller stuff but the lack of RPM is more likely caused by the limiting factor of the jet.
You can only blow so much water through it and when the flow gets to its max its like standing on the gas in an automatic where the engine will not rev further.
But from what I have seen in marine they did also use the LS-6 and LS-7 engines in mostly jet-drive boats and some larger pleasure craft as well.
The date codes will be different but basically the same engine but they would use a hyd. cam either flat tappet or Hyd. roller depending on the year