HP500 Valve spring at seat pressure
 

Installing Isky springs on 98 HP500 carb. The Isky spec sheet shows 2 different installed heights possible, one gives 135# at seat pressure and other gives 160# at seat pressure. The engine is still stock and sealed. Which is the correct pressure to install at?

You need to figure out what your installed height actually is.

I need to know correct desired at seat pressure. I can install them at 1.875 installed height and have 135#, or install to 1.812 and have 160#. I guess the question is does a big block with roller cam that turns to 5200rpm need the higher pressure or not?

135 is not enough imo,i would go with the 160.make sure to test for coil bind.

I'm about 95% sure that stock springs were Crane 99896
https://www.summitracing.com/parts/c...6/applications

try to get the seat pressure over 150.I've had the isky 8005s springs in for quite some time and they still spec out to 150lbs on the seat.same as when I set them.

Would that be the 8005-sp springs? I have the 8005-a, I may need to switch

Actually it looks like the 8205-sp is the stock 1.900 installed height, the 8005-sp is 1.875 installed height, both at 150#

Is the cam a hydraulic roller if so 135 on the seat is fine and 335 to 350 over the nose (max lift ) is where you want to be. Going towards 150 you could start collapsing lifters and effectively changing the cam profile. Also putting undue stress on the rollers in the lifters and rest of the valvetrain.

135 seat pressure is not enough.valve float will happen and that will beat the valve train to death.many lifters destroyed from low spring pressure.

Hmmmm guess over the last 20 years of building engines I've been doing it wrong every day. I'll call my friend (the head engineer at comp) and tell him that we've been wrong all these years

Here is from engine builder mag. Given to them by erson cams http://www.enginebuildermag.com/2012...ing-pressures/

I'd love to see if my hyd rollers would rev cleanly to 6500rpm like they did with 130/300 psi springs lol

Anyhow, in my Mercury racing manual, spring specs for the HP500 engine, are

150 lbs closed at 1.900
420 lbs open at 1.300

They will and free up extra hp.

Good way to make friends here. Stick around though, you might learn something. There's quite a few here running 1200hp hydraulic roller engines, that might know a thing or two. Hint, they aren't doing it with 300lbs over the nose

There's always exceptions lol if you want higher spring pressures on hydraulic roller cams use short travel lifters that's the reason they make them.

Looks like crane's recommendation is a little different than Erson's. Crane might know a thing or two, considering they have been supplying mercury racing's camshafts and valvetrain specs since the 80's.

http://www.cranecams.com/bulletins_listview.php?s_id=16

130 to 160 not that diffrent I'm doing a 598 for a jet boat right now that's going to the dyno I'll video the spring pressures and a dyno sheet if you want or I have a pair of 525's for a fountain. But that said if your forced induction you will need more spring pressure due to boost negating spring pressure.

But always go with the cam manufacturer recommendations. The numbers I gave are a general rule and will work.

You said 150 will start collapsing the lifter. Its not the seat pressure that collapses a lifter, it would be the nose pressure. A stock HP500 crane lifter, will work fine with the 420lbs over the nose, as it has been proven in the Hp500 engines. A morel lifter, or Johnson, can take a heck of alot more open psi than that, and still handle it. Heck, the 5045 morels, recommend 550-575lbs open.

Ya they will but look at the ramp rate of roller cams they open and close the valve very quickly to little pressure roller looses contact over the nose to great of pressure the lifter will out accelerate the plunger effective changing the cam profile. The name of the game with valvetrain is getting everything to react to the cam lobe instantly.

joe,it,s guys like this newbie that make me not want to post anymore.for the record the seat pressure on my 1200 hp 588,s is 210 lbs with hyd roller cam,s,but what do i know?

What lifters are you using

morel 5045.

Crane did a reliability / performance test about 10yrs ago with their hr lifters...I posted actual article here on OSO somewhere. They went all the way up to like 250 seat / 500 something open and 7k rpm. They incrementally upped rpm and spring psi's to see where they'd run into issues, which they didn't.

edit in: yes, this was a BBC with it's heavy azz valvetrain and 1.7 rocker ratio

Remember the teague hr lifter vs synthetic oil skid article about HP500's ? Well, we all knew it was from too low of spring pressure. Not the oil. He mentioned the same (springs) finally years later.

There is always exceptions. If you look at the original post to the thread it's a production engine. 135 seat would work I didn't have a manual to see they spec'd something diffrent. And would you put stock lifters up to 250 pounds seat pressure. Let's compare apples to apples and oranges to oranges.

The HP500 didn't use a "stock" GM lifter from a 454 dually.

Also, really not a "production engine" considering they were hand assembled at mercury racings facility using Crane and other various vendors parts. (crane, dart, holley, etc)

looks like you have all the answers.so tell us what engine you have in your offshore boat and what the boat is.

It was a durability and performance test toshow everyone not to be afraid of running some more psi than the old myth that became a 'standard' of 135lbs/350lbs with their lifters.

You'll destroy a lifter/valvetrain/engine much easier running a little too low spring psi on a marine BBC than you will running a little too high, if there is such a thing. And yes, I know all about lifter plunger bleed down and etc issues with BBC's...very well.

These Crane HR's used in the blue motors don't have the mildest of lobes.

I'm just building a ls powered fishing boat nothing special. But have built every engine under the sun in some form or another. Have a 454 ls rhs block with a 4.5l whipple that makes 1400hp in a BMW m3 that I built at 3800 rpm makes 980hp 980 torque. Did a pair of 632 bbc supercharged in a 42 fountain making 1300hp each. Let me find what the wife did with the laptop I'll post a few pics

please do.

cant post attachments let me put them on the net ill find a link to the drift car vids and post that for ya now

[url]https://youtu.be/exoxJ0G

That's all I had on this phone only have had it 2 weeks my old one is at the shop can get more on the album tomorrow

Do you know Greg Landes ?

Ya he's my boss

Never meant to make people feel like they don't know anything every application has a correct need I've been doing this for 20 years if I didn't have couldn't find a spec and know that the engine isn't spinning 6500 plus rpm the numbers I gave is what I would use.

Next time I'll dig through all the archives of info I have at the shop and not give a safe number