Limits of oem valves?

I recall some small blocks dropping valves back in the day so im wondering if anyone has any input to what might be the cutoff point of going to an aftermarket valve and retainer, ect...cutoff as in spring pressure/rpm.

Ive noticed alot of untouched 340 heads have some angry looking valves, esp, the exhaust.

Thanks.

I actually approach it the other way. A dropped valve is horribly bad and destroys so many parts that I wouldn’t feel comfortable using stock valves/retainers on anything other that a stock rebuild.

Pretty much sums up my approach as well. Aftermarket valves are cheap compared to the carnage they create when they break...

I think most of the problems with stock valves in Mopar SB being drag raced where shops installing new guides and getting the stem to guide clearances to tight which would cause them to seize in the guides and sometime the pistons would break the heads off of the valves
That being said I have shifted more than one stock 340 with a bigger cam and valve springs with stock heads and valves over 7000 RPM drag racing on the street and bracket racing them regularly

Would you open up the clearance a bit on nos heads? But are most factory specs ok, yes, I know I should check them all.

I was going to use the better quality but still oem style valve seals vs cutting them for the better seals that reduce oil to the stems.

I like to have between .0017 to .0020 on the intake valves to guides clearances and between .0020 to .0025 on the exhaust side om new builds

Thanks!

I've put new valves in everything I have had my hands on. On a core motor you often have no idea what kind of miles or abuse it has seen.


Also, as mentioned guides installed but not reamed to the correct size can hang up and cause a real mess.

These are new nos castings from the mopar boxes and nos mopar valves.

Im just gonna cut from 1.78 to 1.88 with a .500 solid cam on a high spring rate single spring.

The 2.02/1.60 SS valves are easy and cheap, the 1.88 not so much. Im not trying to overspend on something so basic.

Are you going to use the heads in a more radical application in the future. If so put the money in good parts now so you do not have to do it twice. Most of the problems in the old days was lack of oil and kicking a rod out the side of the block with a 340. It is all about oiling and clearances do research and pick a builder you can trust to do it correctly, head and bottom end.

Ahh... ummm.... I love the internet because of the interpretations and perceptions people get and the things that also get lost in translation.

I will explain and post some pics of this lil build fully here.

But first the reason for this build. I have a very bad habit, street racing and im trying to get away from it. My street racer is a big inch small block R block based stroker, I actually just recently did an inspection and slapped it back together.

Its your basic 13.5 gas ported nitrous slugs, good heads and and with some spray is just north of 700 and its hooked to a g force 101 then to a spooled 4:30 dana.

Most should know what they are looking at here.

Here is a few pics.

So now to this lil 318 build.

Very simply a small domed hyper piston.

Since its going to end up under 400hp I could of used some of the lightweight scat rods ive got sitting but long ago I worked over a set on new 340 rods like to be like the DC race rods sold, not to be confused with the dc small block dirt track heavy ass hemi style rods.

Simple bushed, magged, polished beams, shot, good arp bolts and sized to .0028. And light, only 15 grams heaiver then a oem small 273/318 rod.

Well done factory rods should support 400hp

Now to the block, a good running core that with over 100k miles should be seasoned enough for anyone, fifthly like a 40 year old motor that never had its oil changed.

I sonic it, it will go .040 no problem...

Take it in for a quick hot tank, bore, hone, come back home and see what the deck situation is.

block is dam square. But pistons are a bit low.

So I get out my magic wand and it looks to me like im .011 in the hole.

So I head on back to the machine shop to where ive a good relationship with the machinist and tell him "here" is what I need. .010 would be good, .012 would be good.... .011 would be perfect and id buy him a good lunch if he nailed it.

Hes a younger guy who has been training to take over the shop for 5 years and wants to do a good job and he does.

He nailed it, block is perfectly squared and he hit the .011 I asked for.

Now for the block prep...

I never pay the machine shop for anything but actual work, no prep as id just do it again and mo better.

This stage was simple flash removal, initial cleaning of the oil passages, check all the lifter bores, make sure I wont have a lifter rotation problem...ect.

I use a good cleaning/pentrating oil for this and you can see in the pics alot of the crude the hot tank missed.

So I let that marinate for a day or so then its off to the final wash.

Like most do, simple block brushes, alot of soap and water and more soap and water and more soap and water.

Look at the cam tunnel at what still was lurking after the machine shops hot tank and even some initial cleanup.

So work work work... wash wash wash.... cut hands cut hands cut hands....If the weather allows it I like to let blocks sit in the hot sun to hold heat, use hot water and it all helps prevent flash rust.

So here it is, ready to have the block plugs and cam bearings, ect installed....

but before I will run a oiled piece of cloth through each passage to take out the small bit of residue and any flash rust that occurred.

Crazy all this cleaning just to run it and start it all over again... is it really worth it... kidding.

Although many builders do things slightly different I dont think there are any real big errors in my ways, because my builds run good and dont come apart.

Back to the point of this build, everyone says plan for later and thats good thinking. But not every build needs a forged crank, pistons, and h beams.

Not every build needs to be a stroker.

Many seem to forget the old days when "worked" stock parts and a level head behind the wheel could go a long way.

I know this build here will come apart easily if I tried and it needs to stay under 6500.

So for me knowing all this its just a 318 that will run well, I wont be looking for street action in this build or this car, well maybe run a stock 340, or a 302 or 327 but still I know a modern V6 would hammer it.

But im having fun with this build and alot of the questions I ask are simply because im not well versed in some of the more simple oem parts and there uses and limits.

Ive a really nice set of J heads with 2.02 stainless valves or a nice set of edelbrocks sitting on the shelf, but ive chosen to use a new nos set of castings with hardened seats already installed, but with some port work and bigger intakes and see how it does.

But the basic things with this is no different then a big inch stroker, good machine work, good planning, being clean and clean again AND not being afraid to ask others questions.... and for me these things lead to good builds.

Time for more coffee and back to the shop.... its only 11:45 pm.

Id like to run SS valves in the heads but not many make the small valves, the ferra 5000 series might be an option but its like $200 bucks and for a single spring .500 solid in addition to added machine work on the heads in the spring pockets and cutting the guide diameter, I just dont think its needed... but maybe. But then I know I can beat it harder, then I think why not forged pistons....see...we all know where it leads.

I ran stock valves in my blown 340 for years. 7000 rpm all the time. Last freshen they got upgraded after 20 years.
Doug

The '73 440 currently in my C body still has the OEM valves and pistons in it originally installed by Chrysler.

I learned alot and made many mistakes with this engine through the 90s when I had it in my B body for many years.
MP .484 cam and 933 valve spring was the most I never used.
It did see 6200 on occasion, mostly by mistake. I was not easy on it.
These days in the c body it's stock exhaust manifolds, a dual plane, .474 cam +4, and all done at like 5300.

It doesn't really seem like there's much to worry about with the small block, it's got the same 3/8 valve stems but the valvetrain is a little lighter which should help. What are you planning for cam and springs?

If I wanted to go really mild im curious about this old manely hydro from there 73 book.

On thing I might add as well is im at 4100 ft. And the intake I will be using will be the 6bbl while my T/A sits in the barn waiting for me to die.

This also will go in a 76 duster, I can run manifolds and a bigger y pipe, or ive a extra set of tti 1 5/8 to 1 3/4 full 3 inch system or Id even consider the cheap 1 5/8 SS ebay headers and ive a set of new dougs show tubes 4 inch side pipes id like to play with as you can take the inset out and change things.

And if I need to mix fuels, that normal in my world.

But here is the manely specs. Ive some hughes single 111o springs I think I could shim and make work with this one.

My other choice is ive a mopar solid oval track cam, 509/280 106 and I really have always liked oval track cams on the street but have mostly used comps.

I like 106/108 cams rather then the wide ones.

Now the other one im considering is I ran a cam I like in some 360s ive done and fast68 suggested a hair smaller. I like the newer more modern comps because the intake closes alot sooner.

Let me check my pms for those approx specs.

268/272, .503/.510

Im good at hunting and setting up proper spring pressures but im not sure id sneak by with a single on this one.

This cars got a mild vert and 4:56 gears.

Ive some new, old manley adjustables that seem like oem mopar but just finished a hair better that cleaned up great I can use or a simple old set of 90-s comp pro mag rockers.

Im kinda just winging it as I go but will get the shortblock together this week and im waiting on a new cutter as I cant find my old one to cut the heads for the bigger valves.

Then the fun couple days cleaning up the heads. Im a little torn on hiw much to do on the heads, they are the same port like on the old MP big valve over the counter 302 heads that made good power with alot of velocity...

I wouldn’t be afraid of actual nos oe valves with a flat tappet cam one bit.

Just keep the rpm limited to below the point of valvetrain unhappiness and it should be fine.

I don't think you'll have any problems at all with stock valves.