NewbVetteGuy

I've got the valves and springs out of my heads AGAIN to blend the bowls (got one head done yesterday) there were some real sharp lips going into the throats above the valve seats in the intake ports (exhaust ports were about perfect), BUT the exhaust valve guide bosses are just huge and really stick quite far into the exhaust ports. I don't really want to cut the valve guide boss shorter because this is a street motor and longevity matters, but my understanding is that there are cutters that can cut around the outside of the valve guide boss that extends into the port and cut then thinner. I could use my carbide cutter or flapper wheels to try to thin the guide bosses by hand but I'm not skilled enough to make it uniform and pretty looking and I fear slipping and marring the inside of the port, so a tool designed to do this would be better.

Does something like this do what I want? I have 11/32" diameter valve stems and 0.530" valve stem seals which makes me think the outer diameter of the guide bosses is also 0.530". The cutter linked to below says it's for valve guide diameter of 0.530" but it doesn't say how much material it removes / how thin it makes the bottom of the guide boss.
https://www.summitracing.com/parts/pow-pow351345?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-powerhouse-products&gclid=EAIaIQobChMIr5j_ztC13AIVl IV-Ch2pcQnBEAQYAiABEgL_H_D_BwE

I know I stand to make very, VERY little air flow gain from such a modification (1 CFM???), but I'm honestly finding all the head work the most fun part of the entire engine build and I've already cleaned up the chambers, chased the spark plug threads, polished the exhaust ports, blended the throats, measured spring height and installed new springs, seats, shims, retainers & keepers, so one more thing isn't that big of a deal.

I've torn the heads down enough times now I can remove 8 valves and springs in about 10 minutes, too. (I've only screwed up one valve stem seal, so not too bad of an "education fee" so far, either.)



Adam

jim2527

Adam, I think that tool is for the cutting down/sizing on the spring end of the boss not the throat end. It cuts the outer diameter down to .530

If your guides are honed to .342 and the boss is cut down to .530 they'll be .188/2 or .099" thick

cv67

Try the largest carbide you can get in there, very low speed and go to it.
Youll need to regulate it for sure so you dont damage anything.


Going slow here will net a quicker result.

NewbVetteGuy

NewbVetteGuy

jim2527

Physicaly measure the valves. They're closer to .341X...regardless. Guides are not 'thinned' they're 'opened up/honed' to a particular inside diameter.

Guide boss: Physical parts of the head sticking up
Valve guides: Presses/screwed into guide bosses.

Think of a physically uniform donut. The 'hole' is where your valve goes in. Boss tools cut down the outer diameter. Hones fine tune the inner diameter. (OD-ID)/2 = wall thickness (530-342)/2 = .094 wall thickness.

NewbVetteGuy

Thanks Jim. This clears up so much for me.

I was definitely misunderstanding the term "Guide boss"-I thought it was used to describe the part of the guide sticking into the port.
I do not want to modify the inside diameter -there's some tight spots in there with a few valves and I don't think Jegs spent a great amount of time on them, but I don't know what I'm doing and can only make that worse so I'm going to run them like I got them.
I don't even want to shorten the guides that stick into the exhaust chambers, I just want to thin the outer diameter so it sounds like I need a "Guide boss tool". (Given your definitions it IS confusing that the purpose of a "Guide boss tool" isn't to cut the guide boss, but to trim the valve guide itself, so I feel a LITTLE better about being confused as it seems to be confusing terminology.)

A few specific questions now that I think I have a BASIC understanding of the space enough to ask a more intelligent question:
1. How do I know the right guide boss tool for my application? Are all the guide boss tools designed for 11/32" essentially the same and will thin the guide to the same degree?
2. Do the tools just thin the part of the guide that sticks into the port down to a certain thickness as dictated by the tool, or is it something where the longer you use it, the thinner the guide gets?
3. Is there a thickness target I should work towards and will a simple el cheapo dial caliper work for this purpose?



Adam

NewbVetteGuy

I've actually watched that YouTube Video before; Ha!

Do you agree with the video's author that you're safe to cut the valve guide down to 2" of total length? Or for longevity, in a street motor is longer better? (My understanding right now is that longer valve guides keep the valve position more stable and are better for longevity and for the exhaust valves, the longer valve guide also helps to dissipate heat; this is why I'm leaning towards not shortening the guide at all, but thinning the outside of the guide.


Adam

jim2527

Well beyond my knowledge base. My definition of 'valve boss' may not be correct....I interpret it as the part of the head that's cast and where the valve guides are inserted.

Again...just a guess, but if you already have 'positive stop' valve seals you don't need a boss cutter...there're already cut. Those cutters cut to specified OD.

Your question about 10 vs. 12 degree valves on ST. I believe it refers to the angle of the back of the valve face to the face. Stand a valve on its face....10 or 12 or whatever is the angle the back makes to the flat surface the valves standing on.

Scroll to figure 3.39
http://what-when-how.com/automobile/...ms-automobile/

Scroll down..
http://www.crankshaftcoalition.com/w...lve_guide_boss

derekderek

The OD of the guides in the air stream is cut freehand with a carbide cutter in a valve grinder. And not worth the trouble. You want to clean up the transition from valve seat to bowl and the inside turn (floor) of the exhaust port.

derekderek

Big block or small block?

NewbVetteGuy

I was afraid someone would say that. Seems like something that takes real skill to make it pretty. I was hoping for a magic tool that would just thin the OD. Dang. -I also almost COMPLETELY clogged up my carbides with aluminum last time I used it on my intake.... I didn't know I was supposed to oil it before use and I'm not so sure I'm going to be able to get all that aluminum out; I might need to buy a new set of carbides... *Sigh* Learning the hard way seems to be the only way I can learn...

I'm proud to say that part I've completed.

Small block 4" bore.
Adam

NewbVetteGuy

That's my understanding now, too. -I emailed Ferrea with a very related question this morning. The 12 degree valve makes the airflow more like you had a steep seat, but with a normal 45 degree seat profile; you get more high lift flow and reduced low-lift flow / reversion. That's pretty much what I'm looking for, BUT... The Ferrea 12 degree 2.02" valves are only available with a +0.050" valve length. -I can obviously get 0.050" shims and make that work (I haven't measured for pushrods yet), BUT I was hoping to stick with stock length valves because I didn't want to replace the exhaust valves- only intake valves -it would be weird to have two different valve lengths and two different length pushrods between the intake and exhaust sides -so I'm either buying new intake AND exhaust valves for some pretty small gains, or I'm just going to run what I've got. The gain in HP for the $$ is bad in replacing the valves so I'm definitely leaning towards running them as-is until rebuild time.

Ferrea said that whether the engine will benefit from moving to 12 degree valves depends upon the intake port in the head and that I should reach out to Profiler with this specific question. I'll let you know what I find out.


Adam

NewbVetteGuy

Jim, just so we're clear, I'm not looking to cut the valve guides / guide bosses on the TOP of the head, like in the Vortec mod. I'm looking to cut / thin the UNDERSIDE of the valve guide - the part that protrudes into the exhaust port.

-I'll take pictures tonight and post them back up. The profilers have pretty significantly raised, D-shaped exhaust ports, which just exposes a huge amount of the valve guide into the air stream.


Adam

jim2527

I'm with you... I'm no expert but every exhaust port I've seen has them hand ground/tapered as others have mentioned.

NewbVetteGuy

So here's a quick shot of just how far the valve guide sticks into the exhaust port in these heads. The bottom of the black marker line would represent 2" from the top of the guide, if I were to cut it down to 2" total length.

I'm 90% certain that the "right" tool to use for cutting the valve guide down shorter is this Beam K1280 Cobalt Guide Trimmer for $33.40 (and another $8.60 for the 11/32" pilot). http://www.beamequipment.com/Valve_G...e_Trimmer.html

Then I'd have to thin the guide / try to make it bullet shaped by hand because as far as I can tell there's no tool for thinning the guide / adding a bullet nose to a guide that didn't already come with a bullet nose.


Adam

lionelhutz

Interesting, there is no aluminum boss cast into the head to help support that guide as it extends into the porrt? Look at that YouTube video and see how the head has a boss cast into the port that goes around the guide.

I didn't think the brass guide extending past the boss around it would do much for helping to support the valve. I thought it was too soft a material to be structural when like that. In other words, you could cut those guides off flush with the port and not lose much for valve support.

NewbVetteGuy

There's a "wing-style" boss in the intake ports with very little guide extending past there, but in the exhaust ports of the profiler heads, they come exactly as you see them in my picture (except obviously I've sanded out the casting roughness with an 80 grit sandpaper flapper wheel.
My understanding is that the shorter the valve guide is the more than the valve can rock side to side, especially as the valve / guide wears over time. The video author said not to go less than 2" in total length. (Having said that, I DO have less lift and less weight with the exhaust valve vs the intake valve, so it's potentially safer to trim down...)

I've also heard Chad Speier say that cutting down the valve guide is a bad trade-off in terms of the amount of decreased longevity vs the amount of flow gain. (If you need valve guide inserts @ 50,000 miles instead of 90,000 miles and you only gain 1 - 1.5 CFM, is it really worth it?) I've also heard that the extra valve guide length is important to cooling the exhaust valve.

-This is why I'm considering removing only the last 0.2", if I do it at all...
I'm honestly having fun with all the little head and intake "hacks"; the most fun I've had with my Corvette restomod project to date, so I'm willing to do these labor intense, low return, cheap mods, just because it's fun. 1.5 CFM is only 3 HP, but it's 3 HP I can get just by doing something myself vs. buying another part and I find that 3 HP gain the most rewarding. (Having said that I'm probably giving my future self Alzheimers with all the aluminum dust I'm breathing lately... It's too @#$# hot in my garage to work in the heat under my hot garage light to wear a mask, too...)


Adam

derekderek

You have a pic straight down into the port from the valve side. The guy jn that porting video sounds like a hayseed, but he kniws what he is doing. And that 2 inch guide length is for 11/32 bbc valves with longer stems and bigger heavier heads than a small block guide. So i would think a small block guide would be fine at that length. I also don't run valve seals on exhaust guides. No vacuum tryna suck oil in anyway. That is a LOT of guide sticking into the exh port. I am thinking cutting them down some wouldn't be a bad idea.

NewbVetteGuy

Good call on BBC valve length vs SBC, I didn't pick up on that...
I have somethings to think about and some second opinions to get. Appreciate you making me think.


Adam