Putting the heads together - did a 3-angle valve job (60/31/46) on all the holes, going to use GM swirl-polished valves with undercut stems, seat widths are right and seats are on proper place on valves, stem-to-guide clearances and runout are all within factory spec, all roughs removed from chambers and sanded smooth plus a little extra trick but basically left the ports excellent shape unmolested other than removing flashings, sanding and smoothing the transition to the seat to be smooth as a baby's sss and a little work to improve in-cylinder air swirl.

http://www.patentsearcher.com/valvejob.jpg

Next is to backcut the intake valves. According to this dude, I'm going to get 10% bhp increase: "Note how important just the valve shape is. A 30 degree backcut to reduce the seat on the valve from about 3.5mm wide down to 2mm to match the seat in the head and blend nicely into the back of the valve has raised mid lift flow by a massive 17% at 200 thou lift....."

http://www.gofastnews.com/board/tech...trictions.html

Factory single valve cuts are definitely an area for improvement. Looking at the seats and valves prior to my cuts, I don't know how those things were sealing. I used a magnifying glass and measured everything.


My question is, WHICH SPRINGS to use !!! ???

I'm keeping the stock cam in there for now but will probably go with the GM 846 cam eventually. My goal is to achieve substantially the same gains others do by cam swaps (ok, there is a limit), by optimizing valve angles for increased low and mid-lift flow on the stock cam, thus maintaining driveability and OEM valvetrain geometry (read: long-term reliability).


I noticed that this stroker uses the LT4 springs with the 846 cam:

http://www.crateenginedepot.com/prod...Product_ID=764

Stupid Question: Are the LT4 springs good enough ? Crateenginedepot seems to think so. I've got new sets of LT4 springs and retainers here that I could pop on these heads, but before I did I thought I'd ask if maybe I'd be happier with different springs, for reasons unbeknowst me.

Thanks.

Then its on to do two more sets of heads that materialized in my shack, for the fun of it or whatever. Why do I get into these things ? To get my valve profiles to be EXACTLY what I want. A 3-angle cut from the local shop or mail order house, Edelb, etc. isn't always correct and is rarely matched to the backcut on the intake valves. The cost of paying someone to do that would be lots of buckets of chicken. I'll dyno the car again after the heads-only swap.

Aqueous oxalic acid is great for removing crud from the water passages. They look spankin new.

 

Not if you are going to be running 1.6 ratio rockers.

 

thanks. Is there a GM spring you can recommend ?

I like to keep my GM cars all GM, to the max extent.



Unrelated, pondering a bumper sticker:

Only Americans, buy American.
or
Friends don't let friends drive toyotas.

 

LT4 springs might be fine depending on your cam selection as long as your not going over a .525" lift.

click the "more details"
http://www.jegs.com/i/GM+Performance...5494/10002/-1#

 

Here's the approach I'd take.

First I'd research exactly which spring the 846 cam calls for. I wouldn't just settle on a set of springs that can handle the 846 valve lift, but also seat pressure, OD and spring rate.

Since you want to run GM springs, the specific spring recommended by GM for the 846 is what I'd run. Of course, you probably know, GM doesn't wind springs; they buy them from a supplier that does. I suspect GM spec'd the springs to the supplier then slapped on a GM part number.

As a personal aside: If I had to list all the available springs which met the specs for the cam I was going to run and then priortized the list, based on which ones I felt were best at the top, down to the worse at the bottom, the LT4 springs would be at or near the bottom.

To me, they just don't give enough wiggle room, but that's just my view.

Jake

West Point ROCKS!

 

Yep, I'm skeptical about the LT4's, but only because they are production springs, and a big part of the equation is cost.

I'm going to go with the LT4's anyhow though, since my approach is to get the most flow and cylinder filling possible out of the stock cam, by removing manufacturing variances and a couple other goodies.

Like backcuts on the valves, of course:

"We talked with many cylinder-head specialists, and they all made one common point: Adding a back cut to the valves almost always results in improved flow..."

http://www.carcraft.com/techarticles...gle/index.html

I cut at 30 degrees on both int and exh, 035 & 050. I'll go 60 on the exh of my next set.

Bought a block off ebay, brand new 4-bolt LT1 block. Sheeeit. Now I have two bare blocks and three sets of heads. I understand better now why my wife buys Christmas dishes out of season because they're cheap and cute. I've been going slow with these goodies though, not buying unless I get a "deal".

It would be a cool project to set one of these motors up to run off hydrogen..... Hydrogen and nitromethane. Better use forged pistons.

 

Thanks again for that. I decided on the LS6 springs, GM# 12586484.
$ 52 for a set of 16 brand new from Lingenfelter. Retainers are comp 787-16. Should be no problemo for the 846.

 

Wow revelations...LOL.. You are learning what every kid at 19 learns running a flow bench and valve grinder.. I suggest getting a patent on back cutting valves no doubt they will issue one as the recent college grad won't know the subject anyway... do you know they issued a patent on a bar graph as it applies to the information displayed yet a bar graph was prior art on a desktop computer for at least 10 years before that... the patent biz is no more credible than the lack of prior art of the inspectors.. LOL.. India is calling....

 

Perhaps I am young at heart at 19 as you suggest, but, my initial thought is that your reply and its unwarranted antagonism makes me at least seven years your elder.

"The True Gentleman is the man whose conduct proceeds from good will and an acute sense of propriety, and whose self-control is equal to all emergencies; who does not make the poor man conscious of his poverty, the obscure man of his obscurity, or any man of his inferiority or deformity; who is himself humbled if necessity compels him to humble another; who does not flatter wealth, cringe before power, or boast of his own possessions or achievements; who speaks with frankness but always with sincerity and sympathy; whose deed follows his word; who thinks of the rights and feelings of others, rather than his own; and who appears well in any company, a man with whom honor is sacred and virtue safe. - - John Walter Wayland"

 

So true, I hope and expect your effort to result in decent gains.

 

I'm not sure if this will be of any help to you, but here goes anyway. My new Dart Pro 1s use the following "Valve Seat angles":

Int.= 32/45/60/70/80

Exh.= 37/45/radius

Jake

West Point ROCKS!

 

Thanks Jake, that's useful and good to know. Those guys have it easy cutting those, I think they do multiple angles in one shot. I'm using the Neway cutters, one hole and one angle at a time . radius/31/46/60/radius on both int and exh. Valve faces are 45. The most time-intensive parts involved blending the top cut with the chamber wall for the upper radius, and then cutting the seats to the exact desired widths, and then making sure they were positioned where they needed to be on the valve faces. I narrowed the intake valve faces so the sealing width is just 020 wider than the sealing surface on the seat w/specific backcut of specific width. Compounding matters on the stock heads were the non-flush stock exhaust seat rims, which had to be ground to be flush to eliminate the sharps. Int & exh valves are now level with one another but there's a 3/64 difference at the stem height side, requiring shimming and possibly diff. pushrod length. My guess is that the exh seats on the stockers were intentionally made to protrude into the chambers, favoring valve stem tip distance uniformity over priority of not having sharps in the chamber. Not to mention the work on the ports themselves.... All in all, you got your money's worth on those for not having to go thru all this BS. I got the satisfaction of some custom features. Was it worth it ? I hope so but even if they aren't the hottest ticket in my life of cylinder heads, it was worth the learning experience plus I've still got the tools. One lady thinks I'm hot because I know how to cut valve seats. I'll never understand the human female mind.

 

Thanks alot, I feel the same. I narrowed the intake seat width on the valve and did all the things the gurus claim are beneficial, and am expecting these ought support around 450HP. There's a ton of info out there and my modus operandi is to look for agreement by different authors on the same topic / principles, especially those authors with 30+ years experience. They don't always agree exactly on everything but in principle almost always. I would have hired this stuff out but I read from a few different sources that this stuff is so work intensive that shops can't give you what you want unless you're willing to pay a ton of money and even then there is no guarantee you'll get it. Getting those seats to the right place on the narrowed valve face was a chore. Here's a link to one of the sources I used for info and I hope you find something interesting and useful in it, and have a good evening too.

http://www.enginebuildermag.com/Arti...fications.aspx

 

Chris
How wide are the seat angles on your valve job?

How big are they in releation to the valve size?

We typically run .080 INT and .100 EX on most Hi performance street stuff. .060 INT and .080 EX (and sometimes smaller) on race stuff that gets freshened every year.

For size I like to run them about .005 smaller than (or from the edge of) the valve on street stuff. On race stuff I hang right on the edge.

30/45/60 is the standard 3 angle valve job. Varying the top angle and the bottom (throat) angle can make some gains/losses in flow. Depending on the head the top cuts can be as shallow as 15* and the throat cuts as steep as 90* in SBC's. I personally have never been an beliver of interference fit valve seats (ie 46*).

Any you are correct that no 2 professionals will agree on which combination is optimal.

Unfortunatly without a flow bench you'll never be able to see what's optimal for yourself but I can positively say that a radius cut under the intake valve will hurt. They are good on the exhaust but bad on the intake. If you don't have an 80* bowl hog cutter, the best thing IMO you can do is take a die grinder and cut the intake bowl until it is 80-90% as big of the valve size.

Don't feel bad about only having Newen single angle cutters as (I learned on Sioux rocks and grinders). You can still do a "good job" but it takes longer and you better know what your doing/pay attention to what you are doing. When we got our first MIRA cutters for our Van Norman PH2000, I thought that would be the end of us needing any real training for our machinest. I thought the same thing again when we bought our first Serdi seat and guide machine. Heck on some high end Newan seat and guide machines, now all you have to do it punch the button.... but it does a better job than any human hand ever could.

At any rate good luck with your project.
Will

 

Thanks alot for your time and reply. I originally shot for 0.040 - 0.060 on the intakes and 0.060 - 0.080 on the exhausts. I ended up with intake seat widths of 0.046, and seat runout is essentially zero. Here's a shot of a dychem'd seat

http://www.patentsearcher.com/seat.jpg

I never thought I could cut them so sweet, but I actually did two other sets of heads before this third set so I had a little experience. Then, check out the comment by the poster "FlowSpecialist" in this link, down at the bottom of the page in the forum section where he posted a chart of various gains. Of course not all engines respond to the same mods but I though it worthwhile to reduce the seat on the valve to more closely match the width on the seat itself, and did the backcuts a little differently than a standard backcut.

http://www.gofastnews.com/board/tech...trictions.html

My read is that I need at least a 60 thous exh seat for heat transfer and an intake seat on the narrow side to increase flow even beyond low lift.

Valves are 194's and seat inner diameter is about 1.740 so I'm at about 90%. I pondered eating into the seats but didn't want to upset the interference fit by doing an imperfect job. I went wide on the exhaust seats, they're about 75 thous and I did it for heat exchange purposes. I'm amazed you're running 0.010 on the exhaust seats - is that a typo ? How can the exh valve not glow with only a 0.010 wide seat ?

I used the 46 degree interference fit because my vette manual says to !! (Can you believe I followed a book ? !!!) plus also thats how Neway's been making them since before I was born so I figure it's probably not going to hurt although I do realize this is an area of differences among headmakers. Had neway supplied their cutters with a 45, that's probably what I would have used. I don't see one degree meaning much for my application.

Here's a chamber shot, you might notice this looks a little different than this stock head used to look !!

http://www.patentsearcher.com/cham.jpg

I guess I wrote it wrong, I didn't use a radius cut under the intake, only the 60 deg throat cut.

I used a jeweler's eyepiece and went over every square millimeter on these chambers and various sizes of carbide grinders. They're gems, I hope they work like gems. I really appreciate you taking the time and sharing your tips on widths. I remain amazed at an exhaust seat only 10 thous wide. You must be running sodium valves, right ? have a good night....


add this link

http://www.popularhotrodding.com/eng.../photo_13.html

 

The exhaust for regular old hi perf stuff is .100 or a hundred thousandths... Your correct that .010 or ten thousandths would not work very well.

Pics are funny sometimes and don't really show what your trying to show very well.... Just by looking at the pic I would think that intake seat is much wider than .046, thats why I asked.
Will

 

Crikey, I read your post wrong, it did say .100. Yeah, I have an older camera, tried all the functions on it to get a clear close-up and that was the best shot out of about 10. It's a nice little seat. Those heads were full of sharp edges. I'm optimistic that since many 350 engines easily achieve 450 HP on Gen I blocks, that if chamber sharps are eliminated to enable full benefits of reverse cooling to be achieved AND proper quench height is provided, substantial gains over that 450HP can be seen. Then again, do I really want this ? I don't think the U-joints on the indep. suspension can handle it....

 

Do you know whether LT1 heads respond to radiusing the exhaust valves themselves, on the chamber side ?

http://www.chevyhiperformance.com/te.../photo_03.html

I don't know what tool to use to do that......

 

Yes it will respond well because the valve sits so high in the combustion chamber.

Most Ferrea and REV valves I use these days already come radiused that way, but back in the day I used my valve grinder/refacer.

Take the valves chuck them up in your valve grinder, set the angle to 30* and then run the adjustment on the grinding head all the way forward. Then use the side of the facing wheel to put about .60-.80 wide 30* cut on the margin. Then you set the angle to 45* and cut that 30* you just put on it in half. After that you take some 80grit cartridge rolls on a die grinder and just lightly blend the 2 angles together. I know it seems scary with the valve turning and the die grinder running and all but it dosen't take much pressure to blend it.

You can also forgo any of the steps and just put a strait 30* or 45* angle cut on there as its better than nothing and sometimes one or the other works better than a radius.
Will

 

Thanks alot Will !!