Compression ratio concerns

[IQ52]

I don't think I can afford to have the seats replaced and cut. My plan was to use copper grinding paste in two grit-steps.
My budget is really the biggest block here.
Of course I could wait and save up, but the goal is to be a part of the "Street Week" this summer. It's swedens answer to your "Hot Rod Drag Week".

Now i'm off to the garage to get some pics of the heads

That's sort of how I figured you needed to handle it. It'll be interesting to follow along.

 

[RRSweden]

Here's the chamber with the broken boss.

 

[IQ52]

No problem, run it.

 

[RRSweden]

Here is the port from intake side.
How would you recommend me to start? Walls, roof, floor, cup or just above the seats?

Sharp material removed from the guide. I liked your idea of putting a smaller seal around it. It measured 0.500 as you guessed.

 

[RRSweden]

Exhaust valve. These ones I guess could be back cut 30*

But on the intake valves I guess it's another story... Here's the "ski-jump" I've read about

 

[IQ52]

I don't teach cylinder head porting.

However this man attempts to............

http://www.hotrod.com/articles/cylinder-heads/

http://www.hotrod.com/articles/cylinder-heads-ii/

http://www.hotrod.com/articles/cylinder-heads-iii/
And whether you want to or not, from the pictures, it appears you will have to have the heads surfaced.

 

[RRSweden]

Yes, I guess I'll have to have them surfaced.

Does anyone know if there is porting templates for these heads with the bigger size valves that I've got?
in: 2.14
ex: 1.81

pretty sure there is not

 

[RRSweden]

I don't teach cylinder head porting.

I hope you don't feel I'm being pushy. I'm happy with ALL the help I get here wich is much more (and better) than in swedish forums.
So I'm just throwing questions (stupid and less stupid) left and right

 

[IQ52]

I certainly don't think you are being pushy. I think you are being inquisitive. That is a good thing.

I just hope you don't think I'm being rude because I don't share everything I know. Sometimes there is just too much to explain as to how we go about things and others have covered them in simpler terms.

 

[Cranky]

Hand porting takes practice just like anything else. If you've never done it before, you need to get a head to practice on. It doesn't have to be a Mopar head either. It helps to have someone to show you and stand by for guidance. A buddy of mine who was a professional did one intake and exhaust pocket and it seemed like it didn't take him no time at all! I've seen others do it that claimed to know how but never ever saw anyone do it as fast as he did and look so good. My job was to do the rest but I knew that wasn't happening lol so I asked him to finish the rest and I started practicing on a junk head. My confidence got better and better and it wasn't too long before started working on the good stuff. There's also a lot of pics on the net of what the ports should look like. On a mild street engine, I don't worry too much about the runners but concentrate on the valve pockets and do a smooth blend into the runners. It also helps to make sure the intake matches the heads....

 

[miller]

All the guys are giving you good straight up info. Will say...if your in a hurry...won't help much, since working a set of heads does take time, no way around it. No so-called expert here, since I only know enough to make me dangerous, always worked my own heads, including machine work. Know enough to understand what it takes. Whew!
Working up heads, going by what kind of shape their in, like any thing else, a little or a lot, can be done.
Those heads are worth working on, but depends on what you want out of them. Looks like at least all the basic work, re-surface, seats, and guides. Personally, I'd cut every one of those guides OUT, and flat start over with them. But, probably just me. The heads have plenty of time on 'em...just need some TLC.
Those guides are one of the most critical areas of heads...since they control how the valves act. Aw hell, I'm gettin' out of hand...

 

[miller]

Back-steppin'...at the very least, I'd heavy hand check every guide first, and go from there.

Exhaust guides bad on getting belled out at the bottom. Both can get out of round (internally), or bellied out in the middle, besides getting out to max.

 

[RRSweden]

Thanks Miller!
How do I measure valve guide play? And what's the tolerances?

 

[Garys1969RR]

There is soooo much work that should be done to those heads. Or you could just re surface them, lap the valves in, clean them up good, and they would work. The valves SHOULD slide easily into the guides, and have little or no side play when you wiggle the valve head back and forth. Seems the factory allows like .001 to .0015 clearance, but I'm not sure. You can measure that with a dial indicator. I think it's better to back cut the intake valves first, as the incoming charge has to jump over that little ledge before it crosses the seat. Also, put a couple of old valves in the head, and blend the 70 degree top cut into the as cast combustion chamber. That takes that little disruption to smooth flow out of there. Also blend the machined area just below the valve seat into the as cast port on both int and ex. You can also gasket match the INTAKE ports. I wouldn't do the ex side though. That should keep you busy for awhile.

 

[Garys1969RR]

You can put a valve in there, and hold it open about 1/4 inch (.250) which is about halfway open with most street cams. Then visualize the air racing through that small opening at several hundred miles an hour. Any small protuberance will look like a mountain to the airflow, and will disturb it. You want smooth, unhindered flow across the seat. At this stage, most of your airflow gains are most likely to be made within 1/2 to 3/4 inch of the valve seat. The Porting templates will work ok with larger valves, but you may need to modify them slightly. Every Hi Perf head I've ever looked at, seems to have the throat drop pretty much straight down from the seat. Look at a Hi Perf (dare I say Chevy) head and see how they are contoured. Air flow behaves the same, irregardless of make. Don't do much on the short side radius, as that area is critical. And the 915s/906s have a pretty good one. There's plenty to think about. I'm no expert, but I have done alot of home porting on the 915s, with good results. It's trial and error. Lot's of trials, and lots of errors. Good luck! Feel free to ask questions as you go along.

 

[miller]

How do I measure valve guide play? And what's the tolerances?

Sure thing...

Just off the top of my head, intakes are .001-.003, exhaust .002-.0045...but, don't go by my chicken scatchin'. The recommended clearances, and max, will be in the service manual. Doing almost anything on a motor, that book is a must. (Exhaust clearances are bigger, because exhaust valves take more heat, and the valves expand.)

As far as measuring the guides...#1 one ingredient is the hand doing it. Or, maybe just a little common sense. Also should decide if you want those heads to give you some good miles, or just get by...until.
Any good engine machine shop will have what's called a ball mic. Has a split ball end that expands, to read the I.D. of a hole, and can check the entire length of the hole. But, if one is not available, there are a few other ways. One, that I've used alot, is a snap gauge, since it has 'reach', but it takes a good hand to be accurate! Snap it in, get a base measurement, and then 'feel' the remainder of the guide, to see if that measurement is the same, top, middle, bottom. Tedious work, must do work, if you want it right.
Another way is to make a 'go/no go gauge'. It's a piece of quarter inch flat stock, and ground on the two edges, stepped...first at the low clearance measurement, second step at max. You simply push it into the guide, from both ends, to check them.

 

[Garys1969RR]

Here's a few more things that I feel will improve the flow, after you have done all the other things I mentioned. The intake port wall has a narrowing just inside the port for valve guide clearance. You can cut this down, reducing the size of the hump, from floor to roof, and that should help flow. Don't go too far as oil is on the other side. I have actually gone all the way thru a few times, but some JB Weld fixed that! Ha ha. 5 years and holding! Also, on the intake bowl there is a bump in one of the channels as it goes around the valve guide. I like to grind that out. It actually lines up with the ex stud I believe. Don't get too crazy here as there is water on the other side. Just take out the little hump. I like to smooth the channels below the valve into a nice smooth contour leading up to the valve pocket.

 

[RRSweden]

today I took what I had and made a measurment of the guides and valve stems.
As I only have a digital caliper at hand right now I understand the measurment of the guides does'nt really tell the hole truth. It only shows the diameter at maybe the top 1/3" of the guide, but I figured I'd do it anyway.

 

[RRSweden]

I also wonder what springs you guys think I sholud use with the xe268 cam.
The ones I got with the 915 heads was a bit different than the ones I had on my 906 heads.
They were shorter, but thicker diameter of the spring steel.
The retainers is also different.

Above: the "906 spring"

And here is the "915 spring"

 

[Garys1969RR]

It looks like the 915 springs are a stronger spring. I would use those. That 268 cam has a duration of 268/280 and a lift of .477/.480. Int/Ex. We used the next one up in my Son's 383, the XE274 H, and it worked fine with the stock 383 Magnum springs. It's best to measure spring pressure at the installed height, and open height. My guess is to have about 120 pounds closed, and 250 to 280 pounds open. Check with Comp for exact pressures, or someone here prob already knows what they need to be.