Compression ratio concerns

[RRSweden]

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.

My feeling was also to go with the stronger springs.

Another thing I heard was that the pushrods from 67 is taller than 68 ->. Is that because of the 67 block or the 67 heads? I have a 70 block. Just thought I'd hear if anyone here knew for sure wich ones to order, otherwise I guess I'll get a dial-rod to measure the lenght I need for the setup.

(excuse me for all the "what parts will fit" questions... But, as I said, I do have a time limit, and it takes time for the parts to ship from the US...)

 

[miller]

It's best to measure spring pressure at the installed height, and open height.

What Gary says should be a must, for any reasonable build. Like any other part, springs can get wore out, too. Best to know if they fall into pressure specs.

Suppose you already know most of your valves/guides are at, or out, of limits. Valve stem wear is the usual reason valves are replaced, since that's where all the action is, and the most wear.
Your guide measurements are probably even worst, at the bottom end, where the flame front is, on the exhaust guides.
Any rate...your call. There's things you can do to work around it, such as reaming the guides, and tossing in sleeves, and/or (if they can be found) valves with oversize stems.
Good luck on it!

 

[RRSweden]

Went to the machine shop today and picked up my block and left my heads for surfacing. The machinist also recommended me to have sleeves inserted. He will measure the guides adequately and let me know tomorrow. I'll probably end up with new guide sleeves. Seems dumb to pay so much money for a good block and crank just to put whatever on top..

 

[miller]

Yeah, probably something you didn't want to hear. None of us do!
But, these old, but good parts don't last forever, without a little help along the way. That work will at least help, and you'll get better performance out of 'em. And, your valve guide seals will like you for it!

 

[IQ52]

Went to the machine shop today and picked up my block and left my heads for surfacing. The machinist also recommended me to have sleeves inserted. He will measure the guides adequately and let me know tomorrow. I'll probably end up with new guide sleeves. Seems dumb to pay so much money for a good block and crank just to put whatever on top..

Okay then, the rules have changed? Now we are going to do them correctly? Then there is a lot more that needs to be done. Just dropping valve guides in there isn't going to fix the worn valve stems, so are you prepared to replace the valves? Proper valve guide replacement involves installing guides and honing them to the proper guide to stem clearance. Reams don't do it right. You can't get those clearances right with with worn valve stems. .001" stem wear is excessive. Now to run on pump gas there will need to be hard exhaust seats installed in the heads. Replacing guides means a complete valve job will have to be done, lapping won't be sufficient. To do a proper valve job you need to set all the valve installed heights while doing the valve job. Cutting the tips of the valves more than a few thousandths to get the valve tips the same heights is BS. So if you don't install all new intake and exhaust seats in the heads, then, after sinking the valves in the combustion chamber you need to know what to do to the combustion chamber and the short turn radius of the seat to retain the air flows.

As to the porting and valve job, I must say one more thing. Cutting the bowls straight down from the seats destroys the low/intermediate flows, it's a stupid move. A lot of research needs to be done on the combustion chamber, valve seat, throat, bowl transition before you start hacking away and destroying cylinder heads.

My apologies to all of you, I'm done and out!

 

[Garys1969RR]

You can use the head porting templates as a guide for porting the area below the seat. It seems they contour the throat area in towards the guide a little, from what I recall. It doesn't go straight down from the seat, but curves inward slightly. If you don't have a flow bench and years of experience, porting the heads using the porting templates are one way to get improved flow. As you can see, there is alot of work and money that goes into making a good set of heads.

 

[Garys1969RR]

My feeling was also to go with the stronger springs.

Another thing I heard was that the pushrods from 67 is taller than 68 ->. Is that because of the 67 block or the 67 heads? I have a 70 block. Just thought I'd hear if anyone here knew for sure wich ones to order, otherwise I guess I'll get a dial-rod to measure the lenght I need for the setup.

(excuse me for all the "what parts will fit" questions... But, as I said, I do have a time limit, and it takes time for the parts to ship from the US...)

The blocks are the same deck height, the heads are the same pedestal height. I would use the pushrods that came with your motor. The hydraulic lifters may have something to do with it. Check the lifter pre load with the pushrods you have. I like to see the plunger near the top of it's travel.

 

[miller]

Don't know if it helps...

But, like Gary says, on your push rods. From year to year, the difference is the style of tappets used. Your 70 model block 'could' take the push rods out of it...should be 5/16" diameter, straight, ball ends.
Since your using a non-stock cam, and needed 'new' tappets for it (get the right year application), a good chance you'll need a different length push rod.
You can use the stock push rods, for mock-up, to see what pre-load you'll get, and go from there. Check both intake, and exhaust!

 

[RRSweden]

I'm picking up this thread again.

What valve seals would you recommend for my application?

 

[Garys1969RR]

Hey how's the build coming along? Been so long since I ordered any seals, I don't have any recent experience. I have used the Perfect Circle seals back in the day, they worked good. Required machining the top of the guides. Have you done any porting yet?

 

[RRSweden]

Hey how's the build coming along? Been so long since I ordered any seals, I don't have any recent experience. I have used the Perfect Circle seals back in the day, they worked good. Required machining the top of the guides. Have you done any porting yet?

Hey Gary. No porting done, and I don't think I dare to try at this point either.
Maybe another build, or rebuild
I've had a couple of weeks off now, but I'm having the 915 heads worked on by the shop now. They will mill the surfaces and insert new valve guides. I came to think of wich seals to use, and if that choice will involve machining the top of the guides, as your suggestion does
Do you know where to find them?

 

[Garys1969RR]

I looked on the summit site, and only umbrella seals came up. I would think they have the other ones available too, I'm just not looking in the right spot. Umbrella seals work pretty good for a stock type build, after all that's what Chrysler sent them out the door with.

 

[Garys1969RR]

On Summit I found some seals to fit .500 guide diameter, 3/8th inch valve stem. They are the comp cams, Viton, with the positive stop. You will need to determine your final diameters and order the right seals. I think someone earlier had mentioned a replacement valve guide with .500 outside diameter. Your valve stems are 3/8 inch? Try the 514-16, comp cams. They are a nice light blue color. They're only about $20 plus who knows what for shipping to Sweden. Lol. You will need to cut the outside of the valve guide to .500 diam. I have used a tool that you put in your drill and cut the valve guide tops to .500" with it. It has a shaft that fits in your valve guide and acts as a pilot for the tool. Your machine shop may have one. It worked good for me.

 

[khryslerkid]

I looked on the summit site, and only umbrella seals came up. I would think they have the other ones available too, I'm just not looking in the right spot. Umbrella seals work pretty good for a stock type build, after all that's what Chrysler sent them out the door with.

(Positive Stop) Look in "My Photo Garage" for what's involved and tools needed.

https://m.summitracing.com/search/part-type/valve-stem-seals

http://www.forbbodiesonly.com/moparforum/showcase/member/khryslerkid.3078/

 

[IQ52]

Are we going to buy seals before we know what guides are going to be used and how they are going to be finished under the spring?

 

[RRSweden]

Are we going to buy seals before we know what guides are going to be used and how they are going to be finished under the spring?

I'm just asking around wich seals people use and likes before I talk to the machinist today.

 

[miller]

I'm just asking around wich seals people use and likes before I talk to the machinist today.

The ones Gary mentioned. Ones called Ironclad is what I used, after trying the Perfect Circle ones, with no luck. Seems the Perfect Circle seals aren't made like they used to be...tore way too easy.
Either way, machine shop, or using the cutting tool, both diameter of the guide, and when needed, the top of the guide gets cut. That allows clearance from seal top, to the spring cap.

 

[Glenwood]

This is a great thread...a real eye opener!

 

[RRSweden]

The machine shop will now ream new guides (copper I think) and also install new seats.
I asked them today how much extra they'd charge for a 3 angle valve/seat grind.

However the head of the shop (as well as Gary1969RR) told me that umbrella seals wold work fine for my application, so there's where it's leaning to for now.

Exited to get the heads back now!!!
After that I "just" have to make a final decision for the cam, buy a few pushrods and then I think I'm good to start putting it all together

 

[RRSweden]

Still... The thing that worries me the most is my flat top pistons without valve relievs.
Will the large valves hit them or not with the cam I'm choosing..?

Cliffhanger of the (at least my) year