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  • My first valvejob/seat replacement

    The more I start measuring and checking their work, the more I'm fed up with automotive machine shops. The latest is a set of Dart aluminum heads for the 496 in my boat...every aspect of the valve job was done at +/- .015...and I suspect all of the valve seats are ground too deep which consequently increases my chamber volume past where I would like it, and I've got a 6cc variation amoungst all 8 chambers, which results in a compression ratio anywhere between 9.8:1 and 10.4:1.

    I'm gonna try and fix it. I'm after perfection here. I've ordered up new guides, new seats, and new valves. I've acquired a valve refacer, a valve seat grinding setup, and a guide hone (real one, not once of those ball things). I've got a bore guage in the range of my valve guides (11/32) that will measure to 0.0001". Along with my bore guage, I'll also use a selection of guage pins to verify not only the diameter, but also the straightness of the guides.

    I know, seems like I'm spending a lot of money for one valve job, but I do quite a few engines and I anticipate doing considerably more engines over the course of my life, so I might as well tool up to do 'em myself. The initial investment sucks, but I'm hoping it'll pay off.

    I'm in the process of building a fixture that will allow me to spin/cant the head on my mill table for the guide honing and seat work.

    The seats on these heads are interlocking...which means that after one seat is pressed in, the counterbore for the other valve will have to cut into the first seat slightly. This is where I might need some help. Most of the real machine shops do this with piloted tooling. Piloted tooling for this operation will run me about $1500 to purchase...so I'm not gonna. The plan is to use a boring head with a .750 shank brazed carbide tip boring bar after using a coax indicator on 2 spots of the valve guide, as well as the existing seat to get the head located correctly. I've got a fat and short one for rigidity. The seats are made from Ductile Iron, and the cut for the "interlock" is a section about .040 deep and over about 25° of the 2.5" diam. seat. I've ordered .010" oversized seats becuase I'm doubtful of my abilities to complete an interupted cut without touching the rest of the existing bore. I figure a multimaterial cut will be easier than an interupted cut. This procedure scares me a bit, but with care and light cuts...should turn out well. Minor concentricity issues shouldn't be a problem as I will grind the seats using piloted tooling concentric to the guide. I'm shooting for a .0.005-.007" interference fit.

    Any words of advice?

    I'll update with pictures as I make headway on this.
    Last edited by lbhsbz; 12-23-2010, 06:14 PM.

  • #2
    I can't offer any advice other than: if it were me, I think I'd want to try it on a junk head first.
    I'm interested in Cyl. head work on a knee type mill too and will be following your thread with interest.
    Hope it works for ya !
    Take lots of pictures !

    Comment


    • #3
      i got into head work many years ago for the same reason you are now. could not get a good job.

      i found that most guides are machined after being installed. which can cause a problem if putting a new guide in. if the valve guide center line is moved even a little bit you have major problems getting a seat with out going too deep. the best way i have found is too relinf the guides that way you are working off the old center line. i use an old walonea set up.

      Comment


      • #4
        Have same problem

        Theres no one around my area good at engine work. I just paid a bunch of cash for a **** valve job at a speed shop in Brantford. The thing was nasty. I have been gathering equipment and anm working on a fixture for holding heads. People just dont take the time to do anything rightn anymore. Thats for sure. You have to almost do everything yourself if you want it done nicely.

        Comment


        • #5
          Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

          Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

          Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...

          Comment


          • #6
            Ductile iron valve seats in an engine running on unleaded gas? Are you sure you want soft seats?

            Whether you use soft seats or hard seats you'll get push off when it cuts into the other seat. Cutting into an aluminum head and part of an iron or hard seat will produce an out of round hole. The reason they use a pilot is to keep the cutter centered.

            You better find a scrap head to experiment on because I think your going to find out why you need a piloted cutter.

            Doing heads on a Bridgeport type mill works if you have a good fixture to mount the head in that is adjustable in two axis's. It's real important to align the valve guide your working on concentric with the spindle.

            The last automotive machine shop I worked at had a level that slipped on a shaft that was a snug fit in the valve guide. Then you leveled the valve guide in two planes. You may want to look into getting one of them.

            You can make almost any pilot cutter you need.
            Last edited by Carld; 12-23-2010, 08:39 PM.
            It's only ink and paper

            Comment


            • #7
              I do a lot of cylinder honing but for valve guide and seat work you need a GOOD automotive machinist with the latest equipment. I send anything like this to Ken McDonell in Stettler Alberta. The only guy I know who can turn out a perfect job. It just isn't worth the hassle of trying to set up a head with no suitable mounting surface and having to do it multiple times in a mill. This guy builds race engines as well as regular run of the mill engines and knows his stuff. Trying to find someone who takes pride in their work can sometimes be frustrating. There has to be a reputable engine shop somewhere in your area, ask the racing fraternity, they'll know. Peter
              The difficult done right away. the impossible takes a little time.

              Comment


              • #8
                Originally posted by lbhsbz
                Piloted tooling for this operation will run me about $1500 to purchase...so I'm not gonna.
                Top of the line - $800

                You need to correct for the slightest angular misalignment. That is the reason for the piloted tooling.

                But yes it is quite a bit of money especially considering once you purchase all that "Head Rebuilding Tooling" your gonna want a "Flow Bench" to go with it

                Comment


                • #9
                  Having been to J&M Machine (Southborough MA) and seen the machinery they have and their mastery of it, I wouldn't even attempt to do it myself. And I've been a machinist for over 30 years.

                  John and Mike (brothers) have the latest in the specialized machine tools and tooling, can cast their own babbit bearings (using a variety of compounds) and do impeccable work.

                  I'm not saying you can't do it or shouldn't try, I'm just saying I know of at least one shop that is top-notch and carries a great reputation to back it up. And there's knowledge of the motors, tools, materials and methods that 30+ years of doing nothing but that kind of work has benefited them, and left me "knowing what I don't know."

                  http://www.jandm-machine.com/

                  BTW, the fact that you'd be using a brazed carbide boring bar right off tells me that you may not be any more successful than the shop that didn't do a good job. This a job for quality tooling, and that ain't it.

                  P.S. - .005" to .007" isn't a press fit, it's a "not a chance" fit.
                  Last edited by PixMan; 12-23-2010, 09:38 PM.

                  Comment


                  • #10
                    Originally posted by RussZHC
                    Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

                    Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

                    Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...
                    I kinda screwed up.....maybe not. I was looking at seat cutting setups, that use a single carbide blade to cut all 2-3-4-5-6- whatever angles at once...and that was somewhere in the neighborhood of $1500 realistically. That's will multiple toolholders so I could leave each one setup so everything would be dead nuts the same on all the seats. The "base" package is about $750. Instead, I bought a seat grinder setup, but you can't use this to cut the counterbores with any level of accuracy.

                    I'm not sure what you're asking about the overlap thing....please elaborate and I'll try to answer. You may have touched upon something I haven't thought of...but I don't really understand your question.

                    Comment


                    • #11
                      Originally posted by Oldbrock
                      I do a lot of cylinder honing but for valve guide and seat work you need a GOOD automotive machinist with the latest equipment. I send anything like this to Ken McDonell in Stettler Alberta. The only guy I know who can turn out a perfect job. It just isn't worth the hassle of trying to set up a head with no suitable mounting surface and having to do it multiple times in a mill. This guy builds race engines as well as regular run of the mill engines and knows his stuff. Trying to find someone who takes pride in their work can sometimes be frustrating. There has to be a reputable engine shop somewhere in your area, ask the racing fraternity, they'll know. Peter
                      I'll spend more money trying everyone in the state to find someone who cares than I will to tool up and do it myself. Every machine shop in the world comes well recommended by those that like shiney surfaces but don't disassemble and measure to check their work after delivery. Plus, the kind of job I'm looking for is $$$. Most shops simply won't do it.

                      Comment


                      • #12
                        It would seem that engine rebuilding is rapidly becoming a lost art. When I was in the trade, there were 3 local automotive machine shops that were good to excellent, and 3 that weren't. Now, 30 years later, they're mostly gone. The place I worked was as good as any, offering the run of the mill stuff, plus balancing, align boring, and driveline service. Lots of good guys worked there. Picky, knowledgeable guys. I learned a lot from them. I left because I couldn't see any future in it. Turns out it was a good move, but now the company I work for won't rebuild any engines or gearboxes in-house. There's still plenty of other work to keep us busy, but who wants to replace king pins when there's engines needing rebuilding?

                        I would suspect that in many cases the reason that people find it hard to get the quality of work they want, is because the good men who are skilled and knowledgeable enough to the required work have moved to greener pastures. In my case it was a long time ago, and it was for the money. Like 35% more and double the benefits. Last time I knew, it was more like 50% nowdays. That is comparing auto machinists to diesel mechanics. Other trades may be similar, I don't know.

                        Last summer my daughter's Escort spit up an intake seat and I considered fixing it here. The proscess seemed pretty involved for 4 seats and a valve job, so I farmed it out to the last local shop here I'd trust. Cost, if I remember correctly was about 150 bucks. 4 seats, 4 cyl valve job, and the laundry. They did a nice job. I wonder how those guys keep bread on the table.

                        When I was rebuilding engines for our fleet at work, I used to send blocks to B and G in Seattle. They do first class work on things that count. The biggest engine we have is the smallest they work on. Perhaps that's the secret, find a shop that does first class diesel work, and see if they do any gas or race stuff?

                        TC
                        I cut it off twice; it's still too short
                        Oregon, USA

                        Comment


                        • #13
                          Originally posted by RussZHC
                          Its been awhile but...a bit confused as you mention piloting tool(ing) twice, the first time its is too costly ($1500; as an aside, is there any way you or someone else could duplicate it for less?) but then later you say you will do the seats using a pilot via the valve guides (this is where I am a bit sketchy, "awhile" but I think I got it right?).

                          Are not both ops using the same valve guide to lead the pilot? And if so are those not either the same item or parts for doing the different ops but often sold as a set?

                          Another aside, are you concerned at all with how precise the timing of the valve train once completed has to be?...isn't the more there is overlap the more risk is run of contact by say not rigid enough parts in the rest of the valve train...
                          I dont see what fitting guides and seats has to do with the timing , all of the range of engines that I have either had work done on by others or have completed myself the only timing was done by the camshaft and its associated parts.
                          Just curious, not doubting anyones knowledge.

                          Michael

                          Comment


                          • #14
                            Originally posted by Carld
                            Ductile iron valve seats in an engine running on unleaded gas? Are you sure you want soft seats?

                            Whether you use soft seats or hard seats you'll get push off when it cuts into the other seat. Cutting into an aluminum head and part of an iron or hard seat will produce an out of round hole. The reason they use a pilot is to keep the cutter centered.

                            You better find a scrap head to experiment on because I think your going to find out why you need a piloted cutter.

                            Doing heads on a Bridgeport type mill works if you have a good fixture to mount the head in that is adjustable in two axis's. It's real important to align the valve guide your working on concentric with the spindle.

                            The last automotive machine shop I worked at had a level that slipped on a shaft that was a snug fit in the valve guide. Then you leveled the valve guide in two planes. You may want to look into getting one of them.

                            You can make almost any pilot cutter you need.
                            Ductile Iron is what the Dart assembles their heads with, and I haven't heard of any issues with them. I'm sure there are better parts out there, but I just called up Dart and ordered everything from them. Prices were decent, and I'm getting stuff that I know will work with their heads.

                            I agree with you about cutting this with non-piloted tooling. It may be impossible. My fixture is ridgid. It consists of a 2" wide 8x10" block on each side with a 3.5" hole bored in each piece. I made 2 pieces of a 4" long piece of roundstock that will fit and clamped into the holes in the blocks (blocks have a slit and bolt to pinch the bore around the round stock)...Then a piece of 1" thick x 3" x 24" material that will bolt between the roundstock "spindles" and bolt to the intake or exhaust surface. The mounting holes in the big crosspiece are slotted to give me the 4° of cant that I need to hit the intakes. I'll use some kickstands off of the other side of the head to brace it to the table. Should be pretty stout.

                            Comment


                            • #15
                              Originally posted by JoeFin
                              Top of the line - $800

                              You need to correct for the slightest angular misalignment. That is the reason for the piloted tooling.

                              But yes it is quite a bit of money especially considering once you purchase all that "Head Rebuilding Tooling" your gonna want a "Flow Bench" to go with it
                              Where? I'm dealing with 2.460 OD intake seats....most don't even make cutters that big....so that puts me into the adjustble cutters which are big bucks.

                              I'm seriously considering reselling my valve grinding setup and nutting up for the ball drive setup...then I can cut seat counterbores with the addition of a $30 blade. I hadn't thought of counterboring for the seats when I made the decision to buy the grinder setup for $300.

                              Maybe I'll throw a chunk of iron into a block of aluminum and try to bore a hole threw it....for the amusement if for nothing else....I kinda know what'll happen.

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