Cam for 1965 300hp rebuild...MOTOR GUYS? - NCRS Discussion Boards

Cam for 1965 300hp rebuild...MOTOR GUYS?

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  • Jim V.
    Expired
    • November 1, 1991
    • 587

    Cam for 1965 300hp rebuild...MOTOR GUYS?

    Ok cam guys...here's your chance...don't be shy

    There are forces at work trying to convince me to up-cam my old butt from the old 3896929 (or 14088839) 327/300hp cam to a Summit k1102 (same as CLevite 229-1730). I am rebuilding with a targeted 9.7scr (H660cp pistons) with blueprinted stock everything else. Currently have small valves but may go with 2.02/1.6 depending on seat condition. Net duration change of +8I and +18E

    Specs @50 IDur EDur ILift ELift LSA IPOML EPOML TPS
    OE 196 196 .399 .399 112 109.5 112.5 (11)-27 / 30 -(14)
    K1102 204 214 .420 .442 112 107 117 (5) -29 / 44 -(10)

    Over cam or wise choice..you be the judge Let me hear ya????

    Thanks all
  • Jim T.
    Expired
    • March 1, 1993
    • 5351

    #2
    Re: Cam for 1965 300hp rebuild...MOTOR GUYS?

    Check the posts this week of Duke. He mentioned that he has done research and has the data for the optium cam for a 327/300.

    Comment

    • Joe L.
      Beyond Control Poster
      • February 1, 1988
      • 43221

      #3
      Re: Cam for 1965 300hp rebuild...MOTOR GUYS?

      Jim------

      I think that cam would work ok for you. I don't think that it would result in the engine being overcammed. However, keep in mind that the 3896929 and its direct successors are pretty hard to beat for a street cam.

      Also, don't even think about enlarging the valve size from 1.94/1.50. That valve size is the best for your engine. Secondly, you may destroy the heads trying to have the valve size enlarged. Thirdly, if you are successful in enlarging the valves, the heads will be much more susceptible to cracking. Absolutely not the way to go for your application with either cam.

      By the way, keep in mind that 1962-63 Corvettes with 360 hp FI engine used the 1.94/1.50 valve size.
      In Appreciation of John Hinckley

      Comment

      • Jim V.
        Expired
        • November 1, 1991
        • 587

        #4
        Joe...and motor guys.....

        Thank you Joe! The nice thing about the cam decision is that it can be readily changed. The heads will never grow original cast iron.

        I dropped my heads off earlier today. The highly experienced machinist who has been doing performance heads for about 15 years made quite a case for hardened seats. He mentioned a recent article which made a rather convincing argument in favor of hardened seats: original heads hold up to unleaded fuel since they have been preconditioned with TEL and work hardened over the initial years of there life. Once they the seats are reground the workhardened TEL conditioned material is removed. Unless this virgin surface is reconditioned with TEL they are subject to damage with todays unleaded fuels. Seems logical. Maybe there are some more qualified folks than I who care to comment on the thesis.

        At any rate... The only reason I would consider the larger valves is in the case the seats being to low after being reground. Geometrically, it seems with each valve job the valves would recede deeper into the head chamber. Is this a valid concern? Wouldn't going to the larger valve allows for lifting the newly ground seat to original camber height?

        New tech vs OE specs decisions are always difficult when restoring these old cars. Suppose it is part of the madness...luckily we are not alone

        Thanks!!!

        Comment

        • Mark #28455

          #5
          how much will it really be driven?

          In all honesty, my L89 has been driven 6000 miles in the past 23 years. It doesn't matter what valve seats it has. If you were concerned about "regrowing cast iron" as your reason not to go to larger valves, it seems totally inconsistent that you want to cut your heads to add hardened seats. The cuts for the new seats are really pretty big. The thin spot in 461 heads isn't at the valve face, it's where the 2 seats come together and by cutting for a new seat, you've actually made the remaining seat about 1/2 as thick. In addition, due to core shift, you can sometimes get into the water jacket at the upper side of the valve seat cut (the side away from the chamber). Even if you go for the exhaust seats, there is really no logical reason to add hardened intake seats.

          If the TEL theory is true, you could just get a 5 gallon can of avgas (2 grams TEL per gallon) or racing fuel (2 to 4 grams per gallon) and add a gallon or so to every second or third tank for the first 1000 miles - it really didn't take that much TEL to protect the valves - the last leaded gas had about 0.1 gram TEL per gallon so one gallon of the above noted fuels would be enough for 20 gallons of unleaded.

          Mark

          Comment

          • Jim V.
            Expired
            • November 1, 1991
            • 587

            #6
            Dirve....L89?

            L89 (427/435 alum head)....wow...congrats on driving something that rare at all! I do hope to drive my little L75 (327/300hp). That is why I bought this car. That said, by drive I suppose 2000mi/year would be about it.

            The hardened seat issue is but one of many little debates along the way in this process. The exchange of ideas and experiences is what makes this hobby so interesting.

            Thanks Mark, you make a very convincing argument for periodic TEL use.

            I wonder if ANYBODY in our hobby has ever experienced seat recession with OE heads. Anybody...anybody...?

            regards

            Comment

            • Verle R.
              Extremely Frequent Poster
              • March 1, 1989
              • 1163

              #7
              Re: Joe...and motor guys.....

              Jim,

              I recently removed a set of "186" heads from a 69 because the owner complained of a lot of white smoke. We assumed the heads were cracked but they were not. I had them pressure tested and several of the hard seats leaked on the bottom. The machinist had cut into the water jacket, installed hard seats and sent them home.

              It junked a fairly rare, expensive pair of heads.

              The owner has to now find another pair of the right casting number and date heads; not an easy task.

              Unless you plan to drive the car hard (road race?, autocross) I doubt you will need hard seats. Recessed valves are a combination of things, seats ground down and valves cut down in size. New valves will go a long ways to correct the problem unless the seats are seriously cut. If the seats have been cut that much/many times, the guides may be worn beyond normally available oversize stems; you may have to install guides.

              I personally would install hard seats unless there was no other option to keep using them. I would ask the machinist for a guarantee against leaking. Get the heads pressure tested before installing them.

              Verle

              Comment

              • Mark #28455

                #8
                I had 461 heads in a Monza

                I had a destroked 400 in my Monza in the mid 80's with 461x heads. I used to abuse it all the time - 6500 to 7000 RPM shifts, etc. I was pretty poor at the time and left the 1.94 intakes but had the exhausts opened to 1.60. The heads were old and needed 2 or 3 exhaust seats. Other than that, I used stock cast iron. After 30,000 plus hard use miles, the heads still looked great with no seat recession. I did run a little leaded gas in it from time to time, but mostly unleaded.

                Mark

                Comment

                • Jim V.
                  Expired
                  • November 1, 1991
                  • 587

                  #9
                  Verle. & Mark..

                  Thanks for the real life stuff. Verle, I suspect you meant to say you would NOT install the hardened seats unless...

                  Thanks

                  Comment

                  • Verle R.
                    Extremely Frequent Poster
                    • March 1, 1989
                    • 1163

                    #10
                    Re: Verle. & Mark..

                    Correct, would not install hard seats.

                    Not only are the fingers dyslexic but getting old and forget what they are saying.

                    Verle

                    Comment

                    • Joe L.
                      Beyond Control Poster
                      • February 1, 1988
                      • 43221

                      #11
                      Re: Joe...and motor guys.....

                      Verle-----

                      Were these 186 heads with 2.02/1.60 or 1.94/1.50 valve size?
                      In Appreciation of John Hinckley

                      Comment

                      • Terry F.
                        Expired
                        • September 30, 1992
                        • 2061

                        #12
                        Re: Joe...and motor guys.....

                        Joe,

                        Sorry about high jacking the thread. But, do you know of any difference between early and late big block rods? One has a narrower beam than the other?? Also, do dimple rods have to be used with full floating wrist pins? Thanks, Terry

                        Comment

                        • Verle R.
                          Extremely Frequent Poster
                          • March 1, 1989
                          • 1163

                          #13
                          Re: Joe...and motor guys.....

                          Joe,

                          They were 2.02 heads.

                          Verle

                          Comment

                          • Mark #28455

                            #14
                            Big block rods

                            There are several types of BB rods. The original 3/8" bolt BB rods came in two types - dimple and non-dimple. The dimple rods were a slightly more robust forging. If you look at the side recesses in the "I" beam, the earlier rods used a recess that got significantly wider as it apprached the crank, the later rods (1970's) had a recess that stayed constant in width and ended as a semicircle. Likely a stronger rod as there was more meat near the rod bolt head seating area. In the mid eighties, the entire rod was significantly thinned across the width of the "I" beam.

                            The 7/16" bolt dimple rods first appeared in 1969 model engines with the L88 and ZL1 and used floating pins with a tin coplating and good boron rod bolts. They were forged of an improved steel alloy (4340?). In 1970 they were also used in a pressed pin form for the LS6 engines with knurled shank bolts. They are heavier than the 3/8" dimple rods. They were available in service till the late 80's or early 90's. They were replaced with a new design 7/16" bolt rod which had a "parabolic" shape to the "I" beam and is supposed to be more durable than the previous design.

                            Mark

                            Comment

                            • Terry F.
                              Expired
                              • September 30, 1992
                              • 2061

                              #15
                              Re: Big block rods

                              Mark, you seem to know a lot about connecting rods. I am trying to gather information about the rods in my 68 390hp. I don't have the engine apart yet. I want to use a factory rod, I might just end up using the rods that are in there. Who knows?? But, I am trying to improve on the quality of the engine rebuild. I am thinking of putting together/collecting a set of rods that are specific to my car but are physically very similar in appearance and weight. After that I was thinking I would have them resized and balanced within a gram of one another. That is my starting point.

                              Any good book to recommend on rebuilding big block chevy's? Just what to do a high quality rebuild. Terry

                              Comment

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