Rod to Cam Interference

Discussion in 'Tomahawk Block Buildups' started by Bruce Kent, Aug 15, 2012.

  1. Bruce Kent

    Bruce Kent Well-Known Member

    I just ran into this issue when assembling my engine. I'm using GRP Aluminum rods, Ford sized cam in the stock location and 4.5" stroke. Rods 1 and 6 hit lobes on opposite bank. The interference is right where the side of the big end starts to curve around towards the beam and lasts for about 15 degrees of crankshaft rotation. The rod is chasing the cam lobe. The fix will be to trim some material off of this area of the rod. I've noticed on R and R rods that they have an assymetrical profile on the big ends to aid in clearing the cam. I've mentioned this to Mike at T/A so that he may caution others can avoid this situation. I didn't experience with my other engine assuming it was because it was only a 4.4 stroke and R & R rods. Stuff happens. This block is really nice to work with. No band-aids required. Must be what it is like to build a chevy.
  2. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Can't wait to see what you come up with Bruce.
    Not too many people pushing Buick performance like you.
  3. buicksstage1

    buicksstage1 Well-Known Member

    Bruce, I sent you a PM....
  4. Bruce Kent

    Bruce Kent Well-Known Member

    Well I hope to make a little more power than the old engine that the internals came out of so we will see how it works out.
  5. Dave Mongeon

    Dave Mongeon Well-Known Member

    Hey Bruce
    How much lift and duration? Your right about being like a Chev
    Seen the same thing in a 632 Chev with GRP Rods!
    I Think he was up around .900 and 300.
    Notched the rods and ended up loosing a rod in that motor.
    I'm not covinced notching caused the problem but he sure is.
    I used GRPS in my build as well but its only 4.4 stroke
  6. mpvance

    mpvance Well-Known Member

    Chevy guys can buy raised cam blocks. Is that available for Buick?

    JESUPERCAT No Slow Boat

    Yes it is, it just costs more:grin:
  8. Bruce Kent

    Bruce Kent Well-Known Member

    I promised Scott Brown I wouldn't divulge the specs of the cam. Not that big or long though. The notch amouted to about 1/8" deep adjacent to end of bolt and I had to add a big chamfer to end of rod bolt. Nothing like having something to worry about for the dyno test. photo.jpg
  9. Bruce Kent

    Bruce Kent Well-Known Member

    I had a chance to dyno my engine yesterday. Needless to say I was pleased. My plan had been to use as many of the existing parts from an iron engine that last ran in Oliver's GSX a few years back which developed a cracked cylinder. It produced 880 hp on Q16. It was a 542 ci, the bore was 4.380, stroke was 4.5", compression was 14.5, with solid roller, B1 intake, stepped headers, 1250 QFX carb and dry sump. The new build required new pistons to acheive proper compression (CP), new cam of Scott Brown's design, pushrods (Manton), head gaskets (cometic), rings (total seal) and wet sump oil pan (SRE). I wanted good horspower but simple engine. No wet sump, no oringed block, stock oil pump, etc. The head gaskets came without lower row of holes, apparently a T/A only option and they were out of the .027" thickness I needed but the assembly went ahead anyway. You know about the rods and cam issues and thanks to Bobb Makely, Scott Brown and Dave Mongeon for proping me up and telling me it would be o.k. It was.
    The results are attached. Q16 was the fuel. View attachment 237972
  10. pmuller9

    pmuller9 Well-Known Member


    That is absolutely outstanding!!
    If you don't mind my asking, What did the intake and exhaust ports flow?

  11. Dave Mongeon

    Dave Mongeon Well-Known Member

    Nice work, Gotta like those numbers!
    I noticed the oil psi, very un-Buick and worth a few hp .
  12. td99

    td99 Well-Known Member

    very nice
  13. Jim Weise

    Jim Weise EFI/DIS 482

    Awesome numbers Bruce.. Having used that Dart mopar intake before, I figured it would need that type of rpm range, where it's making power, to shine. We saw very little difference vs the SP-2 on an 825 HP combo. Only the sheetmetal tunnel ram was considerably better, on that more conventional 6300 rpm engine.

    You must have a whole lot of camshaft in that one, considerably more than the 270@.050 that we had in our 555 here. It would be fun to build one like that, much more on the ragged edge.. my customer specified requirements were 2 seasons and 400+ passes between freshens, along with e-85 for fuel, so the wild compression ratios required for the bigger rollers were out the window.

    All the numbers look great, but you might want to give back a little vacuum for some oil pressure. We have had no problems at all with durability at 80psi at 6500 rpm, but I don't think I could have slept at night if I sent him out of here and told him to rev it to 7200 with 60 psi. Priority oiling or not..

    I never run more than 8-10 psi of vacuum with the pump, my testing has shown that any more than that has minimal affect on power output, but serious negative affect on oil pressure.

    Speaking of that, did you build a windage tray for yours? got any pics? I did not and I wish I would have. With only a 4.365 Stroke, we did have some windage issues on the dyno, that seem to be not as big an issue in the car.. I would imagine that with your longer stroke, the problem would be more severe.

    What jet size do you have in the restictors.. I am interested, because the first motor I did we used TA's scavenger system on it, and I want to go back to a stock type pump, with internal wet sump pickup, for ease and packaging in the next motor (a supercharged, SFI 555 pegged in the 1300-1500 HP range. I would be interested in your input, and understand if you want to keep it private.

    Anyway, great job, look forward to seeing it in the car and running.

  14. Bruce Kent

    Bruce Kent Well-Known Member

    377 peak on intake and 314 peak on exhaust.

    ---------- Post added at 03:25 PM ---------- Previous post was at 03:19 PM ----------

    We had some issues with oil pressure that day. First too little, then too much. I asked the operator what the big fords run with similar mains and the answer was 55-65 lbs. He showed me a dyno sheet from a nitrous Chevy making 1400 hp. 62 lbs.

    With that said i didn't feel real comfortable watching it dip into the forties then inch back up so i will do some more work on that. Yes, very un-Buick. Pulling to 7200 was tough for me to watch even though with all the good parts 7500-7800 should have been fine. I did the Scott Brown a dis-service by not pulling to 7500 to see how the power dropped off. Call me Mr. chicken.

    ---------- Post added at 03:34 PM ---------- Previous post was at 03:25 PM ----------

    The intake and stepped headers certainly push everything up. Every time we have put an engine in the Apollo from a GS the stall in the converter drops 500 rpms. Only difference is the headers.

    Thanks for the feedback on crankcase vacuum. I will adjust for that.

    Steve Reynolds built a work of art oil pan with all his tricks inside. Really nice piece. If i were to change something next time it would be to fabricate a internal pick-up and eliminate the external line. This would tidy things up even more.

    I kind of followed your lead on the restrictors and used a #65 holley jet, the smallest i had. After talking to Mike at TA I should have opened up or added more drain back holes in the valley. This is all new territory for this Buick guy
  15. Jim Weise

    Jim Weise EFI/DIS 482

    Hey Bruce,

    Steve has a built in windage tray in the pan?.. man I must have missed the boat on that when he built mine.

    And I have a set of 25 jets from a Holley 2 barrel in the restrictors.. I started with 70's, and that was way too much. The restriction here is critical, as it will flood the top end if you have too big a jets in it. On the one we did here, the band of the lifter sat in the lifter oil galley when on the base circle, and it will just pump oil into the valley.. The restrictors eliminated this as being an issue.

    I drilled no extra holes in the valley, as I recall. I would have to go look at one of them out in the shop to see, and compare it to the pics on the board here, but I don't recall doing it. I do recall the flood of oil in the valley when I spun the pump with 70 jets in the restrictors.

    We certainly did not run the pan dry.. in fact, removing 1 qt of oil, increased HP by about 10 or so, and the oil pressure, due to the windage issue.

    I beleive that with the smaller jet in the restrictors, and a slight adjustment of vacuum pump, and you will be just fine. But it is good to hear that the BBF does live at 55 psi.

    What main clearance did you run?.. Use the Fed-Mogul Ford Race mains?

    I can related on the too much/ too little oil pressure deal..

    When we started that one up, it damn near pegged the 200 psi oil pressure gauge.. Ron clicked it off when went past 160.. After bit of head scratching, I came to the conclusion that with the room temprature 20-50, and my -6 bypass line, we could just not by-pass enough oil. Of course, I had Steve build in a nice Steph's oil pre-heater in the pan, and I had used it when I was doing my oil feed/flow tests while building it, but we were all so excited to get it running, that nobody bothered to plug it in.

    WE made it thru till we got some heat in the oil, but that was not a happy time. Lesson learned.. bigger bypass on the next one I used that setup on. I did have the long gear HV version of that TA Scavenger kit. Scotty had me scared that it would not make oil pressure, with his stories of Alum BBC motors that were lucky to make 40psi.

    I will be interested to see if I can package a 3/4 internal pickup, in conjunction with a HV stock type oil pump.. and make the pressures we need. I should, techincally we should have less volume requirments with this motor, depending on how much those mains really "grow" when they heat up.

    Nice to work on a big HP motor without all the bandaids.. isn't it?.. Speaking of that, I have a iron block out in the shop that needs to be filled, and is calling my name..

  16. Steve Reynolds

    Steve Reynolds SRE Inc

    Jim here are a few pics. Anything is possible for the right amount of green. :TU:


    Attached Files:

  17. GS Kubisch

    GS Kubisch THE "CUT-UP" BUICK

    Gorgeous pan Steve.Excellent work!
  18. Steve Reynolds

    Steve Reynolds SRE Inc

    Thanks Gary!!

  19. staged2ny

    staged2ny Silver Level contributor

  20. Jim Weise

    Jim Weise EFI/DIS 482

    Ain't that the truth... very nice Steve


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