Time to draw the curtains back on my new motor...It's a 66 MT block out of a Wildcat with about 90 k on it (when the grand-daughter hit a deer in the mid 70's) I cant remember the guys name who I bought it from, but he put it up here on the board years ago with a ST400 for 300.00,and I hustled down there the next day. I wish I could remember his name. he lived in lower PA near Harrisburg and was into Wildcats.... I brought it down to Tommy a couple years ago and we planned out the build: a mostly stock motor with the bottom end strength to rev to 6k and take much more power down the road --1/2 fill with hardblock, off the shelf grind with similar characteristics to an 091, stock rods and lightly bullnosed crank with Tom's custom pistons at an .028 overbore (to use off the shelf .030 Pontiac 455 rings) , balanced with careful detail on oil control. The idea was we could run a number of combinations off the shortblock - we'd go deep on piston reliefs to accommodate mild or wild lift and duration, deck and CC to be able to change CR a full point with head gaskets, Stock or Bob's heads, hydraulics with 5/16" pushrods or solids with 3/8", stock or roller rockers and any form of NA induction that I've got - Stock, Doc'd or Edelbrocked square or spread bore manifolds with AFB's or big/small Q-Jets. And I still owe Doc some results with a beautiful 3bbl Holley he's lent me. The idea is that I could run the PSMCDR's one minute, and go for all out banzai runs up at LVD the next with just component changes. So in it's current form, we're going . 028 over (and I forget how far down the hole), heads CC's to factory spec to come up with 10.25(or close) with composite head gaskets , TA-25 110 LCA cam with .415/.433 lift at 218/228 installed straight up, hydraulics and stock rockers, balanced with SFI damper, blueprinted/safety wired oil pump. Bob/66GSConv "looked' at these heads, and we tried to keep them as stock as possible for port velocity (But you just cant leave those valve guides hanging down in there like that, can we?) and backcut 11/32nd Ferrea valves (for PSMCDR applications I'll CC the 65 heads that are on the car now) The idea is to bring this motor from stockish to wild over the next few years, and document the real world results on the track, while still being able to run in Stanton with the PMSCDR guys every fall. The engine is at Tom's machinist's now, shortblock is together and balanced (look at the counterweights! He had to drill to China!) as Tom and I work on the heads for oil control and mock up the valve train geometry and decide on valve springs and pushrod length. We're working to have this motor in and ready for opening day in April! Wish us luck! Attached are few pics taken over the last couple weeks (and one obligatory action shot) .
Looking good. Need a write up for the newsletter with your details. See you at tb ed slring meeting April 2nd
Good job Rhett! With all the weight that had to be removed from the crank for balancing, how close would it of been to neutral balance it? Them do look like some deep holes. :shock: Can't wait to hear about your journey! Thanks for sharing. Derek
Good catch Derek. I think the holes in the C-weight aren't quite in the right spot lined up with the dampner, but it's really tough to tell. It looks like it could easily be doable, however...his options for neutral flexplate/dampner might be limited. That would be considered a heretic practice on a run-hard, over 6500 v-8 normally, but this isn't one. I'm sure they've done a bunch like this with no ill results.
In actuality the intake lobe lifts mentioned of .294" are NOT what were measured. Intake was between .282"-.286" which = .451"-.457.6". In actuality with the stock rockers ends up being closer between .410"-.415" The exhaust lobe of .309"= .494.4" ended up closer to .299" ( I did not spend the amount of time to measure ALL the exhaust lobes as I did the intake) which = .478". With stock rockers in actuality will measures closer to .430". A standard bore 455 Pontiac is 4.151" + .060" = 4.211" which = .0235" overbore. This does NOT take into account the finished cylinder bore of 4.214"-.4.215" after the nec. clearance of .003"-.004" cylinder wall clearance. So now the actual overbore will be .0265"-.0275". If you look closely at the balancer you can see the machining that was required to bring it into balance. The rounded ends you see had quite a bit removed to bring it within specs. WAY TOO MUCH weight would have to be added to the bob weights of the crank for a NEUTRAL balance making it totally impractical for this use. Even the racing "Nails" aren't Neutral balanced. Tom T.
Good info on balancing. I take it that's a 455 dampner? What bob weight would you estimate would allow a neutral balance? Being that a BBC rod CAN be much lighter as well as the piston. Obviously a TON of unneeded work when the top end has trouble breathing to begin with, more for setting people at ease because it's not what people are used to seeing. Just by the pics, I'm a bit confused by what appears to be weight removal on the dampner (making the imbalance side heavier, sort of) coupled with more drilling on the crank. Was this crank, by chance, already drilled out a ton? I forget what needs to be done using an aftermarket dampner for 455 on a nail, but it seems counterproductive to do it that way.
Hey! Thanks for your interest, and forgive me for getting some of the technical details wrong. I will defer to Tommy on some things, as (for instance) what I know about balancing can fill a thimble. I love that this has spurred discussion, and we'll all be better off for it. But remember, this is the combo that we landed on, and you'll have detailed track numbers to back up whether it was right or could have been done better. And I invite anyone who has contrary ideas to put them to the test! Stick yours in a 3900 lb car and lets find a track halfway between us! More to come!
Sorry for the sidetrack on the balance question. Can't really tell how deep the holes are, was just agreeing with what you had said, didn't think you would of been attacked for that though! ou: I was just curious how close it would be to be internally balanced, not that you should of went that way(Tom answered my question). Was only trying to get some general discussion going, not so much specific with your build. I love what you're doing here Rhett, keep up the good work don't let the 'peanut' gallery get to you. :TU: Derek
Not an attack Derek, I welcome all thoughts, theories and questions. Just at some point someone has to put their nickel down and build it, right or wrong ( I say that like I'm doing the actual building!) We're all gonna see how this runs soon enough,....cause I'm gonna beat it like I caught it kissing my daughter!
You think that ST400 and a set of drag radials is in any of that future testing? :BrowNO trans debate intended, just curious about plans) Derek
Attack from the peanut gallery? lol. :laugh: No need to apologize for me, I'll ask it again. I was asking 'at what point could it be done internally' as in grams of bob weight, because it may help the forum or anyone else considering such objectives...even though 'race engine' Nails don't balance internally...I'm sure it's been done before. Is a 1600gm bob light enough? There is no negativity to anything about my post. I'm sure there are very good practical reasons for the way things are done, and this is a perfect place to offer up the tech. I bet the pics are a bit deceptive. There are quite a few cranks that just have the C weights in the wrong place to do it without distributing some Mallory around, negating it's practicality. That's and what needs to be done to use a 455 dampener on a Nail is what I'd expect as an answer.
8Ad - I'll take your interest at face value, and thanks for being a part of the discussion. I know its difficult to convey tone in print, and maybe I'm being overly protective of Tommy, cause I dont want him to endure a rash of sh1t because I took this engine build public. Not pointing fingers, but we've all seen other threads in other sections devolve into "my brain is bigger than yours" from guys who never seem to put up any timeslips. But like I said, I assume good intent here, and welcome anyone's opinion as long as we keep it civil. So all of you - keep it civil. That said, I'm not smart enough to be able to answer your question, so I'd have to defer to Tommy to either answer that or get the answer from the machinist. In the process, maybe I'll learn something about balancing and god forbid the conversation actually leads to the realization we could have actually made a mistake, we'd be able to catch and correct it before this thing sits between the frame rails. And Derek, down the road when I'm running something else with the stockers, nothing is out of the question. In fact, I just bought a terrific TH400 assembly manual: https://www.amazon.com/gp/product/B000HZTJ9G/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 My plan is to try to learn on a Riviera TH400 I have on my garage floor for my 71 GS, and if that works well, who knows? I love the ST300, but I'm not married to it! Thanks again to everyone who chimed in.
For example, some of the scat 9000 cranks or Eagle I've done were impractical to internal balance, due to the counterweights being kind of 'in the wrong place'. The aforementioned 'holes all the way to China' are not centered to the direction of the mass...the trailing edge of one C weight and the leading edge of the other. It happens when mass produced for the entry level market parts are loosely copying OEM designs that were made more for manufacturing conveniences for engines with a different purpose than what we do with them now. No negativity. Nobody needs to feel pressured, maybe I'll delete this. There are oddities about niche engines most don't have to deal with.
The sole issue with attempting an "internal" balance on an OEM Nailhead shaft is the fact that the c'weights are too "shallow", in other words they are too short as measured from the top of the main brg's radius to the top edge of the c'weight. You have about 1.750" at the closest point. There's just not enough room to drill the required 1.000" holes to get the "Mallory" installed safely. It would probably take about about 8 pieces of "Mallory", 1.000" diameter by 1.250" lengths to even come close to "internal". For all intents and purposes I would say it can't be done on these shafts. Tom's friend in Mass. was running a pump-gas "Nail" with a some 6.750" aluminum rods (628 grms on Mopar forgings), some Ross slugs (600 grms), SBC pins and rod brgs, we were only able to hit a 1950 bobweight. We did attempt at first to "internal" this build but passed on it! As it ended up we removed over 600 grms total from his shaft, still "externally" balanced. One important fact with respect to balancing ANY heavy-metal job, the closer you need to place the metal towards the main brgs (center of the shaft) the less effective it becomes with adding the needed amount! Another item to remember, you are removing 1.000" round x 1.250" deep of the original steel in the c'weight just to get the "Malory" in place. The "net" gain is a lot less due to the "missing" original steel. On a side note I would "aim" for about 235+ CFM intake and 150+ CFM exhaust flow numbers @ .600" lift on the heads! Stepping the guides down to .343" SBC stems goes without saying?? (Add) Hi Tom T., give me call when you get a minute! Hope all is really well? Thanks, Gary in N.Y. P.S. The picture below here may show it somewhat clearer, that shaft beside the Nailhead is 454" BBC, originally "external" that we did an "internal" on it using 8 pieces of 1.000" x 1.000" "Mallory", just about made the 2350 bobweight!
Gary - Thanks for chiming in, and I learn more abut engine balancing with every post. As it happens, due to Tom and Bob in St. Louis's " attention to detail in head selection", the flow numbers you mention are very very close.
Thanks for the descriptive balancing info! I wouldn't attempt to internally balance one at 1950 gms either. I was more or less curious HOW low the bob would need to be, not that it gets much lighter than an aluminum rod. Too bad these don't have center counterweights.
