Marty, you are correct! I was thinking .586 is a lot! .568 sounds more like what I remember talking about, I'm going to double check EVERYTHING!
Mark, what is the rest of your setup consist of? If your running the SP3 intake, isn't the rpm range about 3500-6500+ Are you running 1.6, or 1.65 rockers? Roller rockers? What are the spring pressures open/closed? More info please.:grin:
I'll start from the bottom. Crank is crossdrilled Rods are capscrew Pistons are H522NP (IIRC) Pistons sit .005 "in the hole" Block is a '78 350 block, its a bit different structurally as there are a few more reinforcement ribs in the casting VS my original '71 block, tho they don't appear to contribute to a stronger blocko No: BUT there is no provision for the factory windage tray as the '71 had:af: Block is bored .030, line bored also. Decked .050 TA grooved cam bearings TA timing cover with booster plate and stock pump gears The past two cams I've had (TA 310, TA 413) have had and the roller going in, the oil transfer groove in the #1 journal spray welded closed as its not needed with the TA grooved cam bearings. I started doing this years ago with my GN cams, Michael at Michaels racing Engines in Macedonia does this to all his Buick builds since I had him do this for me back in 2000 My reasoning doing this is theres more journal surface to ride on the bearing, instead of two skinny journals digging into the bearing, plus without oil in that groove, theres less oil hemorrhaging from the bearing, it usually picks up a couple pounds oil pressure. Heads are iron '69 castings, milled .030 TA bigger stainless valves (1.92-1.55) Mild bowl work, port matched Have no idea what they flow Heads were cut on intake side so intake lines up, so I can switch intakes, even tho the heads sit .080 lower I cant use the rubber end seals, I use RTV as the gap is only about 1/8 inch now:grin: I had the TA Stage 1 intake w/my original Q-Jet rebuilt/calibrated by Everyday Performance (WAY better performance than the 750 vac. sec. Holley) Currently have the SP3 with an AED 850 DP, The SP3 with a DP carb is the way to go with the single plane design, INSTANT throttle response and no bog when slamming to WOT The 850 carb is VERY responsive and linear, there is absolutely nothing bad I can say about the SP3 and a DP carb as far as drivability and performance when compared to the Stage 1 intake. TA 1.6 roller rockers TA 1130 dual springs 110 lbs @ 1.72 320 lbs @ 1.205 IIRC TA headers (1-5/8) RobbMc 550 fuel pump, 1/2" fuel line from tank. RobbMc 1/2" in-tank pick-up I'm sure I forgot something LOL-
Wow, that's a lot of info Mark. Thank you for sharing it. I wonder if you can order the roller cams without the front oil transfer journal cut into them? (They should make it an option)
Mark. Not sure about your specs but I'm getting clear over 11 to 1 compression for you. .030 off head not including big valves can be about 50 cc . hyperutectic pistons are about 11 cc . and are .020 taller compression height then stock 68-74 pistons add .050 ? Off deck? That's .015 popup over deck . 11.9 compression. I'm sure I'm off but I'm thinking at least 10.9. Unless you polished a lot of chamber away?
I never checked the actual comp. ratio when I assembled it. I measured those pistons at .055 in the hole, I was told to leave room for "piston rock" at TDC (transition from TDC to going down) so I figured .005 was good. If it is indeed over 10.5 that explains the pretty smooth idle with the 413 cam, same as the 310 cam also. I could idle down in neutral to 500 rpm. I wanted something over the stock 8.5 comp ratiop I never had an issue with detonation, but I believe the cam had a lot (everything) to do with that, as far as bleeding off compression, I'm hoping this new roller with about 7 deg. less overlap doesn't create an issue, if it does, well I'll deal with that. Starting/cranking was never an issue either as IIRC, my starter is a high torque 455 starter. Correct me if I'm wrong, but YEARS ago I read/was told, that, on the starter, if your starter has the long copper sleeve from the solenoid to the metal tab rising from the starter body, it was a high torque unito No: It cranks fast, hot or cold, Plus the factory starters are beasts, yeah they're big/heavy but I broke the nose off a mini starter I had on there the day we were leaving for the GS Nats, Back on went old heavy reliable!!!!!!!!!!!!
Thanks Bill, I was tired when I wrote that and forgot about my AWESOME JW 9.5" convertor, I cant say enough about that convertor:TU:
All else equal, less overlap creates less cylinder pressure and a slightly lowered tq curve. Idle is somewhat smoother, peaks are spread a bit. This potentially helps against det. in the midrange. Temps in the chambers and incandescence have as much or more to do with det. than simply the cam and DCR.
Straight pattern cams are very versatile on where you can put them, and with an intake to exhaust ratio of around 70-75%, work perfectly fine (and can in many cases make more power than split pattern). I've been spending an unhealthy amount of time in my dyno simulator over the past month or two, and have come across some interesting discoveries using many, many different combinations (too many to list). Seems the 'old' way was always to install cams at a default 4* advance, but according to the math, the engine prefers the majority of all cams I've 'tested' to want to hover around the straight up position--some a degree or two advanced, some a degree or two retard--depending on the durations and separation angle. I pay more attention to the valve timing events than the durations or lobe separation, which to me are incidental as to where your valve timing events should end up, depending on what's going on with the rest of the engine. I've been seeing some distinct patterns on how the timing events influence the air flow, and have noticed that the cam indeed needs to match the engine (nothing new here, just clarification). However, there is still some leeway on where a cam can be installed, and there is no 'correct' position that could be put on a card to say this is where you must put the cam in order for it to function correctly--it depends on the rest of the engine. There's a LOT of dynamics going on inside an engine, a lot more than what you could see 'on paper', and have to pull out some Einstein visionary skills to 'see' it in your mind, then find the math formula so you can show it to others and make sense of it all. (if that makes any sense lol) Anyway, that's my 2c on all this so far...
.355 x 1.6 is indeed .568 valve lift. It's probably a typo, since the numbers are inverted (68/86). In order to have .586 valve lift with 1.6 rocker ratio, the lobe lift needs to be .366. The '66' is a double number same as '55' and could also be a typo when using a calculator after typing the '6' on '1.6' for rocker ratio. It's pretty abstract, but things start to blend together when you're tired and have crunched numbers for hours on end, muscle memory can take over despite what you're thinking. We're all human.
Another abstract example of timing events is Steve Caruso, who uses the Crower level 3 cam installed 2* retard (from the true straight up position, not taking into consideration the 4* advance 'built in' to the cam from Crower), who says his car runs best with it in this position. His combination is one of many I've been fiddling with in the dyno simulator, and it does indeed show this to be the best position for it, and aligns pretty accurate with his real-world dyno findings. What makes a split pattern cam perform better than a straight pattern cam is exhaust restrictions, since the added exhaust emphasis is needed to overcome restrictions. All one needs for an example of this is to take a look at the Buick Big Block's OEM and stock Stage 1 cams to see the ridiculous amount of emphasis needed on the exhaust lobes in order to overcome the highly restrictive factory manifolds and exhaust used with them. One could encounter a pretty wide powerband with a split pattern design also, since when the exhaust is freed up--coupled with high exhaust emphasis on the lobes--it tends to have a stronger draw on the intake side, which is then the restriction--but works well at lower RPMs and can overcome this lower RPM restriction on the intake side through the scavenging effect of the larger exhaust side (but only up to a point, then becomes progressively inefficient). This would make the cam behave smaller at lower RPMs and larger at higher RPMs, giving it a wider powerband (or tends to, depending on a myriad of other factors that exist inside the engine as a whole). Things change a bit when you increase durations and lifts to match, along with the heads to accommodate this, particularly when the intake to exhaust ratio is around 75%. Exhaust emphasis is ultimately a 'band-aid' to fix the restrictions found on stock or near stock combinations. Getting back to Steve's combo, the valve timing events with the Crower level 3 installed at 2* retard show opening and closing events to be happening close to the same time on either side of bottom dead center (close to even *'s on either side--which is exactly what a straight pattern cam installed straight up would have), but what makes this split pattern cam shine on an iron manifold engine is where the timing events are occuring before and after top dead center. They occur closer to, and after, top dead center, which helps the exhaust draw harder on the intake (with less intake reversion), further enhancing the cam's ability to evacuate the exhaust using iron manifolds, as well as draw harder on the intake side. A straight pattern cam installed straight up will have even timing events on either side of top/bottom dead center, and with an optimally flowing engine, is a good starting place (if not the best place) for the cam's timing events, since the engine is most efficient this way. Adjust timing events on either side of top or bottom dead to accommodate the rest of the engine's behavioral patterns to overcome any downsides and emphasize its strengths. Again, my 2c so far on all this...
Hopefully the cam will clear the crank and you will not have to grind away material.... I know that scares a lot of people away from going to a roller.
I had asked Tim this very thing, he said he hasn't heard of any issueso No: Just for kicks, yesterday afternoon, I checked the cam tunnel with my bore scope to see if I was clear to slide the cam in, all was good, slid it in, it spun real nice. I'm sure that itself means nothing, as nothing is moving (crank, rods) What exactly is it that likes to hit the cam? Rods, crank counter weights?
That's what I was thinking Gary, Tim had called late Monday and said "your cam is back, I'm filling out the cam card, then box it up and ship it out to yah" From talking to him, I feel he's a VERY busy guy, and he does his best:bglasses: He probably just got the numbers transposed.
The TA 310 cam I ran for years was a straight pattern cam, it ran strong, it would smoke the tires thru all three gears, BUT, never had that cam to the track, so it was just a butt dyno experience :laugh: Makes me wonder tho how the 310 would have run at the track, oh wellp
