Intake valve closing is (255/2 + 106) - 180 = 53.5 degrees ABDC The cam is installed with the intake lobe center at 106 degree ATDC Add 1/2 the intake duration 255/2 or 127.5 to give you the intake valve closing ATDC. Subtract 180 to give you the intake valve closing ABDC. Paul
Believe it or not, that had crossed my mind, based on what I see with the narrower advertised and wider @.50 I can see where it's trying to open it faster than the other cam. These are the 'fast ramp' cam profiles i take it. Well nevermind then, TA RV-12 it is. lol They're just trying to make maximum power I guess, but never at the cost of stability! Thanks Paul. Those numbers always that amount? Give me a formula, like (xxx/2 + xxx) - xxx I.E. I know where the 255 comes from, but why cut it in half then add 106 (where's 106 come from) and then subtracting 180 is the degrees for BDC i presume. Ok cutting it in half gives the top of the lobe, but I'm not sure where the 106 comes from. 360-255=105 so that's not it. ACH SO. Danke schn! Macht sinne jetzt! ---------- Post added at 08:30 PM ---------- Previous post was at 08:00 PM ---------- So having a SCR of 9.5 would put the DCR at 8.2, which would be pushing it for 93 octane? This would be at sea level; at 500 ft. it becomes 8.1, and presumably lose .1 for every 500 ft. above sea level. so at 1500-2000 ft. above sea level, 93 octane should be fine (with 9.5:1 SCR with this combo), though once past a certain point, I know they don't sell 93, but go down to 91, like in Denver, CO. where it's 5,280 ft. How would one go about figuring the spark knock danger zone @ DCR vs quench, or are the dynamics of that too fluctuant to give any forumla? Maybe just go by tried and true experience and rule of thumb sort of thing, eh?
When you get the cam there will be a card with it that will give you the timing specs. The TA RV-12 cam for a 350 has the intake and exhuast lobe centers 110 degrees apart from each other on the cam or 220 crankshaft degrees apart. The card will tell you to set the intake lobe center at 106 degrees ATDC which will put the exhaust lobe center at 114 degrees BTDC. This is a 4 degree advanced postion from straight up where the intake lobe center would have been 110 degrees ATDC with respect to the crankshaft. So if the intake lobe center is at 106 then half the lobe width @.050" from there gives you the point ATDC. I think you answered your own question. Always design for worst case scenario. Also you are correct about high altitude locations adjusting their octane level down. It would be nice if they also adjusted the price down. The 8:1 DCR has come from a lot of Buick members tried and true results. Aluminum heads can push this figure higher. There are many other factors like engine running temp, ambient air temp, timing, chamber design as in turbulance or swirl, that will determine detonation resistance. You assemble your engine with the best plan you can put together, then after it is running you get to adjust your timing and A/F ratios for the best results with the octane you want to run. Then post your results for everyone else. Paul
Interestingly enough, the engine this cam is actually advertised for is the 455, and here's the specs based on that engine: [TABLE] <TBODY>[TR="bgcolor: #b0c4de"] [TD="align: right"]Number of Cylinders : [/TD] [TD]<INPUT value=8 size=5 name=cyl> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Bore in Inches : [/TD] [TD]<INPUT value=4.3125 name=bore> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Stroke in Inches : [/TD] [TD]<INPUT value=3.9 name=stroke> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Rod Length in Inches : [/TD] [TD]<INPUT value=6.608 name=rod> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Static Compression Ratio : [/TD] [TD]<INPUT value=9.5 name=cr>1) [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Inlet Valve Closes ABDC : [/TD] [TD]<INPUT value=55.5 name=abdc> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Boost Pressure in PSI : [/TD] [TD]<INPUT value=0 size=10 name=boost> [/TD] [/TR] [TR="bgcolor: #b0c4de"] [TD="align: right"]Target Altitude : [/TD] [TD]<INPUT value=0 size=10 name=alt> (Feet) [/TD] [/TR] </TBODY>[/TABLE] (255/2 + 108) - 180 = 55.5 With results of: Static compression ratio of 9.5:1. Effective stroke is 3.25 inches. Your dynamic compression ratio is 8.08:1 . Your dynamic cranking pressure is 161.04 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.08 :1. V/P (Volume to Pressure Index) is 183 Advertised compression recommendation 8:1 to 9.5:1, so this makes sense. Max static compression with 455 would be 9.5:1 if 8.1:1 dynamic is borderline, so that would make the 350's borderline SCR 9.3 Man I'm havin fun with that calculator! ;p
Don't forget on the link I posted there are other cam calculators as well Camshaft Calculator Camshaft Intake Open/Close Calculator Overlap Calculator LSA and Overlap Calculator These really take the math out of everything:Smarty: I could play with numbers all day, it is a lot of fun. That is how I got the numbers I posted in my build thread. All you need to know is lift, duration, LSA and IC and you can play with all sorts of stuff.
Yeah I plan on checking those out too. I'm just beginning to have fun with it. If I play with it too long I might go blind! :Brow: @Paul: I hear ya loud and clear bro. I've always liked to err on the conservative side too. Nice to know where the (theoretical) limitations are so you can then back it down a bit to be safe! So the 8:1 rule of thumb is for sea level? Set it up for 8:1 at sea level so you can be safe further up in altitude? Sounds logical to me. So instead of shooting for 9:1, I shoot for 9.3:1 which puts me at 8.03 DCR @ sea level with this combo. So zero the block and .020 off the heads with a .040 gasket will give around 9.25:1 SCR, plus with the deck zero'ed and heads shaved, the quench factor would be up there to help with detonation anyway. 9.25:1 SCR comes to 7.99:1 DCR @ sea level with this combo. Sounds solid.
You are having way too much fun! In the online catalog you will see an * next to some of the Lobe Center specs. That means the cams ground for a 350 will be on a 110 degree lobe center. It looks like you figured that out already. The cams shown in the catalog are just a sampling of the cams available and were chosen as "off the shelf" TA will grind you a number of other combinations using the cam lobes from the Master Lobe Catalog. You can also vary the lobe center as long as the cam blank has the material to cover the grind. If you really want a short duration cam with high lift for killer torque and a wide power band, a Roller RV cam would be the ticket. Paul ---------- Post added at 09:52 PM ---------- Previous post was at 08:09 PM ---------- Gary If the crank turns freely on an engine it does not mean the main line is ok. We try to hold the bearing clearances within 2 tenths (.0002") of a chosen clearance spec, let's say it's around .0025" clearance in your case. With worn bearings the main line can be out .001" or more and the crank will still turn just fine. When you go to assemble the engine with new bearings and a crank that has been turned to get proper bearing clearance, guess what? Very few times does a new cam and stock timing gear set just bolt together with the right cam timing. A lot of people just install the cam and never check to see what the cam timing is. You can find a few posts on this forum where the stock or even a 3 keyway gear set wouldn't work to get the timing in. You will find even more where the engine is pinging or not running right and when we ask where they set their cam the answer is "I just put it in and didn't check it" Paul
You're right of course. Ok, now that we're into that can 'o worms, what about the fuel pump clearance on the timing chain now? Elongate the holes? Anything I'd have to do on the wear pad actuator? And how does the align bore affect the piston and rod distance in the cylinder bore? Doesn't the oversized bearings re-center the crank? What causes the main line to go out of line? Torquing it over and over, temp fluctuations, and time? How far out of timing could the cam and stock timing gear/chain be? I guess I'm not too saavy on the machining part of building engines. Not a professional engine builder here, but I have built them. If they looked good and the crank turned, just rebearing and Bolt them back down. It's been a while though, and maybe I just got lucky. From what I'm gathering, the block somehow gets out of alignment, or at least the main line does somehow, and that properly turned cranks and oversized bearings will make this painfully obvious when installed, but weren't obvious before due to crank and bearing wear, and replacing stock sized bearings on an unturned crank will still provide clearance. Well shuck mah drawers an whoop mah ayass. Makes sense! How about the crank? Do those get warped over time? I imagine rods and cast pistons that are 35+ years old could have some wear and tear on them, perhaps imperfections in the castings that never made themselves known in stock form, but once power is boosted on an engine, could show up later on. Best way is to just replace everyfrickinthing, even if you're going stock, but that would be kinda expensive! Was rather hoping to get away as cheap as I could, because you start upgrading this, you need to match it with that, and next thing you know, you got 5g sunk into it.
Yes, elongate the holes and move the pump forward just enough to clear the timing chain. The crank moves up just a few thousands and it is not a real concern since the cylinder bores are unlikely to be perfectly in line with the crank center. When the cylinders are bored for the new pistons the cylinder can be repositioned for perfect alignment if that is a priority. Most of the time a cylinder is repositioned during the boring process to correct core shift so the cylinder wall thickness favors the major thrust side of the cylinder. Piston and rod combination is chosen so there is some clearance between the top of the piston and the block deck. Around .020" is a good. Then the block is decked to get the final clearance needed. Decking is one of the last block machining steps. So no problems with the crank position here either. Initially the crank line move as the block goes through the many heat cycles over time. The block becomes "seasoned" and is unlikely to move around afterward. New stresses will cause new movement. Things like main studs with higher clamping forces. If you don't need them for your application don't use studs. A new set of bolts will work fine. As far as cam timing, I have had a case where I had to jump a tooth with the chain on the timing gear so I could get the timing in. (Different than the link below) Most of the time the error is within 8 degrees. Here is a classic example: http://www.v8buick.com/showthread.php?261932-Cam-degree-issue-losing-my-mind!!!!!!!!!!!! Paul
Hmm. Sehr interessant. So the alignment on line boring isn't so much in the main caps as it is in the block itself, which moves the crank up. Everything you said makes sense, and some of it I've read about. I figured it was probably a 'curing' process the block went through, like a house settling over time or whatever. New stresses introduce new movements. So with a basically stock rotating assembly and new bolts on mains and rods, align boring really won't be necessary, will it? I knew about the stud thing, failed to mention it in my last post. Using the same crank, rods and cast pistons shouldn't introduce new stresses. Rotating assembly retains original weight, unless those ARP rod bolts are heavier, or if it gets overbored and the greater piston mass is an issue, or perhaps even increased compression, since the dish is smaller and there's more material in the piston. But if I use the same stuff, shouldn't need anything other than bearings and bolts. 8* off??! Thats nuts! So like what's the point of a stock gear being 4* advance preset if it could be off 8* in either direction? lol Why? Are the aftermarket cams that different than the OEM cams? Let me guess...Variables in the building process when many things are done to the engine cause the standard locations of parts to shift slightly, and when enough of them are off, could result in a dramatic shift in timing? Seriously, that was a guess. It would make sense though...so again, if everything is mostly stock (if that guess was close), then the odds of that happening are much less, and if it IS off, it wouldn't be by much. Which would make sense for standard rebuilders who use 100% stock stuff and don't have the time or tools to check every little thing when there's an assembly line of engines behind him to get built. I know much power can be gained by simply truing everything up, in effect, 'blueprinting' the engine. Making sure all the bearing clearances are exactly the same, and 'loosened' up with more oiling to compensate, etc. Lots of small things add up to big power, as opposed to an engine just being tossed together in someone's backyard. After thinking about it for a minute, I realized that zero decking the block would be enough to throw the timing off by using a standard gear, right? Then different length pushrods get thrown into the mix. Then .020 off the heads. That would be about it I think. The pushrods would be at a slightly different angle on the rockers, right? Or maybe I'm just plain wrong and it's a cam grinding issue. lol Bottom line is get a 9 keyway and be done with it (AFTER align hone/check is performed to make sure it's true) _____________________________________________________________________________________________ While all this is fascinating, this is like off the deep end for your average engine builder. I was just hoping to put some parts together and have me a nice running engine! lol If I were to build engines professionally, I would certainly look into buying all the tools required for the more advanced stuff. You must build them in your sleep, eh? ____________________________________________ Since my engine will be basically stock, what are the odds of me getting away with just using a stock timing gear and chain?
Let me see if I can clear this up. Main Line Boring: Material is machined off the bottom of the main caps. Then the caps are torqued in place. A good machinist takes only what is needed from the block side of the bore to make it straight. Most of the material is bored off the caps. That's why align boring is preferred over honing. Honing doesn't allow control over bore location. Most of the time the main line needs to be corrected. Remember that these block are a thin wall design and don't have the stability of the heavier type blocks. The stress I was referring to is from the extra clamping force of using main studs on a thin wall block design. The extra force distorts the main caps which in turn causes block distortion. Any changes in the rotating assembly mass is taken care of when the piston, rods and crank are balanced. No problem there. Going to a lighter rod and piston combination does help reduce forces on the block. To do a complete rebuild correctly you need a good machinist that can do a complete inspection of the block and crank and tell you what operations and parts are needed. "Truing everything up" has more to do with engine life than making power. If all these checks we have been discussing and more are not performed, then it is a craps shoot on whether the engine will last past 5 minutes or 200K miles. Cam timing: When the cam and gear set is made in the same house there is control such as OEM. Aftermarket is at a disadvantage. A cam manufacturer may choose to grind the cam with the advance built in and some may not because the engine builder may want to deviate from the recommended cam timing. Then what if the gear set is designed with the advance built in and some not? Then there is the mixing of tolerances between parts being made at different locations like Asia. Cam timing is strictly a relationship between cam and crank and has nothing to do with deck height or anything else. Paul
Ok Paul, thanks. Sorry to be such a little kid with 101 questions. You pretty much summed it up for me, any confusion is now clarified. Thanks for all your time and effort! It's not going to be wasted, I can assure you of that. I'm soaking this stuff up like a dry sponge. :TU: :beers2:
Quality machine work is the foundation for a solid reliable engine that will perform. Don't cut corners here! Paul is nailing it on the head! This is the area were most people fail when building an engine!
I do not doubt. Simple re-ring builds have been done incorrectly by so many people for all these years. We need to support our local (and not so local) machine chop--I mean, shops! If the engine was running fine when torn down, and all one want's to do is upgrade the cam and do some port work, well, he'll just have to re-machine everything if he wants it to live longer than 5 mins! Putting a fresh set of bearings and rings, re-honing and new bolts is just asking for disaster. I have been schooled. There was certainly some confusion going on here, but I think it's been cleared up now I hope. Paul is loaded with information, and I was hoping to pick his brain for a few items, even if it was ring around the rosey for a while. Thanks all.
Everyone on this forum is loaded with information. The combined successes and problems here makes an incredible amount of information available. I had my fair share of screw-ups in 2012. Also We have never seen so many parts from top name brand suppliers be so far off or just plain wrong as we did last year. If you don't double check everything and assume the part is alright to use right out of the box you can be in trouble. Yes you are right. One choice is to find a good running engine. If it shows good oil pressure and a leak down test shows very little leakage past the rings, then you can change the cam and timing gear, do head work and run it. Once you pull a piston then the rod bolts need to be replaced. When a rod bolt is replace then the rod needs to be resized. That leads to new bearings so the crank needs to be polish or turned. Once the crank is pulled the main line needs to be checked and so on. You got the picture. Don't hesitate to ask questions. We rely on Sean to answer the difficult SBB questions. Paul
Well I tore down a '70 455, put fresh bearings in, did a hone and re-ring, used the same bolts on everything, put in a mild torque cam, put it all together, broke it in and ran it like a wildman and never had any issues. The engine revved to the point of floating the valves on a daily basis, and stripped out a TH400 with some frequent neutral drops in a '69 Electra. I pulled the engine out of a '70 Electra to put in my '68 LeSabre, and when I totalled it, I bought a '69 Electra. I blew up the 430 in it, so decided I'd freshen up that old '70 455 and stuff it in there. Worked great. The engine had 153,000 miles on it when I tore it down, and everything looked so good I didn't bother with any machine work. Once rebuilt, I got into some trouble with the Georgia Stage Patrol and had to keep it parked for a while. Though they complimented me on my driving skills, it didn't stop them from continuing their escort of me down to the patrol station where they commenced to write up 7 tickets... I then sold it to a young fella who put it into his '78 Trans Am. He took it to the drag track and ran 13.4's with it, running through the traps at 5600 rpm on factory stock springs. I guess I got lucky on that one.
This is eactly why I still have a 455 sitting in my garage torn down and its why I'm not rebuilding the 350 just yet. If I am going to spend $1000 in parts to rebuild an engine I want to make sure every single thing is right, and that means that you gotta check and double check everything and almost every time it means you will need machine work done. Sometimes you get lucky, others not so much.
Ich verstehe ganz gut. Ja wohl. Seriously, I do. I rolled those craps dice and won the jackpot apparently on that engine! Thanks to all for their valuable input. ---------- Post added at 04:46 PM ---------- Previous post was at 04:26 PM ---------- Putting everything on the table and seeing what you can and cannot get away with, what the limitations are for everything, then back off to a safety zone. Absolutely nothing is ever guaranteed, we're all just rolling the dice. Even with new parts. Anything we can do to increase our odds of winning though is what this is all about! I've learned a lot by talking with all you guru's and I feel like we've become friends. :bglasses:
Rebuilding and refreshing an engine are two different things,and both have there place. Refreshing an engine is to prolong an engines' life by cleaning, re-ringing,new bearings,new gaskets,new timing chain and gears,re-use or re-place cam and lifters,and as little machining as possible,which would include just ball honeing the bores,crank polishing,or grinding and possibly a valve job. NOTHING is wrong with doing an engine this way if the engine's intention is to be close to a stock configuration creation. Of coarse this should only be done if the engine is in good running condition(but possibly tired,as in high mileage, low cranking pressures,oil burning....and so on) when it was taken apart,and the bores aren't to far out of spec. Saying that every engine that is taken apart absolutely has to be machined is just insane. Drag race engines have this done to them after so many passes,which puts much more stress on an engine than regular street driving. The load that has to be put on an engine to make it need line boring is a lot greater than the light duty most engines do in a street car,if the mains are out enough to need line boring,then that engine was either heavily abused,or it was not properly seasoned before it was machined at the factory. And when assembling an engine this way,if everything is CLEAN and checked when it is put together it should be good to go. Typically a refresh like this is only good for around 50,000 miles before it will start wearing out again.(but it could last a lot longer?) New rod bolts are only needed if the power level is going to be cranked up,and rod reconditioning is only needed if the rods are out of round,or bolts are replaced. In other words,if its not a performance build,factory rod bolts can be re-used. And of coarse when the engine is taken down this far,any oiling upgrades that can be made,this would be a good time to do them,like changing,or rebuilding the oilpump.This kind of build is NOT recommended for high HP,or high RPM applications,although the factory balance should stay very close when doing a build this way,a factory balance isn't typically good enough to exceed the intended RPM or power range the factory built it for. Rebuilding an engine is when the bores are to far out of spec that the block needs to be bored,and new pistons are needed. Or when more HP,and RPM is wanted out of that engine,and high performance parts are wanted to be used,this is when machining becomes a critical operation for an engine to be reliable for many miles. Theres nothing wrong with either method,but if its going to be taken apart that far,I would rather spend the extra $$$ and make it better than factory,on an older engine those production machining standards were sub-par,to say it mildly.Plus,when I do an engine for myself,its has to have more power than the factory gave it,or it isn't really worth doing it,when a good running used engine can usually bought a whole lot cheaper than building one from the block up. It all boils down to dealer choice. Derek
Exactly how I feel,there is nothing wrong with refreshing an engine. One should just make sure that when you take an engine apart everything needs to be inspected to be within tolerance. If its not in tolerance, dont expect it to last. If I tear down an engine I do so anticipating machine work and replacing any wear items, but if they check out and everything is within spec, there is certainly nothing wrong with reusing it.
