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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi What rocker ratio goes where?Go | New | Find | Notify | Tools | Reply | |
| What rocker ratio goes where? | Login/Join |
DRR Sportsman |
So long story short, I purchased a "Divorce Deal" engine and parts. The engine is complete and all together except for intake and rockers. I don't have any paperwork on it or who the builder was but I do know its a 583 BBC. I have 1.7 and 1.75 rockers with it, so what ratio goes on the exhaust and/or which one on the intake? I have heard a back and forth with this and some have said since they are Jesel to make sure one side of the rocker stand has a washer under it (not sure why), but they do have washers in the bag. Also if you put the wrong rocker ratio in this case it wouldn't hurt anything motor wise because the ratio is so close but it would rob a good bit of power. Possibly .10 to .15. Anyone ever have any experience with this? This motor is a 583 with BB2Xtra heads. | ||
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DRR S/Pro |
If the exhaust is close to the piston it could. ____________________________ 2017 and 2018 Osage Casinos Tulsa Raceway Park No-Box Champion 2018 Div4 Goodguys Hammer award winner | |||
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| DRR Sportsman |
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| DRR Elite |
Being most run cams with not enough intake lift for best power/performance and the fact that the intake valve is chasing the piston, put the 1.75 ratio on the intake valves. | |||
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| DRR Sportsman |
That's somewhat what I was thinking but wasn't sure. Trying to figure out lash also. I don't wanna tear it all apart. | |||
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| DRR Elite |
.024 hot is safe | |||
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| DRR Sportsman |
.025 is what was on a paper with it but didnt specify intake or exhaust or both. | |||
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| DRR S/Pro |
99% the intake gets the larger rocker. As for lash, unless you have the cam card it's a guess but most typical bracket type solid roller cams at between .022 to .028 hot. No idea what the washer deal means, gonna guess it's a rocker geometry thing. Long shot, maybe the bolts are just a tad too long also. Rocker geometry is easy to check, same for the bolt length... | |||
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| DRR Sportsman |
I agree but no way I would run it without checking valvetrain geometry and piston to valve clearance. Cheap insurance for a few hours of work.  | |||
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| DRR Top Comp |
The ratio is to determine the action of the valve dependent of the lobe design, it's critical you get it right. You need a stand height checker from jesel to get the geometry perfect. It's simple to do, 600 to 800 lift you want the valve stem flush with the top of the tool. Each stand set up individually, determining the shims to be used. You must've got this dirt cheap to roll it without looking! I'd have it torn down and I'd re-assemble it to my standards, no matter how cheap!! Now that's carazy!! | |||
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| DRR Trophy |
There is a tool for setting the stand height. This is why they give you different thickness washers. There is a way to guess the valve lash if you have a dial indicator and degree wheel. A solid cam lobe will gradually take up the lash before aggressively opening up the valve. You can watch the dial/ degree of rotation and see what lift you are at before the dial changes its rate of gain. My guess would be about .015" of take up ramp. 1.70 rocker * .015= .0255 (call it .026) Likely a safe bet. I do some small block dirt track engines that have tight lash settings like .014 hot. If you lash one of those .026 you are asking for trouble. Lash does matter. | |||
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| DRR Sportsman |
The higher ratio rocker arms go on the intake on every split ratio set I’ve seen. Doesn’t mean someone out there doesn’t have them on exhaust but I haven’t seen it. As far as lash, I have a cam that calls for .018/.020, another that is .028/.030, and another that is .026/.026 hot. These are all very similar in lift and duration cams and they’re all made by Bullet so it does depend on the lobe and opening ramp. If it were mine I would disassemble it and go through everything then reassemble. Learned that lesson before with used race stuff. It would be cheap peace of mind as your good deal will turn into a bad deal quick if it kicks the rods out on the fifth run...plus all the time spent. | |||
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| DRR Sportsman |
Thanks for all the feedback, I appreciate the info. Yes I do understand I can take it apart and that may happen. I wanted to get some insight first that's all. Yes it is a very very good deal price wise with the purchase. | |||
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| DRR Top Comp |
Good for you. More reason to insure it's perfect. The interesting part... It's like getting to know a guy on the drag strip, you've never spoken a word with. If you can remain impartial, you can learn a lot about a guy critiquing his approach on the compromises in play, for the assembly. You'll either admire his work, or know him as a hack. | |||
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| DRR Top Comp |
Beware of traps. I've seen guys number one rod cap incorrectly. Pay real close attention on disassembly. Look it over real good. I had a guy bring me a BBC that had one rod cap numbered to the inside, they didn't catch it on the previous freshen and installed the cap backwards. The cap bearing was half spun, it didn't lose oil pressure but was heating the crank for who who knows how long. The 4.25 crank was cracked ready to go off. | |||
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| DRR Elite |
Be honest, you have no intention of disassembling it and I'm not saying you should. You bought it first and foremost because the price was right and secondly because you believe it is what the previous owner said it is. Is this still a very very good deal if you have to give it to a shop and rebuild it followed by dyno time. That's a $5k rebuild minimum from professional race engine shops. If the answer is yes and you have the $ burning a hole in your pocket than do it, if not, do a leak down, compression test, lash the valves, check the spring pressures, maybe pull a pair of lifters and run it. That all said and not that you would ever follow my advice so don't, follow TOP38's advice as to the cam lash. Also there's not a "typical bracket type solid roller cam" which includes the cams in 600+ cubic inch BBC making 1300+ HP, that the lash can't be tighten/loosened .008 from spec, so you've got nothing to worry about. | |||
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| DRR Top Comp |
Every engine you've ever run is in the condition of the OP's (assembled), what other perspective could you have? There's way more to it. I could care less either way, but the OP got a deal, good for him. If it were me I'd insure it stayed that way by going over it with a fine tooth comb.This message has been edited. Last edited by: Mike Rietow, | |||
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| DRR Elite |
STFU you're a clown that ain't ever done shyt except at your local duck pond! | |||
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| DRR Top Comp |
You're changing the subject to another you know nothing of. I asked, what other perspective could you have, than to suggest the OP run an already assembled engine, you nor he really know nothing about? The same as every engine you've ever ran. You're only taking it as an insult, when the question is only based on reality.This message has been edited. Last edited by: Mike Rietow, | |||
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| DRR Elite |
again, clown STFU! Talk about what you know, not what you think you know. You are clueless!! My perspective comes from over 30 years of bracket and class racing, 43 years tuning engines and suspensions/chassis, turning wrenches and even assembling my engines starting back in 1979 with the original 396 in my Chevelle!  | |||
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Bracket Talk Bracket Talk Forum Tech Talk - by Abruzzi What rocker ratio goes where?
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