73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: TexasRed on September 16, 2009, 12:12:42 am
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OK. Seems the neighbourhood association around here may send me a "notice" from what I hear on my pickup even though it's sitting in the driveway, ain't hurtin' nobody waiting for an engine. Which when I get it in may be the time I pack everything up and move to Austin or Atlanta. Grrrr.
Anywho. I've got questions. Which cam do you think would be best for this engine/drive train. I believe it's a 3.42 rear end (it's an '84 shortbox that originally came with a th350c), it's now got a 700r4. I've got a 383 I'm grinding the block on now. The compression ratio should be around 9.3-9.6:1. Vortec heads clearanced for some more lift. For now, just to get the beast rolling, it'll prolly keep the exhaust manifolds it has but it is a dual exhaust with glass packs. Keep in mind, I may like to go back to daily driving this. I'd also like some decent mileage on the highway. Four barrel carb.
http://www.summitracing.com/parts/SUM-K00052/
or
http://www.summitracing.com/parts/ISK-CL201264/
The summit's cheaper and I could get it fairly quickly.
The other question would be, I haven't purchased pushrods yet, but can I get some decent ones at the autoparts store? I'm not sure what length and such. The heads have been milled every so slightly to get a more compression out of them. I think I have pretty much everything else, except radiator and heater core, but I think the four core radiator that autozone has may be the ticket. Thanks for any help!
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I like the Isky between those two because it is on an LCA that is closer to the optimal. But you'll have to decide how much you want to spend and how much you care about squeezing power out of your engine. Using a cam that is 5° too wide on the LCA can cost 15-20 ft-lb everywhere in the rpm band and a NA 383 with most performance heads currently available tends to want a 106.
Call Lunati and see what they charge for this cam (you have to call it's not in their catalog):
DV266-06HFL
266/266 seat duration - 217/217 @ 0.050" - .484"/.484" lift with 1.6:1 rockers - 106° LCA - 4° advance
Oh, and I would not use the springs Lunati recommends (73943). I think they give way too much over the nose pressure @ 331 lbs for this cam. Shoot for around 105-115 seat pressure and a max of 280 lbs over the nose if you want it to live. And be sure to check for coil bind (a guaranteed killer of valve train components).
Also, you could go a step larger and still have a very docile street 383, but I wouldn't unless you know you won't be using those manifolds for long. Stock exhaust manifolds and high performance cams don't mix.
If you are losing the headers but still want monster low end torque and a very good idle this would be a good cam (install it 4° advanced):
http://www.summitracing.com/parts/ISK-201271-6/
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I should also mention that the cams I posted above are medium intensity cams. They are in line with the cams you posted. There is more power in a higher intensity cam (faster ramps/more lift), but the risk of wear/break-in problems rises. I think high intensity cams are the best choice power-wise, but I would only run one if it was nitride hardened. That service costs you about 100 bones but just about guarantees a long cam life provided the appropriate spring is used.
I thought we'd had this discussion before. Just found it again:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=12203.15
So you decided to have the heads machined in lieu of beehive springs? And the block is cleaned up and coming along?
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Yeah, we did discuss it before. There's some good springs on there, I forget the rates but I think they're the rating for the 270 megacam from isky (pretty much a high performance spring). The block is getting clearanced and soon I should be able to watch everything spin without hitting or getting too close to something else.I had the heads gone through by a performance dude and he got some good springs in there.
There's also this:
http://www.summitracing.com/parts/TFS-K31401000/
OR
http://www.summitracing.com/parts/SUM-K00172/
I'm afraid of the summit cam being too much for a truck though. I mean there's prolly enough compression there and if I install it a few degrees advanced, maybe I can bring the power curve down some. Is there a way to find the gear ratio without pulling a cover? Is it stamped on the diff somewheres?
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Which ever cam you chose it needs to be a small base circle cam for the 383
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Which ever cam you chose it needs to be a small base circle cam for the 383
Not necessarily. And unless the rotating assembly is already balanced I would grind the rod bolt heads to clear the cam before running a small base circle. A small base circle cam will exacerbate wear issues on a flat tappet cam.
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Which ever cam you chose it needs to be a small base circle cam for the 383
Not necessarily. And unless the rotating assembly is already balanced I would grind the rod bolt heads to clear the cam before running a small base circle. A small base circle cam will exacerbate wear issues on a flat tappet cam.
Is that what ARP recomends grinding on there bolt heads. The ONLY grinding that should be done is in the oil pan rail area to clearance the block.
If you break in your cam the right way wear issues shouldn't be a problem, unless you use some of that offshore crap(lifters)
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I'm sure ARP frowns on it, but I don't care. Don't get me wrong, it's definitely possible to screw up the rod bolts royally if you aren't careful, but for minor clearance issues it's perfectly safe.
Certainly the best solution is the use of stroker rods which have the lowered shoulders and cap screws to clear both the cam and the block. But there is no good reason why the ONLY place to grind is on the block (that can get you into trouble too if you aren't careful).
TexasRed: I would seek a experienced professional opinion in this matter, if it concerns you. Consult the machine shop you have used and the one you will use should things go wrong. They may very well tell you to go with a reduced base circle cam and non-clearanced rods. This forum is a great way to bounce ideas/opinions around, but you are on your own when decision time rolls around. I'm just stating what I would do. There's my disclaimer.
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The rod bolts were clearanced by PAW. It's a balanced rotating assembly. I only grind the block and pan rails, yo. I'm kinda leaning towards the trickflow cam. . . . . .doh!
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Well if the rods are already clearanced, then the work is done for you. No more need to squable over that.
What has you leaning towards the trickflow cam? Single pattern cams tend to make more low end torque and thus get better gas mileage, according to David Vizard. The idea that vortec heads NEED dual pattern cams to make good power is not true, unless you are primarily concerned with top end numbers (as the magazines are).
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I think that summit cam K00052. I think the power range is a little higher up there than they say. I think I'd rather prefer the isky cam but Oct 2 to ship. . . .YIKES. Hopefully I'm starting the engine on the stand 'fore then.
The trickflow cam just cuz if it was a single pattern would be good. Plus I'm still running unported manifolds. I've read page 98 too. ;)
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I've read page 98 too. ;)
Cool, so you bought the book. Well if you've read it, you're already a cam expert. Did you see there is a new edition (http://www.amazon.com/Build-Chevy-Small-Blocks-Budget-Performance/dp/1932494847/ref=sr_1_1?ie=UTF8&s=books&qid=1253333578&sr=8-1). Everything has been updated and it includes 7 new builds (the first three remain the same). I just got my copy not long ago, and I'm still looking foward to reading it cover to cover (so far I've only picked through the cam and cylinder head chapters). BTW the cam I mentioned earlier is a grind that David has spec'd and teamed up with Lunati to produce on a special order basis. It's all in the 2009 edition.
Check out "Cam School" here: http://www.motortecmagazine.com/ (Warning: new website under heavy construction)
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I can bet that's a lot of money to spend to get a little closer on power generation. Plus what's the business about Post-87 roller blocks needing the appropriate snout for the thrust plate? I have a vortec block, I thought I could just put a flat tappet cam in there and be okay?
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87-up blocks have accommodations for a thrust plate on roller cams. To use the thrust plate the cam must have a stepped nose. But this only applies to roller cams. All (properly machined) flat tappet cams have a slight taper ground into the lobes that keeps the cam pushed back into the block. Any flat tappet cams will fit any gen 1 SBC. Just be sure you use an early timing chain because the later roller timing chains are machined to accommodate the thrust plate that you won't be using.
You should also know that because you have a late model block, retro-fitting a roller cam is much cheaper. If the budget allows that is something you should seriously consider.
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Unfortunately, the budget doesn't allow it :(. Well, looking at summit's site, I can get the cam and lifters separate shipped on Monday (for quite a bit higher) but if I want the kit (cheaper), it'll be october 2nd. OR I can order the cam and a different company's lifters. They're having a sale:
http://www.summitracing.com/parts/CRN-1410/
are these fairly quiet?
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There is nothing wrong with Crane lifters.
But actually of ALL the cams you have mentioned I like this one the best by far:
http://www.summitracing.com/parts/SUM-K00172/
It is on the proper 106 LCA and with 1.6:1 rockers it would have decent lift for those vortecs at .480". And it certainly ain't too big for a street 383. My guess is you'd be very happy with this cam, just lose the exhaust manifolds and pick up some long-tubes ASAP. Oh, I should also mention this cam is right out of the pages of a Crane Cams catalog.
Look at engine build #4 in Vizard's book. He used a slightly larger cam with Comp 270 Magnum lobes on a 106 LCA.
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The only problem I have is the overlap is around 62. That'd be a little hard on a daily driver. I'm not an old man, but this engine'll be carb'ed so no injector noise, it's also balanced, so it should be even smoother than a new engine, plus it's bigger so it can handle some more cam, but I just don't want to throw it all away. Plus I need to check the RPO code in the truck to find the rearend ratio.
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That cam, since it is a Crane Cam, was measured at 0.004" (which means it appears a bit larger than a cam measured at 0.006"). It is safe to assume that David Vizard's overlap measurements are based on 0.006", since that is what Comp Cams uses and he mostly uses Comp Cams. My best guess is that cam's lobes are very similar to Comp's 268 High Energy lobes, so I would guesstimate more like 56-58° overlap @ 0.006". On top of that, since it is a 383 it will feel more like 50-52° of overlap would feel in a 350.
You should also know that Isky measures their seat duration at 0.007", so their cams are actually a bit larger at 0.006".
I feel very comfortable sticking with my recommendation (especially since I won't be the one to suffer the consequences :P). If your compression ends up where you said it will and your rear gear is 3.42 or greater (preferably 3.73 - 4.10), you're good to go. The fact that you are running very efficient 170cc heads on a 383 will also give you some leaway in terms of cam decision as port velocity will be excellent.
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Oh, and I never touched on your pushrod question. Since you had the heads milled, you ought to grab an adjustable pushrod to find the perfect length that gets the rocker sweep right across the center of the valve tip. Then order that specific length. Are you using 1.6:1 rockers? Roller tip rockers?
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http://www.youtube.com/watch?v=sDEthCakytU
That's the summit cam idling. Sounds fairly lopey to me. Plus he says narrow power band :(.
Stock rockers, I may make my own pushrod length checker with a wooden dowel or something.
Would the RPO code be under the hood?
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You really can't tell much from a video like that. What was his initial timing, vacuum advance hooked to full vacuum, idle mixture screw settings, etc? My guess is with more initial timing and the vacuum advance canister hooked to full vacuum, that idle would clean right up. I can make my stock 929 cam sound close to that if I screw with the timing and mixture screws enough, and drop the exhaust.
As far as the narrow power band, it probably just feels that way because narrow LCA's tend to have less flat power curves, but notheless I'd rather have higher average power with a "peakier" curve rather than lower average power with a flat curve. And we have no idea what compression that engine has. That would affect the power curve as well. On top of all this it's a 350, not a 383, so that 106 LCA is not optimal for that engine and needlessly increases overlap.
In conclusion, I wouldn't put any stock in that video.
UPDATE: I just watched the other vids on this engine. It's a Goodwrench 350 (8.5:1 rated compression) that quote: "Needs a tune-up as the plugs are not so hot anymore"
RPO code would be in the glove box.
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Well, I don't remember seeing any codes in the glove box. Just a .357. But under the hood it says GQ1 standard ratio. I have a feeling that's like a 3.08.
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Pull the diff cover off and look for the ratio stamped in the ring gear or count teeth (it'll give you an excuse to change the fluid).
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personally i dont liek single pattern cams for DDing..
i have ran this cam on a couple SBC power form 1500-6000rpm
http://www.summitracing.com/parts/SUM-K1103/
Intake Duration at 050 inch Lift 214
Exhaust Duration at 050 inch Lift 224
Duration at 050 inch Lift 214 int./224 exh.
Valve Lift with Factory Rocker Arm Ratio 0.442 int./0.465 exh. lift
Lobe Separation (degrees) 112
i ran this cam wiht 1.6" rockers make for .471/.495 at the valve.
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Well I ordered the isky a couple days ago. . . . . I had the carrier rebuilt a couple years ago and the truck's been sitting for about 6 months less than that. . . . so. . . .I don't think the fluid needs to be changed yet. I have a feeling it's a 2.73 rear end which may not be enough gear for that cam in 4th. I'll keep it in 3rd or less. How hard is it to change the ring and pinion in one of these? I'm thinking either a 3.42 or 3.23.
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If you do a gear swap don't go for anything less than 3.42 (3.73 - 4.10 would be better). 2.73 gears behind a 700R4 is too long for even a stock engine IMO. But you should be able to use fourth at highway speeds with the 2.73's and that 264 Megacam in a 383. It just won't be useful for anything other than high speed cruising.
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I agree with that. I had 2.76 gears and they sucked. A change to 3.40 ratio was much livelier with my new cam and heads.
Event, why is it that Vizard likes the 106 LCA so much? I thought the lower the number, the more narrow the powerband and the more rumpity the cam ie. less street friendly. I guess if all-out power is the goal, that doesn't matter but 110 is usually what I see recommended for something streetable and livable.
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I agree with that. I had 2.76 gears and they sucked. A change to 3.40 ratio was much livelier with my new cam and heads.
Event, why is it that Vizard likes the 106 LCA so much? I thought the lower the number, the more narrow the powerband and the more rumpity the cam ie. less street friendly. I guess if all-out power is the goal, that doesn't matter but 110 is usually what I see recommended for something streetable and livable.
LCA/LSA then smaller then number then closer then cam profile are together..
take 2 examples a 106* and a 114*. run then same duration/lift and you get somethign similar in results
this controls how long then exhaust remain open at then end of then exhaust stroke and then begining of then intake and when then intake vlv opens.. esentially have both intake and exhaust vlvs open at then same time.. with a tube head exhaust.. once it hit then exhuat pipe it rapidly cools off..
example we took 10ci of air and heated it to 100ci then rapidly shoved it out then exhaust... were it rapidly cools and shrinks back down ot 10ci... this is calls scavanging effect of then intake air.. it allow you to get more fresh air/fuel in were you would generally not thuse increasing power.
the 114* will generat ~20inhg at low rpms and increase as then rpm get toward the top end of then power band.. efrfectively sufficatein then air flow.
a 106* will behave the oposite.
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Event, why is it that Vizard likes the 106 LCA so much? I thought the lower the number, the more narrow the powerband and the more rumpity the cam ie. less street friendly. I guess if all-out power is the goal, that doesn't matter but 110 is usually what I see recommended for something streetable and livable.
You are looking at it the wrong way. Vizard says the way to spec a cam is to first find the optimal LCA. This is the most important aspect of the cam and there is only one LCA that will make the most power. Then select duration figures that will give the desired amount of overlap. Then go for as much lift as the valvetrain will allow. For most 383's with 2.02-2.08 valves the optimal LCA will be 106.
If you select the duration first and then a tight LCA second, then, yes, the idle will get much rougher and the cam will become racier, because the overlap has gone up considerably. But this is the wrong way to spec a cam.
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For lower-lift and duration cams though, you don't often see (or at least I haven't) a 106 LCA. Perhaps I'll keep an eye open for that some more. Curiously, what would the optimal LCA be for the motor I have? Specs are in sig below.
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So if I had a cam in a 2.02 valved 383 that had a 110 LCA and 236° @ 0.050", and I wanted to find a more optimal cam. I would first look at the LCA. That should be narrowed to 106. Now if I simply apply a 106 LCA to my current lobes, overlap will go up considerably and may peak torque/horsepower will shift upwards. But I want the same powerband, so I would like about the same amount of overlap as the first cam had. So I will now select lobes will less duration. Lobes of the same intensity as before but with 228-230° @ 0.050" should fit the bill. Now I will try to achieve the most lift I can with 1.6:1 or even 1.65:1 rockers.
Cam 1: 236° @ 0.050" - 110 LCA - .520" lift w/1.6:1 rockers
Cam 2: 230° @ 0.050" - 106 LCA - .522" lift w/1.65:1 rockers
Cam 2 will make significantly more average torque. It does still have slightly more overlap, so the idle will be a bit rougher, but not much.
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For lower-lift and duration cams though, you don't often see (or at least I haven't) a 106 LCA. Perhaps I'll keep an eye open for that some more. Curiously, what would the optimal LCA be for the motor I have? Specs are in sig below.
These rules for speccing cams apply across the board for NA gasoline engines (Towing to full circle track).
Based on David Vizard's advice, a 350 with 2.02" valves is typically best served with a 108 LCA. A better cam than the XE268 might be one that uses XE268 intake lobes #5443 on both intake and exhaust on a 108 LCA at 4° advance. Then use 1.6:1 rockers across the board.
BTW Vizard recommends single pattern cams for any street engine as they tend to make more low end torque and improve fuel effiency. Dual pattern cams begin to pay off in the upper mid-range and top-end, and, before you ask, the LCA rules still apply to dual pattern cams. Also when using dual pattern cams, I notice Vizard tends to use 1.6:1 rockers on the intake only and 1.5:1 rockers on the exhaust. He recommends this because the exhaust side is much more sensitive to changes in the duration than in the amount of lift. Higher ratio rockers on the exhaust side of a dual pattern cam may only serve to further reduce low end output.
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SUX if you are genuinely interested in this topic I'd strongly encourage you to check out this book:
http://www.amazon.com/Build-Chevy-Small-Blocks-Budget-Performance/dp/1932494847/ref=sr_1_2?ie=UTF8&s=books&qid=1254072084&sr=8-2 (I've noticed a few typos in the new edition, but none that will alter your understanding of the material)
Here is a very informative Vizard article on cam selection: http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/index.html
Also you can check out more Vizard tech articles, as they become available, at this address: http://www.motortecmagazine.com/ (it's a new website and under construction so beware).
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The thing to remember about Vizard is that he's also got to sell magazines. So take some of his advice with that in mind. (What's sells magazines? MAX POW-UH!)
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You're right, he does make his living by authoring articles and books. But to dismiss him, even partially, for this reason alone would be ignorant. Everyone should be fortunate enough to get paid for doing what they love and contributing to their area of expertise. And it's never been the max power figures that have impressed me about Vizard street engine builds, but the overall torque curve, which is more telling of "how" he got there, and his constant aim for total streetability with the power.
I'm not saying he is the "end all be all" of engine building, as he most certainly is not. But for me personally, I just decided to find one "expert" to follow in my future engine building pursuits, since if I tried to follow the advice of as few as ten different people, I'd most certainly end up moving in ten different directions. I feel David Vizard is a qualified expert and have chosen to follow his advice so I can make my decisions as easily as possible. If Smokey Yunick had spent some serious time on street engines and then spilled the beans on everything I need to replicate his results, then maybe I'd follow his advice instead.
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I'm not dismissing him at all ("I READ YOUR BOOK!" Patton talking about Rommel in North Africa). I just don't know what people consider streetability. I live in Houston currently so I deal a lot with traffic. So a better idle is going to be a benefit to me. Along with the fact that a lot of his stuff isn't for building trucks (a few are, but they require almost a lower rear end ratio) so I take his advice with the attitude that I'm happy to lose a little bit of power if it means my engine is smoother and possibly lasts longer.
OK, what's the min clearance on a stroker? I just started putting things back together after grinding and cleaning. Is .050 ok? .040? I may need to get a file so I can get one spot a little better now that I can see it's actually fairly close once I got where it was hitting clearanced. The dremel was putting filings everywhere.
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I would think 0.050" would be OK. Why not give your machine shop a call?
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The day I picked up my block was the day they shut down.
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You shut 'em down, huh? Well I hope they did you right before they shut down, but you'll still need to find another machine shop.
As far as your clearance isue goes, I look at it this way. How much is the crank/rod really going to grow/move around? A piston can be run tighter than 0.030" from the cylinder head and it expands much more than the crank or rod. You can go for more clearance, but sooner or later you'll hit water jacket (it's not unheard of on 383 builds). If you're in the Houston area, these guys (http://www.houstonengine.com/) look like a reputable shop. Give them a call and see what they say about your block/cam clearances.
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I'm in NW Houston . . . .Pasadena's a bit of a drive. I read a few places that .050 is pretty standard. I'm fairly close to that so I think I'm good.
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I wasn't suggesting going down there, just calling them.
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Not sure why you deleted the Smart Aleck response.
Just an update, I'm never going to build another stroker again. Well, maybe, if I ever have more time and more money. I think next time I'll do the rod by rod method whereby I put a rod and piston in and THEN grind. That way I can clean everything up at one time and then build. So as soon as I finish clearancing everything (getting close) then I will probably start the final build (please God).
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Not sure why you deleted the Smart Aleck response.
Just decided I might have come off as a [fill-in-the-blank]. I was just being goofy anyways.
So it's been fun, huh? Hang in there and don't get impatient (careless) now. Make sure everything is super clean before assembly and check, double-check, and triple-check everything as you go. Keep us updated.
Just so you know for the future, these rods (http://www.summitracing.com/parts/SCA-26000716/?image=large) are supposed to make 383 building a snap (little or zero clearancing required). Unfortunately they aren't cheap.
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Any new updates on your engine build?
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Not much other than I bought one of them ring compressors from OReilly's/HiLo (I think they're called Ring Breakers by some) and a Husky-brand torque wrench from Home Despot. Also some Delo as my breakin oil along with some EOS. Just gotta find time now. . . . .
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Actually now I've hit somewhat of a roadblock. When I have both # 7&8 pistons on the crank, it locks up. I have a feeling it's number 7, because if it's on there by itself, I can't get number 8 on there, but if #8's by itself, I can get #7 on there but when I do, it's locked. I thought I had fixed it by cleaning behind the bearing shells and the surface where the bearing goes on the rod and cap. But it seems not to have worked. Any thoughts?
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When you say "locks up" you mean the rods seize the crank when installed? I won't move at all?
Are the piston-rod assemblies correctly assembled? First establish that the pistons are being installed in the block correctly (is there an arrow indicating the front of the piston?). Then hold the rod big ends against each other (with caps removed) as they would be installed on the crank. The bearing tang grooves in the rod should be at the opposite end and opposite side of the crank journal from each other.
Wasn't this a complete rotating assembly from PAW? Try contacting them.
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I've had it all together before and it turned. Yeah, the pistons and rods are right. Yeah locked up like it won't move at all. If I loosen the rod cap, it allows it to turn. I've checked to make sure the piston is put in correctly and the tangs are the right place.
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Well what has changed since the first time you assembled it? Are you installing the rod caps with the bearing tang grooves on the same side of the split?
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Well I've narrowed it down to something with that rod/piston combo. I'd tried it on a different odd numbered journal, same story. So I'm going to try O'Reilly's during work and get me a bearing, maybe it's something there? I used some 000 or 0000 steel wool on the edges/sides of the bearings to see if that's it, but I haven't checked it yet. 2 sealed power bearing shells are like $3 so I'll try me that.
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Have you attempted to install #7 rod/piston with the bearings from another rod? That'll answer whether or not it is a bearing problem. What is your clearance on that bearing? If you haven't already, now would be a good time to confirm all the bearing clearances with some plastigauge. Does the crank journal show any nicks or scoring now that you've installed/removed that rod a few times? Is the crank standard journal or has it been turned 0.010"?
Maybe the rod is bent :D....sorry, that would suck. Also your rod-cap surfaces may not be square.