Opinions on a 393 stroker build |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Posted: August-17-2011 at 6:25pm |
This is my first time posting but I've used this site as a resource for the last few months working on an 84 SN I got last fall primarily for wakeboarding with ballast. I'm rebuilding the 351 as a stroker and thought some of the folks on here that have them or know engines can offer some general opinions--or just tell me if what I'm doing is dumb! Keeping it reverse. stock 83 block, bored .030 over and thinking of going with somewhere around .0037 piston-to-wall for the marine use considering the Eagle stroker kit 16526 which has: Eagle crank 103513850 - 3.85 stroke (was gonna repolish in reverse) Eagle SIR5956FB rods Keith Black hypereutectic pistons Clevite bearings Already have: GT40P heads, gonna mill them to end up with about 9.75:1 comp if the hyper psitons are used (if I go forged pistons, then more like 10.5:1) Cam Research cam 212 intake, 220 exhaust, .460 lift on both, 112 separation, flat lifters 4160 Holley carb Thinking about getting the Air gap intake Here she is before I pulled it out a couple of weeks ago after it trashed the main bearings in about 8 hours of use :( |
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kapla
Grand Poobah Joined: March-27-2008 Location: BA, Argentina Status: Offline Points: 6148 |
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sounds like an interesting thread! lets see what the gearheads have to say!
good luck with the build up! |
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<a href="">1992 ski nautique
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Eric,
Welcome to CCfan (or at least posting!!) What do you attribute the blown mains to after the 8 hours? |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Thank you for the welcome! I really wish I could tell you. It was the stock crank, rods, and pistons. The local builder just did a re-ring and new bearings.
I've got a top-notch builder on it now and he says they don't appear to be oil starved, like chewed up dry. Just smoothly worn thru in the direction opposite the pistons. The crank is salvageable but I just want all new stuff and the idea of some power gains seems cool. |
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boat dr
Grand Poobah Joined: June-27-2004 Location: United States Status: Offline Points: 4245 |
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I agree with the parts list for most of your parts, negatory on the KB pistons. Forged cost a little more, but worth every cent if your building a stump puller.
The one piece rear main seal is still available from PCM, I used Cam Research #CR 272 Left.. lobe sep. 112 degree.Compression ratio at 9.5 is plenty for Karen's 331, it will spin 6500 w/12x15 OJ prop. That is 57 plus mph in her 1964 American Skier, a bit lighter than your hull.Be careful about raising the CR too high, instead keep it low and a 143 thermostat will allow quite a bit of advance. There is a lot of HP left on the table without the added advance......Twist it till it PINGS..... Karen has over 550 hrs. now on her stroker, HARD HOURS, money well spent...Boat dr |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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Cool build... hopefully you havent ordered any parts yet?
Im sure someone (like Joe) will come along with some words of wisdom, but here are a few tidbits that I noticed. -piston to cylinder wall clearance cant really be set properly without discussing particulars with the piston manufacturer. -The P heads are really 302 heads. They still work well on our low RPM 351w's, but theyre going to be a pretty decent bottleneck on a 393ci. If you can pony up the cash for something better, there are big gains to be had here. -That cam you mentioned is TINY TINY. Its not much bigger than the stock 351w cam. I went middle of the road with my warmed up 351w and have .490/.490 of lift. With more cubes, you'll want more cam. I realize that youre primarily wakeboarding, but the set up youre describing would probably be good for 300-350hp at 4000-4500 RPM... rough guess. By selecting different heads and cam, you could easily end up in the 400hp @ 5000 RPM range, and pick up both low end and midrange power to boot. I would highly advise against building a low-RPM motor... these boats simply dont operate off-idle like cars do. Joe's 408-powered '83, for instance, is good for 500hp+ @ 5500rpm, and has a huge cam and a single plane intake. Despite turning a monster sized prop, his boat comes out of the hole faster than most jet skis. Now THAT is something to shoot for. |
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81nautique
Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5778 |
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Yeah scrap that cam with those cubes, I was expecting you to post something around .490+. I think you've been talking to Scott, grinds good cams but ultra conservative.
Also agree on the p heads, they will be fine but there are some much better options if there is any money in the budget. CR I would never build again less than 10:1 so I think you're close. I've never had a problem with pump gas at 9.97:1. A set of aluminum heads would allow for more CR. Not sure on the air gap, don't think there is much benefit of the air flow under for cooling and could be a PITA to keep clean. There are several here running RPM's or equivalent and getting good top and low end perf. I am a believer in forged pistons and again agree the piston to wall clearances are dependent on the piston itself. Is your builder familiar with marine applications? That will have an impact on clearances too. the stock exhaust will limit you a bit on top end. anyway, motor builds are fun, keep us up to date. |
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You can’t change the wind but you can adjust your sails
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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I really appreciate you guys chiming in on this. I didn't expect any action on my post so this is great!
I called Cam Research as soon as I read "TINY TINY" and had them hold off on the cam grind until I did some more learnin. After talking again with the builder and reading on here, here's the new list: Since the Eagle kit doesn't have the option of changing the piston dish to get a higher comp ratio, I'm thinking about a Scat assembly with forged pistons and forged crank. (still 3.85 stroke), and tru to land about 10.25-10.5:1 In the cam department, I would really like to go with something that will work with the GT40Ps for now, but allow for some aluminum AFR heads later (maybe with 1.7 rockers for more lift). Can you guys recommend me something? And yes 81nautique, I was talking to Scott! haha Funny that you knew. And your other question: the builder has done some marine stuff, not a ton. But they do build a bunch of high performance engines. Mostly 600+ HP kind of stuff so my little boat engine is... well, little. |
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81nautique
Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5778 |
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Thats the same cam he sold me a few years ago. I later went with 1.7 roller rockers to get it to .488. I would not settle for anything less than .490 but you'll need to get better advice than my speculating. I ran that set up with gt40p's for a year and it ran very well but still lacked. There is a myth with these motors that if you go more cam to get the motor to run better on teh top end that you will hurt the holeshot/low end torque. There are several of us here that have played with the 351's and as much as we've dumped horsepower into them for top end we have only improved the bottom as well. I can't recall one single upgrade that hurt one end or the other, typically the result was improvement across the ful range. |
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You can’t change the wind but you can adjust your sails
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Very good to know. I can already tell this website is gonna be my new best friend.
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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There are a few guys here who are running cams with more than .550 of lift on their hot 351w's, both stock stroke and bigger cube versions. With a stroker, you'll have more torque everywhere and it will be hard to hurt low end power unless you get really carried away, like Alan said.
I would think that shooting for a power level of 400hp @ 5000 RPM would be a very easy goal to achieve with reasonably priced components, and would be a terrific all-around ski boat motor. With 393ci, I would think you'd want no less than .520-.530 of lift to get there. Do you already have the P-heads? They dont pick up any more flow above .500 of lift, so I really think theyre going to be a bottleneck for you. If you were to go with a P-head, .490 lift cam combo, my guess is that you'd be looking at 350hp @ 4500 RPM and you'd be leaving quite a bit of power on the table. |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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I do indeed already have the P heads, ready to go from the first round on this engine. I'm not against getting some big heads at this point, but would I realize that 400 hp without a big carb/exhaust? |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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You may benefit from a slightly larger carb, maybe not. Thats really more dependant on how many cubes you have, and how many RPM's you want to turn. It wouldnt be hard to swap that out later if you want- it wont cost you much in extra gaskets, etc.
Id say youre just fine with the original exhaust. Alan cross sectioned a PCM manifold a while back and they dont look aweful. There are some gains to be had here, but the bang for the buck on an exhaust upgrade is very, very low. If you can scrape together the cash now for a better set of heads, thats where the money would be best spent (besides the stroker upgrade). That way you can pick a cam to work with the whole combo, rather than having to compromise to make everything work with the P's. AFR, RHS, Twisted Wedge are all great heads... not sure if you can find something decent for less money. |
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5698 |
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Hello Eric – glad you started a thread it is more fun to talk this stuff out online here..
I think you have to be careful what doors you start to open on these builds. Bigger heads lead to bigger exhaust lead to forged bottom ends and big cams and high tensile strength shafts and bigger fuel systems and fancy ignition setups and then you have a hot boat but no money.. That being said I have wanted to work out for a while what would be a good reliable reverse rotation setup with much more power (around 1 hp per cubic inch) and still considerably less than a dealer installed replacement engine. It is not necessarily an easy task.. the 351 stroker vs the 302 stroker is a different animal . Be a little more careful on timing than what you would do with a 302 based engine.. I messed up one engine that way.. and something tells me the nasty noises coming out of my engine compartment last night might have a little something to do with that as well. My advise You have the GT40p heads.. use them – see what happens (I certainly want to know myself)—you are a relatively mechanical guy so changing them out later will cost you no more than some time and gaskets. On the bottom end – use whatever cast crank you can find scat and eagle both have reviews all over the board but if you work with a good shop that balances the crank and does the final polish their work is going to be more important to your success than which brand you used. I use forged probe pistons they are usually in the range of 550 a set .. might be worth spending the money there.. but I wouldn’t spend a g on pistons. The piston to wall clearance is fully dependent on the piston you choose.. not worth discussing until you choose.. in fact once you have the pistons in hand you need to measure the actual pistons you are going to use before the finish hone.. you cannot expect that they are exactly what they should be.. although all the major manufacturers will give you a pretty good matched set. You or someone will need to grind your ring gaps a prefit set will not be right, be aggressive when picking an end gap… that means on the large gap size. I don’t know how many rod choices you are really going to have after you choose pistons.. once you find out post prices and part numbers and we will comment. Compression—I am running pretty high there and it is a lot of fun, but I tend to break things, something around ten is a good compromise. Balance the bottom end.. have someone good and local do this.. with your balancer/dampener and your flywheel. If they don’t ask for these items don’t let them balance your engine. I am using a stud girdle.. they take some adjustment sometimes but I think it is a good idea .. Good main bolts and head bolts are not cheap.. not as bad as studs but not cheap.. probably still a good idea though. I vote you try a single plane intake manifold and the most aggressive cam you can get that will not cause you to melt lobes, suck in water, or cause spring issues. I don’t have direct advice because the reverse rotation, flat tappet thing I don’t have experience in. My cam guy I am convinced is a genious but he deals with billet rollers matched to springs and valves.. I think Cam research can get you where you need but tell that guy you aint looking to pull stumps at 1500rpm. Whatever cam you get will not be a good solution if you switch to aluminum AFR heads later.. and don’t do that btw .. I believe you would be much happier and less poor using a well prepped set of Trick flow heads should that day come around. That is all that I have time to write about at the moment.. keep talking it out here and then you spend your money and you make your choice.. |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Awesome, awesome, awesome. Thanks for all the input! Time for me to do some homework.
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Alright, I'm decided on having a forged crank and pistons. But I'm losing sleep over whether to get aluminum heads and which ones. It's mostly the the snowball effect I'm looking at:
Big heads will need a big carb (eventually if not immediately I'm assuming) and with this newfound power is my 84 model transmission the next thing I'll be pulling out? I'm all about the power gains but at the same time, there are a lot of other things I'd do to the boat before sinking 5-6K into the engine. And it would actually be kinda nice to use it for recreation instead of "work at the lake" days Just curious what you guys think as I'm hunting stroker parts... |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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You dont need to go aluminum if you want good heads. There are several good cast iron options out there (RHS being one of them).
Big CUBES are just as likely to require a bigger carb as upgraded heads will. I think this is something to plan for regardless of your head choice if you go stroker. You can always hold off on a bigger carb, so long as youre ok with it being a bottleneck. Dont worry about the trans. The Velvet Drive is a stout piece. Throwing a bigger prop on it may stress it more (which you may need to do with a stroker) but it shouldnt decrease its life significantly. When it fails, send it to Eric and it will get a new lease on life for <$800. There is absolutely no reason that a well built motor should be any less reliable than a stock one. Using better parts (tighter tolerances, stronger, etc) is a good thing. If youre not pushing the hard parts past their limits (1hp/ci is relatively conservative) then you can expect a long life out of a warmed up motor. |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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Why steel crank? Puts more stress on the block.
A 600 holley is good over 6krpm , no need for more Nevermind, got confused with the 302 thread. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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current parts list:
Scat stroker kit--forged Scat crank, I-beam rods, Probe pistons Moroso 22939 windage tray ARP 154-5503 main studs AFR-1420 - 185 heads - curious as to why Joe says no on these. Everything I read says they are good heads right out of the box, and they are 350 cheaper than the TFS. What gives? TRBenj: I was thinking aluminum for keeping chamber temps lower/timing higher... plus they look cool. :) Cam size and roller rockers... TBD Performer RPM intake |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Picked up some AFR 185s with roller rockers on Craigs for 800 that appear to be in good shape. Figured I couldn't go wrong with em at that price. In cam land in looks like I'll be going with a 224/230 .512ish lift from Comp instead of Cam Research. I found out that a lot of Cam Research's recommendation on that .460 lift cam had to do with the fact that's the biggest core they have for the 351 in reverse. The things you learn. They were nice enough to refund my money even though they had already started on the grind which is cool. |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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That makes very little sense to me- Im guessing you misunderstood what they were telling you. I have never heard of a blank being limited in the amount of lift you can grind into it- at least not in the super-tame world of ski boat cams. Of course, CR only has one type of blank for the RR Fords, which have a set amount of lobe separation built in (112 deg, IIRC)... but they should have been able to grind anything you want (within reason of course) in terms of lift and duration. If its too late, good luck with the Comp... but that still seems ultra small for a stroker. There are guys running significantly more cam in their 302 based motors. |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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His words were VERY precise when he told me they couldn't do a bigger lift in reverse rotation, but maybe he was still trying to save the cam they had already started by telling me that.
I guess I'll see what Comp has in the .550 range. Thanks for the input. |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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Hopefully Comp is taking all of your other components into consideration when making a recommendation... intake, heads, compression ratio, etc... and of course, what your goals are for the build. I wouldnt necessarily shoot for the .550 range, though thats not out of the question if their analysis shows that it will work well for you.
If CR is limited to .460 of lift that would be a very recent development, as theyve ground bigger RH cams for many people here. Even if that was the case, they could always have ground you something with a smaller base circle that would give you more lift... you would just need longer pushrods. Something isnt quite making sense. |
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65 'cuda
Platinum Member Joined: July-12-2005 Location: Cincinnati, OH Status: Offline Points: 1091 |
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here is my cam data from cam research:
Gross valve lift intake .478 Exhaust .486 Duration 272 285 duration at .050 208 220 Valve Timing Open Close Intake BTDC -6 ABDC 34 Exhaust BBDC 48 ATDC -8 Lobe separation 114 Wish I would gone more, boat pulls very well though, wish it had a little more top end. I'd like to try a 430 on the boat, i think it would spin it 4900. Anybody got one to lend me? |
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jbear
Grand Poobah Joined: January-21-2005 Location: Lake Wales FL. Status: Offline Points: 8193 |
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I will testify to this...can't imagine you needing anymore..... john |
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"Loud pipes save lives"
AdamT sez "I'm Canadian and a beaver lover myself"... |
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65 'cuda
Platinum Member Joined: July-12-2005 Location: Cincinnati, OH Status: Offline Points: 1091 |
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Three deeps jbear!
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jbear
Grand Poobah Joined: January-21-2005 Location: Lake Wales FL. Status: Offline Points: 8193 |
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3...easy.
I know me, Eddie and HW would have no problem and I bet Tim, Brad and Larry could match. Bet it could do 4! john |
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"Loud pipes save lives"
AdamT sez "I'm Canadian and a beaver lover myself"... |
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eric lavine
Grand Poobah Joined: August-13-2006 Location: United States Status: Offline Points: 13413 |
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i put a used set of AFR' 210's om my car, smoke a little when i fire it, check the guides
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"the things you own will start to own you"
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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Gary, I would have sworn up and down that you put a bigger cam than that in your '73. I know we discussed it at length a few times- you were concerned about going too big. I remember the cam in question was slightly larger than my .490/.490, and I was sure you pulled the trigger on it. Am I misremembering? I assume youre running a 540 now... how many RPM's are you pulling it? Have you had Alan plug your numbers into his desktop dyno to see where your hp peak is? Propping your WOT as close to that peak as possible should give you the best top end, in theory. Youre probably right on the verge of where a 430 might make sense. |
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littleshop
Newbie Joined: August-17-2011 Location: Tennessee Status: Offline Points: 21 |
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Well it's about time to start thinking warm. I figured I might post some pics on here as we go along putting the engine together. forged stroker crank from Scat to make a 393 de-edged Ross pistons picked up used AFR 185s for cheap, CNC ported and with Crane roller rockers included spring pressure checked out good for flat tappet cam, so we lapped the valves, surfaced the deck, checked guide clearance, cleaned, and reassembled with the inner springs left out until the cam is broken in. Looks like I did good on these considering the investment. :) Waiting on some rings to come in so we can finish the bottom end. With any luck I'll have this thing in the water by the end of the month! |
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