crankshaft questions
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=40763
Printed Date: April-29-2024 at 5:46am
Topic: crankshaft questions
Posted By: kelpfish
Subject: crankshaft questions
Date Posted: March-28-2017 at 9:55pm
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Good evening, kicking around the idea of putting a short block together for this winter project. Was looking around and there some good kits by eagle and scat to turn stock 351w into a 393 or 408 from what I read only change crankshaft out. So I call scat there about 20 miles from me here in calif. Guy tells me that gonna cost me 5oo extra to make a reverse rotation shaft so the shaft is 400 but gonna cost 900 to have it reverse. That's kinda bad math. Does anyone make a stroker crank that is reverse rotation? Or could I polish out the hash marks or use a speedi seal looking for options? ------------- Live Your Dreams |
Replies:
Posted By: Gary S
Date Posted: March-28-2017 at 10:23pm
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I used a speedi sleeve on my RR. Would they make one up with no hash marks at all,it would eliminate one manufacturing step. Do a search for JoeinNY and his stroker, he built a 408 but uses a LH with a PCM trans which changes prop rotation ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: TRBenj
Date Posted: March-28-2017 at 10:38pm
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393 uses 351 rods and 302 pistons IIRC. Maybe take a step back and tell us what you have and what you're trying to do. |
Posted By: kelpfish
Date Posted: March-29-2017 at 12:42am
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OK lmao my motor has 1200 hr on it. Was going to start gathering parts for this winter and go thru the motor when I park her for the season. Being that me and friends are not getting any smaller thought a few extra cubic inches would not hurt. Was thinking a 3.850 stroker crank, H beam rods and a set of trick flow forged pistons motor will be at .030 most likely. already have a set of gt40 heads that will be going back on it. now the only concern I have is getting a stroker crank for a fair price. ------------- Live Your Dreams |
Posted By: Duane in Indy
Date Posted: March-29-2017 at 6:50am
IMO, forged pistons and H-beam aftermarket rods are not necessary You won't be turning the RPM nor have the compression to warrant them. That said, I have a set of Sealed Power + .040 pistons with 5 hours on them that are yours (or anyone elses) for the postage. I had to go .060 and they are just setting in a box. Save your $$ from the piston/rod combo and spend it on a nice intake and a Quick Fuel carb setup. Mild port polish and port matching will give more results per $$. My $.02  (not trying to thread jack, just trying to help you out w/ no personal gain.)------------- Keep it as original as YOU want it 1978 Mustang (modified) |
kelpfish wrote:Posted By: TRBenj
Date Posted: March-29-2017 at 9:23am
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gt40 heads will be a choke point on 393-408ci... power may taper off after 4000rpm. What hull do you have and how do you use the boat? |
Posted By: Duane in Indy
Date Posted: March-29-2017 at 11:07am
For aluminum heads (save 40 pounds and make plenty of power) you may want to look at these. The first set are by Flo Tek based in SW Indiana. I have a set of these and they are nice. eBay item number:131483374036 First time I have seen these so don't know any history. eBay item number:182295760986 I can post or send pics of the Flo Teks if needed ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: TRBenj
Date Posted: March-29-2017 at 11:23am
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Duane, I think we'd all be more interested in hearing how they perform!
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Posted By: Duane in Indy
Date Posted: March-29-2017 at 11:31am
Here you go. For our RPM range Flo Teks are a good value http://www.hotrod.com/articles/ccrp-1302-six-budget-ford-heads-that-work/" rel="nofollow - SBF alum head comparison ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: TRBenj
Date Posted: March-29-2017 at 11:45am
| I mean in an application similar to ours... I think you're the only person who has opted for them thus far. |
Posted By: Duane in Indy
Date Posted: March-29-2017 at 11:59am
Hopefully I will test them this weekend. ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: MrMcD
Date Posted: March-29-2017 at 1:24pm
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Watching Craigs list I have seen several Ford small block AFR Heads sell used for around $1,000. I would trust the used AFR before some of the off brands. I was tempted to grab a set for my GT40 but it runs so well I decided not to mess with it. I keep watching trying to get a set of AFR small block Chevy heads for a project. Chevy heads are harder to come by on Craigs list. ------------- |
Posted By: kelpfish
Date Posted: March-30-2017 at 12:18am
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Are They fordged or cast learned my lesson long ago ? if they forged love to have them. Let me know. And I know I don't need to over build it but will be boys boat someday and going to make bullet proof since he better at computer games than turning a wrench. Can text me or call em Andrew 714 721 9237 asilinsky@yahoo.com ------------- Live Your Dreams |
Posted By: MrMcD
Date Posted: March-30-2017 at 2:03am
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Forged or cast applies to Pistons, can't say I ever read that about heads? ------------- |
Posted By: kelpfish
Date Posted: March-30-2017 at 2:21am
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was talking about the pistons he was offering up but think there cast which are fine but I going to run forged spend a couple bucks now save a few later. Also the kit I was talking about is really affordable for the crank piston and rods plus bearings and rings was 1500 don't think that to bad for a engine I hope outlives me :) ------------- Live Your Dreams |
Posted By: JoeinNY
Date Posted: March-30-2017 at 11:09am
I don’t know Duane I don’t think we have enough information to know about that. Compression comes at you quick with these ford strokers. It would depend on the pistons and head chamber size how much he ends up with but with the gt40ps I have sent more high dollar pistons to their grave than I care to admit with my 408 stroker. I have been running custom pistons and MLS gaskets to lower my compression for the last couple years, that along with 93 octane and a super conservative tune, and a relatively low load prop has kept me happy. Mostly a moot point anyhow as you typically are going to need to buy all new parts for the stroker anyway as the crank, rods, and pistons are all likely to change dimensions. By getting a bit crazier with the heads and the cam I have been required to go past the level of the cheaper kits – but no reason they shouldn’t work here. First thing to be answered is whether it is a one or two piece rear main seal block. It is the fact that this boat is a 2 piece rear main seal that makes the crank custom and more expensive. It might be cheaper to get a one piece block and have it machined as the basis for your new build – if you get the block cheap it allows you to keep your current bottom end together as a saleable or usable backup- and then no custom reverse rotation crank is needed. Just a custom reverse rotation rear seal – which is probably still available somewhere. If it was a 302 and not a 351 switching blocks and cranks from a one piece rear main to a two would be more complicated to differences in the balancer and flywheel. That being said lets get a thread started on them there flo tek heads seriously dying to know how they roll in the real world of ski boat engines... ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: MrMcD
Date Posted: March-30-2017 at 5:32pm
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Aluminum heads usually allow a half to full point more compression without detonation. How much compression do you have in your 408? The stroker engines by design are more prone to detonation than a 302 or 351. Personally I would build the engine to run happy on 87 octane. When you hit the waterways many times that is all you can buy. ------------- |
Posted By: JoeinNY
Date Posted: March-30-2017 at 5:57pm
At the moment I am in the mid 9s - have had as high as 10.6 - both with aluminum heads. It ran pretty good at 10.6 until it didn't. Either from a little sketch gas or running a prop that loaded the engine more than it was tuned for... melted or broken pistons were pretty easy to create. Broken blocks/cranks - also possible. 87 octane is not realistic if you are trying to better than 1hp/in3 in my opinion and even then you would be leaving hp on the table or running on the edge if you aren't running something computer controlled with minimally a knock sensor. Nothing wrong with a stock engine but not a lot of point in my mind of throwing a stroker kit or a set of aluminum heads at something and then not giving it at least 91 - which I have found everywhere I have ever looked. . ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: MrMcD
Date Posted: March-30-2017 at 6:51pm
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Not knocking you Joe, I understand completely and have built and own high HP engines. I am really surprised you can't run full timing with 9.5 compression and aluminum heads in a boat. Some of the new head designs work best with less timing than the OEM heads. Vortec GM heads, some like as little as 28 max timing. Even some AFR heads max at 34 timing. I don't know the Ford engines nearly as well as GM but I would expect similar issues with the newer designed chambers. Running thicker gaskets to lower compression can sometimes make detonation worse by reducing your quench area. Running close to zero deck will help reduce detonation. ------------- |
Posted By: 81nautique
Date Posted: March-30-2017 at 6:53pm
I love Joe's way with words. LOL Another good one from one of his early stroker builds "I break em so you don't have to" |
Posted By: skutsch
Date Posted: March-30-2017 at 7:17pm
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Good stuff here! Now what can we do for my little Graymarine 4 banger - HA! ------------- Our http://www.correctcraftfan.com/diaries/details.asp?ID=4669" rel="nofollow - 98 Sport Nautique My Dad's 63 Ski N |
Posted By: 8122pbrainard
Date Posted: March-30-2017 at 7:56pm
 Seriously, mill the head and chuck the flywheel up in the lathe to remove several pounds. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: skutsch
Date Posted: March-30-2017 at 8:44pm
You're not kidding I bet that flywheel weighs 150lbs (Ok, maybe 50lbs at least)! Anyway, that is a subject for another thread, sorry for the thread jack... ------------- Our http://www.correctcraftfan.com/diaries/details.asp?ID=4669" rel="nofollow - 98 Sport Nautique My Dad's 63 Ski N |
Posted By: MrMcD
Date Posted: March-31-2017 at 4:20am
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As far as breaking pistons so you don't have to, I was working the NHRA tour back in the early 90's, one of the top fuel team owners was talking with me and said he had just poured a new driveway. He had used Top Fuel Pistons like rocks in the concrete. They were working on a newer higher HP fuel systems and working out the bugs melted many pistons. He said they were too expensive to throw away so now he has a driveway reminder of how many pistons they destroyed. ------------- |