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360 crank in a 308 block

Discussion in 'Technical Q&A' started by duck.co.za, Feb 26, 2008.

  1. duck.co.za

    duck.co.za Formula Junior

    Jan 9, 2007
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    Has anyone put a 360 crank in a 308 block ? What pistons and rods did you use .
     
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  3. mk e

    mk e F1 World Champ

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    It looks like nobody has ever actually done it or atleast not admitting to it :)

    Russ (snj5) was thinking about it and is where I heard of it. I'm not sure who we spoke to, Carabu maybe??? There si also a rumor that a 360 crank is replacing the big dollar billet crank in Nick's 4.0 liter kit. You may have to get one in your hands, the going rate in the states is about $1000 if you shop around.
     
  4. Fred2

    Fred2 F1 World Champ
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    How many of the parts on these engines can be upgraded?
    From what I read, the bore and bore centerlines are the same for most of the range.

    It would seem that putting newer internal and heads on a 308/328 would yield more power out of a naturally aspirated motor.
     
  5. duck.co.za

    duck.co.za Formula Junior

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    Thanks Mark
    Any idea what a complete motor costs in the states ? A $1000 is not a bad price for the crank .
     
  6. mk e

    mk e F1 World Champ

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    The 85mm bore 348/355/360 liners won't fit without a little machining on the block and an adapter to get the o-ring in the right place. A better bet is a custom liner, you'll still have to machine the block, but then you won't need a spacer and extra o-ring.

    The 348 heads are the same casting as the 308/328 but with bigger cams and different porting on the intake side. I think I would lear toward porting the stock head and getting whatever cam you want, but if a set of 348 heads came a long at the right price it's not a bad option.

    The 355/360 heads have the right bolt pattern but oil returns at least are wrong. I had a thread on 355 heads on a 308 block when I was thinking about basically this same project.
     
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  8. mk e

    mk e F1 World Champ

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    You probably should send a note to a moderator asking that your 2 threads be merged sice both have good and different info on the same subject.
     
  9. mk e

    mk e F1 World Champ

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  10. smg2

    smg2 F1 World Champ
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    I'm actually doing just that, however there is a one problem, cost. cranks are far and few between and cost about 2k. rods would be another $3500. so just crank & rods you're over 5k then you have custom pistons, liners etc...i'm looking to see where it goes power wise but I know it'll probably cost well over $15k first time through. what I plan on doing is offering it as stroker option to the superchargers. gear it up for production to cut down on the cost a bit. for a one time deal it's not cost effective and you'd get better gains HP wise by just dropping in a complete 360 engine/gearbox assy. and the body work that goes with it. or get crazy like mark :D
     
  11. group77racing

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    Is there enough rod journal material to offset grind the 308-71mm stroke crank to get to 360-79mm stroke specs? I beleive you need 4mm offset grind to yeild 8mm in stroke. If so then all you need are custom rods and pistons. I didn't check yet but what is the rod journal diameter of a 308 crank? There has to be an off the shelf rod length/big end diameter combo out there some where.
     
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  13. smg2

    smg2 F1 World Champ
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    all the cranks from the 308 thru to the 360 have the same journal size and rods size as well. the journal dia on them is 43.6mm give or take a few .02~.01mm. the best you could get with a regrind would be a 74.93mm stroke and that takes the journal dia down to 35.3mm.
     
  14. plugzit

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    Dave-SOMEBODY needs to look into a stroker for the 348. Now, who might that be? Let's see....we need a guy who has a lot of technical knowledge....big cajones....a 348....mechanical skills.....hmmmmm....any ideas?
     
  15. plugzit

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    Back in the stone ages when I was young, they used to weld on the journals to make strokers...still possible?
     
  16. mk e

    mk e F1 World Champ

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    It sure is. Some say it's all good other say only a fool.......I'm guessing the truth is in between and it would be fine for street but road racing might be an issue.
     
  17. mk e

    mk e F1 World Champ

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    Scott,
    you can't get the 308 rods to work with new pistons? On the 400 I it looked like I could go 10mm on the stroke and still use stock rods....and since you're making pistons you might as well add some bore.....in fact skipping the crank and just going to an 85mm bore gets you almost al the displacement with a lot less work and cost. or say 86mm bore get you a 3.3

    The other problem is that the 308 heads won't feed a 3.0 liter without work much less a stroker. Head /flow work alone will get you more power than any of these displacement bumps.
     
  18. mk e

    mk e F1 World Champ

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    Scott,
    I know you've looked at this, but I going to go back to the 360 engine on the 308 trans? I know it's probably not simple but it may be worth the thouble??
     
  19. group77racing

    group77racing Formula Junior

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    nope...still looking......

    But then you'd have to raise the rpm limit to get more power with a big bore. Adding stroke gets you more torque within your existing rpm range. I was going to get custom rods and pistons for an over bore, but doing some research on 348/355/360/430 engine specs I see we need more stroke first. The 348/355 and 360 all have the same 85mm bore. The strokes are 75mm, 77mm and 79mm in the same order. In traditional hotrod mentality we think longer stroke means lower rev limit, but, the 355 and 360 are even higher limits than 348 then the 348 should be able to spin at 9500 given its short stroke. So, stay in our rpm limit with more stroke or raise the rpm limit and spin it higher for more power. The 430 engine is 92mm bore and 81mm stroke. Also, the 348 has 10.3:1 compression, the 355/360 are 11:1 and the 430 is 11.3:1. The least expensive way is hone the liners and put in higher compression pistons, deck the heads. Then its up from there but the dollars go up too. Bigger pistons, better rods, longer stroke, custom cams, ported heads, bigger valves, custom headers, tuned EFI.....where do you stop?
     
  20. mk e

    mk e F1 World Champ

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    No. Torque is proportional to displacement, not stroke. to 3.3 liter engines, one long stroke small bore and one big bore short stoke both with identical heads and cams will make identical power curves.

    The 355 and 360 make power ay higher rpm than a 348 because they have better flowing heads.
     
  21. group77racing

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    Mark, using the "bowtie" motor for example.. the old '69 302 Z-28 engine with 4inch bore and 3 inch stroke made a round number 400hp even thought it was rated at 290hp from the factory. The 305 engine from a 80's Monte SSwith 3.75 small bore and 3.48 stroke made 180hp. Given cams and compression were different but not that different and both had 4bbl carbs. The 302 could turn 8000 rpm all day the 305 would blow up at 6200. I know, I had them both. I see your point but I don't agree with "identical power curves".
     
  22. enginefxr

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    Traditionally, large bore/short stroke engines will turn more rpm. The bigger bore unshrouds the valves, allowing larger valves. Larger valves= more airflow= more horsepower. The problem with long stroke motors is thrust loads on the cylider wall/piston skirts.
    500 inch NHRA engines (worked on alot of them) use the large bore/short stroke theory and make about 2.8 hp per cu. in. and rev at or just above 10,000 rpm
    815 inch IHRA engines have big bore and big stroke but only make about 2.2 hp/cu.in. and only rev 8200 rpm (as I remember, been along time since I was around those). The longer stroke gives diminishing returns on performance
    Most engine builders lean towards big bore/short stroke... unless your building a truck/tractor pull engine.
    Then again, F1 engines are small bore motors that turn 19,500 rpm... but then we're talking about pneumatic valve trains, etc.

    The 302 Z28 engine had 2.02 dia. intake valves, the 305 has 1.94 or even 1.72 intake valves, no contest as to which one would rpm higher.. also has to do with cam profiles, spring pressure, etc.

    Just my take on the situation....
     
  23. J. Salmon

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    I am pretty sure there is a lot more that goes into the power and torque output than just displacement. Everything from burn timing to rod angle will affect how much actual force is applied to the crankshaft. Sure, the motor is an air pump, so equal fuel burned per revolution will give a theoretical equal output, but the reality is much more complicated.

    In general, a larger bore shorter stroke motor will be easier to turn to higher rpms because of the reduction in reciprocation (as compared to the same size motor with long stroke). And you can often improve torque by adding stroke to a motor (but here you are comparing to the smaller displacement). But I don't think you can prove your theory with either of these two concepts. In fact, I had thought that the bigger bore was preferred, since increasing stroke has the downsides of more reciprocation and increasing rod angles. If you are limited to working with a particular block, you are often limited by cylinder wall thickness. And it's a much easier job to put in a stroker kit without re-machining the block and getting new pistons, etc.

    I guess what I am trying to say is a stroker kit is often great for increasing torque in a motor, but if you had your pick, you would increase bore.

    If you go to Nick Forzas site, he has great pictures of new liners for the 308 which allow for an increase in bore to up displacement. He also mentions using a different Ferrari crank to increase stroke to 3.6L or so. Since he's been down this road before, I would think he could be of help.
     
  24. Horsefly

    Horsefly F1 Veteran

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    I don't know about the intricacies of Ferrari blocks, but in the Chevy world, what "seems" feasible is not often so. For example, a 302 Chevy consists of a 327 crankshaft in a 283 engine block. So one would think that when rebuilding a 283, just grab a 327 crankshaft, drop it in the 283 block, and get 302 cubic inches with no apparent modifications. Wrong. The counterweights on a 327 crankshaft will not clear the engine block of an early 283. Supposedly some mid 60s Nova blocks were machined with crankshaft clearance, but they would be the exception.

    Don't know if similar situations exist in Ferrari land or not.
     
  25. mk e

    mk e F1 World Champ

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    You're right. As pointed out by others an engine is a complicated thing and "identical" was not the right word....similar would have been a better.

    My real point I guess was that with the heads fixed upping the bore vs upping the stroke wn't make any real difference in hp. The piston speed and therefore loads will be lower in the big bore engine but the piston friction and comubstion chamber will be better in the long stroke engine.

    From a practical stand point I think building the big bore engine would be easier and cheaper. It would also allow more extensive head modifications if high hp was the goal. The 360 crank retro fit is not a bad option but it wold be my second choice
     
  26. group77racing

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    Dude, your way off, maybe you meant 327 block and 283 crank.
     
  27. mk e

    mk e F1 World Champ

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    That my friend is why god gave us milling machines and die grinders :)
     
  28. group77racing

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