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Old 10-05-2011, 06:39 PM
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Cam selection, my turn

Ok, guys, This is a great forum, a great wealth of knowledge. I love reading and answering questions here when I can. Now I have one. As some might know, I am building a 355 for Jersey Speed skiff. 9.5 :1 TRW flatops, Scat rods and crank, Dart 200CC Iron heads, 1.6 Scorpion roller rockers. This has to go to 6600 RPM or so. Looking for Solid lifter cam, 238-240 duration, .500-510 lift, 112 C/L or so, Who has recommendations? So many cams and profiles to look over. I thought I had a nice Lunati but im afraid too much lift,and duration, dont want to be tearing up valve train parts

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Old 10-05-2011, 11:18 PM
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Camshaft/SCR mismatch. You need more SCR to run that cam.
http://www.crankshaftcoalition.com/w..._compatibility
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Old 10-06-2011, 03:52 AM
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I don't know what profile you need but don't let them talk you into a retro-roller cam. My machine shop is up there there arm pits in retro-roller lifter failures..
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Old 10-06-2011, 08:20 AM
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Quote:
Originally Posted by Bonneville462
I don't know what profile you need but don't let them talk you into a retro-roller cam. My machine shop is up there there arm pits in retro-roller lifter failures..
Strictly old school.....Solid Flat tappet
BTW this is my first hot rod without wheels, so Im not new to this stuff
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Old 10-06-2011, 09:25 AM
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That duration range will work fine with that compression (that linked article isn't worth much after you get above 7.5:1 compression), and you're not asking for a lot of lift, which will give you better stability. I would call up Mike Jones at (704) 489-2449. He is an independant camshaft specialist and one of the best in the business (much better than any Comp or Lunati tech help).

He does cost a little more than an off the shelf cam but a LOT of race winners swear by him. Drag, circle track, import, domestic, boat, plane, etc. he's done it all.
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Old 10-06-2011, 02:21 PM
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Quote:
Originally Posted by ap72
(that linked article isn't worth much after you get above 7.5:1 compression)
I consider your statement irresponsible at best and would be interested in knowing how you arrived at your decision.

After reading post after post of fellows who don't have a clue what cam to use, I went through the entire Crane catalog and took their recommendations for cam timing to use with what static compression ratio. If you don't like the chart that I put together, register your gripe with Crane, it's made from their numbers.

I clearly added disclaimers in an attempt to explain that this is not a strictly scientific approach, but it's one hell of a lot better than what we had to work with before I published it.

Last edited by techinspector1; 10-06-2011 at 02:38 PM.
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Old 10-06-2011, 02:44 PM
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Quote:
Originally Posted by techinspector1
I consider your statement irresponsible at best and would be interested in knowing how you arrived at your decision.

After reading post after post of fellows who don't have a clue what cam to use, I went through the entire Crane catalog and took their recommendations for cam timing to use with what static compression ratio. If you don't like the chart that I put together, register your gripe with Crane, it's made from their numbers.

Crane can publish whatever they wish, and people can use it as they like, some of it is reasonable some of the time, some of it is WAY out of line almost all of the time, and some of it in in that gray area where its not total crap but not really useful.

Compression is ONE factor to consider on a cam's duration but I don't think any cam manufacturer, EVEN CRANE would claim it is not the only one nor the most important one. I think they would all agree the intended usage, intake and exhaust tracts, and engine dimensions are all just as (if not more so) important than compression.

Compression is important, but not the whole story.

THIS IS ALL JUST MY OPINION and should be treated as such.
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Old 10-06-2011, 02:56 PM
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Quote:
Originally Posted by ap72
Crane can publish whatever they wish, and people can use it as they like, some of it is reasonable some of the time, some of it is WAY out of line almost all of the time, and some of it in in that gray area where its not total crap but not really useful.

Compression is ONE factor to consider on a cam's duration but I don't think any cam manufacturer, EVEN CRANE would claim it is not the only one nor the most important one. I think they would all agree the intended usage, intake and exhaust tracts, and engine dimensions are all just as (if not more so) important than compression.

Compression is important, but not the whole story.

THIS IS ALL JUST MY OPINION and should be treated as such.
Working with the premise that ignorance can be cured, I present herewith a statement from Crane....
http://www.cranecams.com/faqview.php?s_id=9

Like I said, argue with THEM and please refrain from badmouthing what I write if you have no evidence.
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Old 10-06-2011, 03:40 PM
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Quote:
Originally Posted by techinspector1
Working with the premise that ignorance can be cured, I present herewith a statement from Crane....
http://www.cranecams.com/faqview.php?s_id=9

Like I said, argue with THEM and please refrain from badmouthing what I write if you have no evidence.

I did not bad mouth you, just what you copied from Crane, and since you didn't write it I cant see how you can take offense to it.

Also, I read what you added in the link, basically it boils down to "compression is important", I never saw "compression is the only factor or "compression is the determining factor" or "the rest of your engine doesn't matter as long you you know the compression ratio".

Call Crane with the OP's engine specs and ask for a cam recommendation, then do it again the day after, and the day after- you'll end up with 3 different recommendations that are all "the best", and perhaps 1 will follow that chart. None of them will be the best.
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Old 10-06-2011, 04:39 PM
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Quote:
Originally Posted by ap72
I did not bad mouth you, just what you copied from Crane, and since you didn't write it I cant see how you can take offense to it.
That's the point, I DID WRITE IT. You will not find that verbage anywhere else on the planet. I researched Crane's data and re-formatted it for the use of hotrodders.com board members. It's no different than doing research for writing a book.
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Old 10-06-2011, 05:20 PM
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I was always taught that if you use a singular source of data (not of public domain) to base your writing on and contribute nothing yourself that you are plagiarising. At best you took some time to collaborate their data, which while I'm sure it took time, you claim it is all their information. Btw, like most cam manufacturers they also suggest a basic usage category, operating range, intake, exhaust, trans/gearing setup. Not once did your source suggest compression was the only factor.

No one has to listen to my opinion, and I will be the first to say TI has helped FAR more people than myself, but I see a HUGE glaring problem with the major assumptions the chart has to make to simplify it to that level.

Also I am sure TI took a lot of time to write the wiki article, but the best of efforts does not always translate into the best results. It took Edison 1,000 failures before he made the light bulb.
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Old 10-07-2011, 10:39 AM
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Contacted Mike Jones this morning, we're working on a setup. Thanks for the referral
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Old 10-08-2011, 10:29 AM
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TI ... that is about the worst chart for selecting a camshaft.

You don't understand cams or how they relate to the engines performance at all.

I hope that's not too harsh a comment. You're a good guy and mean well, but......
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Old 10-08-2011, 10:30 AM
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Cam recomendation: What exhaust is on this boat motor?
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Old 10-08-2011, 02:35 PM
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Quote:
Originally Posted by F-BIRD'88
Cam recomendation: What exhaust is on this boat motor?
This has a wet exhaust, log type manifold (Nicson)
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