383

[hotrod24]

thanks man very nice

[hotrod24]

hey guys is this a good cam

http://www.jegs.com/i/Comp+Cams/249/12-600-8/10002/-1

[eventhorizon66]

Read this article for good advice on selecting a cam. Be the Camshaft Expert  Normally I wouldn't just recommend any article from a major magazine, but in this case it is written by David Vizard, who is an expert on the subject of building hi-perf SBC's.

[Lt.Del]

David Vizard is the guy who wrote the book on SBC rebuilds, literally.

http://www.amazon.com/gp/search/ref=sr_adv_b/?search-alias=stripbooks&unfiltered=1&field-keywords=&field-author=david+vizard&field-title=&field-isbn=&field-publisher=&node=&url=&field-feature_browse-bin=&field-binding_browse-bin=&field-subject=&field-language=&field-dateop=&field-datemod=&field-dateyear=&sort=relevancerank&Adv-Srch-Books-Submit.x=0&Adv-Srch-Books-Submit.y=0

[hotrod24]

thanks guys

[hotrod24]

how big it a 224 roller camshaft

[eventhorizon66]

Huh?

According to my calculator, Comp Cams 280 Magnum hyd roller #12-430-8 would have 60° of overlap at 0.006", based on it's 280° seat duration and 110° LCA.  If you had those same lobes ground on a 108° LCA the overlap would go up to 64°.  If you ground them on the more 383-appropriate LCA of 106° it would be 68°.  As you can see for every 2° you tighten up the LCA, the overlap goes up 4°.  Does this help?

If I were going to build a 383 with 68° of overlap at 0.006" it would have at least 9.5:1 CR (10:1 would be more like it) and probably 2000-2500 stall.  I imagine this motor as very healthy, but very streetable.  But, I've never built an engine, only dreamed of it ever since reading DV's books, LOL.

[hotrod24]

i am new at this and i have been reading about David Vizard but have not got that far could can you explain this to me in another way so i can understand

[eventhorizon66]

Did you read the article?  This diagram explains all the relevant attributes of cam timing.  Note that duration (items 3 & 4) are offered by cam companies as duration at 0.05" (the degrees between the point where the cam first reaches 0.05" of lobe lift until the point where it falls back to 0.05") or as advertised (seat) duration (this is where every cam company seems to differ - Comp measures this at 0.006", Crane at 0.004", Isky at 0.007", and so on).  I've noticed that DV tends to use Comp Cams and uses duration @ 0.006" as his basis for determining overlap (item 5).

So after discovering, with this diagram, that your 383 will tend to like about a 106 LCA (item 6).  You now determine how much overlap you want with this diagram (note compression ratio requirements go up as you work your way up the scale - I use a dynamic compression ratio calculator and try to achieve 7.5:1-8:1 DCR).  Then you determine the seat duration (at 0.006") you are looking for by using the formula ( ( degrees of overlap / 2 ) + LCA ) x 2.  From there, you seek as much lift as possible from a cam with that duration.  In the article, DV admits that this is not a perfect method (for example, it doesn't take into account that overlap is a not a single-dimensional attribute, it has an area - the overlap triangle), but it will get better results than selecting a cam based on duration first and all else second.

I should also mention that when I said grind it on a 108 LCA or 106 LCA, I meant have it ground, as in custom cam.  Most off-the-shelf cams out there today are ground on 110 or 112 LCA.  Also we are dealing with single pattern cams here.  DV recommends them as the best choice, in most instances, for naturally-aspirated street engines.

[hotrod24]

ok i am starting to understand lol i just need to do a little more home work on this. do you need to be a math wis to do this?

[eventhorizon66]

LOL.  No.  Keep in mind, this is for those who want to come as close as reasonably possible to optimal cam specs.  If 20 or so lb/ft of torque isn't that important to you don't worry about it.  I'm gonna try it as soon as I get an opportunity to build my first engine, because I have faith that DV really knows what he's talking about.  If you want a good source for info on building a Hi-perf SBC in general buy this book.  I've read it cover to cover several times and all I can say, is it's the best $14 I've ever spent.

[hotrod24]

what should i have the machine shop do if i want to rebuild it myself? because they wanted $2500 for cleaning and some other stuff?

[Fish]

what should i have the machine shop do if i want to rebuild it myself? because they wanted $2500 for cleaning and some other stuff?

Hot tank
Magnaflux
Bored if needed
allign hone if needed
recondition rods - if you aren't buying new ones
mount new pistons
Balance crank - if needed
etc.


You might do some shopping around for machine shops.  Seems a bit steep to me. 

I had the whole shabang done for my 350.  They even ordered my rebuild kit from EPW, and sold me a new crank and heads for $1500. 

[hotrod24]

yea that sounds about right of what they said i might have to look to finding another one

[frogman68]

Shop around

Just had a block hot tanked , bored .030 over, new cam bearings , new freeze plugs, new bolts put in the rods  and new piston put on the rods for 400. Hopefully Saturday I will have time to pick it up. Btw did you tell the machine shop it would be already disassembled ?