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4/24/2017 11:53 AM  #1


351W build, where to start

My 68 has a 351w "crate motor" with around 10k miles since it was installed (according to the previous owner).
We have previously determined it is a 79 non roller block, and I don't plan on rebuilding it, or taking it past 6000 RPM, but I want more power and I'm not sure where to go from here. It will have a toploader installed when these upgraded are made.

The parts I have acquired are...
AFR 185 heads, part number 1422
Edelbrok Performer RPM intake
Melling link bar lifters
Hedman long tube headers
It currently has a Holley 650 carb

I want to add the heads and intake, and add a cam  (hydraulic roller). I want the lopey idle sound, but not at the expense of power.  I would prefer not to get into the bottom end if that's possible.

So I understand that I need to know pushrod length, piston to valve clearance, head gasket thickness and "quench", compression ratio, and at some point choose a cam. But what comes first? Where do I begin? It seems to me like all of these things affect each other, so how can you change one without changing everything else?

 

4/24/2017 12:14 PM  #2


Re: 351W build, where to start

Wow!  you have opened Pandora's box.  I think everyone on this site has their own opinion, and they will share it.  I will not recommend a cam as cam lobes come in 2 degree increments beginning at about 205 deg up to over 300 deg.  take your pick.  But your parts will work fine together.  If those Melling link bar lifters are rollers, you can buy a roller cam just fine.  I spent months choosing mine.

I recommend you call someone like Edelbrock to get pointers on things like pushrod length, etc.  You also need to determine things like how much track time will it see, how many miles per year it will run,   How do you want to want it to sound,  is it a driver or cruise night only.  In short, how will you use it.  What chance you will want higher performance.


Original owner - 351w,T-5, 4whl disks, power R&P
 

4/24/2017 3:29 PM  #4


Re: 351W build, where to start

Do you REALLY want my opinion on camshafts!??
One thing fer sure  looks like you got the right heads! 58cc chambers  are better than the other heads because you are closer to ideal compression with these...and compression is the KEY to good power boost.
When the heads are off....take a look at the deck. See how far down the pistons are in the hole. IF they are at the top of the deck.......that's good!!!!!
Intake is good......carb is just barely big enough. "I think" something around 700-ish (715...........750 for example) would be "mo good-er".
One think I've learned about cams.......the tighter the LSA# the lopey-ier it sounds. Keep in mine the bigger the cu. inch.....the milder a cam grind will be.
My 5.0 camshaft  has 230/236@050 duration with LSA of 108*.It sounds bad-to-the-bone and has mega power from 2000rpm up!  Its a little snotty for most of these guys... butt-eye  find its about like an old 327-365HP Corvette. It needs to be occasionally cleaned out when loafing along at low RPM/speed. If I had a decent rear gear ratio...(3.55/3.73)the problem would most likely go away.
Your bigger engine would behave VERY nicely with this camshaft figures IMHO.
I would  think 10 degrees more on the duration figures and maintain the 108* LSA  would be near ideal....maybe 107*LSA.
I'm no camshaft expert but-hey....we're just "bench-racing" and this sounds good to me if I was building a 351.
Ignition/distributor re-curve is probably even more important  than anything thing else as far as ideal performance is concerned.  Quick advance......limit on total advance...lotsa initial advance with a healthy camshaft is VERY important. 
6sal6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

4/24/2017 3:41 PM  #5


Re: 351W build, where to start

My advice is first to figure out what compression ratio you will have with the new heads and intended gaskets.  Then I would take the compression ratio and all other pertinent facts about the car and engine and call Crane Cams tech line.  They will get you a cam that will do what you want without what you don't.  I've run Crane rollers exclusively for over 15 years and have always been happy.  They actually answer their tech line too, and customer service it seems is important to them unlike XYZ brand cams I've dealt with in the past. 

When it comes to a rarified combination I find the best course is to let the experts pick it.  I've built a lot of engines in my life, but I'm not a professional engine builder.  I don't have decades of dyno tests I can reference when choosing a cam, but the guys at Crane do.  With cams I know all the terminology, know all the conventional wisdom (and some unconventional), but in the end I know about enough to be dangerous.  Bench racing is fun, but I want my car to perform as intended on the street and strip.  They picked the cam I put in my 347, which was a semi-custom grind, but I think its going to be killer.  I had a 350SBC and still have a 383SBC that both got Crane cams and they have been great engines. 

 

4/25/2017 9:15 AM  #6


Re: 351W build, where to start

Thanks guys. So if I need to determine compression ratio first, how do I choose a head gasket? And won't it "quench" a certain amount that will also affect compression ratio? 

     Thread Starter
 

4/25/2017 11:48 AM  #7


Re: 351W build, where to start

And another question while I'm at it- due to my lack of knowledge in this subject, I have gotten a quote of $3-400 to do all of this for me. That is i bring him the engine, he builds the top end with my AFRs, does all the math and picks gaskets, camshaft, etc. Then I put it back in myself. Now money is tight, but this seems like an area I could really mess up, so it might be worth the extra 4 hundo. Am I overanalyzing this? I'm definitely coachable, willing to do the research, willing to do the work myself, but I might be in over my head on this one. 

     Thread Starter
 

4/25/2017 4:29 PM  #8


Re: 351W build, where to start

That's not a bad price.  Usually the money you think you're savings ends up costing you in the end.  There's a lot to a top end with valvetrain geometry, cam timing, etc.  If I didn't have the skillset and given the couple grand you'll have in parts it seems like cheap insurance.  On the other hand, if you want to learn there's no better time. 

 

4/25/2017 6:41 PM  #9


Re: 351W build, where to start

You gotta pretty big "knowledge bank" right here! With all these "boring topics lately".....you will have all the input you  could want!! Engine builds are ALWAYS popular on here!
I did my first one (before PC's) and looking up tolerance in a big book!  I did read Tom Monroe's how to rebuild your Small Block Ford engine book. 
Here...YouTube....Google...and a smart phone...should get you answers to just about ANY question you may have.
When you think about how the guys did it back in the 40's-50's-60's....you shouldn't do any worse! And they built some real powerhouses!!
Dive in
6sally6

Last edited by 6sally6 (4/25/2017 6:45 PM)


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

4/26/2017 6:57 AM  #10


Re: 351W build, where to start

I agree to a point with 6sally6.  There are some very good books out there.  The issue I've found is that most of those books deal with stock type rebuilds, which isn't what you're doing.  There's a lot of nuances to building a dedicated high performance engine be it for street or track, because there are considerations you simply don't have to worry about with stock type parts.  For example, an aftermarket rod and crank are designed to fit together a specific way because the crank has a wide fillet where the rod throw meets the counterweight for strength.  Each rod has a side that has a wide relief and a narrow relief.  This makes it so that the pistons can only go on the rods one way.  If you get it backwards the crank will be locked immobile if you try to put it together, or you'll find you won't be able to get both rods on a pin.  I've yet to find that kind of detail specific to aftermarket parts in a book.

The top end is no different because now you'll have pushrod guide plates for example.  How do you set the clearance on those?  How do you check valvetrain geometry?

I'm not mentioning all this to scare you off of trying to do it yourself.  I figured it out once and I'm sure you can too.  Just be prepared because sometimes this process can be a two steps forward two steps back kind of deal.  There's certainly help here and some great articles on the web, but this may take you a lot longer than you think it should to get it right.

The guys "back in the day" mostly figured this stuff out by trial and error and wrote the book we now read.  If you read through some of the stuff from those guys you'll be amazed at how much they knew before it was "common knowledge".  Guys like Smokey Yunick who built his own flow bench and used to sneak wind tunnel time from guys in the aviation industry.  Even my neighbor, who was a very successful Pontiac racer and car builder from the '50s-'70s is an amazing guy to talk to.  The stuff they figured out just shows that they have a particular kind of mind that is quite rare.  Its a combination of raw intelligence and the desire for knowledge coupled to an inventive spirit.  But make no mistake, just because these guys didn't have engineering degrees doesn't mean they didn't understand scientific method and how to set up an experiment and interpret the results.  They learned a lot of that stuff old school by reading books on chemistry, physics, and engineering and then applying those concepts to real world testing.  If there had been computer modeling and 3D printing available back then they'd have been on the cutting edge of that stuff too. 

 

4/27/2017 9:10 AM  #11


Re: 351W build, where to start

I'm thinking I'll just pay the man. Honestly I think I'd wind up with close to 300 in tools. I don't have a torque wrench that I trust, plus time is an issue with a 2 year old running around. I was hoping to do it myself to put that money back in the budget, but lack of knowledge/time/and torque wrench, seems like maybe it'd be smart just to cough up the $. I also have a 68 Bronco with a 289 that I'll start on eventually. Maybe it will be the one I learn on... 

     Thread Starter
 

Board footera


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