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any advantage to switching 351c-4v heads


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On 10/25/2020 at 9:52 PM, Animal Lawyer said:

I just started looking at the aussie heads, I just added a 1970 4v cast iron intake manifold and hooker 6915 (4v) headers. Would I have to swap those to 2v, too to use the aussie heads?

btw i am saving all original parts to be able to return to stock

just my 2 cents...   70 4V cost to purchase plus refurbish $$$, same for 2V aussie [I just had a set done $3,000, all good parts] 

So I would keep the 73 4V, fyi you can have them redone with 4V CC valve sizing, yes just had a guys head done.  he had a 72 & 73 CJ heads [miss match]

The 70 intake is a good one, for performance check carb to intake bores  ... 750 carb square bores are 1 11/16, 70 .  can be bored out to size of cab ...   The L looks like a square bore but is actually a spread bore ;^)

Open chambers just need more compression.   If you have newer pistons you can just order news pistons same size.  YES custom pistons will be about $1,000 - 1,200, BUT if you do the math for 70 4V CC heads ...   FYI, JE Pistons has what is 'in stock', or made to order.  So they are not completely custom, just pay a couple of dollars per change, bore, move the pin to fit rods, pressed pin, set compression etc...   the ones you'll want are the Boss 302 pop-ups   with your changes.  

Get to keep and use OEM parts too ...  with more Vroooom

 

pic D3-head, 70 L intake, aussie 2v cc

edited to add Boss 302 pistons in a 351C 

no talk actual things DONE

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You can bolt on a set of closed chamber heads to your factory 73 351-4V engine. The '73 was the first year with dished pistons, which reduced the compression further than the open chamber head alone,

What Hemikiller said and nothing to be lost, gains from idle through max RPM. Consider a .030 MLS head gasket for more gain in compression. If you are concerned about deck and head surface being too r

By the time you buy the Aussie heads, have them machined and the valves/springs/retainers replaced, you could spring for a set of aluminum.  FWIW, there's nothing wrong with the 73 4V heads. The

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Cleveland guys have old motors... the more you deck the heads/blocks and bore cylinders to just fit a piston will kill their longevity fast ...  adjust the piston to fit the motor you have.   jm2c

Cheeper than I thought...    retail plus YOUR changes [samples of what they have].  find one close to what you need then alter.  My JE's started with 351C flat top changed bore to 4.005, moved pin for long rods, had top cut for custom dish & set compression for a 4V '4' 61.5cc heads.  

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On 10/24/2020 at 12:23 AM, Hemikiller said:

/) Another "quick" fix is to replace the timing set with one that allows you to advance the cam 4° to compensate for the retarded timing ground into the factory CJ cam. 

Rereading this can I avoid changing the timing set (and still regain the 4 degrees by simply going to a different (earlier?) cam?

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8 minutes ago, Animal Lawyer said:

Rereading this can I avoid changing the timing set (and still regain the 4 degrees by simply going to a different (earlier?) cam?

The 72-up cam is ground with 4° of retard built in, The simple and easy solution is to swap the timing chain set to an adjustable one with a +4°/0°/-4° keyway on the crank sprocket.  

 

https://www.summitracing.com/parts/sum-g6621r-9/make/ford

 

 

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13 hours ago, Hemikiller said:

The 72-up cam is ground with 4° of retard built in

I understand the idea of the adjustable timing set, what I am trying to understand (more for my own understanding and education than anything else) If I switch to a 1970 or 71 cam (which I infer does not have the 4 degrees of retard ground in) do I avoid having to use the variable timing chain set? And (follow-up question) if that is correct, what advantage is there to the chain solution over just changing the cam (which I expect I would do anyway to maximize power)?

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47 minutes ago, Animal Lawyer said:

I understand the idea of the adjustable timing set, what I am trying to understand (more for my own understanding and education than anything else) If I switch to a 1970 or 71 cam (which I infer does not have the 4 degrees of retard ground in) do I avoid having to use the variable timing chain set? And (follow-up question) if that is correct, what advantage is there to the chain solution over just changing the cam (which I expect I would do anyway to maximize power)?

The 71-74 Q-code (351CJ) cam is a long duration cam with specs of approx 205/220 duration @ .050", .480/.490 lift. The specs are identical for all three, with the '72-up cams being ground 4° retarded. Using an adjustable timing set "makes" your 73 cam into a 71 timed cam. 

The 70-71 351-4V M-code cam is much smaller cam and to my knowledge, no one manufactures that specific grind anymore, in favor of the 351CJ or an aftermarket offering.  

Yes, you could swap cams, but you're doing a lot more work for no real gain if the intention is to keep the factory 351CJ cam profile. If you're looking to swap to an aftermarket cam, then there are hundreds of options.

FWIW, 351C engines are tough on timing sets due to the heavy valvetrain. A new timing set will be needed regardless of which way you go. 

351CCamData.jpg

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10 minutes ago, Hemikiller said:

Yes, you could swap cams, but you're doing a lot more work for no real gain if the intention is to keep the factory 351CJ cam profile. If you're looking to swap to an aftermarket cam, then there are hundreds of options.

FWIW, 351C engines are tough on timing sets due to the heavy valvetrain. A new timing set will be needed regardless of which way you go. 

Thank you, I plan on doing the chain anyway, just like understanding.

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