351 2V CLOSED CHAMBER BUILD

[howard2121 9]

Hi All,

 

Long time reader first time post.

 

Looking for help/guidance on a my 351 Cleveland build for a XT Fairmont.

 

Car will be 4 speed toploader and 9 inch diff 3:75 ratio.

 

I have OEM 2V closed chamber heads that I was thinking of using.

 

Looking to achieve 350+ FWHP

 

Is this achievable? What combos have others had success with using 2V closed chamber heads?

 

Appreciate your help in advance.

 

 

 

 

 

 

 

[gerg 10,875]

Good choice in parts thus far. I would at minimum, clean up the ports on the 2Vs as they can be pretty terrible in the casting. I did that on mine and despite only having only about 3 hours in them, I would guess that they're easily 10% better in flow. A properly cleaned up set of iron 2Vs should be good for 400hp.

Before getting them skimmed, determine what compression you want to run (thus chamber size) and pistons (stock rebuilders or good zero deck ones). The compression number hinges on what cam you are running by figuring out what dynamic compression you actually will have. I have said for a long time, pick your camshaft and build the engine around it.

Upgrade valve springs to suit cam specs, get heads done up and guides machined to suit press-on seals. Up to you if you get the rocker pedestals machined to suit stud mounted rockers, it does allow a bigger selection of rockers but there are decent pedestal mounted ones out there, namely Yella Terra and Scorpion. Stock steel rockers aren't a deal-breaker, they just work the oil harder and can't deal with much above 0.500" lift and/or high spring pressure.

Many folks on here have had good results with the Comp 268 and 274 cams, but for any cam aim for around the 220 mark at 0.050" give or take. I would save up for a retro roller cam in that range only because I've wiped 2 flat tappet cams on my clevo in less than 100,000 km. It's getting harder to find good oil to suit flat tappet cams now.

Your inlet manifold can be the stock iron 4 barrel, but if you can stretch to an Edelbrock air gap that would be a no-brainer. The other good name manifolds are probably only slightly better than the stock one (which isnt bad) but you'll save a lot of weight up top using them. Don't use cheap Chinese ones. They are poorly made clones and they rob the original designers of their hard work. Their cylinder balance will also be poor.

Using the hotrodder's rule for carbys, take target HP and double it to get the CFM you need. So either a 750 vac or pumper will be perfect. These are said to be the sweet spot for size in a square bore carby.

4-into-one headers are obviously ideal but are a tight squeeze in an earlier narrow chassis. Tri-Ys are a good compromise between stock manifolds and proper tuned length 4-1s.

1 horse per cube shouldn't be too hard in this day and age. If you do get it chassis dynoed though, don't be too disappointed by the figures. My 302 gets along ok but didn't even crack 200 hp. I know my cam is drastically holding it back for top-end power but I like the low and midrange it has.

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[howard2121 9]

Thanks Greg,

 

Appreciate your input. 

 

Regarding Compression I have read your previous posts on this but lack the confidence too say my working-out is correct.

 

I have contacted crow cams with some figures and they recommended Crow Cam - 21649 Hydraulic (see attachment)

 

What is the "magic" compression number...and how does one achieve it..

 

I have read a common mod for the 2V CC head is to fit 4V exhaust valves obviously this is to increase flow. Is it a value added mod?

 

At this stage my block is at the machine shop and has been bored to 4.030 (block from an XD Ghia).

 

I will also fit MSD (or similar) ignition and I have a Edelbrock 2V performer manifold on the way (a lot of parts are in low supply atm).

[gerg 10,875]

Thanks Greg,
 
Appreciate your input. 
 
Regarding Compression I have read your previous posts on this but lack the confidence too say my working-out is correct.
 
I have contacted crow cams with some figures and they recommended Crow Cam - 21649 Hydraulic (see attachment)
 
What is the "magic" compression number...and how does one achieve it..
 
I have read a common mod for the 2V CC head is to fit 4V exhaust valves obviously this is to increase flow. Is it a value added mod?
 
At this stage my block is at the machine shop and has been bored to 4.030 (block from an XD Ghia).
 
I will also fit MSD (or similar) ignition and I have a Edelbrock 2V performer manifold on the way (a lot of parts are in low supply atm).

That cam will be pretty lumpy but with your short gearing and relatively light car, it won't bog down like it would in some thing heavier with highway gearing. Just don't expect the car to be comfortable at highway speeds as you'll be sitting at around 3500rpm or so.

There is a calculator on the Wallace Racing site that does dynamic compression, but a ballpark figure for a 351 closed chamber would be 11:1 aiming for a dynamic of 8:1 after cam specs are entered. 8.5:1 can be used if running a fully programmable ignition to stay on top of the pinging issue.

http://www.wallaceracing.com/dynamic-cr.php

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[bear351c 10,412]

Ahhh, ok. Should have read this first. LOL.  What he said....^ ^ ^  Yes, 4v size valves are worth it. and at very least, grind the manifold/head/exhaust to the same size as the gasket. Basically "port matching".

[deankxf 20,937]

1 hour ago, bear351c said:

and at very least, grind the manifold/head/exhaust to the same size as the gasket. Basically "port matching"

 

is that the go on a clevo? i have been reading not to do it on many other engines.
 
 

[gerg 10,875]

 
is that the go on a clevo? i have been reading not to do it on many other engines.
 
 

I think the 4V issue is on the inlet, not exhaust side. Plenty have done that though, so maybe even that's not an issue as such, but maybe considered just not worth it?

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[howard2121 9]

Hi Bear,

 

Thanks for your input as well,

 

Sorry about the message and then the addition of the topic, Greg doesn't accept direct messages lol, added the topic hoping he would answer.

 

Greg,

 

3500rpm on the highway no thanks. I will need to revisit the cam.

 

Great input, I really appreciate it.

[deankxf 20,937]

22 minutes ago, howard2121 said:

3500rpm on the highway no thanks. I will need to revisit the cam.

 

diff ratio dictates the revs at 100kmh  see below. 

7 hours ago, howard2121 said:

 

Car will be 4 speed toploader and 9 inch diff 3:75 ratio

 

is it a 3.75 ratio diff ?
2.75 is the highway standard standard gears most LTDs etc got, they'd have you doing about 2250rpm at 100kmh.  (make sure the cam choice is ok to cruise on that if so)
3.7 (not 3.75) would be doing about 3000ish from My calculations at 100kmh.  

 

your 3.75 number doesn't sound anything i've heard before. so probably should confirm what it is.

 

 

[gerg 10,875]

Hi Bear,
 
Thanks for your input as well,
 
Sorry about the message and then the addition of the topic, Greg doesn't accept direct messages lol, added the topic hoping he would answer.
 

I am happy to take messages, but I'm on Tapatalk (phone) so dunno if website messages come through.

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[bear351c 10,412]

6 hours ago, howard2121 said:

Hi Bear,

 

Thanks for your input as well,

 

 

 

 

 

Very nice......  

[bear351c 10,412]

7 hours ago, deankdx said:

 

is that the go on a clevo? i have been reading not to do it on many other engines.
 

 

The castings from 1970 were average at best, if you stick a standard inlet gasket onto a small port Clevo head you'll see what I mean. I'm not talking full port and polish, just match the inlet port, to the manifold, exhaust port to the extractors, using a store bought gasket. It's not hard work, just a lick with a die grinder, its free HP...

 

Unshrouding the valves is great if you know how, but, not for the beginner. The hours involved in getting all 8 ports to flow similar, and the added weight of cast iron, just cheaper to buy an aftermarket head. They weren't around 25 years ago, so keen builders did what they could. Nowadays you can grab some AFD, CHI, or SCM heads. 

[gerg 10,875]

 
Unshrouding the valves is great if you know how, but, not for the beginner.

Vizard did an episode on valve shrouding and it's interesting to see his view on it. He takes the bare minimum to achieve the results and no more. It's all in where you remove metal and not how much

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[bear351c 10,412]

True. I've watched a few of his vids. I'm guessing that Mitch is a new builder, and not keen to start drilling out a head. 

[howard2121 9]

17 hours ago, bear351c said:

True. I've watched a few of his vids. I'm guessing that Mitch is a new builder, and not keen to start drilling out a head. 

Well yes a new engine builder BUT a very experienced boiler maker welder by trade and a lot of hours spent on the die grinder . I have all the carbide bits and have been looking in to doing the clean up myself, especially when many hours are needed. Vizard?? I guess this is a youtube post??

 

[gerg 10,875]

David Vizard has been a prominent author of performance books since the 70s and is a successful race engine builder and performance guru. He's been around since before aftermarket parts were a thing so knows how to squeeze every last bit of performance out of factory parts while at minimal cost.

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[Outback Jack 6,352]

Gerg is right, Vizard is a head working legend.
When you get right into his head work you realize HOW smart he is.
He was into 2L pinto motors in the 70's.

It's not all about just grinding stuff out, any dill with a die grinder can go that... And muff it up.

It's about the approach angle of air and velocity at the back of the valve.
Sometimes metal or resin is added to the port to change the approach angle of the air.
Then you want to go further its valve relocation. That's how it's done properly.

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[howard2121 9]

On 12/17/2021 at 1:54 PM, gerg said:

I would save up for a retro roller cam

 I'm leaning toward the roller... Options soooooo many options.

Maybe I'm overthinking it...A standard 351C will feel like a rocket after driving 3.0 TD Nissan Patrol (daily driver) .

[howard2121 9]

5 minutes ago, Outback Jack said:

It's not all about just grinding stuff out, any dill with a die grinder can go that... And muff it up.

Love it..

 

Case in point

 

 

[howard2121 9]

So.. I got my heads out and pulled them apart. good news is they have already been ported. Regarding the photo of the exhaust bowl is the hole supposed to be there?

[Thom 6,708]

So.. I got my heads out and pulled them apart. good news is they have already been ported. Regarding the photo of the exhaust bowl is the hole supposed to be there?

That hole is for the exhaust srossover that runs under a stock intake for manifold heating/egr valve, if you're using an aftermarket intake they will be blocked off

[gerg 10,875]

So.. I got my heads out and pulled them apart. good news is they have already been ported. Regarding the photo of the exhaust bowl is the hole supposed to be there?

Looks like a very light tidy up, only taking off sharp edges around the bowl, short turn and guide. Still, an improvement on stock for sure.

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[bear351c 10,412]

You'll be happy with a warmed over Clevo. Don't overthink it, just carb, cam, inlet manifold, ignition and extractors.

 

Don't rev her over 5 grand, last for years and enough torque to pull a house. If you want to go racing.......well, that's a WHOLE different Cleveland.