Improved 351C 2V (H code) motor on a budget

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Sly_drums

Well-known member
Joined
Aug 13, 2011
Messages
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Location
Grenoble, France
My Car
72 Mustang Grande / 351 Clev. 2V + Weiand XCelerator intake + Holley 600 CFM carb
Hello guys, my Mustang is a Q code Grande but the original 351C CJ 4V motor has unfortunately been swapped long time ago, for a stock 1972 351C 2V motor coming from a Ranchero. Transmission came with, original FMX has been replaced by a C4.

Since one year I own the car, I tried to improve the performances of the motor by doing the following :

- new long tube headers (Hooker Comp)

- new 2,5" Pypes dual exhaust with x-pipe

- new aluminium Weiand single plane intake and Holley 600 CFM four barrel carb

Now it's not the fastest car on earth but it drives good, especially between 2800 and 4500 RPM with the 3.25:1 axle.

I think this combo provides around 240-250 hp at the wheels when tuned right.

Here's a video of me driving around :

Sly's 72 Mustang on the road, stock H code 351C

Question is : I'd like to increase its power, my goal is something like 350 hp at the wheels. Is this possible ?

I think this car would be fun to drive with such a motor.

Conditions are :

- I need to keep the 2V heads because I don't want to get rid of my actual exhaust and headers ; or maybe getting aussie heads that provide same exhaust port size ??

- my motor is 40 years old so I'll have to replace the worn out parts.

- the new motor needs to be streetable and has to provide good torque @ low RPMs, and good top end too of course.

My thoughts about this is that it' will be no problem but I can't figure how much it may cost ?? I read somewhere that just a hotter cam and different intake will do the job, but if I go for such an upgrade, I want the new motor to be reliable and will for sure replace all the used parts in it.

I'm trying to list the parts I'll need :

- hotter cam kit, which one ?

- improved valve train, which parts ?

- forged pistons and rods ? Is it vital for reliability ?

- good electronic ignition ? which one ?

- bigger oil pan and pump ? which one ?

- new intake ? I thought about the famous dual plane Edelbrock Air Gap

- bigger carb ? Or maybe keeping the Holley 4150...

- 3.50:1 axle ratio switch ? Not sur about that. 3.25 sounds good to me already.

What's your opinion on this ? How can I improve my H code motor ?

How much do you think it can cost for just the parts ?

Thanks !

 
Though I am still learning about the Cleveland myself, I know what I can do with a Windsor. A 351w with 224/232 hydraulic roller cam and Edelbrock heads will get you 400 flywheel HP. Seeing as the Cleveland heads are suppose to be superior, a similiar cam should get you in the same, if not more, power. I always liked the 224/232 dual pattern or 226' single pattern. For carb, I like Holley or BG deamon 700-750cfm with vac secondaries. Ive always had good luck with MSD or Accel distributers. I think 3.25 gears woukd be OK, but I would opt for 3:50:1 gears personally. And the Air gap intake woukd be great for your application.

 
Sly,

When you say you want more "power", it would help to know at what RPM you want this power?

I don't want to insult your knowledge but in most cases automotive performance modifications comes down to compromises to get the desired results. It is true that a "hotter" camshaft could give you more power at a certain RPM but again it comes down to what RPM you want the power.

For example, if your cam is making its "Big" power at 4500 RPM and you are doing a LOT of highway driving where you want to go "FAST" and not "QUICK" (there is a difference), your current camshaft with a lower (Numerically) rearend will give you a higher speed than another higher gear set. If you are into short bursts of speed where you want to go quick (such as 1/4 or 1/8 mile racing), going to a higher (Numerically) gear set is a better way to go until your cam runs "out of breath."

It should be noted that you may also be able to get "there" by going to a shorter or taller rear tire as a given performance can come down to your final drive ratio which is the combination (tire Size, rear end gear ratio, and transmission gear ratio).

In short, it REALLY is a science that begins with making a determination as to where you want to operate at MOST of the time. You can then run the formula to make an informed approach to the required modification.

As to valve gear, it is generally an accepted practice to order the associated valve gear with the camshaft selected. Forged pistons and deeper oil pans (and the like) are usually only necessary when you are turning really high RPMs.

A better ignition is usually always worthwhile, if you really want to spend some money:)

BT

 
I think BT gave you some very good advice. I wouldn't insist on a particular HP at the wheels, or anywhere else, approach. I'd rather focus on what you want the car to deliver in general terms. I want it to accelerate, better, a lot better, or a whole lot better. Temper that with practical considerations like cruise speed, RPM, mileage, level of effort, and budget. Bare in mind the effects of drivetrain loss. 350 HP at the wheels is about 425 at the flywheel. Plan on spending more on the heads than you think you should need to. I do not feel anyone should use the stock multi-goove valves on any kind of performance rebuild. The quality of the valve job does much to determine the flow especially at low to mid-lift values. The key to any good rebuild is using a very high quality machine shop that has the appropriate tools and experience to perform the tasks properly. Good cast pistons are fine for your application although the difference in price compared to speed pro forged is shrinking (the piston to cylinder bore tolerances are different for cast, forged, hyper). I'd keep the static compression ratio between 9:1 and 10:1. Pick a cam that is suited to your entire combination of parts (gear ratio, convertor stall speed, exhaust, SCR). If the 3.25:1 gear is used, convertor is stock, and SCR is 9-10:1 probably something like 216-220 intake and exhaust duration, .500-.515 intake and exhaust lift, with a lobe separation angle of 110 degrees. If you use the stock pan do not use a high volume pump. Use a stock volume pump and use an extra quart of oil in the pan. Use restrictors in the block to send less oil to the cam and more to the crank and rods. The performer RPM air gap is a good intake but is substantially taller than stock (hood clearance/ram air issue). The Edelbrock performer is available used at reasonable cost and is good to about 5500RPM, a bit more with some porting and an open carb spacer. This combination will not make 350 HP at the rear wheels, more like 290-300 HP at the rear wheels. It will make the car a lot more fun to drive, cruise OK at 75 MPH, and will not cost a fortune to build and operate. If you decide you really want the 350HP at the wheels with the 2V heads you will need to have them ported by someone who has lots of experience with 351C 2V heads, buy a convertor with a higher stall speed, strengthen the C-4, use a more aggressive cam matched to the heads, single plane intake, larger carb, a lot more RPM, better oiling system, and an adjustable valve train. The combination will not like the 3.25-3.50:1 gear ratio very much. This approach does not fit my idea "on a budget". Given what you've written, I'd go with the first option. Let us know what you decide to do. Chuck

 
I also used Camquest (by CompCams) to not only help select a cam, but to also help decide what I wanted to do to the rest of the engine to get to the 400hp range.

According to this site, a 274/274 @.566 lift cam, with 9.5:1 flat tops, roller everything (including 1.73 rockers), Edelbrock 600 cfm carb & Performer Dual-Plane intake, Hooker Long Tube headers, running stock 2V heads with mild port work, should put mine right at 401hp on pump gas (estimated at the crank, I'm assuming).

Budget-minded? Not so much. I'm about $7500 into my engine now and very close to finally hearing it run. An old adage: Speed costs - how fast you can go depends directly on the size of your bank account.

Will I ever dyno mine? Nope. Will I ever race mine? Nope. Will I ever push it over 100? Doubtful... but maybe once or twice after break-in.

So why am I doing all that to my engine? Because I can.

Good luck with yours.

 
1. I would DEGREE your cam. You can do this by removing a valve cover. This will let you know if you are running a stock cam, a milder than stock cam, or a wilder than stock cam.

2. You need to find out what your current compression ratio is. I don't know how to do this while the motor is in the car and while the heads are on the motor. Typically, you decide on what compression you want, measure the CC of your heads, and then purchase a piston to match your compression.

With this information, you can have a better idea what your starting point is.

 
Good point about "type" of power. 1st of all, I never think of having to wind a V8 past 6000RPM. 2nd, I thought I read 3.25:1 gear ratio. That wasn't screaming high RPM.

As far as the pistons, forged really is cheap insurance.

 
As I recall, you just installed the intake and carb (or was it someone else?) Play with the cam numbers and rear end ratio. If memory serves me right you can do about .450 lift with .260 without spring changes and a 3:70 rear I'm pretty sure would make that smile even wider at about 5200 rpm

 
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