Author Topic: 351C to Mock Boss 351  (Read 9110 times)

Jeff73Mach1

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351C to Mock Boss 351
« on: August 30, 2009, 10:01:02 PM »
Since the plans have changed, I wanted to update the thread.

Upon inspection my current short block looks to be in excellent shape and has probably had a recent overhaul.

I want my car to have more power and a distinct sound and personality.  To that end what I am trying to do is make it similar to a 1971 Boss 351 engine.

I have a set of 1971 Quench chamber heads and have had them rebuilt with one piece stainless valves with a 3 angle valve job and I have had them fitted with guide plates and adjustable studs.  The shop that did them builds Busch Car Series, Nascar, and drag race motors- they did a beautiful job, but painted the heads black-I'm pretty sure it was a slam on me building a ford, but it is one that was easily repaired with a can of paint.

Camshaft is a Competition Cams 282S with solid lifters and I have hardened pushrods to replace the originals.  I went ahead and got the cam kit with a double roller timing chain and adjustable sprocket.

I am using Felpro Gaskets throughout with the exception of the header gaskets.

Stock exhaust manifolds are being replaced with Hooker headers.  1 7/8 primary tubes running to a 3" collector, reduced to 2.5 inches to match the true dual exhaust in place at this time.  I'll piece the current set up together as it is in good shape.  To facilitate fitting the headers I swapped to a gear reduction starter from Napa for a 92 Ford Bronco with a manual transmission.  Fit like a champ! 

To improve the oiling, I am running a line from the front galley plug to the rear and using a fitting to allow both the oil line and the oil sending unit to fit at the rear of the block.

Initially I am going to retain the dual points distributor, as I don't want to introduce any additional variables into the initial start up and cam break in procedure.  Once everything is broken in, I will eventually upgrade to a Performance Distributors DUI ignition.

I will use the Edelbrock Torker intake off my current motor with the Holley 4150 700 CFM double pumper.

I expect with the dished pistons to have a reasonable 10:1 compression ratio.

The car is my 73 Mach 1 with a factory 4 speed and 3.50 gears.  I recently installed an 11" Centerforce dual friction clutch and am hopeful it will handle any amount of horsepower I am likely to throw at it.


Jeff73Mach1

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Re: Going to build a new 351C-looking for suggestions
« Reply #1 on: September 23, 2009, 01:58:32 PM »
Update on my plans and progress.

I have sourced all the parts for my heads and am only waiting on the valve springs before I take them in to be built.

I decided on a Comp Cams 282S (solid lifter cam)

I was hoping to keep my existing engine together til I rebuilt the spare, so I changed the rear main seal and found the following

Rear main seal was installed BACKWARDS
Current engine is a 4 bolt main
Main bearings are standard and show no wear
From underneath it appears as if the cylinder walls are in excellent shape and the pistons have no signs of scuffing or other noticeable wear

SO . . .

I am going to swap heads and install the new cam and a set of hooker headers.  While it is apart I will go ahead and put a new water pump on it.

For right now I am going to let it be fired off by the original dual points distributor because it works so well and I am sure of the ignition system and I don't want to take any risks before cam break in, but after that a DUI Performance Distributor is still in the plan.  I'll probably go ahead and add a 95 amp alternator while I have the current one off, even though it looks to be a recent replacement (darn show car guys buy the original crap even when there are better parts available)

Camquest6 predicts horsepower at 520 @6000 RPM and torque at 475 @ 5000  More importantly the curves are fairly wide.

I am sure it is optimistic (as it helps sell cams) but if I actually had 400hp at the rear wheels, I'd be way ahead of where I am now.

If anyone sees a problem with anything mentioned, please shout out and let me know

jethat

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Re: Going to build a new 351C-looking for suggestions
« Reply #2 on: September 27, 2009, 02:35:11 AM »
Go to this board here
http://www.network54.com/Forum/119419/
Those guys are the Cleveland experts they will tell you the right stuff to do..

Tim175

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Re: Going to build a new 351C-looking for suggestions
« Reply #3 on: October 20, 2009, 11:49:30 PM »
i just dropped my 351c off at the machine shop yesterday ;D having hardened seats put in and new valves etc. they're also maging and boring my block. once i get it back im putting in a new cam, new pistons, and all that fun stuff and then ill be set haha.

Soaring

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Re: Going to build a new 351C-looking for suggestions
« Reply #4 on: October 21, 2009, 06:07:13 PM »
I have always wondered the advantage of flat top pisons over dished pistons.  How about some enlightment here. 

Jeff73Mach1

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Re: Going to build a new 351C-looking for suggestions
« Reply #5 on: October 23, 2009, 10:28:45 AM »
Flat top pistons are not always better, but for the sake of trying to answer your question

Flat top pistons increase compression over dished.  As I said, Flat tops are not always better, increased compression can lead to detonation.  But increased compression generally will lead to more horsepower too.


This is probably more than you wanted but

A 351 Cleveland can be built with one of 5 basic sets of heads

Quench chamber or closed chamber heads increase compression by having a smaller combustion chamber.   Almost all quench heads will have the large 4V intake and exhaust ports.  I say almost because the Australians did build some smaller ported 2V style heads with quench chambers.

Then there are open chamber heads in 2V and 4V configuration. 

All heads being discussed are 2 valves per cylinder  the 2V and 4V designation is for the original carb type associated with the head.  4V heads have huge intake and exhaust ports.  the 2V heads while still large are not nearly as extreme.

Finally there are the aluminum heads in pretty much all of the above configurations and combinations of the above.




Quench heads with the increased compression, you might think would be prone to detonation, however the flame front upon ignition travels differently in chambers as the chamber shape is changed and the quench heads actually detonate less than the open chamber heads.  As I generally understand it the flame front in the open chamber heads  sort of bounces off itself creating detonation, where as the closed chamber heads flame front is "Quenched" by the minimal space between the piston and the flat area of the combustion chamber and pushed all in one direction generating more power before detonation begins.

For this to work, however, the distance between the piston at the top of its travel and the bottom of the head needs to be pretty tight.  A flat top piston still does not come to the very top of the bore necessarily.  Zero decking the block and other techniques are used to take advantage of the  flat tops with quench heads, but valve clearances can become a problem, requiring pistons to be notched.  You don't want to go too deep with notches or you can damage the integrity of the piston.

So it is all a balancing act of matching chamber shape, piston shape, deck height, valve clearance etc to make an engine produce good reliable power without detonation.  What works for a 351C with one style head will not necessarily work with a different style head or a 351W or a 302.  All engines tend to have combos that work better than others, but if you change to a supercharger, or turbo or nitrous or a heavier car or a different gear ratio, or an automatic vs a manual-what may be best for you can also change.




rmodel65

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Re: Going to build a new 351C-looking for suggestions
« Reply #6 on: October 26, 2009, 12:09:54 AM »
make sure to install all new valves in the heads so you dont drop one :P

ask me how i know

Jeff73Mach1

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Re: Going to build a new 351C-looking for suggestions
« Reply #7 on: October 26, 2009, 11:02:41 AM »
Thanks for the heads up.  I have a set of heads being built as we speak (type) with one piece stainless valves.  I know about the two piece ford valves and am driving the car with the current heads with a fair degree of caution while the new heads are being completed.  Hope to get them, the new cam and lifters and the new headers on in November. 

I may go to an aluminum water pump while it is apart and have a few other ideas in mind that I am trying to decide on.

Jeff73Mach1

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Re: Going to build a new 351C-looking for suggestions
« Reply #8 on: November 04, 2009, 03:41:12 PM »
Heads are complete, headers are in, I'll be picking all up tonight.  All I lack is a new water pump, thermostat, and gaskets and a warm place to work.

Jeff73Mach1

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Re: Going to build a new 351C-looking for suggestions
« Reply #9 on: November 10, 2009, 10:55:02 AM »
Thought I'd give an update here.  Before starting this head and cam swap my engine had developed a ticking noise in one bank and was not producing quite as much power.  During the tear down, I pulled a push rod out that the ball end had collapsed back in on itself making it way too short.

Piston tops are clean and bores look good.  Recently changed the rear main seal (It was installed backwards!) and the rear main bearing looked great.  As best I can tell the engine was recently gone through and has std bore and standard main bearing diameters.  There was no ring groove at the top of the cylinders, so I have elected not to rebuild the bottom end at this time.

Still need to check valve to piston clearance as the new cam has .570 lift, but with factory dished pistons and stock valve sizes, I'm expecting to have plenty of clearance.

Hope to finish up getting everything back together and tuned as well as getting the headers hooked into the exhaust system in the next few days.

rmodel65

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Re: 351C to Mock Boss 351
« Reply #10 on: November 10, 2009, 05:35:29 PM »
make sure to upgrade to some 1 piece pushrods :P

jethat

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Re: Going to build a new 351C-looking for suggestions
« Reply #11 on: November 10, 2009, 09:05:23 PM »
Thought I'd give an update here.  Before starting this head and cam swap my engine had developed a ticking noise in one bank and was not producing quite as much power.  During the tear down, I pulled a push rod out that the ball end had collapsed back in on itself making it way too short.

Piston tops are clean and bores look good.  Recently changed the rear main seal (It was installed backwards!) and the rear main bearing looked great.  As best I can tell the engine was recently gone through and has std bore and standard main bearing diameters.  There was no ring groove at the top of the cylinders, so I have elected not to rebuild the bottom end at this time.

Still need to check valve to piston clearance as the new cam has .570 lift, but with factory dished pistons and stock valve sizes, I'm expecting to have plenty of clearance.

Hope to finish up getting everything back together and tuned as well as getting the headers hooked into the exhaust system in the next few days.
Sounds simular to my combo but I didnt go with adjustable valves.. I have the 4v closed chambered heads hooker comps and all. How did you do the rear main? in the car? Thats fun.. I did that to. Ended up pulling the motor the next year.. (lesson make sure your damper is good and the cranks keyway is in good shape.) Sounds like an interesting project it should make good power. Good luck!

Jeff73Mach1

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Re: 351C to Mock Boss 351
« Reply #12 on: November 11, 2009, 01:19:21 AM »
It's alive!  (sort of)

Engine is back together and cam is broken in.

Holy sh*% does it run!  Sounds pretty good but for the exhaust leak between the collectors and the muffler.  Hopefully this weekend I can get it into an exhaust shop for a bit of welding.

Valve float limits RPM close to 7,000 RPM I think, but it was so fast i didn't see the tach.  I wound out 1st and second gear without breaking the tires loose in just over 200 feet.

I did one obnoxious burn out through 1st, second and well into third gear that pulled my rear sway bar out of the bracket/ (one more thing to fix)

The bad news is the first time out the header burned into the starter cable and grounded out the electrical system and literally melted the negative terminal off the cable at the post.

Got that fixed and drove a bit more and when I stopped I had smoke coming from under the hood.  The fusible link was burning. out.  Searched for another short and fount that the battery hold down had eaten into one of the cables to the junction block.  No more light, but isolated it and tested and that was the remaining problem.  Will get a fusible link and fix it tomorrow.

So what's the downside?  Well vacuum is a bit reduced which affects the feel of the brakes with frequent use, but since I do not have A/C it isn't too bad.  I may add a vacuum canister if necessary, but for the occasional drive, it isn't a big deal.  Other than that it was expensive and a bit of a pain at times when trying to get the headers installed, but well worth it.

Should anyone else go with flat tappet cams rather than hydraulic or roller?  I couldn't say, but for me it is the motor that I wanted.

Jeff73Mach1

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Re: 351C to Mock Boss 351
« Reply #13 on: November 12, 2009, 10:48:54 PM »
Everything is fixed and I am happy.

I'll probably add a crossover pipe as the exhaust sound isn't quite what I want, but I have super cheap mufflers on it right now and they may be giving it a bit of a tinny sound.  My tires are going to hate me!

jethat

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Re: 351C to Mock Boss 351
« Reply #14 on: November 13, 2009, 06:52:09 PM »
I'd go with the X-pipe makes a significant improvement over the H.. Did on mine noticeable difference.

Soaring

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Re: 351C to Mock Boss 351
« Reply #15 on: November 13, 2009, 06:55:42 PM »
I agree...The X pipe helps your engine breathe a tad better, giving you a tad more power, plus helps the "decent"  ;D mufflers sound a bit more throaty. 

Jeff73Mach1

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Re: 351C to Mock Boss 351
« Reply #16 on: November 18, 2009, 01:43:30 PM »
Well I took your suggestion . . . sort of.

I replaced the entire system from the headers back using magnaflows and an stainless x pipe.  2 1/2 to the headers (it was 2 1/4) and 2 1/4 out (was 2) and some nice polished stainless rolled tips to give the pipes a better appearance at the rear.

It sounds so much deeper and better and the shop I used did a beautiful job.

Power was already excellent after the work, so it is hard to tell if it improved any further, but it sounds just right.  No droning noise in the car, just a nice deep, mellow sound til the right pedal goes down a bit

Col

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Re: 351C to Mock Boss 351
« Reply #17 on: November 24, 2009, 01:04:22 AM »
Jeff your Mach sounds very nice. U got pics?? Can U get second hand bits for this model easy over there? Can't get anything here for this model unless I import it. Catch ya later.   

Tim175

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Re: 351C to Mock Boss 351
« Reply #18 on: November 24, 2009, 11:04:52 AM »
Have you dyno'd that beast yet? If so what were the numbers I want to know ;D

Jeff73Mach1

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Re: 351C to Mock Boss 351
« Reply #19 on: November 24, 2009, 05:02:50 PM »
No, not yet.  I'm still waiting on some weatherstripping to seal the hood to the cowl and the trunk lid as well as a gasket to seal the filler pipe to the trunk floor.  I really don't like the smell of exhaust fumes!

I want to put a few hundred more miles on the motor and perhaps change out the distributor before I dyno it.  I definitely want to check the plugs and see if the carburetor needs any adjustments.  Still a few nickel and dime adjustments and such that I just won't have time for in the next couple of weeks.  Heck I haven't had time to really drive the car in the last 9-10 days!

I promise to get it dynoed and share results and I'll go ahead and predict some numbers right now

RWHP @6000  > 400
Torque @ 5500 > 450

 

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