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Old 09/07/2007, 03:48 PM   #1

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347 "Wolf" in 302 "Sheep's" Clothing?

I was wondering just how a stock 302 (or 289), built into a 347 would work in a stock configuration in a GT/CS.

That is, when it's rebuild time, you choose to go the 347 route, but you retain the stock heads, intake, and 2 or 4bbl intake, depending if it's a "C" or "J" code engine.

From the outside, it would look totally restored, but inside it's 347. This would give an edge to accelleration and speed, giving GT/CSs an edge on the street/road. I want to see how we might make "sleepers" out of stock-looking engines when you open the hood. There are a LOT of the C-code GT/CSs out there--about 85% made were the C or J code. I think we need to make them "hotter", but retain the concours, stock look.

How would a 2bbl, stock intake,heads and even air cleaner--347 run? Would you get a noticable difference to make it worth the effort? Maybe port the 2bbl heads and intake, and/or switch to stock 4bbl heads? I'm thinking of how one might do this effectively, and yet look convincingly stock.

I know that a 4bbl would be preferred, but sometimes lower CFM can give great results. Is this a feasible idea?

thanks--Paul N.
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Old 09/07/2007, 04:27 PM   #2
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Don't know if this will answer your question or not but, consider this one -

I'm now running a 428 CJ (built to the hilt). All I have to do is change my air cleaner, take off my monte-carlo bar, put the factory air cleaner bucket back on my car and folks think it's a 390 again. What a snow job. The 390 and 428 both look the same. Same with the 289 or 302 built as a 347. As you said, sheep's clothing. That's exactly what I wanted with my big block. You can have your cake and eat it too at the same time. Since I've made the swap only 1 person at a show actually noticed I had a 428CJ. He actually took the time to check the casting number on the heads. Imagine that.

Now, to answer your original question about the 2bbl, stock intake, and heads, there is no way you would still get the same performance on a 347 stroker. Just ain't gonna happen. Most folks aren't gonna notice the difference between the heads and carb unless they are really into checking what you've got or know high performance pieces. Even with my engine swap and the mods I've done to my 428CJ, I can still make it look like a stock 390. That is until I start it. And even then folks really don't know. Imagine that. That's just my take on it.


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Old 09/07/2007, 04:33 PM   #3
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I was going down this route with my car when I discovered the VIN number matched block had a crack in the number 2 bulkhead all the way from the cam bearing to the main cap. Ended up throwing it away.

There are a couple of sources that will CNC port stock heads. They can flow as well as any aluminum head that has not been ported. The stock intake can be port matched and if a 4-barrel can flow good to 5,000 to 5,500 RPM. Basically a low RPM torque monster could be built that could easily achieve 400 hundred horsepower or a bit more. The have retro fit hydraulic rollers for the older blocks, so a cam selection is easy.

The one limiting factor to this build is exhaust. The stock manifolds will destroy the above thought. Hipo 271 horsepower K-code manifolds are a bit better, but I think they would limit the HP a bunch. Shorty’s or long tubes would need to be used to achieve max power and torque. I have seen pure stock drag articles where stock cast manifolds have been ported and honed to enlarge their passages. That may be a good try on a set of hipo cast manifolds. Maybe some one has heard of this somewhere. Lots of delicate cam head and port matching to achieve max on this thought.

I doubt a 2-barrel would work well with a 347 stroker. You could build a lot of torque and power, but it would run out of breath very low in the RPM range to make much HP. Could work, but seems like a waste to try this on an expensive stroker conversion.

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Old 09/07/2007, 05:02 PM   #4

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I think that this is possible...

Holley makes a high-CFM 2-bbl (500-600cfm?) that should work. After all, some Nascar engines use 2bbls, WITH restrictors, too! LOL!! It would look stock under the stock air cleaner.

The port matching of the intake and heads--as well as the honing of the exhaust manifolds sounds like a necessary thing to do. Cool.

More than one "rodder" has done this sleeper thing with an engine or two... What we need is to find someone willing to actually build one, going this route. It would be a real "first" in the Mustang world; something we could all learn from.

I'd like to see what we can come up with. This will be really cool.

Thanks for your ideas!
Paul N.
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Old 09/07/2007, 06:09 PM   #5
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Sounds like a cool idea to investagate, Paul. I have a line on a built Boss 302 engine and thought it would be cool to make a Boss GT/CS.

Don't mean to get off subject but; Back in 69 I remember racing a SS396, and beating him real bad. He was pissed that a little Cal Special kicked his butt that bad in front of all his Chev friends. When we pulled over and poped our hoods, he asked what I was running. As I ajusted my ram air I said, 289 hipo, prety fast isn't it.
Back then I don't think anyone had ever heard of the 428CJ, or one being stuffed into a California Special.

Sorry for getting a little off the subject, but I think you have a cool idea.

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Old 09/07/2007, 08:01 PM   #6
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I think if I wanted the 347 to look stock, I would put on a set of the '69 351W heads, with port work. Then use a good dual plane alum intake, grind the Edelbrock/Holley/whatever lettering off and paint it Ford blue so it looks like a stock intake. Use whatever 4 barrel you want. Use the stock air cleaner but install a taller filter so the lid has about a 1/2 gap all the way around--looks stock at a quick glance but adds air flow. You'd have to run Tri-Y headers, which wouldn't look stock but if you can keep a straight face, pass them off as a dealer option, since they are period correct. That would be my sleeper.


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Old 09/08/2007, 08:58 AM   #7
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interesting topic here Paul...its possible to have a 347 stroker that only makes 250HP to the wheels with "stock" heads...i know that...but i had hooker headers, msd ign, edlebrock alum intake and 4 barrel carb other than that it looked stock...but the lumpy cam sound lets people know its not stock....but i suppose if you had a really mild cam, going to a 347 would definitely increase your torque...but a stock 347 wouldnt be worth the money imo...i suppose you could compare it to a stock 350 in a chevy...those have pretty decent power when they are stock...i think a stock ford 347 would have even less power than a stock chevy 350
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Old 09/08/2007, 09:14 AM   #8
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Hmmmm...put Cobra valve covers and air cleaner on a Chevy would go with the 'vette door handles.!!!

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Old 09/11/2007, 05:33 PM   #9

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Originally Posted by Mosesatm View Post
Hmmmm...put Cobra valve covers and air cleaner on a Chevy would go with the 'vette door handles.!!!'re still "in so much trouble" for that Vette door handle idea thang, sir!! :-P


So--just to finish out this idea--those who know about a 347 are saying that if you used 351 heads, and a stock, ported 4bbl intake, you couldn't use (honed out) stock exhaust manifolds? Too restrictive to make the 347 worthwhile?

Are you saying that the engine wouldn't work, or that it wouldn't see it's potential without headers? Just for the sake of argument, if the innards are 347, and if you got away with a Holley 600-650; and if the outside looked 100% stock--it wouldn't run at all, or what? Would you end up wit ha lot of low-end torque, and no high end from the stock restrictions? What about the cam? Could one find a cam that would make this stock looking setup run smooth?

I don't mean to ask a zillion questions, but I'd just like to know if one could build a real sleeper, and (from a starting point as looking stock) that it would run smooth, until you stepped on the gas. I'm not necessairily looking for top performance, but a simple, small block that will give CS owners a setup that will give them the stock appearance, but a lot more torque off the line.

I ask this, because too many people have "thumbed their noses" at a 2bbl 289/302 GT/CS, when now, we can surprise them. The HP image of a GT/CS may never be the same from now on.

If a 347 is limited in a stock setup, say, at only 70% of it's potential, It may still be appealing to consider for future small block rebuilds.

thanks for your time helping me think this through,

Paul N.
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Old 09/11/2007, 06:25 PM   #10
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I'm not a 347 expert, having never built one. Joe or David would be the ones to check with but here's my thoughts. If I recall, you have to notch the block on a 347 for rod clearance. I wouldn't go to all the expense and trouble of a 347 build and then decide to choke it so it wouldn't see it's full potential. Stock manifolds, even honed out just don't flow well enough for high performance engines. If you want to restrict the flow just for the sake of looking stock, do a 331 stroker (which I believe doesn't require block notching) or just do a mild RV cam in a 302/289, and your modified exhaust manifolds with a big 2 barrel. Bottom line, wanting mild performance gains while looking stock and building a 347 are at opposite ends of the spectrum. It's like saying you want a rear end ratio that will pop wheelies off the line and give you 28 mpg on the freeway. Just my opinion.


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Old 09/11/2007, 06:39 PM   #11
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I like the idea of the edelbrock aluminum 4-barrel idea from Steve. Now lets go a bit more.

There is a class of racing for 2-barrel carbs only. In fact there are aluminum 2-barrel manifolds especially made for 302’s for this class. And you can get 2-barrel carbs in the 500-cfm range. Couple this with a roller cam that allows the ramps to be much quicker you could build a 347 stroker that sounds pretty tame.

Heads could be 351 windsor, but there are CNC guys out there working with 302 castings that flow just as well when ported and bigger (1.94 and 1.60) valves installed.

So yes you could build a 2-barrel or 289 casting with a hydraulic roller and aluminum manifold painted Ford blue that would flow well with a 500 cfm 2 barrel.

Now the trick is a set of hipo 289 castings that are honed and hogged to match. This in my mind is the biggest challenge and a lot dyno work involved. Once figured out with the proper cam match it could make easily 350/375 at the crank with a lot of low torque.

Certainly a viable sleeper project, but I agree with David. A lot of work and expense to build an engine with immense potential to only choke it back to be a sleeper. I guess if that is your goal then it is a doable project.

At the same time a Camaro with a 350 4 barrel would do just about the same. 350 hp at the crank is 1 HP per Cubic inch. Easy to do. “Owning a Chevy is like chrome plating a toilet handle”! It looks good but why did I spend the money??? Well I guess someone has to drive brand X!!! A long time ago an older mentor told me when I rode up on my Suzuki dirt bike….. “You know Rob, if those 2 stoke engines were any good, Ford would have them in a car”!!!! As you can imagine, only Ford’s were in his driveway!!!

I vote if you are building a sleeper use a 4-barrel like Steve says and give it some exhaust help. You could build a stock looking engine utilizing a roller cam to mask it and build some substantial hp. Enough to blow 350 and 383 strokers in the weeds!! A painted edelbrock RPM air gap or Victor junior under a stock air cleaner is hard to see!! The carb is totally hidden. Stock valve covers and a set of long tubes. At the drive in it would look so innocent. Now add a nitrous power adder on the underside of the intake with the forged pistons. Now you have 500 HP and above potential in a very innocuous package. A true Chevy stomper and the 347 is fully realizing its potential. And the idle could be very mellow with some quiet exhaust.

Man I think I should build one!!!

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Old 09/11/2007, 07:59 PM   #12

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RV and Bob--excellent comments and ideas!!

I guess if I push a questionable idea, I'd get some solutions. Thank you so very much!

These are great options for owners. I promoted the idea, not so much as a performance idea--but as a sleeper idea. Many people still want to go the stock route, but if the car's got stripes and a spoiler on it, I think it should have some sort of "GO" behind it. Even the 6 cylinder folks can use (non-stock) alternatives from a small blower to weber carbs; if not just a header.

Just porting stock heads and intake as well as honing out the exhaust manifolds is well worth it, not only from a HP standpoint, but for economy, too. Doing those things, and a mild cam can make a LOT of difference.

I like the 331 idea, and the use of 351 heads and a Ford blue painted alum 4bbl. intake. It's time to start thinking like hot rodders, and tweaking out what we have. This is the beauty of this site--to get these type of ideas "fleshed out".

Very cool! Thanks so very much. I'm saving this thread's comments for the book.

Paul N.
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Old 09/12/2007, 02:27 PM   #13
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David and I have been PM'ing about doing exactly this for my 289. I wanted low end torque and cam thump with completely stock (MCA occasional driver class) look. It is right that the Edlebrock can be ground off the intake and the 4 barrel can be hidden under the air cleaner. MCA dont take these pieces off and havent said anything.

For now, I am doing the torque part with a rear-end gear change and torque converter change (no one sees these).

As for the engine, I will make the changes next year, BUT there is one part I can't figure out to keep stock and that is the exhaust manifolds. Headers are great, but wont make MCA. I did read somewhere that Shelby did special exhaust manifolds for power - they look similar to stock, but they arent technically stock (but at least look stock).

It is the old "straw" analogy. You can suck a lot of air in with a big straw, but if it is restricted by pushing it out thru a little straw, you loose power. Dont know what to do about the headers part yet.


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Old 09/12/2007, 02:56 PM   #14
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Have you considered cast iron Hipo 289 exhaust manifolds?

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Old 09/12/2007, 04:44 PM   #15

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Yes, the Hipo ones are a good idea, although a sharp judge might know them.

I "think" the 351W exhaust manifolds are of larger diameter for each runner, compared to the 302 version. Not sure...

Due to the new '68 Smog specs, it wasn't possible (at least in Calif.) to get optional dealer-installed exhaust manifolds, such as the HiPo version.

There is this company, "Exude-Hone" that pushes this "silly-putty with grit" stuff through things like exhaust manifolds to scrape out the insides and smooth them out--and enlarge them. Like a Rotor-Rooter for engine parts.... I don't know how much it can cut out. Maybe up to an 1/8th inch larger size to stock diameter? There are limits on the amount of "meat" to the thickness of stock ex manifolds' metal to cut from....

This is the weakest link to this new idea...who can figure out what to do? Are there any car magazine articles (Pop Hot Rodding, etc..) that talk about doing this???

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