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97 Cobra Engine Rebuild

Old 04-03-2006, 01:01 AM
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Default RE: 97 Cobra Engine Rebuild

You can also see in the picture the factory flashing, which was polished off. Here are a couple pictures to show the before and after finish.


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Old 04-03-2006, 01:14 AM
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Default RE: 97 Cobra Engine Rebuild

On the intake, they will be expanded as needed on the heads to match the IMRC plate and Intake Manifold. The goal is to get a seamless transition from Intake manifold to cylinder.

On the exhaust side, the goal is to polish them to inhibit carbon buildup. Also, I want to open them up on the top to create a more straight shot from the exhaust ports. What I do not want to do is touch the bottom. Most of the gas will flow along the top as it is turning out of the head. I need that to match the header for a smooth transition. I want to leave a lip on the head side so the gas goes from a little port to a big opening, which will enhance the performance of the system. I believe this is called a reversion dam... but basically, it helps prevent the pressure wave that travels back up the tube from entering the head, and thus the cylinder. Here is something I found:

"...A reversion dam in your exhaust port to eliminate exhaust from reentering your engine through the exhaust valve during valve overlap. A reversion dam also increases air flow and port velocity, and is designed to broaden the engine’s power band."

This seems like a good thing to discuss, but for now, I will leave it at that.

Here are some pictures of the exhaust, before and after:


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Old 04-03-2006, 01:29 AM
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Default RE: 97 Cobra Engine Rebuild

I just received a buch of parts for the car. One piece that goes well with the head porting is the long tube headers. There are a lot of choices out there, but after listening to a lot of what people said, I went with the BBKs. One thing I don't like much is the "dent" they put into the headers to make room for the steering shaft... But, for the price, what can I say? From what I understand, they perform well, but regardless, they WILL perform MUCH better than the factory cast iron manifold. Here are the headers, and here is the "dent":

As for the rest of the engine, all the work has been done to it and it is ready to be reassembled. Once I get these heads finished up, I'll be bringing them to the shop to have the valve job done and then reassembled. Meanwhile, I'll reassemble the shortblock.



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Old 08-23-2006, 02:45 AM
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I've received a few PMs about this particular post so I have decided to post an update for a couple reasons, one is to bring this back to the front so it can be read, and the other is to complete it.

Since the last update, the block has been completed by the machine shop, and reassembled, heads finished and installed, transmission attached and installed and the whole thing jammed into the engine bay. Well there is more to it than that of course, and a lot of little sticking points I should probably cover... in due time.

The block assembly. I used the original crank (cobra forged) and Manley forged H beam rods and forged pistons (flat top). The original dish was about 3 CC so the increased Compression Ratio is mild. Again, this will be for a 10PSI boosted engine.

Originally, I had planned on replacing the oil pump gears with billet ones. However, I was unable to get my hands on any, so I chose the crygenically treated oilpump from Modular Mustang Racing, part 400350 (http://www.modularmustangracing.com/)In my opinion, the treated metal pump will serve the purpose I plan to put it through without failure, and it was about 130 dollars cheaper!

I did replace the stock trigger wheel with a billet piece from Sean Hyland Motors (http://www.seanhylandmotorsports.com/) since this seems to be another common failure part.

The engine assembly was pretty straight forward, torquing to specified values, and taking my time to ensure every bolt was in the right spot and torqued properly.

The next step was installing the heads that had just had the new valves installed. I used ARP studs instead of bolts. Why? I figured it is probably easier to pull the to remove a head instead of trying to do it in the car. If you ever think you might need to pull the heads with the engine in the car GET BOLTS, NOT STUDS. Also, don't even think about reusing the ones you just pulled out, they are torque to yield and have been damaged (by design to hold better). I torques the heads to 65 ft lb following the original torque pattern.

It is best not to put the rockers in before you mount the heads since you will need to take them out to time the engine. You can install the cams prior, but I found it easier to just do it on the engine (learned the hard way, of course). Also, when mounting the heads, set the crank keyway at about 10 oclock and make sure none of the pistons is all the way up (don't want to bend those nice shiney new valves!)

There are a lot of fancy tools you can get to time the engine, but all I used was a big bar, a screwdriver, and muscle to get them all in. First, install the cams and torque the covers, use LOTS of lube. Next, set the cams keyways straight down. Align the timing marks on the chain to the two timing marks on the sprokets. The timing marks will be at the top. Put the sprokets with the chain onto the cams and put the bolt in (torque later). Next, install the inner crank pulley with the flange out! You want maximum separation betweent he cogs when both are on the crank. Match the timing marks on the chain to the ones on the cam sproket and the crank sproket. Repeat for the other side and your engine is back to factory timeing... I'll leave degreeing to someone else.

Now you need to install the rockers. There is a tool you may be able to get that is a specialized spring compresser. It leverages off the cam to comrpess the spring so that you can slip in the rocker. I used a long socket extension. First, though, install all of the lash adjusters. I started with the intake valves. I was able to put the extension under the cam and lever down the spring enough to slip the rocker under. Just lever on the main part, not any of the lobes. For the exhaust, I slipped the follower under the cam, resting over the valve. Then I used a large screwdriver to pressdown on the spring while applying a little force to slip the rocker end over the lash adjuster. After each rocker was put in, I had to rotate the engine and cams to get the next set on a "not open" portion of the lobe. You will never get the rocker under if the high part of the lobe is down.

After all the rockers were in, I rotated the engine slowly to ensure there was no binding and to make sure everything seemed to operate properly.

Later, I'll talk about the IMRC plates, the intake manifold, the transmission, and other stuff. I'll try to get some pictures as well.


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Old 09-18-2006, 08:06 AM
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Default RE: 97 Cobra Engine Rebuild

Thanks for your extensive knowledge and professional advice on rebuilding your Cobra engine. It seems everything has changed since the "old days," especially the names we put on engine parts. What we used to call LIFTERS are now LASH ADJUSTERS (didn't lifters adjust lash, too?), rocker arms are now called "CAM FOLLOWERS," etc.

At Romeo (MI) Engine, we always built-up the heads as a complete assembly, and a robot placed them on the block (and torqued the head bolts down).

Bare head castings are assembled (in order) with the cam bearing caps unscrewed, and set off to the side, then valve seals, lash adjusters, valves, (all the spring components), cam followers, and cams were set in place. To finish head assembly, a robot put the bearing caps back on, and torqued them down. Then, all the parts were checked to make sure they were in place. All the tools used are the common ones we have always had, including the repair valve compressor, in case a keeper was missing.

4.6 2-valve head castings are completely interchangable from LH to RH, but the 4-valve castings are different from left to right hand. It is possible to put 4-valve heads on a 4.6L iron block. The sleeves in an aluminum block are STEEL (not cast iron; don't ask me why) and we BRUSH them to size with a Bosch wire brush after the hone process. That is why there is NO break-in period for piston rings. Pistons are kept in a constant temperature room for eight hours before they are gauged for size. Then, they are put in four size catagories. When we get an excess number of one particular size, we inform the block machining department to start BRUSHING cylinder bores to the size of piston we will use that day. Fuel injectors run the same way. They are stamped with a +, -, or left blank. That is how they come to Ford. So, we use all 'plus' injectors until our stock is nearly depleted. On the next shift we may use all 'minus' injectors, until they are depleted, and so on. We NEVER mix injector sizes or piston sizes in the same engine. It makes sense, because oxygen sensors sample an average, in the exhaust.

Years ago, when Romeo Engine was new, the bigwigs (at Ford WHQ) brought Red Polling's (CEO) Mark back, because the Romeo 4-valve Engine failed after a few thousand miles. It seems, nobody checked for wrist pin keepers, and this engine was missing a few. They check every one of them now, and have ever since!

I love the 4.6L, but I was really sad to see the 302-351 blocks go. I know they had "old" technology, and they were iron, but you just can't substitute for cubic inches. With all the things we do to a little 4.6, imagine what you can do with 5.8 liters. My Mustang is a red convertible (I watched my buddies put it together in Dearborn Assembly Plant), and I put a Lightening 351W in it. (AODE, 4.30:1 R&P, Performer RPM heads, 4,000 stall converter, General Kinetics cam, and totally electronic (fuel injected). This setup was designed to be driven daily, on I-75 and I-94, thru Detroit to Dearborn, 30 miles each way. What a sweetheart it has been. When the car was new, I put 3-chamber Flowmasters on, and it was 'kind of' loud. Then I built the 351W, and those mufflers quickly changed back to 'stock.' Because of the cam, it was so loud, I couldn't barely THINK! Forget listening to a CD.

I can honestly tell you that NONE of the new Mustangs that rolled off the line EVER beat this one. We frequently raced after work right in front of Dearborn Assembly Plant, so the 'guys' going home could see the race, walking out of the Rouge. Braging rights always followed the next day. My Mustang convertible is truly a sleeper. Typically, the convertibles are geared higher and they are SLOW on the street; not this one. The body may flex a little bit, but it really isn't bad. And when people see it, they just smile because it is really a FUN CAR to look at and even more fun to drive!
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Old 09-20-2006, 03:27 AM
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Default RE: 97 Cobra Engine Rebuild

asmall can u type my college papers for me?
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Old 05-02-2007, 04:00 PM
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Default RE: 97 Cobra Engine Rebuild

dannnnggg man your car is gonna be sick... Just a word from my clutches stay away from centerforce... They are for the most part crap... Killed a few and now i love my spec stage 3!!! King cobras are pretty awsome too but not for the kinda power your gonna be putting down... Laters
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Old 05-02-2007, 04:37 PM
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Default RE: 97 Cobra Engine Rebuild

ORIGINAL: bugpack28

dannnnggg man your car is gonna be sick... Just a word from my clutches stay away from centerforce... They are for the most part crap... Killed a few and now i love my spec stage 3!!! King cobras are pretty awsome too but not for the kinda power your gonna be putting down... Laters
Damn noob[:@]
But a very interesting article, especially about the meth injection which I went with
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Old 08-16-2008, 01:00 PM
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Default the rebulid

hey i am about to pull the motor out of my cobra and i was wondering witch way is the easiest with the tranny or with out ?
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Old 08-16-2008, 04:13 PM
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Sucks this thread wasn't finished. I've read it several times.

Now I just go to Oxs' Engine building thread...

Oh yeah, Damn Noob...
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