Supercharged Turbo Coupe
Latest Modifications for 2000
Well, finally starting to get the car back together. I'm sure those of you who know me could have guessed that there was no possible way that I could have just replaced the head gaskets and got it running, I have to try to make it BETTER!! I needed to start somewhere so I began with the blowers, I'm not sure what there is to be gained here, but it would be nice to try to get a little more efficiency out of them, both adiabatic and volumetric. Here's what I did....
I started by clamping the blower housings to the mill (my third favorite tool; first - die grinder, second - 10 lb sledge, ...) and using an end mill to open up the blower outlet port to what I felt was acceptable. Realize that with these modifications I am shooting from the hip, I will not really know if any of this is useful till I get it running, so you SC tbird guys take this mods with a grain of salt ;). As you can see in the right photo I removed the bolt bosses which are located in the outlet. My intent with all of these modifications is to increase the peak output of these blowers, with no concern for increase in noise or a possible slight loss in boost pressure at very low speeds.
These two shots basically show what I did to the inlet of the units. Once again, shooting from the hip, I spent an evening studying the blower timing in the shop and decided that this is the modification that I was going to make. In the left hand photo you can see a comparison between the inlet of a stock housing and my modified inlet. I just basically enlarged it slightly and removed the sharp edges.
After completing the inlet, I turned my attention back to the outlet to finish it up. Using my die grinder and a carbide burr, I put a nice radius on both sides of the outlet port, then smoothened it even more using a sandpaper roll.
On the left, you'll see a comparison of the stock outlet port and the modified one. After a little bit of gasket surface cleaning they are back together and ready to hit the strip. I did have to shorten the two bolts that extend into the outlet port to prevent them from reducing my new flow area. As soon as the new engine valves get here, we'll get them installed, get the heads bolted back on, and get this thing running again.
Now that the blowers are done, next thing to address are the heads. I planned a couple simple, yet time consuming modifications which hopefully will gain the SCTC a couple more HP. I would have really liked to just get started with a nice set of after market aluminum heads, but that's not in the budget for at least another year, so we'll just have to see what we can do with these heavy iron castings.
On the left is a quick comparison of the old 1.84/1.54 Manley Pro Flow valve configuration compared to the new 1.94/1.625 Manley Severe Duty valve setup which will be replacing the old valves. On the right is a shot of the material being removed from the exhaust valve seat to allow the new valves to be used.
Shown here is a view of a completed exhaust seat on the left and completed exhaust and intake on the right. I used 4 angles on the seat, 30 - 45 - 60 - 75 to blend the combustion chamber into the port. You can see in the intake port, at the bottom of the 75 degree cut, the material which will need to be removed to completely blend in the bowls. Following this valve install I have to spent several hours with my favorite tool - die grinder - and several trips to the flow bench to determine the final port modifications I will make to these already slightly modified iron GT-40 Heads.
In these photos you can see the difference (0.100") between the new and old intake valves.
The differences in the exhaust valves are without doubt more apparent. The new Severe Duty valves have a larger angle on the back of the valve head and no undercut stem like the Pro Flows have. The undercut stem on the Pro Flow was designed to increase the area through the throat of the valve seat when the valve is open, which it does, but this does not mean that it will increase flow in every application. I'm not going to dive into that right now, but lets' just say that undercuts are not necessarily the correct valve for my application. Hopefully I'll have photos of the completed ports and new flow data posted shortly.
The work done to the intake consisted
of nothing more than blending in the bowls, and reworking the area passing
between the push rods. I feel there is still more to be gained in the intake
if I felt I wanted to pursue it. The exhaust port was quite extensively reworked
to achieve the numbers posted here. The exhaust port flowed very good up to
0.300", above that it began separating from the port floor and without more
material available in the port walls for porting, the separation could not
be completely removed. It is interesting to note that by adding clay to the
exhaust port floor while flow testing, essentially raising the port floor,
the exhaust flow was able to be raised to 180+ CFM. Anybody know of any epoxy
that will stay attached in an exhaust port? :).
Expect some photos of these completed ports to be posted shortly.
Well, here are a couple crummy photos of the current ports, I just can't seem to get any type of good lighting on the port to get a decent photo, but these will have to work. The two shots shown here are of the intake port in these GT-40 iron heads. Nothing really special was done to the intake except pay close attention to the short side radius leading to the valve and open up the area of the port which passes between the push rods. This was good for approximately 20 CFM over the previous configuration.
The exhaust in these heads is what I was actually concerned with, I was looking to get as much improvement here as possible. This port is a tough one to work with though, I probably made no less than 10 trips to the flow bench with minor changes each time to get the port to where it is. Virtually every section of it was enlarged and the short side radius required considerable reworking to get some flow out of it. If you want to know what hurts this exhaust port the most - look at the photo on the right, place a vertical line through the center of the valve guide, throw the right half of the photo away and mirror the left side onto the right - you'd then have a good flowing exhaust port :). These exhaust ports in these cast iron heads are always limited by the fact that they virtually all have - and need - engine coolant flowing between the intake and exhaust ports. The after market aluminum heads can get away with less coolant between the ports and therefore can have more port area in this critical spot.
On the left is the complete intake
valve and the exhaust valve is on the right. The intake and exhaust valves
have had a secondary seat ground on the back of as well as the edge between
the seat and margin broken to enhance flow. The intake valve has a sharp edge
on the combustion face to attempt to prevent reverse flow while the exhaust
valve has had a full radius machined on it, which blends the combustion face
into the margin, to help air flow into the exhaust port. Notice the nice SWIRL
POLISH on the backside of the intake and exhaust valves. I hope I don't
hurt anyone's feelings by saying this, but this surface finish has absolutely
nothing to do with airflow as some might believe, swirling air or whatever.
This swirl polish was actually developed in the aircraft industry many years
ago to reduce the stress risers on the head of the engine valves which caused
a radial fracture (and failure) of the valve head. As you might imagine this
was normally a pretty serious failure in an airplane so, the swirl polish
was developed to prevent this failure mode, and if it did fracture, it would
hopefully not mean a complete engine failure. The after market probably started
using it because it looks cool. Hey, at least I think it looks cool ;).
Oh well, enough of that, time to get these heads back on the car and get this thing running again. reassembly photos to be posted as soon as they are available.
Well, winter finally made it to the Michigan area of the country, so my high spirits of being able to drive the car soon have dissipated as well... There has been a slight change in plans, and the engine and transmission have been yanked out of the car. I though it might be a good idea to get a set of forged pistons in the SCTC's block and freshen/upgrade the tranny a little. The last time out with the TT Capri this past summer resulted in a broken C-4 input shaft. I'm not really looking for any failures midway through next summer that can be prevented now so here's what I have in mind.- Basically I intend to upgrade the pistons - possibly lower compression ratio slightly more, finish the cylinder heads, install them with a set of head studs, and install an after market input shaft as well as additional clutch plates in the C-4. Here is a quick look at what I've been doing lately.
On the left is a quick shot of the pistons I will be using in the SCTC, it is an off the shelf TRW - Federal mogul Power Forged piston with advertised 13 cc dish. After a quick cc'ing of the dish as shown in the right side photo the dish was determined to be 11.8 cc. Unfortunately this dish is not quite large enough to produce the desired compression ratio, so some machining will be in order. I am still working on a model of the dish to be machined into the top of the piston, but hope to have it done as well as the piston machining early next year.
Many of you folks may already know, but for those of you who don't, there are a few major benefits for using CAD modeling such as this for a piston top (or design of a million other things). The first, for this application, is that you can easily measure distances and material thickness, internal to the part to be sure that the proposed machining will not interfere, or cause weaknesses, with other features in the piston, like the top ring groove. Another useful feature is the ability to measure complex volumes, such as a piston dish, with just a couple mouse clicks. While these features are handy, the most important one is found during the next step - machining the dish.
On to the next step - machining -
thanks to a bunch of help from a felllow ford nut, Jim Sheren, the project
continues. Using Pro-Manufacture, Jim had the machining code from the model
finished and loaded into the milling machine in less than an hour. If you
are not familiar with this process, don't ask me, I don't know enough to even
be dangerous, well maybe a little dangerous....;). Just kidding... Basically
to throw it into a nutshell, Pro Manufacture builds on the Pro-E solid model
that was used to do your design work. It allows you to create volumes which
are to be machined away from the work piece, creates the code to be exported
through a post processor to the machine, and even is able to do virtual machining
(on screen) showing the cutting tool and work piece so you can preview the
results before ever cutting a chip. While this is an extreme simplification
of the system, guys like Jim make it look almost that easy, while in reality,
to machine with it - and make good parts - requires skills in both operation
of the software as well as machine you plan to use it on. Fortunately once
it's set up, all you have to do is change parts and press start, even a monkey
like me can handle that - and that's about where I come in... Following are
a couple shots of the machining.
First and second cuts were 3 mm deep each, as you can see in the left hand photo, this was about as deep as the original dish was, but the D shape was cut into the portion of the piston where there was no dish. The right hand photo is where the hogging became a little more serious and the dish really began to take shape.
The final cut, photo on the left, was only .5 mm deep and brought the dish to it's final depth of 6.5 mm. On the right is a shot of the finished dish, from here all I did was to break the sharp top edge with a piece of sandpaper and then touch it off with a soft wire wheel. Cycle time (machining time) per piston was approximately 25 minutes. If these parts could have been machined in one of the larger machining centers with better fixturing, that time probably would have only been several minutes per piece.
Finally a comparison between the old piston top and the new dish. The dish cc'd out to 31cc's and the weight of the piston dropped by 50 grams ;). Now to get them back into the motor.
Wow, never got a change to see this intake while the engine was out of the car, short would not be a good word for it.
The engine is almost back together, just have a couple critical valve train components to put in there and it will be ready to drop back into the car. It went together quite nicely, the cam degreed-in right on, and just had to spend a little time setting the valve spring heights to get exactly what I needed. I am still running a single spring (although crane recommends a double for this cam) but after some analysis work I feel they will be OK, but very close to their limit. If they fail, I guess there will only be me to blame. I still have to freshen the tranny and add that second fuel pump/lines, but it shouldn't be too long before I get this thing fired up again.
Whew, finally got all those parts stuffed back in there. Here it is just before being dropped back into the car, the transmission shield is a CSI piece and is wrapped around a fresh C-4 now sporting a hardened input shaft and 10" 3000 RPM converter. I feel the slightly smaller converter might make a nice compliment to the slightly bigger camshaft. Guess we won't know for sure till it makes a trip to the track, but I did keep the old 11" converter just in case ;). Also seen in this shot are the reinforcements which were made to the blower brackets, they worked satisfactorily last year, but figured a little additional improvement in this area was worth the effort.
These photos show some of the new plumbing on the car for this year, I didn't have too much trouble going through tech last year, but did get an occasional frown on the intercooler supplies. Besides being legal for almost any fluid, this Aeroquip stuff looks much nicer. The car is now equipped with two fuel pumps and 2 6AN supply lines. The shot on the left gives the location where one of the supplies and the return pass through the shock tower, the other supply is located on the rear of the tower.
Looking good installed in the cleaned up engine bay. While it may not look much different, the engine compartment was cleaned, painted, and rewired before the engine was reinstalled. I'm currently working on finishing up the new crankcase breather system for the engine, and reworking the blower outlets to fit under the hood, as soon as that is done we'll be getting it back to the track for some tuning.
It's all back together and running, well it was, at least for one day.....a good portion of haste and ignorance on my part put it back in the garage again for a while though. First of all, the blower mods seemed to work as expected, with the old blowers I was making about 14 psi boost and now with the modifications boost was about 16 psi, unfortunately I didn't have enough fuel for that boost level, even for the one short throttle opening to see how much boost it was going to make. I have since changed pulleys to attempt to lower boost back down to the 13 psi range. Second, I think we actually found the real cause for the lack of fuel (after the second blown head gasket), the car had inadvertently been jacked on the aluminum fuel supply line in the torque box area and was crushed almost shut, undoubtedly the reason for the numerous trip to the track last year without problem then suddenly a detonation problem....
Shown in the right hand photo is my crankcase breather and oil separator, I wanted to ensure adequate crankcase ventilation as well as try to keep any blow by from oiling down the engine. Not sure how well it work yet, but maybe we'll be able to get a fresh set of head gaskets in it next weekend and put some more miles on the car. A second fuel pump has been added and is PWM controlled by the TEC II in reference to manifold pressure and engine RPM, basically it allows me to run just the quite in tank pump at idle and cruise, and then have the second pump be modulated as necessary to maintain fuel pressure as boost/RPM increase.
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