Carb'd Twin Turbo Capri

The good old NA 302 before being replaced with the Twin Turbo 351W

That's Al with a rear view of the Capri.

    I guess a good place to start is with the car.  It is a 1983 Mercury Capri 5.0. As seen in the pictures here, this was prior to the installation of the TT351W.  The car has most of the go fast necessities including the 8pt roll bar, 5pt harness, drive shaft loop, etc. The car had a fastest naturally aspirated pass of 12.29 @ 113 MPH using a flat top piston 302, Comp Cams 294S solid cam, 1969 302 cylinder heads w/ 1.94 intake valves and 1.60 exhaust valves, Torker II intake, 1.5" diameter $89.00 blackjack headers, Holly 600 vac sec (stock carb), 4.10 gears, 5 speed, and shifts made at 7500 RPM.
    Trick Flow Twisted Wedge heads were added during the spring of 1997 along with 1 5/8" full length headers and no other modifications. ET worsened to 12.70's and 107 MPH. While the heads did allow for a nice drop in weight, we sure lost power. These trick flow heads and 1 5/8" headers were just a little too much for an already great running low cost combination. Expensive lesson learned, hopefully our last.

On to the Twin Turbo Motor!!!

     It was during the summer of 1997 the my 85 Twin Turbo Bird was smashed. Al, his wife, and my wife, were all standing in my yard as I came home from work that friday night. Al and I were planning to work on my house that Saturday, do a little work on the bird Saturday night an then run the car at the Super Ford Extravaganza, Milan MI on Sunday. Unfortunately as I turned into my driveway I was hit from the rear which totaled the car.
    I think it was that day that we decided the motor had to find a new home, and soon. The easiest option was to pull the current 302 out of the Capri and drop in the twin turbo. We began the swap the next week and completed it in a few days. The first time out at the track we were plagued with several problems stemming from some of the changes we made to the system during the Capri installation and only managed high 12's.

 Getting ready for another pass beside a sharp looking stang!

    A week later we were back at the track, giving it a shot again and made out much better, 11.50's @ 118 MPH! The car felt OK, it wasn't as fast as we expected it to be, but it had a miss we blamed it on the used spark plug wires we were using. We made about 12 passes and called it a season, this was the last test and tune for 1997.
    Winter arrived and the wrenching bug started again. Al decided that he was going to remove the stock heads and headers and replace them with the Trick Flow TW heads from his 302, hoping they would be better suited for this larger displacement motor, and a set of unequal length BBK shorties. I remember getting a call on a Saturday afternoon, "Hey Mike, I pulled the heads off, and eh, we've got a problem, A WHOLE CHUNK OF THE #8 PISTON IS GONE,..... and ...... THE EXHAUST VALVE IS BENT BIG TIME!?!?!". I kinda though our MPH was a little on the low side, it had run as fast as 117 in the bird so we expected at least 120-122 in the much lighter capri. Well it was definitely time for a set of forged units and a complete rebuild anyway.

The limit for a stock cast 1972 351W piston is 12 psi with a 8.3 :1 CR and pump gas.
We have now tested and confirmed this, you need not try this at home.

    We took the block to "Richart Rebuilding" in Coldwater MI to have it bored and honed .030", a new set of cam bearings and soft plugs installed, and the crank cut .010/.010. Dale, the owner and operator, does absolutely fantastic job and we were very satisfied with the machine work. Meanwhile we spent quite a few nights performing the necessary modifications to the new BBK headers and touching up the new heads.  The TFTW cylinder heads received a light pass with a sanding roll and a little bit of chamber work to enlarge the combustion chamber from 61 cc's to 65 cc's.

Click here to see the FLOW DATA for the cylinder heads!

     A new set of Federal Mogul - TRW Power Forged pistons with 27 cc dishes were installed in the freshly machined block. These pistons along with the 65 cc combustion chamber heads yield a fairly boost friendly 8.2:1 Compression Ratio. A new Crane Cam with specifications of  216/228 degrees duration and .484"/.515" lift was slipped between the banks and the cylinder heads dropped on.

What do you mean, your tired? It's only 4:00 AM on friday morning,
heck we only have one more day of real work before we can wrench all weekend!!!!

Starting to look like a motor now.
You can see here where the Turbo oil drain backs are located in the oil pan.

Here are a couple shots of the remaining engine assembly.
The new headers we are using are a set of BBK unequal length 1 5/8" shorties, modified for upside down installation.
To see how much better these headers flow compared to the stock mustang shorties, go to FLOW DATA

Headers are done, time for the intake and valve covers.
The rocker arms are Crane Cams units with a 1.6 ratio.

That about wraps up the wrenching on this project at my place, we then loaded
the engine into Al's truck and installed it in the Capri at his house.

    The maiden voyage to the track with the freshly rebuilt 351 TT. Although he's smiling we still had some problems and never got a chance to make a full pass. Unfortunately the tranny (C-4) was no match for the new found power of the motor. While it worked fine on the street for the drive to the track, it would just slip in third gear with slicks under full boost. On the street it just blows the tires away at any speed in any gear so the problem did not surface until the first pass down the strip. So far in the quarter mile it has managed a 12.78 @ 86 MPH, and 7.3's in the 1/8 at 88 MPH clearly showing that we are out of second and slipping in third before the 1/8 mile. Last year with a broken piston and mostly dead cylinder due to a badly bent exhaust valve our 1/8th mile time was 7.4's at 96 MPH. Hopefully we will be in line for low 11's before the year is over.  We are planning on rebuilding the tranny this weekend, (July 18, 1998) and have it back to the track on Wed night for test and tune. New times to be posted shortly!

The Transmission Specialist,  hmm, I wonder where this goes???

    We got into the C-4 transmission as planned on the weekend and found a cooked set of forward clutches as well as a hardened and broken O-ring in the forward apply piston assembly, the remainder of the tranny looked good but as usual we replaced everything anyway. Hopefully Al and his brother Abe will be able to get the tranny back in the car by Wednesday so we can have it at the track Wednesday night. As we were assembling the tranny, Al commented "Yea, let's get this this thing to the track on Wednesday so we can replace the broken rear next weekend".  Some things will never change.


    The Capri had been brought to my house the previous weekend so I drove it to work all week to attempt to resolve the transmission bugs as well as some tuning issues we had. The transmission problem turned out to be nothing more than too much boost reaching the modulator. We simply removed the hose and backed out on the adjustment screw to solve the problem, now the transmission requires shifting for all gears with no more auto operation. No big deal right? it's still pretty tough to miss gears anyway. I also found another more significant problem while driving it for the week, it was lean under boost, on the order of 16 to 1 A/F with 10 psi boost.
    We (Eric and I) started work early Sat. (9/26/98) to try to resolve these problems which had been found the previous week. We raised the carb jets from 68s to 71s and raised fuel pressure to the additional injector by 10 psi. A quick blast down the street revealed that we were at 13.5 at cruise speed and 12.8 to 13 at WOT full boost. Now that we had enough fuel we also had more boost and unfortunately detonation. Boost was now at 14.5 psi, up from 11, and we were now beginning to see a little color on the outside of the chrome header pipes. Initial timing had to be lowered to 0 degrees to control detonation with pump gas. The car now felt extremely strong and it was about 2:00 Sat afternoon so Eric and I tossed a set of 26x8 slicks in the hatch, hopped in the car, and headed for the track to make some passes.
    Unfortunately, we arrived at the track only to find that the track officials did not feel our firewall separating the fuel cell from the passenger compartment was adequate and we failed tech inspection. Quite bummed out we hopped back in the car and headed home contemplating what we needed to do to make this thing legal.


    Tuesday night Eric stopped over and we got working on the new improved fire wall.

Now the secret is out!!! Everyone now knows why the capri runs so well!!
It's the flux capacitor!!
Also shown is the fuel cell we are using with our old firewall removed.

A view of the business end of the Twin Turbo Capri.

The new firewall was constructed of .030" steel and completely seals the fuel cell from the passenger compartment. We
would have loved to use Al sheet but the budget didn't warrant it, guess we'll have to live with the extra weight. At least it is at the right end.
That's Eric taking some measurements and me drilling some fastener holes.


    Finally got the capri back to the track and passed tech. Look here for the results.


Al decided to drop out last weekend to do some wrenching so we finally back to getting some work done on the Capri. It had a nice long break over the winter in a cozy garage with only an occasional thrashing up and down the road when the "need for speed" hit us on some warm spring days. Unfortunately, it was on one of those nice days that the noisy 7.5 decided to let go with a horrendous "BOOM" so the first order of business with the car this year is to get a suitable rear end in it.

The new rear is an 8.8 out of an 89 mustang, but to make it legal for 10 sec fun in the capri we knew we were going to need a set of good axles and C-clip eliminators.  We chose a set of strange 31 spline axles and the accompanying C-clip eliminators. The above photos can give you a little better idea of the size difference between the 28 and 31 spline axles as well as a quick look at the eliminators, we decided to stick with the 4 lug axles for the capri.

Due to the limited street usage the car sees anymore, we felt a nice spool would help in the hookup and control department. While this car does see a couple hundred street miles a year it is no longer a daily driver in the sense of the word, it will be mainly driven to the track and around town just for fun. Rear gears are being changed from a 3.08 that we had in the 7.5" rear to a set of 2.73s in the 8.8 in an attempt to keep the car in the power through the traps, could we go 130+ MPH?,  I guess we're all waiting to see!!!!!!

The old upper control arm bushing have been torched out and the ends of the axle cut off. The instructions suggest using a hacksaw to remove the necessary material from the ends of the axle tubes but we held the rear up on the band saw to assure a straighter and quicker cut. The upper control arm bushings will be replaced with some polyurethane pieces. Hopefully in the next two weeks we'll have the rear assembled, back in the car and back to the track, we are patiently awaiting to see some time slips with the bigger tires we have for this year.


Just in case you're wondering what's up with the capri, she's alive and well again after a slight tranny problem. We actually took it to the track about 2 weeks ago and unfortunately it didn't survive the trip to the track. When we arrived at the track it only had second gear, the linkage inside the tranny had fallen apart due to vibration apparently, so we didn't get to run it. Some of the updates it received this summer was the new 8.8 rear filled with Strange goodies, 2.73 gears (it's a great highway cruiser now!), a new drive shaft, and a new set of 26x11.5x15 MT ET Streets mounted on 15x9 Weld Wheels. We hope to have it to the track this weekend so expect some new time slips shortly.

 More Coming Soon !!!

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