1971 Turbo Gremlin

I purchased my 1971 Gremlin in December 1970 at Holiday Motors in Memphis, TN. I had decided to buy an American compact car but the Ford Pinto and the Chevrolet Vega were underpowered with four cylinder engines and not very good cars. The Gremlin had a large, powerful, six-cylinder engine and looked different, sort of cute. Who would have thought that I would still have the Gremlin 35 years later.

My first modification to the engine was a Geraghty Dynotune kit in 1972, the article in Motor Trend said it gave a 30% power increase and it felt like it, really made a difference you could feel. The Gremlin came with 13 inch wheels which were too small so I put 14 inch wheels on it in September 1978, they came off of an AMC station wagon in a salvage yard. The next modification was a set of Clifford headers in 1979, really a good addition, picked up two miles per gallon in gas mileage and definitely had more power. Nineteen eighty-two was a big year, I added a Competition Cams 252 High Energy cam, an Edelbrock SP2P intake manifold, an Accel coil, and a Mallory distributor. More power and it didn’t hurt the gas mileage. In the suspension department I had added an AMC front stabilizer bar and an ADDCO rear stabilizer bar in 1973 along with gas shocks. By this time the power and handling were much better than stock. I also added a Carter 2bbl carburetor for even more power. I ran this package for the next nine years, in 1991 I noticed that my oil pressure was low so I pulled the pan and found that the front cam bearing had “flaked off” and was causing a pressure loss. The engine had 250K miles on it and was in great shape but since I had to change the cam bearings I decided to rebuild the engine. I pulled it out and took it to Cabot Automotive, a shop that did a lot of high performance work, mostly on Chevys. They installed hardened valve seats in the head along with dual Chevy valve springs, the block was bored .030 and Keith Black hyperteutic pistons were installed (8:1) along with high quality rings, bearings, etc.

I had subscribed to Dick Datson’s AMC newsletter for a long time and in the early 1990’s he started talking about adding turbochargers to the AMC engines, it seemed like a good idea and a fairly easy way to get a substantial increase in power. The best thing that ever happened to do-it-yourself mechanics in Little Rock was the U-Pull-It salvage yard on Baseline Road. I went out there from time to time to look around and had found a number of parts for the Gremlin. One trip I saw a 1985 Merkur XR4Ti with a turbo engine, after thinking about it for two or three weeks I went back and got the turbo and started thinking about how I could install it on my engine to make a turbo Gremlin. One friend at work had a piece of six inch angle iron that I could use for a mount and another friend had a well equipped shop so after a Sunday of drilling, grinding, and cutting I had my mount. The turbo is water cooled so I had to run coolant to it from the heater hose, I also had to run oil to it from the tap at the rear of the block and fabricate a return line that went where the mechanical fuel pump had bolted to the block. Next I installed a Carter electric fuel pump good for 7-8 lbs of pressure. On the first test run I found out that when the boost matched the pump pressure the engine quit running so I traded it for a Holley 14 lb psi pump with a pressure regulator. Then I had to figure a way to limit the boost to about 8 lbs psi. I did that by installing a spring on the wastegate actuator shaft that opposes the strong spring in the actuator, by adjusting the spring pressure I can control the boost. To direct the air into the carb I found a bonnet off of a Chrysler product with a Mitsubishi “hemi” engine, it had the same 2 5/8” neck as the Carter carb. There wasn’t enough room in the engine compartment for an air cleaner so I mounted a “box” air cleaner from a Dodge Daytona under the right front fender. I ran the exhaust from the manifold under the oil pan and up to the turbo which is mounted to the head and timing cover at the front on the passengers side of the engine. I completed the turbo installation in October 1995. The Carter 2bbl ran OK but never was really satisfactory so I installed a Holley 500 cfm 2bbl carb in March 2001 and it solved all of the problems and has performed flawlessly. Just recently I installed a Mallory “rising rate” fuel pressure regulator so I can run less pressure to the carb but the pressure will increase as the boost goes up so the fuel won’t shut off. I had hoped this would eliminate some of the fuel pump noise but it didn’t help much. I had to drop the fuel tank and add a fuel return line, the tank was in great shape after all of these years.

Dick Datson ran a story and picture of my installation in the January/February 1996 issue of “21st Century Turbo” and it was featured on the Turboforce web site for a while.. I received numerous e-mails from people about my installation and answered a lot of questions. I’ve always wondered how many people actually installed the turbo and got it to work.

I received an e-mail from one guy that said he completed his installation and took it out for a banzai run and collapsed the ring lands on a couple of pistons. Didn’t hear from him again but he said it took off like a rocket until the pistons failed. One thing for sure, if you’re going to run serious boost you need good pistons. I read somewhere that stock pistons are good up to seven pounds boost and that’s it. I run about eight pounds of boost and figure I’m getting well over 200 hp and lots of torque. I do have to run premium gasoline or it will ping under boost. They make spark retard units but I haven’t decided to invest in one yet. If I ever decided to try for maximum horsepower I’ll have to get one.

A couple of other things I’ve done to my turbo Gremlin that really improved performance. Probably the best thing I’ve done is install front disc brakes from a 1978 Concord. The original drums were marginal at best when stopping from high speed. I took the whole disc brake system loose at the ball joints, I also got all of the brake lines, the proportioning valve, and the master cylinder with power booster. It transferred with no problems and stops like an anchor. This past January I had 3.55 gears installed in the differential and they improved acceleration tremendously. After driving all of those years with a 2.73 gear it feels like it needs to shift one more time.

There may be more modifications in the future but I don’t have any planned. The weak link in the system may be the BW aluminum transmission, it has been a good trouble free transmission and ran 250K miles before I had it rebuilt. It was used behind the 304 so it can handle some power and torque but I don’t know how much. If it fails I would like to use a Torqueflite but the 1971 engine has the small bell housing and the TF won’t bolt up to it. Guess I’ll cross that bridge when I come to it. Actually, I’d like an OD transmission since I have the 3.55 gears.

1 reply
  1. Matt
    Matt says:

    Hi. My name is Matt. I live in Kenosha WI, The Hometown of AMC. I own a 1979 AMC Pacer Limited Hatchback. It has a Code C 258 I-6 motor 2 bbl with a torque command auto transmission with a column shift. Rear axle ratio unknown at this time. The car is brown and tan.
    I found this thread about the Turbo Gremlin to be a fascinating read! I too had subscribed to Dick Datson’s magazine some 20 years ago. I think I still have them somewhere.
    I love all AMC’s deeply, and maybe someday I will also have an AMC Gremlin to go with my AMC Pacer.


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