It was the fall of 1999 when I took my Trans Am out to Gingerman raceway in South Haven, Michigan. I had spent the summer building a suspension, as well as upgrading the rear axle and disc brakes to 1LE bits. I had my race tires on and headed out to the track. My 305 has always been reliable, but I soon discovered that 15 years and 125,000 miles had taken its toll on the radiator, engine seals, and valve springs. The motor flooded the top-end with oil, which cascaded past the old valve cover seals. The radiator boiled over after only four laps. The engine couldnt make power past 4500 RPM. I couldn't even overtake a little Miata! I could, however, out-corner and out-brake everyone. I decided then & there to begin saving for a new engine. It was a two-stage plan: A short-term fix for the 305, followed by a long-term fuel injected stroker motor that could make about 400 horsepower.
Well, the original plan was for a TPI engine that used the "soon to be released" Scoggin Dickey intake manifold with aluminum Fastburn heads. However, Scoggin Dickey delayed the release. In the mean time, I picked up an externally balanced stroked 383 engine from Andrew Gunnesch. Sitting right there, next to the engine was this very pretty TPIS Miniram... I had to have it! Suddenly, project creep began to set in. The Miniram would enable me to rev the engine much harder than any TPI system, so I had to make sure the short block was in good enough shape. What I found was an engine that, though equipped well enough for street use, needed a good line bore. I also accidently dropped one of the pistons and cracked the skirt. In the end, we discovered that the clearances on the bores required us to go to a +.040" piston. That's when project creep began to set in. The plan "evolved" from a 5000 RPM, 400 horse stroker motor, into a 6000 RPM, roller cammed, serpentine belt equipped, internally balanced 450 horse stroker.
Word to the wise: Once you decide what you want, stick with it. I have discovered that once you pass the boundary of 1 horsepower per cubic inch, the costs rise exponentially. My modest 400 HP engine project has morphed into a nitrous capable, 6800 RPM Xtreme Street engine, and the costs are at least three times what I had originally projected. Not only have I invested in steel cranks, but I've had to buy stuff like titanium retainers to keep the mass of the hydraulic roller lifter from overwhelming the valve springs. I've had to look critically at balancing. I'll have to install a roll cage into the car. I had to upgrade the car's front brakes. Now, I'm not complaining. I'm just warning you that if you let project creep occur, you might as well throw out either your budget, or your build schedule.
Build schedule: You need one. When you decide to create an engine (or performance car for that matter), you need to establish two things from the beginning:
A statement of work, including a rough outline of the parts you need to buy, and a build schedule. The statement of work describes what you want the ending project to look like, such as "I want a 350 horsepower, carburated engine that costs $1200. It consists if these parts:"
A build schedule describes a time line on which you can realistically build the engine. The build schedule will be the guide that keeps you from getting distracted. Without it, you can easily lose interest in the project and have nothing to show but a garage full of parts. The build schedule is the document that shows you if you are getting behind or not. It is also the document that helps you keep pace with expenses. For instance, suppose your engine is projected to cost $4500 to build. Suppose your disposable income is $300 a month. At that rate, the projected date of completion will be a minimum of fifteen months. In those fifteen months, you will need to design, buy, and build the shortblock, the heads, and the valvetrain. You'll have to assemble, and test. Some things have to happen before other things: For instance, you cannot choose the proper size combustion chamber on the cylinder head until you have decided upon your target compression ratio, and have determined the volume above your chosen pistons when assembled and sitting at top dead center. Thus, you cannot order your cylinder heads until your shortblock design is well underway. Well, I suppose you can go about it the other way, by ordering the proper piston (either dished, flattop, or domed) to make the proper compression ratio with a given size combustion chamber.
Well, enough of my ramblings on engine design. You are probably on this page looking for pictures and ideas, so here they are!
This is the serpentine system with detailed miniram body. When I took this photo, I had done only the yellow powdercoat. I've now finished the pulleys and brackets in textured black. The TPIS miniram has been polished to a high shine, and yellow powdercoat placed on the fuel rails, TPIS inlays, and the finned inlays of the plenum. The fins on the fuel rails have been polished to mirror finish. The alternator was completely stripped, powdercoated, and built into a 140 amp heavy duty unit. The picture shows the cooling fan as yellow. I didn't like it, so I stripped the coating off and refinished it in textured black. In case you are wondering, the parts are sitting on some junkyard heads, and my spare "010" block, which I sold and will be delivering to its new owner on March 8th. |
This is the engine mockup, before powdercoating. I was trying to visualize what it would look like in yellow. The heads are AFR195 castings from Air Flow Research. They are equipped with a 7/16 stud option, L98 angle plug option, 68cc chambers, centerbolt valve cover option, and L98 coolant sensor option. I am porting them myself and AFR is sponsoring the flow testing. Details can be found here. |
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This shortblock has a 4340 forged steel crank from Dallas Export Sales. It also has 6.0 inch 4340 forged H-beam rods, also from Dallas Export Sales. Pay attention to the clearance points in the picture. There are as many as three points per cylinder that may need clearancing. This means you MUST assemble, and run a piston/rod combo through 360 degrees of piston travel in ALL locations. Do this after machining, but before cleanup and cam bearing install. Use a set of junk babbit bearings for the rod. Allow 0.040 inch clearance at all points so that if you spin a bearing, your rods will not make contact with the block. |
| This engine is set up with a complete Comp Cams valvetrain, with exception to the roller timing chain. This Manley chain features roller thrust bearings on the cam button and the cam gear face. The camshaft is a custom Comp Cams hydraulic roller retrofit grind based on the XE-series hydraulic roller cam lobes. Lobe separation angle was specified at 112 degrees, and the cam is installed on a 108 degree intake lobe center. Cam specs as follows: 230/236 @ .050" lift, 112 LSA. |  |
| Here is that aluminum timing chain cover that you see all over EBAY these days. I got it for around $25, after shipping. It needed some grinding in order to clear the cam thrust button, but it's plenty thick so it's rigid enough to keep that cam in place. There is about .010 to .020 inches of clearance right now between the thrust button and the cover. |  |
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The TPIS Miniram was initially owned by Curt Martin, who sold it to Andrew who sold it to me in July of 2000. It's equipped with a 58mm throttle body, 30 lb injectors, and integrated nitrous spraybars. |
Here's the nitrous spraybars. They are copied from Compucar spraybars, I believe. I'll be capping them off for now until everything else is sorted out. |
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Minirammed 385 project specifications:
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How do you design an engine? It's really a good question with a million right answers. For starters, ask around and see what other people are doing. During the summer of 2000, I looked at Lingenfelter motors, TPIS motors, and a host of tuned-port engines. I heard that TPIS was having good luck with 10.75:1 street engines by using AFR aluminum heads. In addition, I read about this carburated Lingenfelter 383 CID engine that made 475 horsepower and 450 ft.lbs of torque. (HPBooks, John Lingenfelter on Modifying Small-Block Chevy Engines, ISBN # 1-55788-238-X, page 157). This is where I got the idea for my engine. If I could get a fuel injected engine to behave with a comparable camshaft as the solid roller used in the Lingenfelter engine, then maybe I could get comparable performance results. |
Bottom of shortblock picture goes here. |
For a stroker motor to be internally balanced, one must either fill their counterweights with heavy metal, or else get a custom crankshaft. I decided to go with a steel crank from Dallas Export Sales, who also matched and balanced the connecting rods and Lunati lightweight pistons. Subsequent checks here showed the crank to be nice and straight, but the big-ends of the rods needed to be resized. Since I had the time and tools, I installed a windage tray and crankshaft scraper to assist in oil control. |
Profiling the engine on Desktop Dyno2000
| There's a lot of hype on whether or not Desktop Dyno2000 can accurately predict power levels of an engine. I guess "accuracy" is a relative term. Can DD2000 get within two percent of the projected power output? No one at DD2000 has been able to answer my questions. However, I will be dynoing the engine on a water brake dyno, and hope to see how close the simulations match the real world. I've flow tested the cylinder heads to make sure that they match the simulation. I've also degreed the cam, and double-checked its profile to insure that it matched the published specifications. (It does.) I'll be CC'ing the cylinder head, as well as the volume above the piston to make sure that I have an accurate compression ratio in the simulation. Then, once I've gathered the data, I will publish it HERE to that I can answer the question of accuracy with QUANTITATIVE data instead of qualitative data. | |
| One problem I have not been able to get help on is how to accurately model a TPIS Miniram. I decided that it was most like a single plane intake manifold. |  |
Here are the tabulated results. The data is based on my most recent airflow data, as well as the cam specifications of my Comp Cam roller retrofit profile. Are those torque numbers believeable? |
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Page last modified: February 26, 2003