My friend Gregg recently bid on, and won, an Opel Manta GT-4 road racing car. It is in need of a new engine, but in general the car is complete and of very high build quality. It has no rust either, having originally come from New Mexico. So, once a fresh engine is put into the car, it will be run in New England in various speed events such as divisional road racing and hillclimbs by Gregg and myself (since I'm donating the engine). I'll delve deeper into the specs and get some closeup photos of the car at a later date.

And another photo of the car at speed with the previous owner driving.

I plead guilty to nudging my friend into buying it. I knew the previous owner, in fact he was my very last customer at C & R before closing up shop. I pretty much knew what was invested into the car, so I knew it was a good deal. The rollcage cost $3500 alone! The P.O. says he had about 15K into the car, so at $1500, it was a pretty good buy!

A few updates on the GT-4 Manta. Engine is being assembled as time and money allow. Here are some of the pieces. The shortblock was assembled 6 years ago and bagged, then forgotten. Nothing special, really, just forged flat-tops, Total Seal rings, stock forged Opel rods, Kamax rod bolts, and a lightened crank. But at least it's paid for...

A view of the lightened crank, about 6.5 lbs trimmed off.

Modified timing cover with direct-plumbed oil lines.

Block oil passages and timing cover oil passages have been matched both to themselves and to the gasket.

Block coolant drain added, and adapter for mechanical oil pressure gauge.

Completed cylinder head with custom tall valve cover for stud-girdle clearance. Internal specs include 1.85"/1.50" Chevy valves, 1.25" double valves springs, titanium retainers, roller rocker arms, stud girdle, and a solid lifter cam with .504" intake/.487" exhaust lift, 257 intake/248 exhaust duration @ .050", and 108 degree lobe separation. Pretty small cam as far as GT-4 engines go (in fact it's a street cam). But I wanted to retain good torque characteristics for other uses...namely hillclimbs and other Solo 1 events. Normally, I'd use/recommend a cam with about 18-20 degrees more duration and .060" more valve lift for GT-4.....

RallyBob,
What are the dimples on the piston top for? Great Looking Engine, BTW.
Paul

Ancient Chinese secret.....
They're to keep the air/fuel better atomized in the combustion chamber. Years ago I found that by strategically adding dimples on the short side radius of the intake port, and on the combustion chamber of the head, plus the top of the piston, I could improve the homogenization (sp?) of the air/fuel mix. The fuel tends to settle out when it hits the combustion chamber walls, and this shows up as heavily carboned areas on the piston top. So I experimented first on my flowbench with aerosol dye to see the patterns it left on the CC walls. I then took it a step further and experimented on the piston tops of racing engines based on the carbon buildup. I didn't gain any power, but gained mpg and was able to lean the engine out a tad, and do it safely. On one racing engine I went from 4 mpg to 6mpg....50% better economy at full throttle. With racing gas costing us $4.75 a gallon, that's worth it in my book

And thanks, I always try to make my engines look good. Not much for chrome myself, but I like trying different 'schemes'. Lately, it's been hammer-tone paints.
It's Krylon Hammertone paint. I have no idea if it will withstand the test of time, this is my first experiment with it. However, if it's any bit like the hammertone paints used on machinery and tools years ago, it should be fairly tough. Not sure about the temps resistance though. I used silver on the block and head, and black on the rocker cover and various other pieces. They also have it in blue, green, gold, and a few other colors I can't recall. I just wanted something different. Not black, not orange, not red, and certainly not 'Unlimited Blue'!

Here are some of the valvetrain parts. The cam is the one previously specced out from Cam Techniques, the stud gridle is from Cam Effects, the adjustable cam gear is a Kent Cams item, and the rocker arms were from my first batch of Opel roller rockers from back in '94.

Got the GT4 Manta delivered to my house yesterday. All in all it's pretty cool. The rollcage is very nice...all TIG welded DOM tubing. There are a lot of details that need attending to, but it will be a very nice car when all is done. And it won't cost a mint to get it running

Here's the interior of the car. While I like the cage, it's a bitch to crawl in and out of the car due to the high side protection bars. I'd hate to have to get out in a hurry, such as in a fire.

Another view of the interior rollcage.

A view of the underhood showing the front hoops and cage reinforcements. The inner fenders have been cut away too.

Forward view underhood. Radiator is a VW aluminum core with plastic end tanks...very light and cheap.

A view of one of the tubular upper a-arms and solid-mounted front crossmember.

The supplied flywheel is all aluminum, and weighs about 8 lbs. It doesn't have a steel insert for the friction disc, but rather has a plasma-sprayed hard surface for the friction disc. Other parts include two sets of 44 Mikuni sidedraft carbs, a set of TWM intakes, hundreds of Mikuni jets, and lots of other bits and pieces.

Lastly, a nice bonus was a set of 15 x 7 MSW alloy wheels with used Comp T/A R1 racing tires.