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78 crank or 82 crank?

Ron ORon O1984/2010 IM, B.C. Canada
Okay, I've finally decided to upgrade. My 1776 is just too slow. I want a bigger motor but I also want to keep my costs as low as I can. CB has a good deal on cranks so I'm considering buying a 78 or 82 to go with my 90.5 pistons. I would like the 82 but I've been told that I will need different rods with the 82 crank because of clearance problems. The guy who will be assembling the motor recommends buying the 78 crank and a pair of 044 heads (I have stock heads now). If I bought the 82 crank, rods and 044 heads I'd be over my budget, since I would still have to buy a better flowing exhaust system (probably a CSP with larger heater boxes). I will be using my 40 Webers. So, how much difference is there between a 2 liter motor and a 2110 (110 cam and near stock compression). I think I've read in past posts that Jake likes using a 78 crank. Most of my driving is on the highway and I put about 3000 miles a year on the car. Any advice would be appreciated.

1959 Intermeccanica(Convertible D)

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Ron ORon O1984/2010 IM, B.C. Canada
Okay, I've finally decided to upgrade. My 1776 is just too slow. I want a bigger motor but I also want to keep my costs as low as I can. CB has a good deal on cranks so I'm considering buying a 78 or 82 to go with my 90.5 pistons. I would like the 82 but I've been told that I will need different rods with the 82 crank because of clearance problems. The guy who will be assembling the motor recommends buying the 78 crank and a pair of 044 heads (I have stock heads now). If I bought the 82 crank, rods and 044 heads I'd be over my budget, since I would still have to buy a better flowing exhaust system (probably a CSP with larger heater boxes). I will be using my 40 Webers. So, how much difference is there between a 2 liter motor and a 2110 (110 cam and near stock compression). I think I've read in past posts that Jake likes using a 78 crank. Most of my driving is on the highway and I put about 3000 miles a year on the car. Any advice would be appreciated.
FM Former Member
One thing that you need to consider is the connecting rod length to stroke ratio. Type 1 stock connecting rods are 131mm long. A stock 1600 stroke is 69mm, for a ratio of 1.90. VW decided that a ratio of 1.90 was a good working number.

With stock rods and a 78mm stroke, you get a ratio of 1.68. With stock rods and a 82mm stroke, you get a ratio of 1.60. A 131mm rod is a very short rod for an 82mm stroke. A smaller ratio should help low end power, however, it will also stress the pistons and cylinders with more sideloading. Many stroker engines use a 5.5 inch (139.7mm) Chevy rod. With the Chevy rod and a 78mm stroke, you get a reasonably good ratio of 1.79.

What I am trying to point out here, is that the selection of a stroked crankshaft is a very complex decision. There are, of course clearance issues. However, there are other subtle issues as well. The 'subtle' issues can have a significant effect on the life of your modified engine.

FM Former Member
Jake likes 78mm crankshafts, and there is a lot to be said for them. I like more displacement/torque and have a 2,110 with 82mm crank and 90.5mm pistons/cyls.

IMO, when in doubt, go bigger. Accumulating parts for my next engine and have a flanged 86mm Scat ultra-light crank and flywheel for it to use with 94mm pistons for a 2,387cc street engine (will use an aftermarket engine case to ease crankcase clearance problems.)

A 1 5/8" merged works fine on my 2,110 and it runs 8.5 to 1 compression with no problems using 93 octane unleaded premium - 044 heads with 42in/37.5ex valves, dual valve springs, Web Cam 121/125 camshaft, dual Weber 48 IDF's, Bosch "blue" coil, NGK DP6EA spark plugs, 32 degrees BTDC full ignition advance.

P.S. Allen (below) was right to mention the rods - my 2,110 has 5.5 and the 2,387 will use 5.7.

(Message Edited 10/30/2002 11:07:18 AM)
FM Former Member
Stroker motors may not need a lot of cylinder shims; for instance, my new 86mm stroker with 5.7 rods and John Connolly's "super squishy" pistons may require very small shims or none at all. This is because his "C" pistons (some strokers are "B", etc., which refers to wrist-pin height in the piston) have wrist pins located very high in the piston. John says the finished 2,387 engine will be very nearly the same width as a stock 1500 type 1 engine.
Ron ORon O1984/2010 IM, B.C. Canada
Thanks for the info. I think I'm going with the 78 crank, 044 heads and the CSP exhaust system with 1 1/2 inch heater boxes. With my 40 Webers and mild Engle 110 cam it should be quite a bit faster than my 1776 (with stock heater boxes and a single QP. I'm not into drag racing the car. I do want the car to 'move' when passing on the highway.
FM Former Member
Ron,
Sounds like a sound approach to a VERY strong motor. However, you remain duty bound to a little stop light racing just to keep up the Speedsterowners reputation. Spank an occassional teenage lad just for the rush and respect. My personal favorite, Rice burners with graphics and aluminum, rear-deck spoilers.

8 )
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