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Wed Dec 18, 2013 7:04 am

Anyone ever run a 88 bore by 78 stroke? I once had a friend that had this combination in a full bodied, street legal bug - bumpers and all. It had a nice set of Clyde Berg heads, old school welded Berg crank, some IDA's and remember this thing being really fast and fun to drive. Great power through the RPM's, especially up top and with slicks, it would run in the mid 12's. You don't see anyone (at least I don't) talking about this type of combo. Appears to me a lot of people are into the big strokers when it comes to the go-fast crowd. I understand why, torque is great and all but there has to be some fun and fast stuff out there that doesn't require extra an long stoke.

I'm currently running a 1776 in my '67 and will be up for a change in the future so just trying to decide where to go next.

Wed Dec 18, 2013 7:29 am

88x78 was a popular big street motor in the 70's. Back then the larger bores (92mm) were thin walled, 88's were very thick and reliable. 78mm stroke could easily be had by stroking the stock crank. They ran it because it's what they had and it worked, not because 88x78 is a magical combination or anything. 88mm pistons made for a stroker crank are not mass produced any more, so unless you find a deal on an NOS set, it's just not worth it.
Today you can easily have the same (actually greater) reliability and a lot more power by building a 94x82+. Or if you want a similar displacement, build a 94x69, very easy to build, much much cheaper than a 88x78 built today, by far the best bang for your performance buck.

Wed Dec 18, 2013 8:13 am

This is one of my favored builds. Motor makes good power, seals up good, very reliable. With the cranks available today the builds are economical. I use the 78 vw journal crank and the 5.325 rods.

Wed Dec 18, 2013 8:29 am

raymon covey wrote: This is one of my favored builds. Motor makes good power, seals up good, very reliable. With the cranks available today the builds are economical. I use the 78 vw journal crank and the 5.325 rods.

The cranks are cheap but that's it. Besides, I'd take a welded German crank any day over a new Chinese one. Don't forget time/cost to machine the case for the crank. And you have to buy aftermarket (more Chinese) rods, shim the cylinders out, making the motor wider (more difficult to fit tin, etc).
Or you can build a 1915 (94x69), stock CW crank, stock rods. Goes together like a stock engine. Bigger bore also allows for more head flow. Simple, cheap, easy. Plenty reliable if the cooling is carefully set up (this goes for all hi po motors). And a lot of fun to drive!

Wed Dec 18, 2013 9:00 pm

:D That's what's so great about this forum. Everyone has an opinion!!! I just happen to like mouse motors.

Wed Dec 18, 2013 9:26 pm

The 88 mm pistons these days (Non Stroker type A) are not for a stroke of more than 74mm or perhaps 76mm but that would be pushing it. Just use the 90.5's. http://vwparts.aircooled.net/Piston-Cylinder-Set-90-5mm-x-82mm-Machine-In-p/vw9050t1s.htm
http://www.geneberg.com/product_info.php?cPath=1_2...c1ceb7fb8a
http://www.mooreparts.com/2960-MAHLEF90S/
Looks like the 78 mm stroke could be too short for them though!

Wed Dec 18, 2013 9:58 pm

thats just a slightly smaller bore than 90.5,I had a 87x78.8, worked great.I uped the bore to 90.5,not s lot of power change(probably 10~20 hp),but able to tune carbs a little better with the added cc. It's not nessarly the added stroke but added cc that makes more power.and added stroke makes adding cc's easyer than a 104mm bore would be.

Wed Dec 18, 2013 9:58 pm

it will just push out 4-5mm each side

prolly no worst than an 82 stroke + 5.5 rods

the 88mm dia skirt is another story : on how much skirt cutting is needed
using stock length rods.. and even more so on 5.325" rods

Wed Dec 18, 2013 10:05 pm

Like already stated, 88s are not easy to come by. I saw Clyde Berg had some sets awhile back. Otherwise, you'll have to find the old Empi/Biral ones or have a set custom made inside AA barrels.

Wouldn't a 78mm crank with 5.325s and B pistons be painfully narrow?

Wed Dec 18, 2013 11:09 pm

I had one in my type 3, 1897cc, IIRC. At the time, 88 was as big a bore I was willing to try in a heavy Variant, and 78 mm stroke was as big as I could afford( China didn't exist back then)... It ran smooth and cool, and spanked many an oil-spewing 1915. I still run those pistons in a 1680 in my baywindow. They were A sized (but forged, so no skirt work needed), stock rods, lots of shimming, and I have since rebuilt the engine narrower, but it worked at the time! With the parts available today, I would go a different way.

Thu Dec 19, 2013 5:17 am

Thanks for the replies. I appreciate the feedback, helps me figure out what to build next...probably leaning towards a 2110 or 2276.

But, when I start thinking about bug engines, the 88x78 combo keeps popping into my head just because of how well it worked. I know it had a lot to do with the cam, carbs, set-up, compression, etc but quite honestly, it was one of the best driving, running and sounding air-cooled engines I ever drove. I've been away from the scene for several years and haven't driven a "modern day" "big" air-cooled so I'm sure the newer big cc stuff is great, just don't know from personal experience. That's why I posted the question here, I knew I would get some great opinions.

Sounds like most people think the hassle and cost factor would outweigh the practicality but it's fun to think about anyway.

Thu Dec 19, 2013 7:10 am

I have a set of 88mm Thickwalls from way back NOS... still in cosmoline.

The box is coming apart but the pistons/cylinders are nice. I just got done balancing them.

The 88mm x 78mm is a very nice stout engine. At one time it was a favorite for busses. I have the Demello crank to match to it too.

PM me. I will sell both.