1641cc slip-in vs machined 1776cc for a summer daily?

1641cc slip-in vs machined 1776cc for a summer daily?#1 · 9/18/2026, 8:22:06 AM

My 1600 dual-port is tired. Plan A: 87mm slip-in barrels and pistons (1641). Plan B: machine the case and heads for 90.5 (1776).

Car does motorway trips to Oslo every summer on 95 E10. Do the 87s really run hotter, or is that an old myth?

Attached engine build: Torben 1641 daily

Bore × stroke: 87 × 69 mm
Displacement: 1641 cc
CR: 7.5:1
Cam @ .050: 215°
Peak HP RPM: 4000

Re: 1641cc slip-in vs machined 1776cc for a summer daily?#2 · 9/18/2026, 1:22:06 PM

Not a myth. The 87 slip-ins have thinner walls at the spigot to fit the stock bores, so they shed heat worse and can distort a little once they're hot. For a car that only potters around town, they're fine.

For long motorway runs I'd machine for 90.5. The bigger spigot means thicker barrel walls, and you also get about 135cc more. Machining the case and heads costs more up front, but you only do it once.