RENAULT LINERSToday's lesson is all about liners. Things get a little bit interesting here, and without playing around with liners, you are not going to get any increase in capacity. Bigger is better right?
The liners all share similar visual characteristics, and at first glance they look the same.
From the outside, there are two flats machined onto the liners. These allow the liners to sit tightly nestled together. The liners are 89mm wide corresponding with the 89mm bore centres of the block.
697, 807 & 821 ENGINES
The bottom of the liner is stepped down to 82.5mm in diameter for 76mm and 77mm bore engines. I understand the very early 697-04 engines had 82mm diameter. This stepped area fits neatly into the alloy block. Between the liner step and the block are “paper” seals, which come in three different thicknesses.
1 –I don’t believe they have any sealing capacity, so I always liberally apply a high temperature silicon type gasket sealer to both sides of the “paper” seals.
2 – I ALWAYS use the thickest paper gasket or shim. This helps to make the liner protrude a bit higher than the block, and ensures excellent sealing between the liner and the alloy head.
841 & 843 ENGINES
These liners look the same but have a bore of 79mm. The stepped down area is 84mm from memory. These liners were sealed with an O-ring. A small chamfer is machined in the block to house the O-ring. Again I always liberally apply gasket sealer. In an early exercise I built an engine and relied on the O-ring to do all the sealing. The O-ring leaked and required a complete engine strip down, simply to apply less than a dollars worth of sealer.
CAPACITY
76mm bore – this was confined to the 697 engine, and with its short 81mm stroke crank, gave 1470cc
77mm bore seems to be the most prolific, and was seen in a wide variety of 807 engines, and the 821. The 84mm stroke gave 1565cc.
77.8mm bore were in some 1600 Alpines, giving 1596cc with the 84mm stroke crank
78mm bores were in some 1600 Alpines as well, giving 1605cc with the 84mm stroke crank.
79mm bores were fitted to the 841 and 843 engines, giving 1647cc with the 84mm crank. Some Alpines used this bore.
Alpine ran up to 82mm bores in their rally cars and pistons/liner kits are available from Mecaparts.
In my first big bore engine, I took some 79mm liners and had them bored to 81mm. I stroked the crank 3.0mm to get a total capacity of 1793cc. This is the engine that leaked around the liner seals, so I stripped it, sealed up the liners, changed the cam and put it all back together. That engine completed many many kilometers on the road. One track day it dropped a valve at 7000rpm and destroyed itself.
But I digress!
The second big bore I built for my mates A110. We had heard of these legendary 1800cc Alpines, so I took on the challenge to build a cost effective replica.
I determined that 81.75mm was the biggest bore I could achieve by reworking a set of old R18 liners I had sitting on my shelf. The main constraint was the diameter of the very bottom of the liner. The step area was 84mm diameter, and the bottom of the liner is machined down again by about 0.25mm. So with an outside diameter of 83.75mm and an inside diameter of 81.75mm the bottom of the liner was skimpy at 1mm wall thickness. Not ideal for a piece of cast iron!
The outcome? Well the bottom of the liner fragmented resulting in a horrible piston slap and a considerable drop in power. My mate persisted and belted around Sandown racetrack until it split a liner and things went a bit south. The pistons and liners were damaged but I successfully rebuilt the engine with liners bored to 81mm.
So my rule of thumbs is you can bore out a Renault liner up to 2.0mm oversize.
Finding a competent machinist is the key, and there are few people around that can do this work properly. It is not expensive, but it is a specialized job.
I’ve had liners machined in the block, but they need to be held down. They need to be held reasonably tight during boring, because they want to spin in the block. An incorrectly clamped liner will result in it distorting. After it is bored/honed, then unclamped, the liner is not longer round. I recommend having the liners bored individually.
With a decent machinist, a 697 or 807 or 821 alloy block can be block can be bored out to accept a larger diameter liner.
The limiting factor is the small bore centre of 89mm. With 82mm bore, and 89mm centres that only leaves 7mm of metal, or 3.5mm per side. Not a lot!
I've finished the Renault liner story, but I’m not finished yet! My desire to build a big bore engine continued, but I needed a liner with more material down the bottom end.
I’ve built a few 105 alloy Alfa engines over the years, and started to look at Alfa liners. Sure enough the liners from a 1750 are a bit beefier down the bottom. They are also larger in diameter and taller. I reworked a set of old Alfa liners from 80mm bore to 81.75mm and these have survived.
LINER STROKE CAPACITY APPLICATION
BORE
76mm 81mm 1470cc 697 and Europa
77mm 81 mm 1510cc Possible piston/liner upgrade for Europa
76mm 84mm 1524cc Possible crank upgrade for Europa
77mm 84mm 1565cc Common size for Renault 807/821
77.8mm 84mm 1597cc Alpine 1600. Maybe R12 Gordini
78mm 84mm 1606cc Alpine 1600
79mm 84mm 1647cc R16TX, R18, R20, Alpine 1600
81mm 84mm 1731cc Hand built Richard Mann for Alpine
81mm 87mm 1793cc Hand built Richard Mann for Europa (destroyed)
81.75mm 84mm 1764cc Hand built Richard Mann for A110. Rebuilt to 81mm bore
82mm 84mm 1774cc Alpine factory rally cars
My S2 Europa currently runs a 81.75mm bore engine with standard 84mm stroke.
