The Definitive :-) Chev 2.5 Page

I found out a lot about the Chev 2.5 engine, and I will probably find out more, the hard way.

Iron Duke

The Chev 2.5 (153 cubic inch) is not the "Iron Duke".

Differences in Chev 2.5 engines

Sump

I've seen two variations in the shape of the sump, a front sump and a rear sump. The only differences are the oil pump pickup tube and the sump shape.

[image] front sump [image] rear sump

I went with the rear sump, figuring that keeping the sump away from the front axle is a Good Thing.In practice, the engine actually sits well clear of the front axle, so either sump should work fine in a Land-Rover.

Rear crank seal

Chev 2.5 engines can have either a rope seal or a split elastomer oil seal. I have no idea how to identify which is which without taking the engine apart, but I have the following three engines as data points: 

Block casting number 3424165 Serial number 171347CBK Elastomer seal
Block casting number 3424165 Serial number 270631CBF Rope seal 
Block casting number 3427500 Serial number 335862CBF Rope seal
OK, so at this stage it looks as if the basic block casting can be machined to take either seal. Bit of a bummer, if there's no way to tell the type of seal from the outside. Maybe the K in the serial number? If you know, please email me.

Some tips for installing the rear seal.

Compression ratio

[image] Two heads

71cc on left, 58cc on right.

[image] Two heads

The first engine I overhauled pinged terribly. I measured the head of another engine, and the head volume was 71cc, which gives a compression ratio of 7.8:1. When I eventually pulled the pinging engine, the head measured 58cc, which gives an 8.9:1 compression ratio. Way high for a Land-Rover. 

Head casting number ??? Volume 71cc CR 7.8:1
Head casting number ??? Volume 58cc CR 8.9:1

Weber 36DCD

From the 4x4 Community forum: 

I have used (if I remember correctly) this combination on my carb for good low down torque on 1st stage, but still good performance on 2nd stage:

1st stage: 23 ventury, 135 main jet, 205 air jet. (Standard on 2.5 was 26 ventury, 140 main jet, 205 air jet)
2nd stage: 26 ventury, 140 main jet, 180 air jet (Standard on 2.5 was 27 ventury, 140 main jet, 180 air jet)

idle jet was 50.
O, just make sure of the emulsion tube. many people forget about these and have endless problems with tuning. F23 emulsions work great on the 36DCD7.
On my 36DCD, I have 
Primary:   135 main jet, 195 air jet, F23 emulsion tube
Secondary: 140 main jet, 210 air jet, F23 emulsion tube
Pump jet: 50
Idling jet: 50
Starting air jet: 150
Starting fuel jet: 400F1
Intake / discharge valve: 55

Back to Wouter's Land-Rover Chev 2.5 conversion page (This page last modified 2014-10-24)