Where to find help when you want to change major units on your CF - engine, transmission, brakes etc. - or upgrade earlier models to later specifications.
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Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by Polly » Wed Jul 19, 2017 8:22 pm
Joined: Wed Mar 23, 2016 5:55 pm
Posts: 5
Hi everyone,

We are having trouble with our current diesel engine, looks like its going to have to be re-built again after only 1000mile (last rebuild was 3 years ago so out of warranty :evil: ) We are not that familiar with diesel engines and find we are able to do a lot more with a petrol. There is a running, low mileage 1.8L petrol in a CF thats local to us and is for sale. It is still in the van so can see it run and will run a compression test before we buy it. Does the the 4108 diesel and 1.8L petrol share the same engine mounts? Does it also fit the same gearbox? If those two fit then I'm more than happy to carry out the change myself if not then I may have to consider having to fork out a fortune yet again :?

Of course the 1.8 isn't going to be a rocket ship, nether is the diesel, most we get is 55mph on a long flat road. We won't be trying to go fast anyway but before we go down this route I'm assuming you guys wouldn't say its a completely underpowered engine thats not worth fitting?

Cheers in advance.

Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

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Post by Phil Bradshaw » Club admin » Wed Jul 19, 2017 9:54 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3669
1.8 (1759cc) Vauxhall OHC engine should be a bit quicker off the mark than the Perkins engine. Low mileage engine should be a fairly safe bet in terms of valve seat recession which the OHC petrol engine is prone to.

Going from Perkins 4.108 diesel engine to Vauxhall OHC ('slant') petrol engine requires the axle beam for the Vauxhall engine mounting posts.

Axle assembly with mounting posts for Perkins -

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Axle for Vauxhall OHC, mounting posts offset from centre -

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The symmetrical Perkins mounting posts can be used for any upright engine that will fit the available space, e.g. Opel CIH 20T with ZF transmission, but staying with the Vauxhall transmission common to Perkins and Vauxhall OHC engines (apart from ratios) involves less of a list of other bits that have to be changed or modified to complete the conversion.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by philbut » Thu Jul 20, 2017 9:18 am
Joined: Thu Oct 03, 2013 11:30 am
Posts: 247
I've had both the 1.8 and the 2.3 petrol in my van (SWB hi-top). The 1.8 was hopelessly under powered IMO. The 2.3 was a much better engine, with a decent amount of torque. if you are going to the trouble of doing the conversion, I'd find a good 2.3. It's a lot of work and you may as well put in the best lump you can get.

I'd also highly recommend getting hold of a Weber 34 ICH carb and the Bosch electronic ignition system if you can find them. Made a big difference to my set up.

I now run a Ford 2.9 EFi V6 lump and type 9 box. Fits nicely in the engine bay , and may actually work with your current engine mounts on the cross member. 150bhp and bag of torque :-) I still get the same MPG as with the 2.3 slant.

Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

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Post by VDUB384 » Club admin » Thu Jul 20, 2017 9:51 am
Joined: Wed Sep 12, 2012 9:01 am
Posts: 1354
Just fo curiosity Phil what mileage to you get mpg wise and are you running a van type or coachbuilt.
Dave
Whilst good maintainece is the best prevention"If its not broken don't fix it."
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Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by philbut » Mon Jul 24, 2017 3:06 pm
Joined: Thu Oct 03, 2013 11:30 am
Posts: 247
Hi Dave

I have a SWB van with GRP hi-top. She isn't coach built. I get about 19-20mpg on a motorway run at 60-65mph. When I had the 2.3 slant and ZF 5 speed box I could get 22-23, but at 55-60mph and she had a pop top then. I guess the hi-top (and large solar array) have shaved a few mpg off. Also got a Cresta diff installed now.

I've just diagnosed a cracked head actually on the V6 (blog to follow) so i'm hoping I might improve the mpg a little when I've rebuilt the top end. Leaking exhaust outlet on cylinder 1 will not be helping cruising efficiency.

Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by philbut » Mon Jul 24, 2017 3:13 pm
Joined: Thu Oct 03, 2013 11:30 am
Posts: 247
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Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by philbut » Mon Jul 24, 2017 3:14 pm
Joined: Thu Oct 03, 2013 11:30 am
Posts: 247
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Re: Converting from a Perkins 4108 diesel to a 1.8 petrol?

Post by Polly » Thu Jan 04, 2018 7:56 pm
Joined: Wed Mar 23, 2016 5:55 pm
Posts: 5
Hi all, sorry for being completely useless at replying!! Many thanks for all of your help and advice. In the end we decided to keep the 4108 and just do a top end rebuild. Its getting there now so hopefully by the early spring she will be back on the road!

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