4.2 crankshaft

[clive f]

as the search facility still seems to be down can anyone help with the following.

I have a 4.2 engine to install in my griff, the crankshaft is cast, so have heard a few stories about these cranks snapping, what are peoples experiences with these, do some last a long time, is it a common occurrence?
are there suitable alternatives without fitting a 4.5 crank and having to have the block machines to take the bigger 4.5 crank journals?

[jammy_basturd]

From what I've read on here, the later 98 4.2 cranks are ok.

From personal experience, and probably about to jinx it, one '97 4.2 crank in my Cerb has seen over 45k miles (I think its the original engine anyway).

[clive f]

I have been wondering if its just a case of mud sticking, a few early ones breaking, so all early cranks get tarred with the same brush, if there was a fault in the castings then surely this would have made itself known early on, rather than 30k miles later?

interesting to hear what is thought.

[Ballsy]

Mine went pop,bang whollop at just under 17k miles, i was in 5th gear at 60mph at the time!!

[clive f]

Ballsy said:

Mine went pop,bang whollop at just under 17k miles, i was in 5th gear at 60mph at the time!!

so did you replace it wih a later 4.2 crank?

[RUSSELLM]

Power recently did a top end rebuild on mine, and I asked about swapping the crank, but was advised not to bother.

The theory being that it's managed 45k miles & 12 years so far, so it couldn't of been all that bad

Time will tell

[HarryW]

The early small journal crank could fail at pretty much any time tbh, if its apart I suppose a quick die pen and or ultrasonic test might reveal if its good to go or not.
Failing that and if you are really keen you could ask the likes of Andy at APM if he can get hold of a small journal billet crank. I beleive they were used in the original Tuscan racer AJP's before they went over to the bigger journal.....or it may be easier just to get it lined bored and fit a later 4.5 crank . I suppose it all depends on how much power and how you intend to use the engine which dictates the final direction you go in. Keep us posted

[clive f]

HarryW said:

The early small journal crank could fail at pretty much any time tbh, if its apart I suppose a quick die pen and or ultrasonic test might reveal if its good to go or not.
Failing that and if you are really keen you could ask the likes of Andy at APM if he can get hold of a small journal billet crank. I beleive they were used in the original Tuscan racer AJP's before they went over to the bigger journal.....or it may be easier just to get it lined bored and fit a later 4.5 crank . I suppose it all depends on how much power and how you intend to use the engine which dictates the final direction you go in. Keep us posted

Its all apart, so I can give it a dye pen test at work, have also mailed Andy as well to see if he may be able to help.
I intend to get aim for 400bhp in the 4.2 with a bit of jiggery pokery here and there, it will only be a road car, but just enjoy the challenge of getting the most out of things if finacially possible.

Edited by clive f on Monday 27th October 19:53

[cupra20v.t]

do companies exist that could make some cranks from better matrials than the cast iron ones so people can just pull out and replace the crank with a stronger but identical throw crank

[jammy_basturd]

Yea, your talking about a forged or billet crank. Lots of money.

[350Matt]

TBH Flat plane cranks aren't that expensive, if you want a billet En40B crank made to your own custom design it'd be about £750-1000 all finished balanced ground and never break

Matt

[jesfirth]

Mine was an early 4.2 and it developed a vibration after 75,000 miles which was eventually diagnosed by xray as an invisible crack in the crank - fortunately before it broke.

As the engine was being rebuilt I went for the cautious option and had the engine line bored and a 4.5 large journal crank fitted just to be on the safe side. The crank was circa £300 and the line bore etc was similar so not a horrendous cost.

[cupra20v.t]

so to get the 4.5 crank the parts cost you approx £750 plus labour?

thats very good, how much was labour if you dont mind me asking. and who did the work for you.