Engine rebuild: any warning signs?
Discussion
Mrs LT is of the misinformed view that her life will be quieter if she removes any objections to a Cerb coming to live with us (she's not heard one recently! 
). As a result, soon going to be going into full blown search mode and hopefully find a good one before this year passes by.
One thing that does concern me a little, having had engine go pop on a previous car shortly after purchase (heart ruling head - probably shouldn't have bought it), just wondered if there were any warning signs to look/listen out for with the AJP that indicate an imminent need for a rebuild?
Also, yet to decide 4.2 vs 4.5 - the power delivery of the former seems appealing on paper (need to drive one) but the latter appears to win more plaudits for tuneability... if one goes for the former, can it be rebuilt later as the latter or are there differences beyond bore/stroke/cam etc (i.e. completely different block)?
). As a result, soon going to be going into full blown search mode and hopefully find a good one before this year passes by.One thing that does concern me a little, having had engine go pop on a previous car shortly after purchase (heart ruling head - probably shouldn't have bought it), just wondered if there were any warning signs to look/listen out for with the AJP that indicate an imminent need for a rebuild?
Also, yet to decide 4.2 vs 4.5 - the power delivery of the former seems appealing on paper (need to drive one) but the latter appears to win more plaudits for tuneability... if one goes for the former, can it be rebuilt later as the latter or are there differences beyond bore/stroke/cam etc (i.e. completely different block)?
I have had the 4.2, and now the 4.5. I prefer the 4.5 engine as it appears to have a bit more low down torque. However my 4.2 did go like .....
I believe that the 4.5 also has larger crank journals. Check for idle oil pressure with a hot engine of about 35/40 psi.
On start up the cams will clatter and this is what you want, and then they will quieten down as she warms up.
Neither of my cars used/use any engine oil, or topping up with water.
The 4.5 is a bit lumpy at around 1500 rpm, but they all do that sir.
Good luck!
I believe that the 4.5 also has larger crank journals. Check for idle oil pressure with a hot engine of about 35/40 psi.
On start up the cams will clatter and this is what you want, and then they will quieten down as she warms up.
Neither of my cars used/use any engine oil, or topping up with water.
The 4.5 is a bit lumpy at around 1500 rpm, but they all do that sir.
Good luck!
SL500 said:
I have had the 4.2, and now the 4.5. I prefer the 4.5 engine as it appears to have a bit more low down torque. However my 4.2 did go like .....
I believe that the 4.5 also has larger crank journals. Check for idle oil pressure with a hot engine of about 35/40 psi.
On start up the cams will clatter and this is what you want, and then they will quieten down as she warms up.
Neither of my cars used/use any engine oil, or topping up with water.
The 4.5 is a bit lumpy at around 1500 rpm, but they all do that sir.
Good luck!
As SL500 says check oil pressure when warm, it will be 40 or more on a cold engine. If starting from cold it will sound like an old tractor which is a good sign. Difference between 4.2 & 4.5 4.2 more free reving quicker throttle response, no real difference in speed until around 150 then the 4.5 has more grunt. I would buy on condition not engine size good luckI believe that the 4.5 also has larger crank journals. Check for idle oil pressure with a hot engine of about 35/40 psi.
On start up the cams will clatter and this is what you want, and then they will quieten down as she warms up.
Neither of my cars used/use any engine oil, or topping up with water.
The 4.5 is a bit lumpy at around 1500 rpm, but they all do that sir.
Good luck!
Buy from a known owner on here and get it inspected on ramps at a reputable indie eg APM, Raceproved, TrackVroad, Strt8six etc etc...
That way you are much less likely to need a rebuild.
Also have a close look at the chassis and the bills. Lots spent on the car over the last 2 or 3 years is generally a good sign.
Edited for typos.
That way you are much less likely to need a rebuild.
Also have a close look at the chassis and the bills. Lots spent on the car over the last 2 or 3 years is generally a good sign.
Edited for typos.
Edited by Gazzab on Thursday 31st March 14:25
I've rebuilt an AJP and seen how variable they can be inside! Whilst all the usual advice is relevant, I wouldn't put too much store in one engine having more oil pressure than another etc, unless there are real signs of wear.
There's a recent thread on here relating to an engine which always held excellent oil pressure and suddenly dropped - investigation shows knackered main bearings.
What I'm getting at I suppose is that one engine might hold 40 psi hot and fail within 1000 miles and another hold 30 psi but go on forever. The build and casting quality of these engines is so variable that there are lots of perfectly good reasons for a fair margin of difference in this respect. If you wanted to have an engine really properly checked out I'd be tempted to get a sniffer test on it for the heads and run a leak down test which will show general wear of rings and valve guides. If they turn out OK and there are no obvious problems then I think that's as good as it gets.
In terms of taking a 4.2 to 4.5 - basically it just needs new liners (or the old ones reboring) and pistons. Crank throw is the same, though the very early 4.2s did use smaller journal cranks which are less robust. Other than that it's just ECU and throttle bodies - and there's a school of thought that the earlier throttle bodies are better anyway.
There's a recent thread on here relating to an engine which always held excellent oil pressure and suddenly dropped - investigation shows knackered main bearings.
What I'm getting at I suppose is that one engine might hold 40 psi hot and fail within 1000 miles and another hold 30 psi but go on forever. The build and casting quality of these engines is so variable that there are lots of perfectly good reasons for a fair margin of difference in this respect. If you wanted to have an engine really properly checked out I'd be tempted to get a sniffer test on it for the heads and run a leak down test which will show general wear of rings and valve guides. If they turn out OK and there are no obvious problems then I think that's as good as it gets.
In terms of taking a 4.2 to 4.5 - basically it just needs new liners (or the old ones reboring) and pistons. Crank throw is the same, though the very early 4.2s did use smaller journal cranks which are less robust. Other than that it's just ECU and throttle bodies - and there's a school of thought that the earlier throttle bodies are better anyway.
Thanks for the advice chaps, most appreciated.
Out of interest, does anyone know the approx. going rate for a vehicle inspection?
Out of interest, does anyone know the approx. going rate for a vehicle inspection?
Gazzab said:
Or use the engine popping on a 4.2 to go to 4.8 :-)
Strangely when the engine in my MGB needed a rebuild it didn't end up quite standard... so wouldn't rule it out. Gazzab said:
Buy from a known owner on here and get it inspected on ramps at a reputable indie eg APM, Raceproved, TrackVroad, Strt8six etc etc...
That way you are much less likely to need a rebuild.
Also have a close look at the chassis and the bills. Lots spent on the car over the last 2 or 3 years is generally a good sign.
This and a possible nod to DonkeyApple - get a known car, put money aside if it ever needs a rebuild (or do it for peace of mind/ warranty. That way you are much less likely to need a rebuild.
Also have a close look at the chassis and the bills. Lots spent on the car over the last 2 or 3 years is generally a good sign.
I cant say what the warning signs are of an engine rebuild, as we've only managed 94.7k so far... 
AJP's are far far stronger than they are given credit for IMHO.Gassing Station | Cerbera | Top of Page | What's New | My Stuff