Overheating Rover V8

[Roger.S]

I have just put a 4.6 Rover V8 in my MGB in place of a 3.5 Rover V8, which never ran well.

She starts on the button, then the temperature rises and keeps on rising until it’s close to the 140 mark (maximum) on the temperature gauge. At the same time the oil pressure which starts around 35 to 40 drops off to perhaps 25 to 30. The old 3.5 ran consistently at an indicated temperature around 90 and oil pressure a bit below 50.

I had the engine from a Range Rover which I saw running with no sign of overheating. I rebuilt the engine; new bearings, valve springs, oil pump gears, gaskets etc.etc, and I had the block (and cylinder head) pressure tested which was fine. So hopefully I do not have the liner problem which I understand is common.

I have just put in a new 1500cfm fan and a new MGBV8 radiator, with no improvement, although it’s not actually boiling as it did before.

Can anyone please suggest what the problem might be and what my next step should be? I am running out of ideas.

Btw this is my first engine rebuild, and probably my last!

Roger

[mgbv8]

She starts on the button, then the temperature rises and keeps on rising until it’s close to the 140 mark (maximum) on the temperature gauge. At the same time the oil pressure which starts around 35 to 40 drops off to perhaps 25 to 30. The old 3.5 ran consistently at an indicated temperature around 90 and oil pressure a bit below 50.


If thats supposed to be 140C and its not blowing steam out everywhere the gauge is faulty. Those oil pressures aint bad either.

Can you check the calibration of the gauge by measuring surface temp of stat housing and radiator top when the gauge is reading high?

I assume your are using the pre sd1 front timing cover with dissy driven oil pump.

Perry

[Roger.S]

Thanks Perry, I thought it was a bit odd, and hopefully you are right as this is easy to cure.

Any thoughts on how to measure the temperature of the stat housing? I can't think of anything I have or can get that will do this.

Yes the front cover is the SD1 with the dissy driven oil pump, off the old 3.5.

I'm a bit surprised you say the oil pressure is not bad, I know RV8 engines have low oil pressure compared to some but that low? I'm only saying this as the old engine definitely had more pressure and these oil pump gears are new......

Roger

[mgbv8]

The engine will survive at idle with as low as 10psi. As long as you get 20psi or more at 2000 rpm it should be ok.

If its road legal and you want a drive over to my town which is about 15 mins off the M40 J9 I can test it for you. post code MK18 7HJ.

I'm here all day tomorrow doing garden clearing + working on 3 other RV8's during the day. 2 MGB's and 1 escort !!

You are more than welcome to drop in for a check up. I wont be going anywhere

There are a few reasons why new oil gears wont give better pressure.
Does it run Carb or EFI
Are you using the original 4.6 rocker gear?

Perry

[mgbv8]

Sorry Roger!

I forgot to say:
If you want to come over tomorrow or pretty much any day / eve next week you can get me on 07824 319587. If I dont answer just leave a message and your number and I'll call you straight back.

I'm at home all next week for car and diy stuff

Perry

[DaveEFI]

Did you change the temperture sensor for the original from the 3.5 engine?

There seem to be loads which 'fit' these engines but are different electrically.

[DEVONMAN]

As Perry said, your oil pressure ain't that bad. You will get lower pressure with a 4.6 due to the larger bearings and therefore greater surface to ouse from.
Re the cooling. Is the manifold and plumbing from the 3.5 or have you changed it to suit the 4.6. It could be something as simple as the thermostat or an airlock. Check to see if the top hose gets warm or stays cold as the gauge rises.
Cheers Denis

[CastleMGBV8]

Roger.

Couple of points re the temps although as Pery said that does partly sound like a high reading.

1. the Rover does suffer with air trapped in the system which will prevent correct coolant flow.

I presume you have the correct thermostat in place should be 82 deg and a couple of holes drilled at approx 10 & 2 o'clock will help the air to bleed out as will running the engine with the cap off and giving a couple of blips of the throttle to burp it.

2. Is the undertray below the chassis rails in front of the bottom of the rad in place as this is meant to stop hot air recirculating around the bottom of the rad, if it's missing then over heating in traffic is not unusual

Also what induction system are you running, if carb which maniflold and carb?

Kevin

[Roger.S]

I have now put a hole in the thermostat, the undertray is there, that is a fibre cover around the oil cooler. The carb is an Edelbrock 500 and the manifold an Offenhauser dual plane with the original SD1 temp sender from the previous installation. The rocker gear is the original 4.6.

I just had it running for about 3/4 of an hour to an hour and it hasn't boiled, but the oil pressure is around 20-25psi, which I find worrying.

I'll give it another go in the morning.....

Thanks, I'm very grateful for all your comments.

Roger

[mgbv8]

I have now put a hole in the thermostat, the undertray is there, that is a fibre cover around the oil cooler. The carb is an Edelbrock 500 and the manifold an Offenhauser dual plane with the original SD1 temp sender from the previous installation. The rocker gear is the original 4.6.
That all sounds ok!

I just had it running for about 3/4 of an hour to an hour and it hasn't boiled, but the oil pressure is around 20-25psi, which I find worrying.
20-25 at hot idle is fine Roger.

I'll give it another go in the morning.....
I dont think it will be any diferent Roger!

Thanks, I'm very grateful for all your comments.
No probs mate, looks like you have possibly just cleared an air lock problem

Roger