My 4.6 V8 Rebuild Thread

[101RRS]

If you are going to run a dizzy why not use one from an early RRC, I have an 85 RRC with the electronic dizzy and seperate guard mounted amplifier with coil mounted on top,out of the engine heat unlike the later dizzy with amp on the side of it,my motor is a 19D 9.35:1 running carbs 175CD-SE, and LPG getting 5+klms to the litre of gas. set at 8 before starts on gas unless O/night temp drops below 8*then petrol until temp and change by running carbs dry and switch as the motor dies. Distributor is Lucas 35DM8 41980B plugs NGK BKR-6-EKB or NGK-BPR-6ES

Hope that is of help

cheers

Thanks Uncle Ho - if I do run a dizzy I will use the one I have on the 3.5 V8 in my 101. It is a Bee Utey special - a Holden Bosch electronic dizzy with a Rover drive - will later mount the coil and amplifier in the 101 battery box - right out of the way.

cheers

Garry

[101RRS]

PLR - Peter

Thanks for your great information.

The three timing covers I have are the 4.0 (no dizzy) sepentine, 3.9 serpentine belt and the one on my running early 3.5 which is a V belt. I was hoping to put the 3.9 cover on but use the 3.5 V belt pulley on the crankshaft. As far as the camshaft is concerned I was intending to either use the 3.9 camshaft (reground as required) or just get a custom cam shaft (most likely option).

The LC pistons I have are in excellent condition so I will use these - it will save having to carry Octane Booster that would be needed in some remote areas where only 91 Ron or Opal Fuel is available.

Cheers

Garry

[PLR]

PLR - Peter

Thanks for your great information.

The three timing covers I have are the 4.0 (no dizzy) sepentine, 3.9 serpentine belt and the one on my running early 3.5 which is a V belt. I was hoping to put the 3.9 cover on but use the 3.5 V belt pulley on the crankshaft. As far as the camshaft is concerned I was intending to either use the 3.9 camshaft (reground as required) or just get a custom cam shaft (most likely option).

The LC pistons I have are in excellent condition so I will use these - it will save having to carry Octane Booster that would be needed in some remote areas where only 91 Ron or Opal Fuel is available.

Cheers

Garry

G`day Gary .

Sorry , i re-read what i typed and have rectified the incorrect information i gave you about the spacer . It`s a long time since i did ours it is a 4.0 and uses the V belts but this part is no different to a 4.6 .

The main problem serpy cover and v belt cover is that the water pumps are different and don`t interchange and the fact that they rotate in opposite directions when using there own belt type .


What follows are figures from a UK specialist taken from the net years ago and i`d suggest are only a guide as all engines are individual and need to be measured as such .

It will show from the figures that the 4.0ltr piston may raise the comp ratio .

Capacity..Ratio...ccs @ tdc

4.0 .........8.13 .....33
4.0..........9.35......23
4.6..........8.13......44
4.6..........9.35......31

I don`t know it for a fact but would pressume the piston deck to height is the same on all , as in the height where the piston stops at the top of its stroke and the distance to the top of the block/deck ( 0.020" on our 4.0ltr which is factory stamped 8.37:1 )and because the rings can interchange on 4.0/4.6 pistons i would presume the volume from the top of the piston down the side to the top ring will also be the same .

These 2 volumes along with the volume of the cocave in the top of the piston make up the CCs at Top Dead centre . The CCs@TDC are for 1 cylinder .

None of this is of any real help to you other than making you aware if you weren`t already because your engine will need to be measured for its own merits .

Peter

[101RRS]

So - remeasure the pistons - no difference between the 4.0 pistons and the 4.6 pistons that I can see.

What follows are figures from a UK specialist taken from the net years ago and i`d suggest are only a guide as all engines are individual and need to be measured as such .

It will show from the figures that the 4.0ltr piston may raise the comp ratio

Capacity..Ratio...ccs @ tdc

4.0 .........8.13 .....33
4.0..........9.35......23
4.6..........8.13......44
4.6..........9.35......31

Peter

I took the 4.6 crank, conrods and pistons down to the engine rebuilder today. He indicated that the 4.0 block that he already had had done very little work and visual inspection of the 4.6 crank and pistons showed they are all in excellant condition - except one journal on the crankshaft had a small gouge that may or may not mean machining rather than just polishing up. As the crank, conrods and pistons are a matched set, balancing will most likely not be required.

I also took a 4.0 piston down for them to have a look at - Peter you are correct - while on visual inspection the 4.6 and 4.0 look the same, using proper measuring gear shows as you indicated that the dish in the 4.0 piston is a tad less deep than the 4.6 and if installed on the 4.6 conrod will make an engine with a compression ration of about 9.16:1.

My immediate excitement was dashed when he said that as the gudgeons where pressed into the pistons that pressing them out of used pistons and the pressing them back in there would be a chance things might get damaged plus the compression ratio may still be a bit high for 91 RON so the engine will stay low compression.

Thanks for the input = all great stuff and helps me make decisions as I go - if I had found out after the engine is built that I could have put the 4.0 pistons in I would have always be wondering .......

Cheers

Garry

[bee utey]

If it were mine I wouldn't hesitate putting the 4.0 pistons in, pressing out gudgeon pins is easy so long as the pins are clean of carbon, plenty of lube and a properly made support for the piston. I've done many P76 pistons in my past, it's a doddle. But then that's my opinion, for what it's worth.

[101RRS]

If it were mine I wouldn't hesitate putting the 4.0 pistons in, pressing out gudgeon pins is easy so long as the pins are clean of carbon, plenty of lube and a properly made support for the piston. I've done many P76 pistons in my past, it's a doddle. But then that's my opinion, for what it's worth.

Thanks - I always value your views . I will always still have the option of using them up until I assemble the engine so opinions for and against are welcome.

So would a compression ratio just a tad higher than about 9.16:1 (the block has now been decked twice so a very slight rise in compression ratio from that) run on 91 RON??

Just to clarify, does anyone know what is the max compression ratios are for 91 RON, 95 RON and 98 RON assuming no knock sensors and ignition timing adjusted to minimise/stop pinging.

Cheers

Garry

[clubagreenie]

I'd be well happy with the slightly extra comp. In fact 4.0 pistons are cheaper than 4.6's so would be an excellent money saver and gainer for rebuilds. I have a 4.6 at the moment and am collecting stuff for an eventual rebuild (it was fitted with on 20,000k's on it so wasn't worth it then and only another 10 or so added since.)

Whats everyones opinions on cams? I know it'll be a can of worms like a tyre question but I figure there's std, mild and wild. But I'm not used to selecting stuff off the shelf. The last cam I did had over 9mm of weld added for lift....

[101RRS]

I'd be well happy with the slightly extra comp. In fact 4.0 pistons are cheaper than 4.6's so would be an excellent money saver and gainer for rebuilds. I have a 4.6 at the moment and am collecting stuff for an eventual rebuild (it was fitted with on 20,000k's on it so wasn't worth it then and only another 10 or so added since.)

Whats everyones opinions on cams? I know it'll be a can of worms like a tyre question but I figure there's std, mild and wild. But I'm not used to selecting stuff off the shelf. The last cam I did had over 9mm of weld added for lift....

Happy to go HC pistons but the engine must be able to run on 91 RON. On my last trip out west to Camerons Corner and Innaminka the LPG ran out at Bourke as did higher octane fuel and it was not until I got back to Bourke that I could get LPG (only from one garage that was not open all the time). So I unless I bought a few litres of octane booster I would not have been able to do the trip with an engine that required 95 or higher RON.

As far as cams go, other than knowing I will have to consider them I haven't give them a lot of thought. At its simplest I could use the 3.9 (or the 4.0) cam and put the 4.0 heads on and I am sure it will work fine, but I do need to have torque coming in a bit higher on the 4.6 than the 3.5 as long as torque still exceeds the 3.5 low down - I need much better torque in the 2500 - 4000rpm range than I do now as the 101 revs around 3500rpm at 90kph and dies when it sees a hill - the higher torque will also allow me to pull the overdrive. The bigger engine will naturally have more torque than the 3.5 but I need to put my mind to whether it will be enough. This then leads to valve sizes etc.

Garry

[clubagreenie]

I have the original 4.0 heads on a 4.6 short engine I sourced. Nothing was decked/skimmed etc. So all things should be equal (correct me if wrong). The engine should be a std low comp but I have issues pinging unless on shell premium or BP100 race fuel (which is magic for the economy but is bad for the wallet, economy is still not good enough to overcome the extra price).

ECU controls it some but on lesser fuels the knock sensing doesn't seem to activate. And on good fuels it only comes in over 2000rpm, which is defeatist as it's down low (1200-1800) under load that it mostly occurs.

[PLR]

G`day Gary .

The Hammil book says and he is talking about racing engines but they are Rover V8s.

91...9.25
95...10.5
98...12.5

Hardcastles book 9.35:1 with 3 deg retard but only specifies unleaded because of the era of the book , i guess .

One thing to remember is that retarded ignition timing will most likely produce more heat .

At different times i`ve searched for info on unleaded and not found much i`d pass on other than it may be that alloy heads are capable of a higher ratio using unleaded , this from US EPA but the V8 chev they used didn`t have an exact alloy copy and although they tested a number of different engines it seems that there are many variables in the engine design that relate to what compression ratio is maximum . Although the US don`t use RON they gave a comparision .

Peter