The V8 Owners Forum -

I am at a cross roads with my current 3.5 engine and am considering other options - budget limited unfortunately.

I am thinking of starting over with a standard reconditioned 4.6 long block that might be available to me fairly cheap. I believe it is 9:35 CR.

So, my plan would be to use this with:-
- A decent fast road cam - piper or kent
- duplex timing chain
- Some stage 1 porting work on the heads (plus uprated springs and retainers)
- Using Edelbrock manifold and 500cfm carb (as they are sitting on the shelf)
- Dizzy spark

I understand I will need to use either and interim timing cover or one of JE Developements hybrid ones.

With the above spec roughly what HP and torque could i expect? something in the 250-265hp bracket?

200 hp I would think.
Reason 3.9 fully worked by John Eales with a JE 102 cam which is fairly radical, fully balanced, stage 3 heads yada yada
That gives 256 hp at 6600 rpm

You have less heads work, less cam and bigger capacity so will not rev as easily which is where my power comes in.

Sorry if this disappoints

Ian

Ian Anderson wrote: ↑Sun Sep 15, 2019 7:44 pm 200 hp I would think.
Reason 3.9 fully worked by John Eales with a JE 102 cam which is fairly radical, fully balanced, stage 3 heads yada yada
That gives 256 hp at 6600 rpm

You have less heads work, less cam and bigger capacity so will not rev as easily which is where my power comes in.

Sorry if this disappoints

Ian

Not a at all - it's why I'm asking the question. I am a little surprised though must admit as my 3.5 9.75cr makes ~190hp and with the same cam and head upgrades as listed above have been told by V8Tuner it should happily make 230hp.

I have heard all sorts of numbers for power, but I have had mine checked 4 times.
Original on engine dyno buy Eales once in the Uxbridge area and twice in Milton Keynes the numbers are within 3 ho
TVR seems to make a lot more horses for same engine capacity, but perhaps. tVR horse is a Shetland pony so you need more of them for the same numbers.

Seriously more cc will generally give more torque so an extra 1/3 engine size should see you feeling a lot more oomph under your right foot.

Ian

Well a standard 4.6 produces 222 hp (166 kW; 225 PS) at 4,750 rpm and 300 lb⋅ft (407 N⋅m) at 2,600 rpm so thats where you need to start.

That's on injection, though, not carbs.

Correct but if you are not able to do better than that in any configuration you might as well stay standard.

No much wrong with the Hotwire. Although not as easy to re-map for a modified engine as some. But likely no more difficult than tuning carbs properly.

I used to have a healthy 3,5 litre with ported heads, uprated cam or two and SU´s. At its peak it made 190 hp. I then ditched the SU carbs and manifold and went to Edelbrock Performer and Holley 390. That increased the power to 221 hp. The next step was to replace the short motor with 4,6 stuff. Rest was kept the same. That gave about 270 hp, change of heads (RS Merlins) to about 285 hp. One detail that you should not forget is that whatever the factory CR rating it may actually be lower. I have always done the math and corrected the engine spec as required to get the CR I want.

garrycol wrote: ↑Mon Sep 16, 2019 7:51 am Well a standard 4.6 produces 222 hp (166 kW; 225 PS) at 4,750 rpm and 300 lb⋅ft (407 N⋅m) at 2,600 rpm so thats where you need to start.

That's what I thought. So with a cam and some head work, properly set-up Edelbrock 1404 and Performer manifold, and well set-up / timed Dizzy +250hp is not a big leap of imagination. I just want to double check with those that have been there before shelling any money out.

minorv8 wrote: ↑Tue Sep 17, 2019 5:13 am I used to have a healthy 3,5 litre with ported heads, uprated cam or two and SU´s. At its peak it made 190 hp. I then ditched the SU carbs and manifold and went to Edelbrock Performer and Holley 390. That increased the power to 221 hp. The next step was to replace the short motor with 4,6 stuff. Rest was kept the same. That gave about 270 hp, change of heads (RS Merlins) to about 285 hp. One detail that you should not forget is that whatever the factory CR rating it may actually be lower. I have always done the math and corrected the engine spec as required to get the CR I want.

Very useful post thanks.

I understand the CR is very important with these engines. What CR do you have with your 4.6? and what did you have done to get it?

Bottom end is absolutely std 4.6 stuff, block has been skimmed earlier to bring pistons closer to TDC. At the time when I assembled the engine 4.0 pistons with smaller cc dish were not that easy to buy. (I did eventually buy a set but they are still stashed somewhere). I have steel gaskets that are thinner and thus raise the CR. Old style head bolts with 4.6 Rover heads. Merlin heads required a specific set of bolts. IIRC the CR was around 10.7:1. No issues whatsoever with local petrol, we have 95 and 98 octane and E85 of course. Runs perfectly with 95.

I have since gone to EFI and programmable ignition and so far best score was 314 hp. The biggest gain with that setup is courtesy of ignition advance where you can add some advance after max torque rpm. That made a significant increase at power above 5000 rpm.

Funny though, having the block skimmed kind of bit me in the ar*e. I was supposed to assemble a stroker engine into that block and I knew that I need to shave some material from the pistons. Well, with the 90 mm stroke and 6 inch long rods they were 60 thou above the block at TDC. Not a biggie if you have enough material in the pistons but being stroker versions they only have some 3/16" from crown to 1st compression ring. Removing 60 thou is a bit scary. Doable yes but longevity ???