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4,6 Ltr with quad Weber power output
Posted: Sun Aug 26, 2018 10:41 am
by dyno
Hi to all,
Maybe a silly question but I have never dyno tested any tuned Rover V8, only 1 standard 4,6 Ltr (Megasquirt ECU).
So, I still try to get an idea what kind of power I can expect from the following setup. Hoping some have approx the same spec.
4,6 Ltr, high compression pistons from the 4,0 Ltr, thinner gasket to get approx 10/1. Fast road camshaft, Quad Weber setup, heads are standard valves, reproduces 5 angle seat, some minor clean up, bronze valve guides, shorter and smaller in diameter, decent exhaust manifold.
Standard engine on my dyno was almost 400 Nm and +/- 230 Bhp. Will I hit 260 Bhp with this setup?
thanks in advance
Dirk
Re: 4,6 Ltr with quad Weber power output
Posted: Sun Aug 26, 2018 4:07 pm
by sidecar
I think that you would be better off skimming the heads/block in order get the 10:1 CR that you are looking for, I would avoid tin gaskets.
I think that you can do any amount of fiddling with cams, inlet systems etc but the big issue with these engines is that the heads just don't flow well anough on the 4.6 to make make decent power, at the end of the day they were designed for a 3.5 engine. You are better off spending your money on a decent flow job which includes fitting bigger valves. With stage III heads, 10:1 CR, a decent cam, a decent exhaust, quad carbs and good ignition system I reckon you could be looking at 285-300 BHP All just my humble of course!
Re: 4,6 Ltr with quad Weber power output
Posted: Sun Aug 26, 2018 5:03 pm
by dyno
Thanks for the replay.
I'm aware of the fact these heads are the one that hold down the power. The idea was, how far I can go without spending a lot money on the heads (and still, will never be super heads). Until now the block is almost stock, did not cost a fortune.
The quad set, I already have, also Holley kit on Edelbrock manifold but Quad Weber will always be better.
If I can't make 260 Bhp without serious money spend on the block I would rater go for a boosted engine. But it has to fit an MK Indy front so I think the V8 will already take all the place available.
Re: 4,6 Ltr with quad Weber power output
Posted: Sun Aug 26, 2018 8:22 pm
by ChrisJC
I would guess 300BHP at the flywheel.
Chris.
Re: 4,6 Ltr with quad Weber power output
Posted: Mon Aug 27, 2018 9:38 am
by sidecar
My guess would be 250-260 BHP at the crank.
Re: 4,6 Ltr with quad Weber power output
Posted: Mon Aug 27, 2018 11:50 pm
by SimpleSimon
If your using 10 bolt 28cc heads I would go with composite gaskets rather than tins you will already be in the mid 10's CR wise anyway , I am going with
maybe 270
HP wont be fantastic with stock heads even with fancy multi angle v seats , intake throats too restrictive strangling more relative to capacity increases just for starters even with that lovely intake fuel system
heads are bottle necking your HP ultimately
Re: 4,6 Ltr with quad Weber power output
Posted: Tue Aug 28, 2018 8:04 am
by DaveEFI
Be interesting to see the torque curve versus injection. I'm guessing you're losing quite a bit at lower revs in an attempt for the highest BHP figure. Which is never going to be spectacular anyway for an engine of that size.
Re: 4,6 Ltr with quad Weber power output
Posted: Thu Aug 30, 2018 5:53 pm
by dyno
From my calculation, I'll get 9,75/1 when I fit 4,0 ltr pistons. I've calculated somewhere but can't remember exact, with thin gasket little over 10/1 and I feel about the max for this engine with fast road cams.
I was hoping round 260 Bhp and seems like most agree. On the other side, I was in the same hope the torque would raise and spread over a wider RPM band. Quite sure I will not have less torque on quad carbs than what I already got with the standard fuel injection setup (and programmed ECU). Individual intake runners will always raise the torque and spread it over a larger numbers of RPM. Seen this more than often on my dyno.
I'll have to give it a try.
Re: 4,6 Ltr with quad Weber power output
Posted: Fri Aug 31, 2018 8:47 pm
by sidecar
dyno wrote: ↑Thu Aug 30, 2018 5:53 pm
From my calculation, I'll get 9,75/1 when I fit 4,0 ltr pistons. I've calculated somewhere but can't remember exact, with thin gasket little over 10/1 and I feel about the max for this engine with fast road cams.
I was hoping round 260 Bhp and seems like most agree. On the other side, I was in the same hope the torque would raise and spread over a wider RPM band. Quite sure I will not have less torque on quad carbs than what I already got with the standard fuel injection setup (and programmed ECU). Individual intake runners will always raise the torque and spread it over a larger numbers of RPM. Seen this more than often on my dyno.
I'll have to give it a try.
Vizard talks about quad downdrafts on V8 in his book on carbs and manifolds, He is of the same opinion as you, if they are setup correctly you can get good torque and power, you can also lug the engine at low RPM, you can get a very low steady tickover AND good MPG! I guess the key to all of this is setting them up well!
Re: 4,6 Ltr with quad Weber power output
Posted: Sun Sep 02, 2018 5:48 pm
by SimpleSimon
sidecar wrote: ↑Fri Aug 31, 2018 8:47 pm
dyno wrote: ↑Thu Aug 30, 2018 5:53 pm
From my calculation, I'll get 9,75/1 when I fit 4,0 ltr pistons. I've calculated somewhere but can't remember exact, with thin gasket little over 10/1 and I feel about the max for this engine with fast road cams.
I was hoping round 260 Bhp and seems like most agree. On the other side, I was in the same hope the torque would raise and spread over a wider RPM band. Quite sure I will not have less torque on quad carbs than what I already got with the standard fuel injection setup (and programmed ECU). Individual intake runners will always raise the torque and spread it over a larger numbers of RPM. Seen this more than often on my dyno.
I'll have to give it a try.
Vizard talks about quad downdrafts on V8 in his book on carbs and manifolds, He is of the same opinion as you, if they are setup correctly you can get good torque and power, you can also lug the engine at low RPM, you can get a very low steady tickover AND good MPG! I guess the key to all of this is setting them up well!
Always worked when using big Weber side-draughts on fast Ford 4 cylinder motors crisp low speed delivery softening of big cam profiles and if set-up correctly good MPG so long you didnt use the available HP to extremes
Re: 4,6 Ltr with quad Weber power output
Posted: Sun Sep 02, 2018 11:38 pm
by dyno
Setting them up correct is not an issue here, it's my daily job. Only wondering where the max would be for this basic engine.
BTW, from the look at both inlet manifolds, I feel the quad DCOE manifold is better for power. The IDF style makes a very short turn and seems to draw air in the wrong direction of the inlet port (bottom). Ford Pinto's also has a manifold like these with IDF and it never make big HP numbers compared to the same engine using side drafts.
Re: 4,6 Ltr with quad Weber power output
Posted: Tue Sep 04, 2018 10:44 pm
by Darkspeed
I would say 230 as before - the heads will be the issue and all the capacity will do is lower the RPM that this figure is reached at and increase the torque - 250-300 is pie in sky on stock valves and "Minor" head work. 250-260 BHP will require Mid size valves at least - 270-280 will need some serious metal removal 300 + Ultra big valves and an expert doing the port works.
Re: 4,6 Ltr with quad Weber power output
Posted: Tue Sep 04, 2018 10:53 pm
by Darkspeed
IDF manifold is no restriction on a RV8 - it's only a 45 bend on an RV8 not a 90 degree bend as on a Pinto - DCOE Manifold is a 135 bend with the swan neck types. Correctly ported the IDF manifolds are about the best you can get for the RV8.
Re: 4,6 Ltr with quad Weber power output
Posted: Thu Sep 06, 2018 9:41 am
by SuperV8
If I can't make 260 Bhp without serious money spend on the block I would rater go for a boosted engine. But it has to fit an MK Indy front so I think the V8 will already take all the place available.
I managed to fit a centrifugal supercharger on my 4.6 in my Dax Rush, so would guess similar sized engine bay to the MK.
Tom.
Re: 4,6 Ltr with quad Weber power output
Posted: Thu Sep 06, 2018 8:05 pm
by dyno
Darkspeed wrote: ↑Tue Sep 04, 2018 10:53 pm
IDF manifold is no restriction on a RV8 - it's only a 45 bend on an RV8 not a 90 degree bend as on a Pinto - DCOE Manifold is a 135 bend with the swan neck types. Correctly ported the IDF manifolds are about the best you can get for the RV8.
The inlet manifold I got in the workshop for DCOE is an alloy cross over, so no bents at all and nice long runner . (good for lower RPM). The swan neck manifolds, I don't like at all. Would never try them.