Power gain figures
Moderator: phpBB2 - Administrators
Power gain figures
Hi does anyone know or can point me to a thread that details possible power gains, specifically looking at stage 1 heads on a 4.6. There's a few figures thrown about by various firms but I'd like first hand opinions if possible. I've tried the search but not found anything yet. Cheers mike
Hi
It is very difficult to say "adding stage 1 heads will give X bhp increase" as Markie implies you need to look at the whole spec of the engine. . .
If you have a "standard" 3.9 at a nominal 168 bhp (ie in good condition assembled mid week) then adding "stage 1" heads will add about 8 to 12 bhp when get the mixture and timing optomised you can add 5 to 7 more.
Take the same engine with the original heads and add a mild performance cam (say an R87) and you will add 10 to 14 bhp once the mixture and timing are sorted, do both mods together you will end up with between about 195 and 205 BHP, match a set of tubular heades and good inlet port matching then then by themselves worth between 2 and 4 bhp for the inlet and 7 and 10 for the headers then you will at best see 212 ish but the lower figure may be as high as 205 or as low as 180 is things do not together. Here you heads are limiting breathing and better heads or a different duration cam may see gains a little.
Like wise the putting a long duration cam on a stock engine may end up with reduced output and a very narrow power band whilst adding the same cam to full rece heads good exhaust and throttle body injection could see yo on the way to 300 bhp. There is also alot in the assembly and parts condition.
As a good guide, the heads you were looking at with tubular headers, a mild cam and SUs, injection or a 4 barrel with the ignition and and a basic match of inlet ports should see you to 200 bhp when the misture and timing are right on a 3.5 3.9 or 4.2 litre engine. Get everything matched assembled perfectly you could see another 10 to 15 bhp.
To get 220 bhp from these engines you need Stage 3 heads a much longer duration cam and a better inlet set up (EFI on a good inlet manifold) and alot more care on machining and component selection. However it can be done on a 4.2, 4.3 or a 4.6 with the first set of components and a realsteel turbo cam, but there is no gaurentee as alot of it is about matching components, particulally heads to cam.
Best regards
Mike
It is very difficult to say "adding stage 1 heads will give X bhp increase" as Markie implies you need to look at the whole spec of the engine. . .
If you have a "standard" 3.9 at a nominal 168 bhp (ie in good condition assembled mid week) then adding "stage 1" heads will add about 8 to 12 bhp when get the mixture and timing optomised you can add 5 to 7 more.
Take the same engine with the original heads and add a mild performance cam (say an R87) and you will add 10 to 14 bhp once the mixture and timing are sorted, do both mods together you will end up with between about 195 and 205 BHP, match a set of tubular heades and good inlet port matching then then by themselves worth between 2 and 4 bhp for the inlet and 7 and 10 for the headers then you will at best see 212 ish but the lower figure may be as high as 205 or as low as 180 is things do not together. Here you heads are limiting breathing and better heads or a different duration cam may see gains a little.
Like wise the putting a long duration cam on a stock engine may end up with reduced output and a very narrow power band whilst adding the same cam to full rece heads good exhaust and throttle body injection could see yo on the way to 300 bhp. There is also alot in the assembly and parts condition.
As a good guide, the heads you were looking at with tubular headers, a mild cam and SUs, injection or a 4 barrel with the ignition and and a basic match of inlet ports should see you to 200 bhp when the misture and timing are right on a 3.5 3.9 or 4.2 litre engine. Get everything matched assembled perfectly you could see another 10 to 15 bhp.
To get 220 bhp from these engines you need Stage 3 heads a much longer duration cam and a better inlet set up (EFI on a good inlet manifold) and alot more care on machining and component selection. However it can be done on a 4.2, 4.3 or a 4.6 with the first set of components and a realsteel turbo cam, but there is no gaurentee as alot of it is about matching components, particulally heads to cam.
Best regards
Mike
poppet valves rule!
Thanks for the advice, from what I gather, I'm probably better off ensuring fuelling etc is spot on first, so think I'll use the money to buy a megasquirt kit, then see where I'm up to, not sure I can afford megasquirt and heads in one go, and I need to crack on getting it in the motor.
Cheers again mike
Cheers again mike
Hi Mike
Sounds like a good plan, if you are going of a mild road engine I would go EFI-Cam-renew rockers and shaft- heads (match the inlet to the heads at the same time)- tubular manifolds- exhaust system. In that order if you restet timing and mixture each time you should see steady gains.
Best regards
Mike
Sounds like a good plan, if you are going of a mild road engine I would go EFI-Cam-renew rockers and shaft- heads (match the inlet to the heads at the same time)- tubular manifolds- exhaust system. In that order if you restet timing and mixture each time you should see steady gains.
Best regards
Mike
poppet valves rule!
