Thread: 3.9 V8i intake manifold

So that two post that say they have gutless V8's
They should have no troubles cruising at 100 or 110 even with a head wind
Im had a similar problem on a couple of the old Ford Falcons i have had

no guts at all compared to what it came out with had trouble cruising at 110 almost had to floor it to overtake
It turned out to be the fuel pressure regulator on both of them
Changed that and it was like a new car

Get it checked and remember its always better to be at the high end of the scale

For example if it is meant to be between 20-22 obviously 22 is better

i run mine on gas 99% of the time, i also run 32" tyres, and have 1.003 gearing in high range (soon to be changed to 1.4), so that is my problem, not the fuel pressure regulator

Originally Posted by steve_35

So that two post that say they have gutless V8's
They should have no troubles cruising at 100 or 110 even with a head wind
Im had a similar problem on a couple of the old Ford Falcons i have had

no guts at all compared to what it came out with had trouble cruising at 110 almost had to floor it to overtake
It turned out to be the fuel pressure regulator on both of them
Changed that and it was like a new car

Get it checked and remember its always better to be at the high end of the scale

For example if it is meant to be between 20-22 obviously 22 is better

with mine it's no so much that the 3.5 was gutless - when i first got it it would do 130+ no probs, stock on gas, 750 x r16's.

but i have since put in a cam that did nothing below 3500 and am now also running 34" stupid jungle trekers. It now has much better oomph than the original setup whilst still getting 20L gas per 100 (hwy).

5th gear feels like 4th in a v6 vt auto, sure its not 400hp territory - but the old county now eats the kilometers without chewing.

I don't know if a 3.9 manifold would have given similar resaults?? Not going to remove the thor to find out either!

If you look at the dyno charts that I posted earlier in this thread you will see that the engine does not make more power at all with the Thor manifold , in fact it loses 10% at the top end.
BUT the engine gains 40-50% at the low end, and it is this increase in "area under the curve" that gives much better real world performance.

I apologise that the picture is a bit small but It should give you the idea of the quantified results that I got . All were done on the same dyno over a long period.
Here it is again

[/IMG]
Maybe this should settle down the debate.



Regards Philip A

Originally Posted by jazzaD1

don't worry about him Hardchina, its hard for some people to not ALWAYS be right

400HPONGAS, calm down mate! not everyone wants to be a dyno queen!

Hardchina,
i think that you have seen/felt a decent result from this upgrade, and that is all that matters, in fact it has inspired me to do the same thing, either in this thread or by PM can you please tell me some more detail about the conversion? im assuming you have put the manifold onto a 3.5?

My disco feels the same as you describe in 5th gear, in fact all the gears feel lacking, so a spread of torque lower down the rev range is just what i need, this seems like a relatively inexpensive way of doing it

400 is alright, he does know his stuff - especially when it comes to building an all out hp beast, but **** 400, i reckon you are miles off with this one .,

re manifold swap, it's easy if you go straight gas. I haven't done the efi stuff yet. About the only problems are

Machining out the thermostat housing. I did mine with a die grinder.
The 3.5 county needed a new acc cable, I used the 4.6 with a county end adapted
Fitted a ford EL gas mixer and inlet elbow, blanked off the injector ports.
The temp sender hole needs resizing to suit the older style sender.
The 3.5 needs 3.9? rocker covers.
water bypass exit needs a hose tail fitted - or get the manifold with the fittings inc.

Originally Posted by Hardchina

400 is alright, he does know his stuff - especially when it comes to building an all out hp beast, but **** 400, i reckon you are miles off with this one .,

re manifold swap, it's easy if you go straight gas. I haven't done the efi stuff yet. About the only problems are

Machining out the thermostat housing. I did mine with a die grinder.
The 3.5 county needed a new acc cable, I used the 4.6 with a county end adapted
Fitted a ford EL gas mixer and inlet elbow, blanked off the injector ports.
The temp sender hole needs resizing to suit the older style sender.
The 3.5 needs 3.9? rocker covers.
water bypass exit needs a hose tail fitted - or get the manifold with the fittings inc.

i have a megasquirt ecu, so i can pretty much use any injectors and temp sensor etc, and i also use vapour injection LPG which simplifies the install

do you have any photos of the thermostat housing grinding?

Originally Posted by jazzaD1

i have a megasquirt ecu, so i can pretty much use any injectors and temp sensor etc, and i also use vapour injection LPG which simplifies the install

do you have any photos of the thermostat housing grinding?

sorry mate no photo's, the only tricky bit is grinding out the recessed lip - kind of need an end faced grinding bit and a steady hand. Its a very dodgy way of doing it, but hey it's only a thermo. A mill would be the way to get a perfect job done, I just couldn't be stuffed sending it off.

There is a boss cast on the inside of the manifold that lines up with a standard thermostat housings lower bolt - just needs drilling and tapping.

I've got an early version MS that will be going on one day, ran it as edis controller on the old series 186. Reckon i'll go cheap arse v6 injectors from the wreckers as I only run on petrol if i run out of gas. The ms / edis never let me down - with this doing the spark control with the dizzy left in the hole, just in case - and old school gas with efi as a backup... plenty of backup if something goes wrong.

You never know Hardchina , you might want to see the worth of $200 plus set of plugs . As for your tuned length mythology , every manifold ever made is a Tuned length , the more you tune it , the less the Torque spread . its all a compromise in the Long run . Helmholz theory is fine is you want a 500RPM power band .Pray tell , when you changed the manifold did you change the Throttle body and Plenum design as well ?