roller lifters with 2.8

[veekuusi]

If your air/fuel stayed between 12:1 and 13:1 from the bottom to the top of the range then that is pretty damn good. How much did you mess with the timing? How much advance do you have at 3000+RPM? Before you hack your intake all apart maybe just cut the one wall where the carbs are mounted and increase the size of the plenum and weld it back on.

Max advance is 30 degrees.
It has little or no affection to hp what the WOT timing is.
It maybe so that when other things are not perfect (in this case runner lenghts, plenum etc...),
it affects so.

You are right, I am not going to hack the intake apart, I just modify the upper part of it.
I mean ,shorten the runners and maybe make the plenum a bit bigger.

The runner lenghts with different carbs:

4 bbl Holley 6-7"
3 bbl PMO 6"
2 x 2 bbl Weber 13"
with those applications above , the power was about 150-166 kW

And with 3 bbl PMO carb with the 3" extension ( together 9"), the power was 186 kW (254 hp back wheels), the best so far.
With this combination, the exhaust temperatures were over 100 degrees celsius different from bank to bank (over 212 F).
It means the other bank did run lean and the other rich.

So, 9 inch may be the best runner lenght .
And the exhaust temperatures are the same with 2 x Weber application .

[veekuusi]

How would you feed fuel? Those ITB are tall, & any plenum added would make it much taller. Are you able to modify the hood to accommodate for such without penalty?

Buying those itb:s was only speculation if I should give up playing with these carbs.
Then I would be forced to go to "A-class", where I willingly do not want go at the moment.
Of course there would be no plenum , just 6 throttle bodies.
And fuel injection of course.
Custom intake or stock 3400 intake.

It says they are 6.25" tall.
Not a mission impossible to put those under my hood.

[1988GTU]

If you decide to mess with the intake a little more indepth, maybe try a design like that?

[3400-95-Modified]

The triple carb seemed to give you the best performance, granted this does have some quicker torque but the question is how often are you at that RPM?

[carbon]

...

[ericjon262]

I'd love to see a well designed dual plane manifold. I'd bet this engine would scream with one. but that's not something easily done on something like this...

[veekuusi]

The triple carb seemed to give you the best performance, granted this does have some quicker torque but the question is how often are you at that RPM?

I am not quite sure what you mean by saying "quicker torque" , but the usable rpm range in the race is from 5000 to redline (7000 or 8000 rpm) .
I desperately need the maximum hp. I have little use of the low rpm torque that the latest Weber version gave.

But the new (and the final I hope ) version of the intake is in production.
Intake runners are going to be 4" shorter.
And there are going to be some kind of plenum tubes between the runners not between the plenums.













We had a day off today.
Good time to spend it in garage.
Very good independence day Finland!

[ericjon262]

I know it's come up before, but I forget the reasoning, why not go ITB?

[3400-95-Modified]

I am not quite sure what you mean by saying "quicker torque" , but the usable rpm range in the race is from 5000 to redline (7000 or 8000 rpm) .
I desperately need the maximum hp. I have little use of the low rpm torque that the latest Weber version gave.

You essentially stated what I meant, the triple carb gave you the best peak power but not as much torque as this latest Weber version did at 3k (lower rpm range aka you fell it quicker from a start)... and from what you said though your never at 3k so that additional torque doesn't help you much at all, you will feel the loss in power and that's it.

[veekuusi]

I know it's come up before, but I forget the reasoning, why not go ITB?

6 x ITB and fuel injection, that would definately put an end to this intake and carb playing.
300 chp , easily.
But that would also put me to another race class, because of different (calculated) power to weight ratio.
And I am not yet ready for that.

http://www.historicrace.fi/

[Purple pit]

I'm starting to love that track. Sure wish I could drive it.

[veekuusi]

I am pretty much done with the 4" cut intake.
The runners were definitely too long, so in this version they are now shortened.
There is an option in this intake to see if the tubes between the runners gain any hp.
The rubber joints can be flatten to completely turn off the connection.
There was same kind of tubes between the runners in the 3 bbl carb intake,
which gave some 30 extra hp.

[Purple pit]

Just something to read, not much use right now.

http://www.emeraldm3d.com/articles/emr-adj-length-intake/

[veekuusi]

Yesterday was a dyno day again.
As you remember , I shortened the runners some 4 ".
Maybe I have to settle with this hp numbers we got yesterday.
Those readings are back wheel numbers ( or more closely drive shaft numbers).

175.5 Kw (238 hp) 7740 rpm
260.9 Nm 4790 rpm

http://www.youtube.com/watch?v=eoOuwYwSIRA&feature=c4-overview&list=UUX30SFBRQv9PiufHKr0sSnw

[1988GTU]

Without digging too much into this thread, what are all the top hp/tq results per manifold design?