Pulling truck engine "again" BBC

[steve316]

It won't matter how high you lift that carb it will still look big

[midnightbluS10]

When you guys start with the comments like that, it screws it up for us that aren't as educated about this stuff. It makes it more difficult to follow along sometimes. Like the whole flowZ thing. I'm still not even sure what word that's supposed to be or mean. Every time I see it, the entire statement gets screwed up by its usage in the sentence. Do I just replace it with "flow" while reading to myself? Anybody? Randy?

Some of us aren't as advanced as the rest of you. I realize you guys aren't worried much about anyone else learning any of this. It'd be nice if us mere mortals could at least follow along without wondering wth one is writing about because of their constant use of inside jokes and references unknown to anyone except a select few in the "crew".

[CGT]

When you guys start with the comments like that, it screws it up for us that aren't as educated about this stuff. It makes it more difficult to follow along sometimes. Like the whole flowZ thing. I'm still not even sure what word that's supposed to be or mean. Every time I see it, the entire statement gets screwed up by its usage in the sentence. Do I just replace it with "flow" while reading to myself? Anybody? Randy?

Some of us aren't as advanced as the rest of you. I realize you guys aren't worried much about anyone else learning any of this. It'd be nice if us mere mortals could at least follow along without wondering wth one is writing about because of their constant use of inside jokes and references unknown to anyone except a select few in the "crew".

So are you looking for a simple explanation for very complex things. Like a "formula" or "simulation" that will give you the "perfect" cam or heads or compression etc??? Their are 2 or 3 other open, existing threads on here that can give you all of that.

A lot of the vagueness and fun amongst the "crew" is knowing their aren't definitive answers to most things, despite what the sim or formula of the week is trying to sell you on. I'm extremely wary of anyone that has "all the answers", and that's not solely exclusive to engines either. I've had to wade through a lot of crap to learn what I've learned. Which is more than some and less than others for sure.

[steve316]

I have told fellow racer the combination thats in my car when asked; and they would do something totally different and run just as fast as my car. There are always different paths to the same result. Use what info that can help you discard the rest.

[randy331]

I CC ed an intake port on the heads going on this big block pulling engine.

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

Wish they'd left the throat smaller and NOT radiused it. Well see what it looks like after a valve job. Hopefully I can get some angles under the seats.

It'll be steeper seats so that will help get some angles on it.

Haven't flowed this one since porting, so no flowz on it.

The intake is out getting milled so it will fit better. Needed dropped a little.

I'll CC it in sections to get a look at the taper or lack of it.

Needs more compression but heads have already been milled and I don't want to get them too thin and get into head gasket trouble.
May deck the block or go to a thinner gasket and take that same amount off the top of the piston deck and hand fit the dome to the chamber.

Randy

[treyrags]

I CC ed an intake port on the heads going on this big block pulling engine.

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

Wish they'd left the throat smaller and NOT radiused it. Well see what it looks like after a valve job. Hopefully I can get some angles under the seats.


Randy

Do you say this because you would like more material to work with to cut your angles or because you would like the throat to be a little less percentage, or both?

[randy331]

I CC ed an intake port on the heads going on this big block pulling engine.

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

Wish they'd left the throat smaller and NOT radiused it. Well see what it looks like after a valve job. Hopefully I can get some angles under the seats.


Randy

Do you say this because you would like more material to work with to cut your angles or because you would like the throat to be a little less percentage, or both?

Both, at least to start with. I like to let the seat angles set the throat size and make adjustments from that point.
And I'm not sure all the supporting things will be there to need that csa.
The CSA math suggests it will want to peak well above where this type of engine is going to peak.
The trade area for efficiency or trade efficiency for area decision. Where's the trade off gonna be best on this build under these rules ( IAMO prostreet 4x4 truck pulling rules ).

Randy

[zums]

Dose he already have all the other parts for the engine, camz , headerz , gearz, tirez, ect, if not since your stuck with more csa than wanted, raise the whole power band, but that means a relook at everything down to the rear
Tom

[CGT]

The CSA math suggests it will want to peak well above where this type of engine is going to peak.

Sounds like a good candidate for a 55 degree valve job possibly. What does your math suggest? 3.5 inch doesnt seem that excessive for that many inches and poor cylinder head architecture.

You have titanium valves right? Whats the problem? Lol

[randy331]

Well, with 3.5" csa at the throat,... and wanting the MCSA at the throat,.. you end up without much taper up the runner to the plenum, or a very large volume intake tract. The 320cc port is almost 34% the volume of the cylinder it feeds. Add in a runner with a larger average csa and the total intake tract volume starts to get up there.
None of this would seem as big if it was feeding 540+ cubes.
Seems the piston should have the total intake tract volume displaced by a certain point ATDC.
And my 421 pulling truck engine peaks at 7200-7300 with a 2.7 ish csa, the equivalent csa for a 462 is 2.97".

And,.. the "problem" is the Eagle rods with lead pistons on them. LOL

Randy

[GARY C]

It would seem the throat areas plays a big part in getting the most out of an intake tract.

[af2]

And,.. the "problem" is the Eagle rods with lead pistons on them. LOL

Randy

LOL

[randy331]

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

It was brought to my attention by pm I did some math wrong here. Not sure what I did to come up with 3.5 for 89.5% of a 2.25" valve but it's wrong.
Should be 3.18 - stem diameter.
Trying to do it with my phone.

Thanks Old school for bringing that to my attention.

Others do the math too, double check. LOL


It does remains true I wish it wasn't 89.5% and wasn't radiused .

Randy

[CGT]

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

It was brought to my attention by pm I did some math wrong here. Not sure what I did to come up with 3.5 for 89.5% of a 2.25" valve but it's wrong.
Should be 3.18 - stem diameter.
Trying to do it with my phone.

Thanks Oldschool for bringing that to my attention.

Others do the math too, double check. LOL


It does remains true I wish it wasn't 89.5% and wasn't radiused .

Randy

Update phone? Lol

[steve cowan]

It's port #4 I CC ed. It's 330 cc now. The throat was already ground out to 89.5% of the 2.25 valve.

I get a CSA of 3.5" at the throat and an average CSA of 3.62 for the whole port.

It was brought to my attention by pm I did some math wrong here. Not sure what I did to come up with 3.5 for 89.5% of a 2.25" valve but it's wrong.
Should be 3.18 - stem diameter.
Trying to do it with my phone.

Thanks Old school for bringing that to my attention.

Others do the math too, double check. LOL


It does remains true I wish it wasn't 89.5% and wasn't radiused .

Randy

Randy,
with the throat at 3.02''- 3.10'' depending on what stem you calculate with,is this still the MCSA in the port??
and does this change the AVG CSA that you calculated or did you measure using your CC method.
you mentioned earlier about welding the combustion chamber,can that include the throat area as well or is that not possible,as usual i only have questions and no answers but very interested in this thread.