These tuning companies are getting outrageous. Changing some variables isn't worth that. Not by a long shot.

It's so nice knowing people with that type of equipment. I make all the changes on my Expedition at a shop a few miles from mine. They let me use their computer for free, and only charged me for pulls. (just as long as I supply pizza for the employees.. )

 

may look like S*it but who going to see it LOL. still will work better than having them on

 

I thought the tunes were well worth it when I paid twice that amount for it. The SCT tuner and defeating the rear end were the best 2 mods I did to the truck to date.

I have a fastman TB and felt like itwas a significantenough difference in tip in throttle response to justify the $225 he was charging. I went with a 50mm TB due to the 318ci engine. Since I've added heads, higher lift on the valves, and upgraded the exhaust and gears, I've often wondered if I should up mine to 52mm, or if that would be too much for the current displacement.

 

im sure with the mods you have now it would be good to run with 52mm , 50 mm like is for stock 318. do you still have the 1.7 HS installed

 

Oh yeah, got that edelbrock airgap too.

To the guy that posted about the 408, I wouldn't go smaller than a 53mm TB to feed that thing. They make tons of torque as is due to the displacement stroke. I read about a lot of guys building a 408 "for torque" and they slap the stock parts back on, keg included, and when they dyno the thing, they get depressed when they see low numbers. Its usually because the engine is either starving for air or choking on exhaust. IMO, an M1 or airgap is a must, as well as a 53mm TB, higher flowing heads like the edelbrocks, and a true dual exhaust with long tube headers around 3" piping. If you can't feed it enough air, or get the exhaust out, you're just wasting potential power.

 

Yeah, the 1.7s are still on it. The only thing that makes me hesitate is the cam profile hasn't really changed. Had the cam I bought worked, I think it would be a no brainer.

 

I agree about the 53mm for top end.. I'm looking at low to mid.. here is my reasoning, and it IS an experiment, but I've got time to play with it..

I'll be using the 52mm FM TB, I'll be port/gasket matching an air-gap to the heads, and the heads in turn to the intake.. I'm also porting the headers.. The headers for now (and likely then, depending on how it works out) are shorties that run true dual into a magnaflow true x, and out the back.. I'll be using Iron Ram heads w/ 2.02 in, 1.68 out..

The only reason I decided on the air-gap is that I'm getting it silly cheap... The RPM range it appears to be comfortable in is above 2100, and the 4.56:1 ratio R&P's I'm using keep me in that range for most of the driving I expect to do with it.. I can count the times using both hands I've had my truck above 5kRPM, and maybe three times that 4kRPM.. In other words, I just don't need the full breath of the 53-55mm TB...

The questions I have currently are being decided by folks who know this business a LOT more than I do, and it is down to 1.92 heads or 2.02.. I'm leaning toward 2.02, but I'm being told the 1.92's are just as good if not better for air-flow, and because of the air-gap's smaller plenum area.. It's being said that 'flow' is the goal, and moving the air efficiently is far more important than volume of air on reserve in the plenum- before you jump on that though, let me explain it as it was explained to me-

I'm being told (and it makes sense to me) that the larger valve will pull the air, but the air reserve in the larger (keg) plenum will have less velocity- where the air through an air-gap, being smaller and being designed more efficiently will create a constantly moving column- couple that through larger valves, the flow volume is slower but essentially the same as faster moving through smaller plenum and smaller valves.. the difference is an engine (great big air pump) that revs much faster and has a lesser tendency to bog (waste gas) .. but still turns out similar performance..

The school of thought is 'more efficient but smaller' is superior to 'larger and less efficient".. They've sold me so far.. The other option being presented is to NOT use an Air-Gap, but instead polish up the keg and put a plenum turtle on the plenum plate, which creates a better flow and decreases the plenum size...

This crap makes my head spin...

as far as the 52mm is concerned, if I was interested in racing in any form, or mudding, where high RPM's (4k+) were the norm I wouldn't hesitate to bump up to a much larger TB.. But the 52mm should be more than fine for the RPM range I'm targeting.. I think.. I think that I think anyway...

 

drew I think you wnt find many to talk to about it since it takes either 1. that beautiful mind, 2. a supercomputer, or 3. flow bench, dyno, tons of spre parts, and laots of time to dicker with it in order to really get good understand this decievingly complicated many variable scenario when speaking of altering flow character in these things. IMO I bet most of us, myself included, don't really feel qualified to comment on it. I assure you there are experts on this stuff though. Because of my bike building I have talked to some industry leading experts and talking to one is usually like trying to speak some foreign language for me, ie way beyond my experiences. I mean I kinda get it but mostly jI ust nod my head and listen. Well I guess I also start throwing money at some of these dudes besides the nodding..... :P

 

my friend, me too- it's way past my grasp.. what I DID lock onto like a heat seeking missile though, is the basic concept they shared that states "for each ADDITIONAL CFM of flow, add a pony"..

the first part is easy.. good air-box (CAI), good exhaust from the collector plate back- make the two match in possible flow as close as possible..

the second part isn't.. basically (no, actually- not 'basically', but 'rudimentary'):

If porting/polishing/matching the intake/head/header creates 5 CFM per cylinder (which according to them is easily achievable) that's 40 more ponies.. add to that the air being drawn into the plenum in a 'stream' that doesn't fight itself because of bad flow design, and you've got the foundation laid out for a truly strong engine..

getting closer now-

get a custom tune on that particular engine that studies and compares different spark timing, and proper squirt of the fuel..

the part I left out was choice of Cam.. to get that rascal to stand on it's head and dance, you gotta know where you're going before you start.. This is SO far over my head it isn't funny.. How long to open the intake valves? How much to open them? When to open the exhaust, and is it enough or too much too short or too long? The volume of air coming through that intake and out the exhaust doesn't matter if the wrong cam is chosen, as it can toss the entire equation off and give you a dog, not a rabbit..

Said engine, if built balanced in all that, would be easier on fuel consumption (if driven reasonably), run cooler (last longer), and have a LOT of power in reserve for when I need/want it.. It would put out less emissions too- not that this is a huge concern of mine.. Sorry tree huggers..

I'm all about seeing what I can squeeze out of as little as possible, but at the same time these 'gear heads' are going to want to be paid for their counseling/building.. I simply want to understand enough about it to NOT be BS'd.. But, hell, I may already have been BS'd for all I know..

 

If you want low end torque, go with the smaller valves, you will sacrifice top end power.

If you want more power in the mid, to upper RPM range, go with the larger valves.

It isn't just about how much you can flow, it is also about velocity. The smaller valves will have a higher air charge velocity, giving better cylinder filling at lower RPM, more low end grunt.

The air gap is also going to cost a bit of low end, but, I am not sure if the kegger would actually choke air flow.... it has longer runners, (which is good for low end grunt) thus, more restriction as well... so, the high end power would certainly suffer in comparison. No big surprise there.

Now, thing is....you are compensating for a lot of any potential low end loss, with more cubes. So, in the overall scheme of things, the 408 is going to have more low end power than the 360, regardless of which manifold/valve size you choose. This is where choosing the correct Cam comes in. You want a cam the developes its power in the SAME RPM range as your intake. For the air gap, I think that is like 2K to 6K?

Still and all, I would look HARD at cams designed to run in the 1500 to 5K range. You will end up with a motor that pulls hard from just off idle, all the way to redline. Power will start dropping off significantly in the Upper ranges though, but, how often to you even get there? (over about 4500 to 5K)