Whats up Guys,



I'm running a 355 with 10:1, Edelbrock heads, 1.5 crane gold roller rockers, crane cam (not sure on size), with an Accel super ram intake, 30 lbs injector, and Edelbrock headers and exhaust. The reason the injectors are 30lbs is because I run a dry NOS. The car also runs 6th gen DFI with controls for the NOS programed in. I use to run it with a 52mm throttle body but I recently upgraded to a 58mm from BBK. The car feels like it has more up top with the 58mm but its hard to say without a dyno run. Before the throttle body switch I dynoed the car and got 323 rwhp. I will try to go get it Dyno again with the new Throttle body to see the difference.

 

A 52 mm flows 900 cfm and the 58 flows 1100 cfm. Unless your running more than 600 horses, there is no need for the 58. I run a 52 and run great

 

Get back to us with the dyno run. Especially if the only change you did between runs was the tb.
I run a 58 on my toy. It's like getting clothes that are too big for a kid. Gives 'em room to grow.

 

I have a stock 5.7 350 TPI on my 92 Formula and I am looking to do some engine upgrades. I want to get a 52mm TB but found a good deal on a 58mm. Would it do more bad then good to get the 58mm? I'm going for 350-400hp.

 

Everybody has differing opinions on this. Some say it'll hurt, others say it won't. I have yet to see dyno runs with just a TB change to prove one way or the other.
I personally believe that it won't hurt to go too big in this instance. The engine is only gonna use what it needs. A larger throttle body won't help you unless you need more air and the smaller one is not up to the task.
I'm not sold on the volume vs. velocity argument.

 

The RamJet502 uses a stock 48mm throttle body. I think that speaks volumes for the size debate.

 

"The RamJet502 uses a stock 48mm throttle body"

Why did they not use it on the LS1 motors? How come they keep increasing the size of the throttle body on the LSx series of motors?

 

The only reason GM uses it, is beacuse they already have them. If you put a 58MM TB on a Ramjet 502 Id bet money she'd pick up a good HP gain.

 

Because the LSx car intakes are designed to use a single blade throttle body, not a dual blade like the TPI and LT1 engines had.

 

I like this guys logic

 

"Because the LSx car intakes are designed to use a single blade throttle body, not a dual blade like the TPI and LT1 engines had."


The point being that the newer LSx throttle bodies flow more than the old 48mm ones.

 

When I started buying parts last year I was planning to build up my stock 350 tpi. Compression checks good, it doesn't burn oil, it only has 70 k miles. I decided to go with a roller cam. Then looking at the prices I thought, well I could go with a mechanical roller for nearly the same price as a hydraulic. Yes it's a little too wild but what the heck I'll live with it somehow. Now this meant I needed better heads and for nearly the same price as other heads suitable for a mechanical roller I could buy AFR 210s. Yes the heads are too big but I will live with it somehow. Now I need bigger injectors. Well 32 lb injectors are the same price as smaller injectors and yes they are too big but I 'll live with it somehow. Now I should get a new throttle body and a 58 is the same price as a 52. Yes it is too big but I will live with it somehow. Now I need a new chip and once I figured out the costs(programmer,etc.) well I bought a megasquirt kit. Yes it's overkill but I'll get it to work somehow. Now to make this long story short I pulled off my old heads and found one scuffed cylinder wall. Further tearing down revealed a couple of iffy looking crank journals. Because I had bought all the wrong (too big) parts rebuilding as a 383 will work out . Unless you know for sure you are not ever going to do more engine work in the future or someone is going to give you a 52 cheap buy a 58. I don't think you will regret it in the long run. Of course looking at the price of engine kits online I noticed a 406 is nearly the same price as a 383............

 

Doesn't mean they use all that airflow. Just because it has the potential to flow 1000cfm or whatever doesn't mean it will pull that much through every time you go to WOT.

Look at the guys running Quadrajets on their small blocks, for example... yes, its demand based, and not a mechanical linkage like a TB... but I'll bet 99% of them will never get the secondary air valve to go to 100% open. The engine will only take in the air it needs, regardless of what max airflow capacity of the carb/TB is. A stock Quadrajet can potentially flow 780-850cfm, depending on the model, but there are VERY few small blocks out there that will suck that much air through them. Most will never need more than 600cfm, so the secondary AV will never be more than maybe 2/3 or 3/4 open.

Same rule applies to a TB. Max flow capacity doesn't matter, untill you exceed it. More flow capacity also will not help you, unless you need it.

 

If you want to see a difference try a mechanical secondary Holley vs a vacuum secondary.

The bigger TB will work if you have the motor to use them.

Why do you seem to always find a good deal on a 58 mm "used very little" for sale, but not a 52 mm?

If they don't work they get sold.

 

That is a very factual statement.