Lol, same here, I'm doing the same thing...my truck died for the first time EVER yesterday. It's running great, except for when I have my A/C on. It idles at around 450-500RPM's with A/C. I would adjust the Idle, but it doesn't have an adjustment for it. I'll probably take it off and keep it until I do some more work on the truck, but until then, I guess I'll keep the old one on.

Matt

 

We're talking about only changing the throttle body on a speed density system. On an intake with a fairly large plenum and long intake runners. For the same reason the "tb spacers" are useless here the larger TB is mostly a waste of effort as well. Short of a precision sensor no measurable change to the airflow has occurred. Much less fuel delivery.

Here is why. There are two sensors that are the primary governors of of fuel delivery. The MAP sensor and the ECT sensor. MAP determines VE and is cross indexed with the RPM and engine temp to determine fuel pulse. The TPS and HEGO are mainly correction factors.

What this means is: if the head can only pump X volume of air per cycle, and the stock TB is rated at or a little above that volume, increasing the bore of the TB can only lead to taking the TPS correction out of range and confusing the computer. Because the SBF TB is fairly close in size to the BBS TB in under most conditions your just within the correction range the computer can adjust for.

I have majorly over simplified this in the hope of getting the idea across.

 

Cjsteak? How long did it take you total to do?

 

I understand what your saying, SR, but why on earth would they put a smaller throttle body on a 4.9 when they use the same throttle body for a 5.0 and 5.8? I understand it would throw the computer out of wack, thinking the throttle is open less than it actually is, but I didn't think it would hurt it, especially since I'm using a throttle body off a 5.0/5.8. I know one's a 6 and the other's 8, but if they have the same amount of cubic inches, wouldn't they need about the same amount of air going in?

I'm most likely wrong about this, so please clue me in on this....

Matt

 

RPMs play a big role in that as well. max hp comes in at 3800 rpm on a 300 and most folks wont see 3500. a 302 and 351 have higher power bands.

 

Evil,

The whole conversion took about 1 full hour to do. I converted my truck back to stock. If anyone wants this 302/351 TB AND my K&N FIPK I'll take a hundred bucks + shipping.

 

Cool... What you didn't like the 5.8 bud?

 

I did all of this before even reading it but my idle was about 900 so i took it off becuse there was no way to turn it down ..any ideas? the TB was off a 302 . would that make it any diffrent?

 

I just did this swap this week (thanks to the posts above) and wanted to add a little.

#1 The original 6 cyl. IAC unit will bolt and work on to the 351W TB, using the 6 cyl, bolts. I used my original one because the 351W was all gummed up.

#2 I used the 351W's original throttle position sensor, but the wire colors were different. I traced down some wiring schematics and this is what I found.

'95 6 cylinder wiring..................351W wiring
Gray/White stripe hooks to Dark Green/Lt Green
Brown/White stripe hooks to Orange/White stripe
Gray/Red stripe hooks to Black/White srtripe

#3 Home Depot is your friend!!! Go to the PVC isle. Get two 2" to 2" PVC rubber couplers. These fit perfect on the 351W throttle body. Then get two 3" to 2" PVC rubber couplers. These fit perfect on the stock air box.

Here is an example of what they look like:

#4 For the air tubes. I went to the auto parts store and bought 2 peices of 2 1/4" inch flexible exhaust pipe. It fit inside the Home Depot couplers perfectly.


Final thoughts: I notice a little bit of difference, mostly in the upper RPM range. It's definately not 15 HP like others say, probably more like 5. The biggest problem is that the 6 cylinder's intake opening measures 1.700" and the 351W's TB bores measure 1.900". (Just for reference the 6 cyl TB measures 1.600"). If you had the time, pulling the upper intake off and opening the holes up to 1.900" would probably be the best option to really get anything out of this swap.

 

Click on pics to enlarge: