I'd just go with a single 3" or 3.5" like I mentioned earlier. I know you can fit a 3" and 3.5" is likely though I don't recall seeing it with my own eyes. You will need to have a well pieced together mandrel bent system though.

Remember, F bodies have single exhaust. I doubt you'll be at the level where you need to optimize every system on the car for maximum power.

granny's car has 3 1/2 on there car, they got a good pic of it on there site under shop mule.

The picture of my exhaust up the page is 3" mandrel bent piping cut and welded and I have more HP than you are planning plus a shot... I ran a flowmaster y-pipe and put a resonator and a muffler to reduce the cabin noise. I think a 3" setup like this is good to 475HP.


NHRA, IHRA, they all have the same safety rules. It is not that you can't get past tech at the local level, or that you will be just on the street, it is just for the safety of you and your passengers. Fuel inside the car is never a good idea. Just think if you had a wreck... Someone rear-ends you which is far more likely on the street, and smashes your plastic or worse metal (spark) fuel cell... body panels ripping the side or corner of it, and you are now upside down in a ditch with fuel spilling all over the interior compartment. worse case scenario i know, but at this point I bet you would be thinking you wish it you would have mounted it on the outside. We build these cars to have fun and enjoy, and deviating from the original safety engineering that was implemented requires careful thought to have a safe and reliable project. If you are not safety, or mechanically inclined there is no shame in consulting a manual to dial you in on widely accepted methods and practices in any aspect of the build... this is all I will say on the matter.

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Thomas Buck
1980 Rx-7 418hp 355/T-56 + 125 shot
1971 Nova SS 547hp 383/TH350
1972 Chevy Cheyenne SB 355/700R4
2005 Ford F-350 Crew/FX4

Theres plenty of room for a single exhaust under the fb as long as you get the correct muffler, I have custom headers on my 383 that go to 3'' then y to a single 4'' with v bands by the y and over the axle similar to the grannys set up, I also removed the stock tank and replaced it with a 16 gal cell and the battery next to it with plenty of extra room. As far as tech goes, ive never had any problems at my local tracks, but i suppose they may be a little more strict at other areas. If your really worried about ground clearance I would go for a 3'' as the 4'' is a little overkill for most engines. The 4'' does hang below the rails by about an inch

I didnt want to put the fuel cell in my car, I just had to for the time being. The car had set next to some dudes house for 8 years with almost a full tank of gas. can we say sludge. I cleaned out the tank, but its was to bad to use and I cant find a tank for like under 200.00. I just put the cell in there so I could get and Idea of how the car drove and so on untill I get a new tank. I used a tank sealer to see if that would fix it but I havent had time to put it back in yet.

in my fb, i had grannys long tubes into 2 1/2 into a y into single 3 1/2 over the axle to flowmaster 40 series delta race muffler then out the back. sounded mean, but was a little loud!