Personally, I think coated EFI's would be your best bet. And if heat is still an issue, wrap the y-pipe with header wrap. That should cool it down plenty! And that way if the starter goes out in a small town in Mexico, you can get one in and get home! I don't think the power gains of headers vs EFI manifolds is anywhere near big enough to make all the trouble worth it.

Sam

 

I've decided on an alternative with the exhaust/heat issue, and how it is affecting the carb. No ceramic coating. I'm going to install the heating/cooling plate I have from a 60's Galaxie. It will take the place of the spacer I now have and should cool the manifold to carb junction because of the coolant running through it. I'll connect it to the heating plate under the manifold and they'll work in unison. I also have a heat shield I may install.

Of course I'll switch to a mini starter while the head is off, and If I go only any trips of length, I'll tuck an extra mini behind the seat, along with my box of spare alternator, fuel pump, and fan motor.

I've never achieved the potential of the header. Now I have the exhaust run 2 into one 2" tube, so I believe two tubes of 2.25" into a turbo muffler and exiting with a 2.5" tube will improve flow a bit. That coupled with unshrouding my valves and removing the ridges, cleaning up the runners, should be a noticeable improvement on performance and latter, once the play phase has subsided, mpg.

I'm Considering changing to a C intake. I believe the orientation of the carb, sitting it further from the header, would make a difference with the heat problem. Fordman75 did you notice a difference or loss of bottom end between the DP and C intakes?

 

I need to get out to a junkyard for some stuff, I'm going to look for some later model V6 trucks and see if they have any kind of heat shielding on the exhaust that might fit a 300. My old Honda had a sweet stainless factory header shroud, if there's a V6 equivalent that may be a way to keep heat isolated from the intake/starter.

What about a 3" exhaust from the duals back? I had a single 3" exhaust coming off the headers in an F250 - with a 5.0 and C6 - and it ran really well with a nice sound. Even with the Flowmaster. I'm going to 3" behind the EFI exhaust with a 14" L x 7" D round Magnaflow muffler, then dumping it in front of the rear wheel (to hopefully keep the exhaust from rolling up into the back window when it's down). Easy tie in when/if I slap on the Hedmans.

I can't prove it but a 3" pipe sounds about an octave lower than a 2.5" pipe to me. The cadence will be different but I want that same tone I got in the F250 from the 300.