Hello All, I pulled the 351W out of my F100 to do a transmission swap. As is usual this is an excellent time to take care of some other minor concerns, one of which is the exhaust manifolds. I currently have the stock manifolds from the 78 T-bird the motor came out of which our fine-ish, but there are a couple of issues. The first issue is the first mounting hole is broken so that it is only half there. I think it clamps on well enough to not leak, but it wouldn't hurt to replace it with one that is not broken. The second issue is the passenger side still has the heat riser block in place between the manifold and the pipe (the valve portion was removed, but the housing is still there). This I know is a source of leaks even though it was tight.

First question, is if there were certain manifolds that work better than others. I have heard the 289 Hi-Po might flow better, but I would think factory 351W would be bigger. I could be very wrong about that as my SBF knowledge is limited to this one engine.

Second question, if I can find replacements, I would want to have cone exits on both sides. Currently the driver side has a cone exit, but the passenger side is flat for the heat riser valve. I know that some years had the heat riser and some years did not. And it looks like some were just flat on both sides using gaskets to connect with the pipes. I am hoping to have cones on both sides. Are there certain years/models that had cones on both sides?

Also, if anyone has usable manifolds in Iowa for a low price let me know. My budget is limited due to finding other issues as I was pulling the motor out.

Thanks in Advance

 

IMHO, honestly the 289 hipo's won't do barely anything for you, just go with headers- long tube of course is the best but if you don't want to "help" them fit then just go with mid-length or shorties... both will perform very well up to about 5500 rpm.

 

You aren’t using the heat riser? Have you done any performance mods to the engine? If not, then stock replacements or shorty headers would be fine.

 

Thanks for the input, I was hoping to keep the manifolds as it is my understanding they are quieter than headers. I am not against headers, but I know they come with their own issues.

 

Back in the mid 90's I literally pulled the motor and trans out of the 78 T-bird, power washed it, quickly painted it, and then dropped it in. I was in a time crunch at the time and the motor ran fine (there were other issues). About 10 years later I pulled the motor and had it properly rebuilt by a machine shop, nothing too extreme, just an RV cam and a factory low rise four-barrel intake. When it came time to put a carburetor I did an Edelbrock with a manual chock, with a 2 inch poly riser. Since the carb didn't need the heat to run the choke, nor would it be able to warm the carburetor through the intake I decided to eliminate the valve flapper and block off the choke oven. I think I kept the actual riser passage open, but exhaust wouldn't be forced through.

Doubt you wanted that much of an explanation, but here we are. Thanks for your input though. I am hesitant on headers as I have heard they are louder than manifolds. I am trying to keep the truck as low-key as possible. As I get older the tinnitus appreciates quieter vehicles.

 

The 289HP EXH MANIFOLDS were pretty much eye candy as they were still log type -


But they would fix your current problem(s) and look nice.

A set of repros might cost as much as a set of nice shorties.

 

I'd suggest buying manifolds for a late model EFI 5.8 in a 1/2 ton, the passenger side has an attachment on the front for the EGR tube but that can be blocked pretty easily, the version for HD trucks also has AIR injection fittings at the collector so avoid those if at all possible, in retailer parlance you want the non smog or nor air injection version.. 5.8 manifolds have larger collector openings than 5.0 versions so they do flow a little better, and both sides have the conical collector.

 

Cool, do you know if this would be all EFI 5.8's or just certain years like 90-97?

 

I saw some of those they look sweet, but they are a bit more than I am wanting to spend.

 

Good quality headers or even shorty headers will be quiet and honestly there are no drawbacks to the good quality units.