Got 0 responses on the 73-39 forum, perhaps this is a better forum to post this on?<hr size="1" style="color: rgb(209, 209, 225); background-color: rgb(209, 209, 225);"><!-- / icon and title --> <!-- message --> 1) Just found two new EFI exhaust manifolds on eBay. I know I will need a new Y-pipe. Is any one pipe considered any better than others?
2) The recommendations I have seen are for 2.5" pipe all the way back?
3) Truck is an F100 Custom and probably has a cat (have not checked) - delete the cat from the system?
4) While I would prefer a new manifold gasket, can I get away with using the old one? Or will the log-manifold gasket even work with EFI manifolds?
4a) - Convert to studs while I am at it, I would guess?
5) I am NOT looking for noise - any recommendations on the muffler?
6) Re. getting heat to the intake - about how much room will I have to
work with between the EFI manifolds and the original intake?


I am trying to 'wake the old girl up' but not seeking huge horsepower.
A) Would replacing the 1bbl with a 2bbl improve mileage and power?
B) If so, could I use the stock intake manifold?
C) Which carb would be a good choice?

Truck is a '78 F100 Custom, 300cid 6, C6 transmission, pretty much bone stock, no rust, only a few dents. Lots of purty black primer.


Dave

 

4) try no gasket - just a film of red silicone sealant such as Permatex
4a) sure. Dont' forget to make two anti-sag clips to hold the EFI manifolds in place. Later heads have an extra bolt boss to prevent this.
5) I like a mellow Flowmaster Series 50 - not the louder Series 40.

A) it will improve power. mileage - not so much.
B) Yes, but an aftermarket is far superior.
C)Autolite 1.02 or 1.08; Rochester 2GC

 

Anti-sag clips? I understand the term but would think the manifold bolts etc. would hold the manifolds - where would these go? Do you maybe have pictures so I can envision them better?


Re the carbs - my understanding is that since the primaries on the 2-and 4-bbl carbs are smaller that there is a definite mileage gain (until you stick your foot in it) ? Or is that like saying "she don't burn any gas until you start it"? Would a small 4-bbl be a better choice?

 

I don't have anything on mine holding it in place and they haven't budged or moved. It can be a little bit of a pain getting them lined up, but if you use studs, the moment a nut starts to tighten down, they're fixed in place.

1. Walker makes an aftermarket pipe Part number 45166
http://www.summitracing.com/parts/wlk-45166

Not the highest performance piece, but very well priced and easy to install. Be sure to check the rear port since sometimes they don't open it up all the way.

2. I have 2.5" on mine from manifold to muffler and love it.

3. That's a personal choice. I, for one, never advise this as they're not just put on there to pass regulations, they're there to help keep our air clean.

4. IF you use a gasket, don't reuse it. Try a Mr. Gasket 260.
http://www.summitracing.com/parts/mr...JgUaAt-58P8HAQ

I've never not used a gasket on mine, so I can't advise you on how that would be.

4a. Yes, this is easy to do and makes installing three manifolds at once SO much easier.

5. I'm a big fan of the Dynomax Turbo Muffler. Smooth, quiet, and has a nice rich sound when you open it up.

6. You'll have plenty. The intake goes straight out from the engine while the exhaust immediately drops down. You won't have ample space, but any nice setup will fit without much trouble.


A. It definitely can if done right. However, many will say that a 4bbl will do better than a 2bbl as long as you don't have too much fun with it. The primaries on a 4bbl are generally smaller than the two barrels of a 2bbl.

B. The stock intake is just big enough for a 1bbl. There are adapters to put a 2bbl on it, but you won't get enough flow through it, and really take away from much of the gains you'll get with a 2bbl. That said, I had just the 2.5" on mine for a while with just the 1bbl and just the exhaust really woke it up. It was probably the best gas mileage I got, too.

However, it's hard to say how much gas mileage I've lost with going to 31" tires and a 4bbl, considering it was right around the era when more and more fuels started to get ethenol in them, and I probably would have lost gas mileage anyway.

C. The carbs FTF mentioned would be good. There are a lot more options if you are interested in the 4bbl route.

 

That's the kind of info I was hoping for; thanks to both of you for the help. I will check manifold/4bbl combos; I guess Summit, Cliffords, Offy are the obvious suspects. I'll ask for help if my Google-fu doesn't turn up any others too.


Much appreciated, gents!

Dave

 

Glad to help!

You more than likely will only find a header/intake/carb combo:

Offenhauser 6019-DPK, Offenhauser Dual Port 6-Cylinder Manifold | Offenhauser

(Note that they give you the wrong gasket . A four hole intake mating to a four hole carb should have a four hole gasket).


Otherwise, if you want to go with manifolds, you'll need to piece it all together yourself.

 

'bout fell out of my chair at the price tag till I realized that included headers etc... manifold alone is $262. I'll check around - thanks!

 

Sounds like the first step is hanging on the EFI manifolds, studs, and 2.5" exhaust, trying it for a while, and see how I like it. I have another project before spring anyway - the condenser leaks and all the R12 is gone, so I am going to switch to a rotary Sanden compressor and R134A. Already have a spare condenser and dryer, so that shouldn't cost me too much. Might even see whether paint sticks to the primer black I have now! Again, appreciate the sound advice!

 

That would be a good way to do it. I did my exhaust and intake upgrades about a year apart. Get your exhaust all set up, see how you like it, and then decide if you want to upgrade the intake, too.

 

Probably missed it, but are you rebuilding your exhaust from the y-pipe back? I will be adding the EFI headers to a 300 I am installing in a 71 F100 that had its exhaust replaced about a year ago. I guessing the Y-pipe won't directly connect to it.

 

Hillcountry - That is the plan - I am planning to use the Y-pipe recommended by Abandonedbronco, the 45166, which is a 2.5" pipe. I am not sure whether the existing exhaust is 2" or 1 3/4" - if I do simple math, the area of a 2.5" opening is almost 5 square inches. A 2" pipe is 3.14" and a1 3/4" pipe is 2.4" - no wonder opening the exhaust up to 2.5" should make big difference! I plan a muffler to the Y-pipe and then a single 2.5" pipe to the rear from there. I want it to be as quiet as possible, and what I do hear I want to be mellow, not harsh. I'm too old for the noisy stuff - it interferes with my too-loud music.

 

That pipe should work out with little to no modification for a different era truck.

This is a review someone posted on the summitracing reviews, which was promising:

"I used this for a 71 ford project i am doing.. it is a good product that worked just fine, with a few modifications to fit a truck it was not intended for .. it just needed to do a little trimming to knock of some of the rough edges they left when it was made"

I think the rough edges are the rear port, which everyone should check. Use a long, drillbit style grinder to clean that up the best you can.

 

Ironically just read the same review in the last 5 minutes!

 

I remember my stock exhaust being 1 7/8" when I originally measured it. So yeah, going to a 2.5" is HUGE. It's a 56% increase over stock.

It's also why going to a 3" is not recommended for this engine. Doing the math, that's another 44% over the 2.5". It's 2 1/2 times as much flow as stock.

 

Looks like a tossup between Rock and Summit on price... Summit has free shipping over $99 and since I need a gasket (I'm just more comfortable with one), muffler, and maybe stud kit, I should easily slide past that. Just got the manifolds and need to paint them first anyway - leaning toward Eastwood but???