1968 Header / Exhaust questions

[dpheyes]

I'm reassembling my J code in anticipation of getting it back on the road in late spring in time for our local Memorial Day parade.

Anyway, here's some background:

Although this is a J code car, a previous owner had replaced the engine with a 351W out of a 69 Mach I. It had Ford Motorsports #G302 chrome long tube headers with 3" collectors. I sold the motor, but kept the headers. I'm putting a 330 hp 347 Stroker back in it.

Here's my dilemna:

Shipping parts to Alaska is outrageously expensive. Because of the weather here, I want to put a stainless dual exhaust on it. I was considering a Magnaflow kit. The only place I can get free shipping is through Amazon.com, but they will only ship the 2.5" tube kit free. They won't ship the 3" kit at all. Weird, but true!

My questions:

Can I get away with using a reducer and putting 2.5" tubes on it? Will I sacrifice much? Does anyone have any experience with ceramic headers?

Thanks!

 

[robert campbell]

Dpheves,
You can reduce down to 2.5 exhaust and it will be just fine. 3 inch may have a “hollowed” different sound, but you should have no performance issues with the 2.5 inch. Plenty big enough for your application.

I have had two sets of ceramic coated headers. LOVE THEM! Reduced heat and no rust! I have a set on my special. Blown 302 with 2.5 inch exhaust.

Hate to rain on your parade, but you may have another problem. The 351 motor has a taller deck height than the 302 stroked to 347. This raises the headers up a bit and towards the shock tower a bit. My guess is they will run into a lot of stuff mounted on the 302 shorter deck height. They will hang lower and may come in contact with the starter and other stuff!

My guess is you will need new headers. Here is a source for the best headers I have found for a small block Mustang. They tuck way up and are of the highest quality I have seen. Stan Johnson knows Fords like few people do!! Of note these his headers will require a smaller diameter starter from a newer 302 engine.

http://www.fordpowertrain.com/FPAindex/Mustang1.htm

Rob

 

[di81977]

Rob, agreed on the 351W headers. I pulled my J code and installed a 393 stroker (351W). I ordered special conversion headers from Summit and they initally sent the wrong ones (for a 302). The collector tube was hitting against the body of the car due to the height of the block. Correct ones fit fine. I suspect if you try to use the 351W headers, they will be very low and be prone to hitting the ground on bumps, etc.

Also, depending on how radical the engine will be, 3" exhaust is probably too big and will not improve performance.

Good luck
David

 

[dpheyes]

Rob, David,

Thanks for the input guys! It really helps to hear from you guys that have been there before.

I talked to my dad again and he believes the headers were on the original 302 before it was replaced by the 351. Does that sound possible?

It turns out my wife saved the day! She told me all about amazon.com "Free Super Save Shipping". I was able to order the Magnaflow 2.5" complete stainless exhaust system plus a set of Hooker silver ceramic long tube headers for less than $800 plus free shipping to Alaska. Just a strange note: Amazon will ship the 2.5" system for free but won't ship the 3" system at all. Go figure.

I'm told that since this is a new motor, breaking it in with the new ceramic headers is a no-no. The Hooker web site says it will ruin the coating. I'm hoping the old headers will fit so I can use them during the break-in. I can't find out anything about the part # from the old headers, so I guess I'll just have to put it all back together and see.

David,

How long in Boulder? Our family lived there from '70 to '92. I graduated from Niwot High in '76. Sure is an interesting place to live!

Thanks,
Doug

I'll also have to figure out how to fit the GT exhaust dual tips to the pipes. Do you think that might work? I think the tube size on them is 2-1/8".

 

[di81977]

Doug,

It is possible your existing headers are for a 302. They would bolt to the heads, but as I explained, mine were sitting against the floor pan due to the taller engine. News to me on the ceramic headers and break in. I put in Hooker Super Comps right with the new engine and have had no problem with the coating.

Been in Boulder since 1997. Came from the Bay Area (as many of us did). I am sure it has changed considerably since 1992. Niwot High in '76 must have been pretty small, but full of kids who's parents worked for IBM. Is that how you come to Colorado?

How did you end up in Alaska? Enjoying it? Going from 300+ days of sunshine to 20+ hours of darkness a night had to take some time getting used to.

Ever come back to visit? Let me know if you do.

david

 

[robert campbell]

When breaking in a new engine with a flat tappet cam, it is normal to run the engine a 2,000 RPM for 20 minutes immediately when it starts. One must have a timing light on it and best with a known adjusted carb. You want to spin the advance way forward, like to 20 or 25 degrees BTDC for this 20 minutes. Do not concern yourself with setting the normal timing until after the break in of 20 minutes. Roller cams do not need this break in procedure.

The biggest reason that they do not want you to do this with new ceramic coated headers is that during this 20 minutes the new engine generates a lot of exhaust heat because of newness and a lean condition as the carb is still basically on the idle circuit. Even a broken in motor or a motor run for a couple years will generate a lot of exhaust heat if asked to idle at 2,000 RPM for 20 minutes.

I have seen many engines under this 20 minute break in actually make the headers glow red close to the exhaust ports on the engine. This will damage a new ceramic coated header that has not been “cured” yet.

So if you can use the old headers during break in. You can weld a couple collectors on a couple mufflers and bolt them right on the header to quiet things down. I never like to start a new engine with open headers. To much noise.

Rob

 

[dpheyes]

Rob,

Wow! Thanks for the info. I've never broken in a new engine like this before, so this is all new info to me. I don't have a dialed-in carb, just a rebuilt one.

I have a couple of new truck mufflers I never used, so I'll just weld some collectors like you suggest before using my new system. If it gets that hot, maybe I'll hook up some hoses to run the exhaust out the garage door and use the engine to heat my garage!

Any recommendations on oil for the break-in? I believe I also need lead substitute for the gas.

David,

Yes, we moved to Boulder when my dad transferred with IBM from WA state. Still have family there in Longmont. Joined the Coast Guard in '77 and after 12 years, was finally able to get to AK and I'm still here! At the solstice, we still have about 6.5 hours of light (10 am to 4:30 pm).

 

[rvrtrash]

I never like to start a new engine with open headers. To much noise.

Rob

My neighbors say the same thing. :grin:

Steve