1970 Fury Log Manifolds

[1970FuryConv]

I measured the outlet side of one of my 440 log manifolds at 2" ID.
If I use the log manifolds in swapping a 440 into my 1970 Fury convertible, is there any advantage in going with 2.25"ID or 2.5"ID dual exhaust pipes?

 

[Davea Lux]

I measured the outlet side of one of my 440 log manifolds at 2" ID.
If I use the log manifolds in swapping a 440 into my 1970 Fury convertible, is there any advantage in going with 2.25"ID or 2.5"ID dual exhaust pipes?

While the flow may be restricted at the 2" outlet, you should still get lower overall Flow resistance going to the larger pipes. The main problem with the log manifolds is not so much the outlet diameter, it is the fact that the ports from the cylinders flow directly into the side of the log manifold without much deflection. This causes turbulence and back pressure inside the manifold that increases as engine RPMs and exhaust volume increases. The large tubing size gives all that a place to go. Exhaust gasses follow the path of least resistance.

Dave

 

[polara71]

The 2 1/4 looks better coming out the back of the car in my opinion compared to the larger 2 1 /2

 

[CBODY67]

As the front pipes might need some tweaking if they were originally for a 383, you might as well seek to find some of the '74-era standard manifolds. I believe they have larger cross-section runners and a larger exit hole?

The exhaust pipe gasket will be specific to the spacing of the mounting studs for the pipes, which might well be related to the outlet hole diameter. Something to check and verify, for good measure. Which is probably why some of the exhaust people desire to know the casting numbers of the manifolds being used.

Just some thoughts,
CBODY67

 

[MEV]

I measured the outlet side of one of my 440 log manifolds at 2" ID.
If I use the log manifolds in swapping a 440 into my 1970 Fury convertible, is there any advantage in going with 2.25"ID or 2.5"ID dual exhaust pipes?

I cant imagine it would make a difference. My 512 cubic inch aluminum head 66 newyorker went 12.80 in the quarter mile with log manifolds and 2.25" duals thru cheap turbo mufflers.

 

[1970FuryConv]

While the flow may be restricted at the 2" outlet, you should still get lower overall Flow resistance going to the larger pipes. The main problem with the log manifolds is not so much the outlet diameter, it is the fact that the ports from the cylinders flow directly into the side of the log manifold without much deflection. This causes turbulence and back pressure inside the manifold that increases as engine RPMs and exhaust volume increases. The large tubing size gives all that a place to go. Exhaust gasses follow the path of least resistance. Dave

I cant imagine it would make a difference. My 512 cubic inch aluminum head 66 newyorker went 12.80 in the quarter mile with log manifolds and 2.25" duals thru cheap turbo mufflers.

Followup Question: I don't want headers. Do you know what the outlet ID is for the HP manifolds? Are HP exhaust manifolds worth the cost in terms of reducing turbulence and back pressure?

Some people race convertibles, but I use mine for a family cruiser. Most important is 0-70mph performance. With Virginia speed limits of 70 mph and below, wreckless driving is 80mph and above. Ticket stays on your record for 11 years. Cops seem to give leeway up to 85mph, but anything above that is asking for a lot of insurance trouble. Thanks, Ben

 

[cbarge]

Followup Question: I don't want headers. Do you know what the outlet ID is for the HP manifolds? Are HP exhaust manifolds worth the cost in terms of reducing turbulence and back pressure?

Some people race convertibles, but I use mine for a family cruiser. Most important is 0-70mph performance. With Virginia speed limits of 70 mph and below, wreckless driving is 80mph and above. Ticket stays on your record for 11 years. Cops seem to give leeway up to 85mph, but anything above that is asking for a lot of insurance trouble. Thanks, Ben

HP manifold outlet is 2-1/2 same as the front pipes from TTi.
The HP manifolds do have an advantage regarding better flow vs lo-po logs but still restrictve vs headers.
HP do look sexy but hold heat for hours on end and known to cook valve cover gaskets,plug wires and pain in the *** to swap plugs.
I have them and they are worth the third degree burns on my hands,LOL!!

Personally the 2-1/2 TTi system works great. and the turn downs do not "look" too big on a C either. Their system is worth every penny,excellent fit,finish and sound.
I had the system on 3 cars,two with the lo-po logs and the BoaB with HP.
My 2 cents.

 

[1970FuryConv]

Thanks @cbarge. Beautiful car and great pics. What paint/finish did you use on manifolds?

 

[furious70]

3" looks right to me

A pleasure craft probably could prioritize price and stick with logs and cheapest pipes.

 

[cbarge]

Thanks @cbarge. Beautiful car and great pics. What paint/finish did you use on manifolds?

After sand blasting them,scuffing them with steel wool I used POR15 brush on exhaust manifold paint. Seems to be holding up well 10,000 miles and third season driving.

 

[1970FuryConv]

After sand blasting them,scuffing them with steel wool I used POR15 brush on exhaust manifold paint. Seems to be holding up well 10,000 miles and third season driving.

Awesome @cbarge!!! Just awesome.
I have a LS 440 hp manifold coming.
Just posted a want ad here for a RS hp manifold.
I'll see what's out there, buy the manifold, and buy the POR product you used. Thanks!! Ben
Where did you buy the special fasteners for the hp manifolds?
1968-71 Big Block C-Body Exhaust Manifold Fastener Kit HP BB 383 440 Studs Nuts | eBay
$54.99 for bolts seems a high price.

 

[cbarge]

Awesome @cbarge!!! Just awesome.
I have a LS 440 hp manifold coming.
Just posted a want ad here for a RS hp manifold.
I'll see what's out there, buy the manifold, and buy the POR product you used. Thanks!! Ben
Where did you buy the special fasteners for the hp manifolds?
1968-71 Big Block C-Body Exhaust Manifold Fastener Kit HP BB 383 440 Studs Nuts | eBay
$54.99 for bolts seems a high price.
View attachment 344858

I bought my manifold hardware from National Moparts.
Thats the goung price nowadays. I paid more in Canadian funds fyi.

 

[cbarge]

For the 70 left side make sure you get the heat shield for the stove pipe if running factory air cleaner.

 

[MEV]

3" looks right to me

A pleasure craft probably could prioritize price and stick with logs and cheapest pipes.

3" Looks and sounds nice.

 

[1970FuryConv]

3" Looks and sounds nice.

Love New Yorkers. And your 12 second quarters with logs and 2.25"s are way cool!!!
However, I'm going with 2.5" duals and Flowmasters. Working on 2.5" outlet HP Manifolds to match. Have Left side coming. ebay: 3418351 casting #, 1970-71 440 C-body, Ordered yesterday $180.71 including sales tax and ship to Virginia.

No I don't care about the chip. Love the chip, got me a discount If you disagree, prove to me that the car will go faster without a chip on a heat release rib.

Anyone know if RH HP manifold 2809600 67-69 casting # is same as 2899879 70-71 440? According to my research, RH HP is same for B & C body cars.

 

[cbarge]

Love New Yorkers. And your 12 second quarters with logs and 2.25"s are way cool!!!
However, I'm going with 2.5" duals and Flowmasters. Working on 2.5" outlet HP Manifolds to match. Have Left side coming. ebay: 3418351 casting #, 1970-71 440 C-body, Ordered yesterday $180.71 including sales tax and ship to Virginia.
View attachment 345013
No I don't care about the chip. Love the chip, got me a discount If you disagree, prove to me that the car will go faster without a chip on a heat release rib.
View attachment 345014
View attachment 345015
View attachment 345016
Anyone know if RH HP manifold 2809600 67-69 casting # is same as 2899879 70-71 440? According to my research, RH HP is same for B & C body cars.

I am using a 67-68-69 left HP manifold and a 70-71 right HP manifold.
The early ones are more prone to cracking,so I recommend getting a later casting.
No difference in them really .
Hope this helps.

 

[1970FuryConv]

I am using a 67-68-69 left HP manifold and a 70-71 right HP manifold.
The early ones are more prone to cracking,so I recommend getting a later casting.
No difference in them really even up to 73. Hope this helps.

So then: are you regretting using the 67-69 Left side manifold and telling me not to do same 67-69 with my Right side manifold?
To be clear, car will run about 1000-2000 miles per year, tops. In fact, I have yet to put a 1000 miles on the car in one year. Would cracking still be a concern?
In response to my RS manifold want ad, @413 on differences between RS cast# 2806900 67-69 and RS cast# 2899879 70-71
"The difference is the heat riser shaft is turned 90 degrees, the counterweight is different, and the bolt clocking is different.
They won’t bolt up to the same pipe.
But they do look the same other than that."

 

[cbarge]

So then: are you regretting using the 67-69 Left side manifold and telling me not to do same 67-69 with my Right side manifold?
To be clear, car will run about 1000-2000 miles per year, tops. In fact, I have yet to put a 1000 miles on the car in one year. Would cracking still be a concern?
In response to my RS manifold want ad, @413 on differences between RS cast# 2806900 67-69 and RS cast# 2899879 70-71
"The difference is the heat riser shaft is turned 90 degrees, the counterweight is different, and the bolt clocking is different.
They won’t bolt up to the same pipe.
But they do look the same other than that."

When I ordered my TTI system,I gave them my casting numbers and the sent the respective front pipes.
You are upgrading from lo-po logs to HP so whatever right HP you get,just match the front pipe.
No problems.
Yet I had seen many early castings throughout my search cracked or poorly repaired.
Just sayin'.

 

[413]

I’ve owned dozens of HP manifolds and never had one crack while using them. So if it’s solid when you buy it it should stay that way. I’ve seen plenty of cracked and welded ones for sale. But seems people sell the junk and keep the good ones.

The RH HP 70-71 is for all BB B C E body all the same part.

 

[rags]

Love the chip

if you don't put the heat stove over it, you could just clean it up, round over the edges and make it look like it belongs there. @FURYGT , any right side manifolds for this guy?