Interesting Comparison
 

Comparison of exhaust note between a 1970 T/A & 1978 Y-82 T/A.

1970 has Ram Air IV Manifolds with 2.5 inch opening going into a pypes 2.5" down pipe into a Flow Master American Thunder Series exhaust mandrel bent with H-Pipe into Texas TA mufflers and 2.5 inch tailpipes.

1978 Ta has Dougs long tube headers with 1 7/8th inch primary into 3 inch collector with a Pypes 2.5 inch mandrel bent exhaust and x-pipe. Also has Texas TA mufflers.

The 78’ SE has a 406 with 6X#4 heads. The camshaft is a comp cam XE274H. Specs are flat tappet 274/286,230/236,.488/.491, 110LSA. Rockers a roller tip @ 1.5.

The ’70 has a 433 RAIV. The camshaft is a Butler custom grind. Specs are hydraulic roller 282/288,230/236,561/573, 112LSA. Roller rockers @ 1.65.

Here is the comparison video with both cars:

https://www.youtube.com/watch?v=DcVQ_recmz0

Here is the 1978 by itself to give you an idea of how the car sounds by itself:

https://www.youtube.com/watch?v=uoPq4dDVyW8

I would think the car with the long tube headers would be louder even with the X-pipe. Evidently, not the case.

I wonder if the angle of the exhaust tips vs straight is a contributing factor?

Couple great looking cars there. I would expect anything with headers to be louder but maybe it's all about the mufflers

Thanks. They both have the same mufflers. Texas TA mufflers.

Compression ratio probably plays a factor between the two....what kind of compression are each running?

compression
 

78' - 9.5, 70' 9.9

I've switched back and forth between long tube headers and factory ram air manifolds on my 70 Formula, with no other changes.

It's actually noticeably louder with the exhaust manifolds on the car.

Yes, it does.

Without getting too technical, the video (and sound recording that goes with it) is shot "off axis" from the 78 and "on axis" for the 70.

From a mic technique standpoint, off-axis recording where the mic is at an angle from direction of sound, produces a warmer, softer sound, while a mic that is on axis, directly in the path of sound will produce a brighter and often louder sound.

That said, you can still glean a good amount of comparison here. Those turn downs will act to quiet the car because as a human you're hearing it from the same angle the video was taken from. The rear exit exhaust of 70 is the same thing, it's not sending sound waves into the ground first so you're going to hear more of it in the real world as well.

Jim, is that X7 coded 400 with milled 6X-4 heads you bought from Len in the early 00's?
Did you later have heads ported?

Larry,

I agree with you.

I think a future comparison might take place with the '73 that is receiving the 496 and the '70. The exhaust will be the same except the '73 will have Dougs long tube headers and the '70 will have the RAIV manifolds with the 2.5" outlet.

Thanks,

Jim

JLMounce,

I hear what you are saying, but I have a friend with a 1979 T/A with the same recipe as I have in my '78. The only difference is I have headers on mine and he has Ram Air III exhaust manifolds. At one point, my car was parked next to his at a show. When both cars were running you could only barely hear my '78.

At another show I had the '70 and my friend had his '79. There was barely a difference between the sound. The '70 was louder, but only by a very small fraction.

Thanks,

Jim

Roger,

Yes, that is the engine from Len Williams.

I had a few things done to the engine since Len built it. The heads were cleaned up, but not ported. The other changes include thinner heads gaskets to up the compression to 9.5, upgraded cam from the Summit 2801 to the Comp Cam XE274H, .30 overbore to get an additional 6 cubes, went from cast connecting rods to Eagle forged H-Beam connecting rods and went with an Edelbrock performer intake manifold. Also, changed from RAIII exhaust manifolds to Dougs long tube headers.

Good to hear from you.

Jim

Another item to bring is the H-Pipe vs X-Pipe. The H-Pipe puts more emphasis on the cam and the X-Pipe tends to quiet things down.

Interesting that Len hadn't previously built the shortblock at .030. Remember you & I chatting about the cam choice, as usual choice of Len's was the Melling RA4 & Rhoads lifters.

Not sure if I mentioned it years ago, but that particular X7 shortblock (maybe complete longblock), I pulled out of a 78 Y88 car, along with it's original T350, 3.23 rear, gold tops, & bunch of other pieces. Was frustrating as in over a decade, it was the only cool car that I couldn't get whole out of 2 local Pick-N-Pulls. A few months before it came in, the long time mgr quit & the scrawny little counter guy that was never made mgr (but thought he was) ruined many a working relationship with several of us that bought a ton of parts, ESP core parts that usually got crushed.

Roger,

Now that I think about it, I think Len was the one to do the .30 overbore. It has been a long time since I thought about this. I remember when I told you about the Summit 2801 you said, "I would lose about 60 horsepower not going with the RAIV cam". The XE274H put the 60 HP into the engine. It has about 380 or 385 at this point.

I remember you told me the X7 block came out of a junk yard in OK along with the other things you mentioned outside of the little counter guy.

dont remember the 60 hp bit, but have had a hand in, & driven several non AC 4spd late 70's T/A' s w milled 6X-4 406's that ran fairly strong (low 13's @ the track on hard BFG's) for milled small valve 6X-4 400's. Each were orig asm with RAIV cam/Rhoads combo & had 3.42's-3.73's in the rear, & two of em ran stronger than in the mid '80's with my '80 with fresh 406; '70 YZ /cleaned up "64"s with HO Racing cam & Hedman 4 tubes.

Roger,

My plan is some time this year to change the original 3.23 to 3.73 rear gears. It should give it a nice kick in the pants. Don't have to worry about highway rpm's as the car has a 700R4. I want to do this so I don't have to go into the engine. Right now the engine runs really good.

Jim

It would be interesting to hear them both fully warmed up. What was the idle rpm of both?
The biggest difference for the sound are the engines. One with a keen ear can hear the higher compression and valve lift of the 70. I like the sound of it. Its hard to hide horsepower.

I used Dynomax Super Turbos on a Pypes system and it sounds real nice but kind of quiet.. I'm thinking on going to a chambered system https://www.ebay.com/itm/1964-72-Che...r/153025854923

That would be hella loud, lol.

There's a reason why GM discontinued chambered exhaust half way through the 69 Chevrolet Abody and Fbody production run.

Never heard of Texas TA? Who are they?

I agree on the X pipe. I put an off road x pipe (no cats) and flow masters on my 87 Saleen and couldn’t wait to hear it. Sounded nothing like the cars I remember growing up due to the x pipe