69 Headers with Stock Exhaust - Any issues?
 

I don't want to get flamed for this question...and admittedly, I don't know much about exhaust. I've got the body off my 69 and I'm planning on installing Hedmen headers (68306) with 1-5/8" primarys and 3" collector to the stock 2" pipe and muffler system. I'll need to have a shop make a reducer as I can't seem to find a 3" to 2" I'm not after performance gains, but simply just a deeper healthier sound. So, that said, are there any concerns I should have with mating the 3" long tube headers to the 2" stock exhaust???

Thanks!

I have not looked recently but I would think Summit Racing has the collector / reducer from 3">2".
Just look for three bolt reducers, sold in pairs. Does not matter what brand, they should be universal fit.

https://www.summitracing.com/parts/b...7flt/overview/

Looks like this is the closest you'll get, which should be a 2" I.D. on the outlet. I would use something like this as HeadsU.P. recommended, and then have the stock exhaust welded up at this reducer.

IF you haven't purchased headers yet, many of them are available with 2-1/2" collectors, which would be much easier to adapt and won't hurt performance if you intend to stick with the smaller pipes for the long term. Reducing from 3" to 2" negates the performance of the headers you're planning on anyhow.

Nobody should flame you for your plan. You can modify your car however you like. I get it - and personally prefer the sound of headers. Keep in mind that mufflers alone, especially with the dual exhaust, can provide the deeper tone you want.

I've got the headers already. I didn't think about the collector size being an issue. I'm fine with reducing from 3 to 2, but wanted to know if it would cause any issues with flow etc and have a negative impact on the motor? I can get 2.5" stock exhaust which was on the SB L71 cars but the stock mufflers still have a 2" outlet for the tips. Outside of the headers, I want to stay as stock as I can. The link shows a 3" to 2.125" will that work with the 2"? Assuming it's welded?

I wouldn't even worry about it. If you have the headers, use them. A shop can weld up the pipes at the reducers - use a set of sleeve clamps when the time comes if you need a temporary connection to get it somewhere. The 2.125" I am assuming is I.D. on the reducer, and your 2" pipe should slide right inside of it. Not ideal but really not an issue with what you are doing.

Something you might look into is switching your 2" system to a 2 1/2" system while you have it apart. That will certainly mitigate any losses you might otherwise encounter reducing to a 2" system from a 3" collector. The '68 - '72 Hi-Po used a 2 1/2" system. It was necked down a few inches below the manifold outlet from 2 1/2" to 2". Your headers will bypass this section of the header pipe anyway.

One thing I encountered years ago when adding Hedman headers to my '63, was that the collector of the headers ended up below the level of the center (trans) cross-member and about even with it lengthwise. I had to go under the cross-member to get to the rear of the car. I would have had to make an "S" pipe to get it through the holes in the cross-member. Hopefully you don't have this issue. :thumbs:

Good luck... GUSTO

I ordered a set. You don't think there will be any problems with flow staying with the 2" stock pipes and exhaust?

Keep in mind you want a little back-pressure anyway. Otherwise your exhaust system will scavenge off valuable unburned air / fuel mix still in the cyl.

Please, man, not that old wives' tale again....:toetap:

I need to find out how the 2 1/2" stock sets are configured (full 2.5 or if it necks down somewhere?) I know the outlet of the muffler has to be 2" to fit the standard 69 tips - they only came in one size. I've got to believe that some people add headers but keep the 2" exhaust set-up. Hedman service says it will be fine and that the end of the headers should be in-line with the stock exhaust so I don't have to come up with some exotic configuration. Thanks for all the comments and feedback. It really does help. If you can imagine, this crazy stuff keeps me up at night! :)

I thought you were the one that told me that?

This is how (and where) the typical 2 1/2" system gets necked down to 2" to bolt up to the manifold...

https://cimg8.ibsrv.net/gimg/www.cor...22d040a524.jpg

https://cimg1.ibsrv.net/gimg/www.cor...e2a738ee51.jpg
From an earlier post... https://www.corvetteforum.com/forums...2-exhaust.html

Good luck... GUSTO

Collector adapters
 

I have a pair of 3” x 2.125” flow tech adapters that are new. I decided to go a different direction. Never mounted. They were shipped to me from Holley performance. PM me if interested

I have the OEM style 2.5" SBC system installed in my 69' Coupe from Corvette Central. You can't beat it for the price.
The pipes are 2.5" past the neck-down up by the exhaust manifolds and the mufflers are what takes the 2.5" down to 2" out the back (mufflers have 2.5" inlets and 2" outlets).
I am running these with Hooker Super Comp headers and I am quite happy with it. :thumbs:

No, not even at gunpoint.

Ha-ha-ha.

Actually, one of those Motor Trend dyno videos did show a torque increase with smaller exhaust size, more back pressure. But we won't get into that.

Whats the part number of the set you bought? Did you have everything welded together? My car is 350/300. Not sure if that matters or not...

I don't recall the part number offhand but if you go on their web-site it's pretty self explanatory.
There should only be 2 different pipe options for the SBC- The 2" or the 2.5". It doesn't matter what SBC you have-
Just order the one for an LT-1 or whatever has the 2.5" pipes.
Since you will be adding headers, you'll be cutting the front pipes anyway.
I did not go with the welded set as I prefer to be able to adjust or modify the pipes individually as I see fit when installing.
:thumbs:

The smaller the pipe dia, the more restriction you add and the higher your rpm level with a given pipe dia, the more restriction you will have. Restricting exhaust flow reduces engine power output. I don't think the difference in pipe size will cause enough power loss to feel by seat of the pants however.