Does anyone know if these are these the same part? It is about $150.00 differance.
http://store.summitracing.com/partdetail.asp?autofilter...700+115&autoview=sku

http://www.dougthorleyheaders.com/details_headers.php?ProductID=13796

Neil.

Yup. I bought mine from Summit for several of my vehicles, including two of my P30s.

Be sure you match what you order to your emissions requirements. If you plan to use a heat riser valve, you will need a bigger one. Thorley sells one. My Thorleys were pretty easy to connect to the existing exhaust pipes. I used band clamps.

Thanks for the reply. After looking at the pictures closely it looks like the Summit units have a donut type gasket at the collector and the other units have flang gaskets. What did yours have?
Neil.

quote:

Originally posted by Neil T.:
Thanks for the reply. After looking at the pictures closely it looks like the Summit units have a donut type gasket at the collector and the other units have flang gaskets. What did yours have?
Neil.

My most recent purchase was the 303YS, which had AIR fittings and donut flange gaskets. Looking at the picture in the Summit ad, it looks like the headers have flange connectors like mine. Perhaps a call to Thorley and Summit will provide the answer. It would be a good idea to talk to them both, anyway, just to be sure you get the correct part numbers.

One more thing.....When I bought mine, ceramic coated Thorleys were not available. I wish I had bought the ceramic coated. Even though Thorley offers a lifetime guarantee, ceramic coating is more attractive.

The 303s fit on my 1973 454; I jacked the engine up to make it less of a pain to get the header on the driver side, it is a tight fit and with my plumbing for the external oil cooler it is actually more than just a pain if the engine is not up a couple of inches (5cm). I also wish I had put the extra money into ceramic coated headers, after a year they are looking less than perfect. No smog on the 73 so I can not say much about that. The 303s I ordered do not have any smog connections.

The gaskets on mine, purchased last year, are a rather unique configuration; half donut. I suggest ordering an extra set, I pulled the headers and had a devil of a time getting repleacemnts in Los Angeles.

I put aluminum coated gaskets on the headers where they connect to the manifolds, these work well, a light coating of red silicone has not proven to be a bad thing. The bolts that come with the headers are steel and mine rusted in no time flat, I replaced them with stainless bolts; I sure hope I don't have to drill them out in the future.

Timothy

Hey Timothy, Did the Thorleys give you a noticeable difference in performance? Any help on fuel economy? Do you think they were the effort?

The Thorley tri-y headers (303y) will give you more mid-range (rpm) torque which will be a big improvement over stock manifolds; you'll notice an improvement climbing grades, towing etc. I have a pair that I was going to put on my sob 454 before I decided to buy the Regency. If you want to get the most benefit from these I would consider:

1-Putting on an X-pipe (universal 2.5" kit) which is about $90 from Summit. This will increase the low-end torque substantially and will actually quiet the exhaust sound.
2-Use 2.5" exhaust pipe all the way (stock is probably 2.25")which is the optimum for these headers.
3-I bought Dyno-max mufflers, although alot of these setups are running Flomaster 70's. Flomasters are louder.
4-Run the tail pipes out in front of your dual wheels (easy install and effective).

Buy the best COPPER header gaskets you can find and install the headers with LOCKING header bolts (use anti-seize on the threads)and you will avoid any problems with them leaking soon after you put them on. In preparation start soaking your existing bolts with "PB BLASTER" daily.

If you can do the install yourself (not real difficult actually)the parts are cheap for the increase in torque and the motor will be breathing a lot more efficiently. just putting the headers on will be an improvement but for just a little more investment you'll get the full potential out of your exhaust.

Actually if you do this you are well on your way to imitating what Banks & Gibson systems offer and for a lot less money.

I had also purchased an Edelbrock carb (750 cfm) to replace the Quadrajet and was going to put this on a WEIAND intake manifold, they make an intake specifically for the small oval port heads (peanut port) that you also probably have on your block. I think the manifold is a 8017 and it's under $180, the carb is about $220 so this is affordable for what it will do (this part should increase your mpg).

Even if you don't add the intake and carb: Make a "cold-air" intake out of a cheap chrome intake filter this would cost under $50 and will increase HP (cold-air system is what Banks uses). If your interested in doing this (it's actually pretty easy) I'll see if I can post how I was doing mine. The more air and the cooler the air you can put thru your 454 at this point alone will really wake 'er up..

Sorry if I got carried away; my son and I used to do this together and I really enjoyed working with him on this stuff.....so much fun...and rewarding if you can do it yourself.
The diesel is boring in comparison...just maintenance stuff.

Please do post your cold air intake setup.