Headers to 2.5" Ramhorns

[1949gmc]

This needs to be brought back to the top again for everyone.

The manifolds from Speedway Motors are the Dorman manifolds, just so everyone knows.

[bigeasycigars]

Originally Posted by 1949gmc

This needs to be brought back to the top again for everyone.

The manifolds from Speedway Motors are the Dorman manifolds, just so everyone knows.

Awesome!! Thanks!!

[1949gmc]

Originally Posted by bigeasycigars

Awesome!! Thanks!!

You got it, man! Thought you might find this helpful!

[TonyJohnson]

Currently I have stock ram horns with custom 2 1/4" to magnaflows and then dumping behind the rear wheels. I picked up a set of the Dorman 204s, ground them down and they're ready to go on, but I need to mate them to my 2 1/4.

Speedway recommends using header collectors for mounting the exhaust to these. Anyone here use them? Any other ideas? I thought about just using some stiff wire and making a template for 2 1/2" head pipes and then using a slip fitting on the other end to clamp over the 2 1/4... What did you guys do? Would I lose much staying with the 2 1/4 after the magnaflows?

[jaros44sr]

Originally Posted by 1949gmc

This needs to be brought back to the top again for everyone.

The manifolds from Speedway Motors are the Dorman manifolds, just so everyone knows.

Looks like they are 60 bucks ea. in my new speedway catalog. Thanks for bringing an ol' post BTTT '49gmc

[LostMy65]

My 65 that I'm still looking for had classic corvette 2.5 RamHorns.

[AlaskaMatt]

Bookmark.

Funny I was reading this same thread a week or two ago after searching for header options. Good info here.

[LostMy65]

So is everyone happy with the Dorman's?

Are you getting the DOR-674-504 or DOR-674-503?

These are the 2-1/2" correct.

[LostMy65]

RockAuto has them for $47.79 for either the DOR-674-504 or DOR-674-503.
They add $8 each for shipping.

Amazon has the 504s for 55.94 with free shipping.

but if you got two rights from amazon, you could have two 503s to your doorstep for $98.40

[LostMy65]

Ok, I found the answer:

Originally Posted by smbrouss70

Mine came in yesterday! Dorman 674504 is what you want, if you don't want the heat tubes.

Also this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=404828

The left (Driver's side) doesn't have the 'heat tube'

[mcmlxix]

another alternative....
http://www.jegs.com/i/Wysco/938/MA035RAW/10002/-1

[72freak]

I just did a set on my 69. Engine in stock V8 possition. They really look nice. I got the ones with no brackets or heat tube holes. I also did extensive research to find a set of plug wires that were long enough to wire it correctly from the bottom without having to buy 2 sets or make them. It turned out nice. Ill take a picture to day of the completed engine bay.

[TonyJohnson]

Where'd you get those collector tubes? Are they just standard header type?

[Effeckt]

Originally Posted by mcmlxix

another alternative....
http://www.jegs.com/i/Wysco/938/MA035RAW/10002/-1

Still available on amazon for $55 each shipped currently also.

[badpeanut]

Originally Posted by 72freak

I just did a set on my 69. Engine in stock V8 possition. They really look nice. I got the ones with no brackets or heat tube holes. I also did extensive research to find a set of plug wires that were long enough to wire it correctly from the bottom without having to buy 2 sets or make them. It turned out nice. Ill take a picture to day of the completed engine bay.

Details please on your exhaust pipes!

Any clearance issues to the starter (and is it the stock full size starter)?

[72freak]

Originally Posted by badpeanut

Details please on your exhaust pipes!

Any clearance issues to the starter (and is it the stock full size starter)?

Normal 2.5 straight runs just like any other dual exhaust with 40 series. No issues. The common myth that there are clearance issues with x-members with the engine in the v-8 position or clearance issues with stock starters is just that...a myth!. I have noticed I will probably need to make a shield for where the exhaust pipe comes close to the front right brake line where it wraps around the frame...its a little close.

Originally Posted by TonyJohnson

Where'd you get those collector tubes? Are they just standard header type?

Yes...collectors welded on to pre bent 2.5 pipe. I told/showed my muffler guy what I wanted and he made them for me. I had 2 sets made exactly the same for the next project.

[TonyJohnson]

Cool...

[rsavage]

Nice "unmod". I'm a firm believer in stock exhaust manifolds for a variety of reasons looks, ease of plug access, less heat in the truck, easier on the starter, etc. With the center dump ram horns, the wires were designed to run underneath along the block and up to the plugs with 90 degree angle boots. Cylinders 1,3 and 2,4 actually come up through in-between the block and motor mount. Run like that with the stock heat shields, they shouldn't burn. One other note, if you are keeping your truck stock, I don't believe that the heat stove sheet metal will fit over the 2 1/2 " exhaust manifolds - you would have to stick with the 2".

[Effeckt]

So reading through this thread, I began wondering if you all would recommend getting the 2.5 ram horns over the factory ram horns? I recently found the factory 2" ram horns that already dump out at an angle in my garage. The PO put headers on my Blazer but I have an exhaust leak so I'm wanting to redo the whole system now. Would the extra .5" be worth while getting the Corvette horns or should I stick with the ones I've got?

[rsavage]

They are 25% larger so they will flow better. Probably wouldn't notice on a stock engine. Your Blazer is a 4WD. 4WD used the straight down center dump whereas 2WD uses the angled. I am not sure whether or not you would run into clearance issues with the angled dumps because I have never tried it. Perhaps someone else can tell you.

[drunkbus]

Originally Posted by badpeanut

Details please on your exhaust pipes!

Any clearance issues to the starter (and is it the stock full size starter)?

It was a tight fit to the starter on mine but there is room to make it happen. I ran heat wrap for the first few feet on both sides since it is so close to the starter and transmission cooler lines and the oil filter on the other side.

[Cap'n Hook]

Does anyone know if the Dorman 674-504 lefts will fit Vortec heads? I've got a nice big hole started on the #2 cylinder and I'm tired of the leaking flanges!

[MrGoodpliers]

Welcome home.

[jaros44sr]

Originally Posted by Cap'n Hook

Does anyone know if the Dorman 674-504 lefts will fit Vortec heads? I've got a nice big hole started on the #2 cylinder and I'm tired of the leaking flanges!

Yep, got them on mine! If it has the molded in boss, you can cut it off with an angle grinder and a cutoff wheel.

Thing is, if you run the heat sheilds, you might have a problem with mounting them up. The Vortec heads are about 1/2" taller

Main question is...do you run gaskets or not...big debate floating around the boards. I don't, I am just using copper shield. Also, I think the factory locking plates will work best to mount your manifolds, no more loose bolts that create leaks

Don't forget you need a new intake, although they make a dual pattern bolt, for the early intakes, the runners are about 3/8" short for the earlier intakes

[Mike C]

Originally Posted by rsavage

They are 25% larger so they will flow better.

It is a 25% larger diameter, but that is not what makes the difference.

If the exit is the largest restriction, the 2" manifolds have a 1 x 1 x pi=3.14 sq inch opening. The 2 1/2" manifolds have a 1.25 x 1.25 x pi=4.9 sq inch opening. That is a 4.9/3.14=1.6 times as much so a 60% increase in area which should have a huge impact on the ability to flow.

My opinion is just about any performance level can benefit with the 'vette manifolds.

On my truck the "butt-o-meter" said they made more low speed torque than the headers they replaced with no loss on the top end. But it has a little cam, 210 @ .050. This is not a fair apples and apples comparison because the headers had 2 1/4" exhaust with some Turbo King mufflers while the manifolds got 2 1/2" pipe with Dynomax Hemi turbos.

Regardless, one of the best mods ever IMO. Good power with low noise and no maintenance.