502 headers

[bobshotrodblazer]

Hi All,
I’m thinking of installing a ZZ 502 into my 71 C/10. I currently have a 454 with
2 1/2” Hedman headers full length but would like to go larger tubes. Obviously concerned about fit problems. Also any other fit problems Thanks. Bob

[bobshotrodblazer]

Sorry meant to say 1 1/2” tubes

[geezer#99]

I’ve never seen or heard of 1 1/2 inch headers on a big block. Normally 1 7/8.
Bigger is not always better!
What’s your intended use? High rpm down the track might need bigger. Street cruiser doesn’t need huge. The 1 7/8 work for that.
What’s the budget like?

[Bones72Super]

You may want to check out the engine Masters series on Motor Trend they do a whole episode on primary size/ length, collector size/ length so you'll get a better idea of what you need rather than guessing. It's entertaining and educational too

[geezer#99]

Originally Posted by Bones72Super

You may want to check out the engine Masters series on Motor Trend they do a whole episode on primary size/ length, collector size/ length so you'll get a better idea of what you need rather than guessing. It's entertaining and educational too

This one.
Above 5500 bigger tubes help but not much difference below that.



https://www.motortrend.com/how-to/headers-dyno-test/

[68Gold/white]

I agree with both Geezers posts.
No telling what brand headers you have, or when they were made.
1-1/2' primary tubes sound unlikely, BUT there were lots of folks making headers in the 70's, 80's and 90's. Many are no longer in business. Many made headers for the business of selling headers. No testing was done, as long as they fit and sold that was the prevalent thought process.
I had a set of Black Jack headers on my 68 396, for a while. couldn't begin to tell you the tube size, I may have NEVER known what it was...LOL

Primary tube size can shift the power range of your engine, some what...
A 502 IS a BIG engine. Since your 502 is a street driver, I would not sweat the primary tube size.

Not every engine has to be dyno'd to make every last HP...Sonce you already have a big block in your pickup, WITH the exhaust system attached...I'd run what you have and see if you like how it performs!!! All it could do is make you happy, spend less $$$ and eliminate the need for potentially a complete new exhaust system!!!

IF, IF you think your current headers are a problem with the 502, you can deal with that later........

[Accelo]

Since the Deluxe 502 is over $10K I doubt the budget is much of an issue.
Although I see engine only is on sale for only $8,654.09
The ZZ502 is rated at 502 horsepower at 5,200 rpm and 567 lb-ft of torque at 4,200 rpm.
Over 500 lb.-ft. mark by approximately 2,500 rpm!
It's going to be a thrill ride for sure no matter the header primary diameter.
And Bob, I want a ride!

[C101972]

Take a look at the Doug’s headers part #D303y at Summit, free shipping and returns. Thanks
Posted via Mobile Device

[jjlett69]

I have the ZZ502 in my 69, and have ran 2 sets of headers. First set were Hooker super comp long tubes with 2" primaries, however with a 4/6 drop they were a night mare with ground clearance. I end up installing Sanderson BB8 (1 7/8") primaries and solved all my ground clearance issues due being mid length headers. If you are planning on dragging the truck , the Hooker headers due to bigger primary diameter and length should give more ponies at the top end, but realistically you will probably never feel the difference unless on DYNO or timesheet.

[Caddylackn]

Yes, with a 502, you don't need to worry about losing a few ft/lbs of torque using mid length headers, you have torque to spare. In fact you will have a heck of a time to get this truck to hook up and get that much torque to the ground.

Most cheap BBC headers I have seen are 1-3/4" o.d. and are suitable for a mild 454.

I believe the exhaust valve is 1.88" on this ZZ502 motor, so you don't want a header primary diameter much smaller than the exhaust valve, that would really choke off flow. I would say a 2" primary or a 1-7/8" as a minimum, but the 1-7/8" would be giving up some top end hp. I think these are D-shaped ports as well, so a 1-7/8" primary may not cover that very well.