273 / 318 Exhaust Manifold Question

[George Jets]

318 first Start Up.

 

[DieWilde13]

Oh, i know this Engine Stand! This Picture is taken in Hamburg Germany!
My 340 had its first Start on that Stand as well! The 70 Dart in the Background is his one.

Long Long time ago...

 

[George Jets]

Oh, i know this Engine Stand! This Picture is taken in Hamburg Germany!
My 340 had its first Start on that Stand as well! The 70 Dart in the Background is his one.

Long Long time ago...

It's a small world, glad you picked up on that engine stand.

 

[DieWilde13]

Yes, in the meantime i have my own Stand and run alot of Engines on it. But that was my first Break in on that stand.

 

[George Jets]

Here is my Run Stand, enjoy the heck out of it.

Run in engines, tune carbs, set up HEI Ignition conversions. All easily standing right there.

Run them on the ground too, when the Run Stand is busy. Lol . .

 

[pishta]

first break in , keep the RPM;s up! Need splash lube on the camshaft for 20 odd minutes. at varying RPMs 1500-2500 RPM. Open exhaust had to be loud, open headers are even louder. My parents HOA complained when I broke my Hi-flow 2 cam in my 351C powered 57 Ford. It was parked in the driveway and I had it opened headers for 20 minutes...oops!
Its nice to see the motor and all its (non) oil leaks when its first started up after a button up. My stand is going to include the 904 so I can run a starter. Ill put a Aspirin bottle into the rear seal to keep the fluid in.

 

[273]

Has anyone ever tried to port/gasket match a pair of OEM 273/318 A body exhaust manifolds? Any noticeable difference in power?

I have a 67 barracuda with a 273 Commando mill, was wondering if I should gasket match the original exhaust manifolds or install the Flowtech full length headers I have. Ground clearance is an issue, my car sits fairly low at the moment.

View attachment 1715917205

There's barely an hp difference between 318 & 340 manifolds on a 300 hp 360, doubt you'll notice any gain on a ported 273 manifold but definitely won't hurt though. Full length headers help mainly not by less restriction even though that helps but scavenging from tube length and collector size, that's why shorty headers don't help much.

Installing Exhaust Headers Into 300hp Crate Engine - Mopar Muscle Magazine

 

[273]

If I was gonna go with manifolds I'd use 360 there cheap and almost make the same power as 340 ones, but only if I doing the exhaust anyways.

 

[superstock64polara]

I agree with most of the suggestions here, the important thing is to pay close attention to the advice being given. For example, if you’re going to use a 318 short block make sure it’s a 68 or 69, so you’re getting the high compression block. Once you bolt your 920 heads on it the C/R difference is minimal, and will make it better suited to modern pump gas. If you want to keep your ride height low, use your 273 manifolds or go with Dougs or TTI headers. Since you have the standard intake bolt setup, an Eddie performer would be good, an air-gap would be better (don’t forget aluminum intakes and headers will also shed weight compared to iron anything) The aluminum vs steel wheels advice is solid... I make sure to determine the weight of the aluminum wheels before buying. If you decide to home-port/gasket match anything you might as well port everything (intake to head, head ports, and exhaust manifolds. Spec your carb carefully and once you decide on your parts list check with the guys here about a cam. I believe you could go for a Comp XE268H with what you have now plus a hi-comp 318 block. 3:23’s are alright street gears, but with the build you’re doing find a 2500-2800 TC - you’ll be surprised how it wakes up a mostly stock setup.

Thanks Topless69, your comments kinda sum up all the replies to my initial questions and are very useful. I do have a good running stock 1972 318, which has an advertised 8.8:1 static compression. I was planning on using Mr Gasket 0.028” head gaskets and milling my 920 heads to achieve around 9.2:1 comp, or a little more.

I have a Comp XE262H cam, an Edelbrock Performer intake, an AVS2 650cfm carb, and a set of 1-5/8” long tube headers. If I open up the bowls & port match the heads and intake manifold, get a good multi-angle valve job, I’m hoping this will make for a way better street only combo with the 4 speed and 3.23 geared rear.

The only real issue I have is that I like the way the car sits now, so I may just port match the exhaust headers and call it a day. The Flowtech headers I have will sit too low. I may look at getting a set of Doug’s 1-5/8” headers that appear to fit better.

 

[273]

Thanks Topless69, your comments kinda sum up all the replies to my initial questions and are very useful. I do have a good running stock 1972 318, which has an advertised 8.8:1 static compression. I was planning on using Mr Gasket 0.028” head gaskets and milling my 920 heads to achieve around 9.2:1 comp, or a little more.

I have a Comp XE262H cam, an Edelbrock Performer intake, an AVS2 650cfm carb, and a set of 1-5/8” long tube headers. If I open up the bowls & port match the heads and intake manifold, get a good multi-angle valve job, I’m hoping this will make for a way better street only combo with the 4 speed and 3.23 geared rear.

The only real issue I have is that I like the way the car sits now, so I may just port match the exhaust headers and call it a day. The Flowtech headers I have will sit too low. I may look at getting a set of Doug’s 1-5/8” headers that appear to fit better.

Here's low Cr 318 build with that cam 282hp @ 5000, manifolds will take some hp away bump in Cr will give some back.

318 Long Block Bolt Ons - Tech Articles - Mopar Muscle Magazine

 

[Topless69]

Keep in mind if you’re using the ‘72 318 block that bolting on your 273 closed chamber heads will result in a higher C/R without any other modifications. If you’re going to shave down anything, you may consider milling the deck and leave your 273 heads stock (with the porting job)
Of course, disregard TC suggestion since you have a 4-speed, which is going to be loads more fun.
Be sure and keep us in the loop on your progress!

 

[dart4forte]

I didn't think there was difference between 273 4BBL and 2BBL exhaust manifolds...

Theres not

 

[superstock64polara]

Here's low Cr 318 build with that cam 282hp @ 5000, manifolds will take some hp away bump in Cr will give some back.

318 Long Block Bolt Ons - Tech Articles - Mopar Muscle Magazine

Thanks 273, I've read that article a couple of times now. I'm hoping that with a little more squeeze, some minor head work, and a Performer intake I can crack the 300HP mark. Not that I'm chasing numbers, I just want something that's fun to drive, will turn the tires, and will run really nice stop-light to stop-light.

 

[superstock64polara]

Keep in mind if you’re using the ‘72 318 block that bolting on your 273 closed chamber heads will result in a higher C/R without any other modifications. If you’re going to shave down anything, you may consider milling the deck and leave your 273 heads stock (with the porting job)
Of course, disregard TC suggestion since you have a 4-speed, which is going to be loads more fun.
Be sure and keep us in the loop on your progress!

You bet, I'll keep you guys posted.

 

[273]

Thanks 273, I've read that article a couple of times now. I'm hoping that with a little more squeeze, some minor head work, and a Performer intake I can crack the 300HP mark. Not that I'm chasing numbers, I just want something that's fun to drive, will turn the tires, and will run really nice stop-light to stop-light.

Have you read and watched 318willrun thread's and YouTube video's show how without doing much putting a 318 in the 13/14's quarter mile times.

Stock 273/318 heads doesn't take much to get close to 300 hp, above that I'd start looking at other head option, even saying that a set of jobber magnum heads would add an easy 30-40 + hp over 318 heads.

 

[Swinger 340]

first break in , keep the RPM;s up! Need splash lube on the camshaft for 20 odd minutes. at varying RPMs 1500-2500 RPM. Open exhaust had to be loud, open headers are even louder. My parents HOA complained when I broke my Hi-flow 2 cam in my 351C powered 57 Ford. It was parked in the driveway and I had it opened headers for 20 minutes...oops!
Its nice to see the motor and all its (non) oil leaks when its first started up after a button up. My stand is going to include the 904 so I can run a starter. Ill put a Aspirin bottle into the rear seal to keep the fluid in.

I use water bottles while transporting transmissions, but I have the cups made for the output for a better seal while running. I also run my motors on the ground and get a kick out of it when people see that for the first time.