3 inch exhaust crossmember dimensions?

x75

Apprentice
Sep 23, 2018
68
18
I'm swapping a 454 into my 85 El Camino. The car is already setup with 700R4. This forum has been extremely helpful, thanks to everybody.

The 454 came from an old 72 Cutlass drag car, and I am trying to use as much of the old A-body as I can. I massaged the old Hedman headers to fit, but now need to figure out the exhaust system

I have 2 pipe setups available. The old Cutlass system runs simple straight 3 inch pipes back to Flowmasters dumping at the axle. I also have a sweet 3-inch stainless MagnaFlow setup from a 72 El Camino with cross-over, mufflers, tailpipes, hangers etc.

Problem is the width of the headers, the 2 collectors are about 22 inches apart. I am looking at Jegs and G-force crossmembers but cannot tell the width of the "humps". They don't look wide enough.

I think the photos show what I am trying to determine.

Thanks for input
 

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565bbchevy

Geezer
Aug 8, 2011
9,265
113
Michigan
I modified my stock crossmember on my Monte to fit 4.5" exhaust that is tucked up very close to the floorboards, I originally ran dumps before the rear axle until I later made 4" tailpipes to go over the axle.

normal_IMG_0329.jpg
IMG_0134.jpg
 
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565bbchevy

Geezer
Aug 8, 2011
9,265
113
Michigan
On my Regal I have the Jeg's crossmember, which I couldn't pass up on when they had them on sale for $99. I fits well for the SBC and the collectors line up pretty well to the openings, I feel with a BBC fitment might be an issue with the wider exhaust especially if it is large diameter.
And yes the rusty driveshaft has been replaced.
20190603_151646_resized.jpg
 
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ssn696

Living in the Past
Jul 19, 2009
5,431
113
Permanent Temporary
This is the best I could do without jacking up the cars. First one is a Jeg's 200R4, and the second is the Jeg's 700R4.
F830862E-418C-421C-8B32-2796545B9C2C.jpeg
3667624D-5968-4548-9AA9-2A030DD1A85B.jpeg
Both look to me to be 15-17 inches center-to-center. You might be better off trying the Crown Vic option.
 
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x75

Apprentice
Thread starter
Sep 23, 2018
68
18
thanks for the photos and advice. yes, the BBC headers are wide, and I can see where S-bends are required to fit through the Jegs. Still not sure about G-Force but it doesn't look much wider. I have mocked up the 3-inch exhaust pipes and the stock crossmember clears fine on the passenger side, but needs help on drivers side where someone already did the BFH notch, but it was a 350 they fitted. I may be able to smash another couple inches of clearance, gonna pull it out and see. Also have an assortment of other vehicle crossmembers that I will check.

My 454 is running a full comp cams High Energy kit, .553? lift, hydraulic flat lifters with roller rockers. I swapped the tall valve covers for stockers, and checked the clearance with my bore scope. The only clearance issue was the lock nuts, I had to get shorty locks, and it's still pretty tight. I have not fired up this configuration so there might be an issue requiring "thick" cover gaskets.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,239
113
thanks for the photos and advice. yes, the BBC headers are wide, and I can see where S-bends are required to fit through the Jegs. Still not sure about G-Force but it doesn't look much wider. I have mocked up the 3-inch exhaust pipes and the stock crossmember clears fine on the passenger side, but needs help on drivers side where someone already did the BFH notch, but it was a 350 they fitted. I may be able to smash another couple inches of clearance, gonna pull it out and see. Also have an assortment of other vehicle crossmembers that I will check.

My 454 is running a full comp cams High Energy kit, .553? lift, hydraulic flat lifters with roller rockers. I swapped the tall valve covers for stockers, and checked the clearance with my bore scope. The only clearance issue was the lock nuts, I had to get shorty locks, and it's still pretty tight. I have not fired up this configuration so there might be an issue requiring "thick" cover gaskets.
Where did you get the locks? I am using Crane rockers and currently the polylocks hit the covers.
 

x75

Apprentice
Thread starter
Sep 23, 2018
68
18
Yes, my 1 inch tall locks hit the stock covers, so I found Crower 86050S-16 locks were about 1/8 inch shorter. Bought them on Amazon for 50 bucks or so. Even the shorter locks are close with a plain gasket, I could not see daylight looking under a cover with my scope. It's not the rockers that interfere, just the locks, and only the intakes I think. I hope when I fire it up again there's no problems, but a fatter gasket might be required.

I read blogs where people had to run stock valve covers and gaskets for drag race rules, but they said the short locks worked.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,239
113
Yes, my 1 inch tall locks hit the stock covers, so I found Crower 86050S-16 locks were about 1/8 inch shorter. Bought them on Amazon for 50 bucks or so. Even the shorter locks are close with a plain gasket, I could not see daylight looking under a cover with my scope. It's not the rockers that interfere, just the locks, and only the intakes I think. I hope when I fire it up again there's no problems, but a fatter gasket might be required.

I read blogs where people had to run stock valve covers and gaskets for drag race rules, but they said the short locks worked.
Thanks for that. I’ll check that number
 

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