Big block in a K20 ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Bernie** · 02-13-2003, 01:49 PM

I am rebuilding a 69 K20. I was planning to put a 350 into it. I have a lead on a big block 454 from a Corvette, not sure what year and I didn't know that Corvettes came with big blocks. Will it fit ? I know that Corvette small blocks have different exhaust manifolds. Is the same true of big blocks ? Will they work with 4X4 ? Thanks for any advice.

**too much stuff** · 02-13-2003, 02:28 PM

The 454 will fit and bolt in ,however the distributer cap is tight (with hei) and firewall clearance on drivers side valve cover is also tight. I don't think manifolds changed much,but those are tight as well. If you are doing a body lift, things will fit better.Good luck,go for the 454!!

Blazer1970 · 02-13-2003, 03:16 PM

In a 4X4, if you try to install a BB in the original engine location, the valve covers will hit the firewall. You have to either move the engine forward to the 2WD position, add a body lift, or both, depending on what kind of valve covers are on the motor. The Corvette manifolds might work out OK, since the original SB exhaust manifolds on a 4X4 of this era are virtually identical to Corvette manifolds except for the diameter of the tubes. If you move the engine forward though, the outlets of the manifolds might interfere with the crossmember. There are a few people on the board who have installed BB motors in 4X4s, so I am sure they will chime in to help. Also do a search on the subject.

70 Jimmy · 02-13-2003, 04:14 PM

My 70 Jimmy in it's previous life as a 4x4 had a 454 in it in the rear position with some (not much) clearence for the HEI and th valve cover. . The difference it seems is that beefed up Small Block motor mounts were used.

**too much stuff** · 02-13-2003, 04:36 PM

In addition to my first thread, i did the swap. My valve covers are from a corvette, i believe. The back corner is notched and dropped for a brake booster. The engine is sitting on the 350 motor mounts. The exhaust manifolds are from a 77 454 pickup. H ad to do a little grinding, but easy to do. I had to "adjust" the firewall with a hammer to get the hei wires to clear.I would suggest a mallory or unilite dist. to get more room. Also if you don't move the motor mounts, watch the wiring for the rear, as it runs behind that one valve cover.(found out the hard way, have new wires now)

02-13-2003, 01:49 PM	#1
Bernie Senior Member Join Date: Jan 2001 Location: Northern Illinois Posts: 516	Big block in a K20 ? I am rebuilding a 69 K20. I was planning to put a 350 into it. I have a lead on a big block 454 from a Corvette, not sure what year and I didn't know that Corvettes came with big blocks. Will it fit ? I know that Corvette small blocks have different exhaust manifolds. Is the same true of big blocks ? Will they work with 4X4 ? Thanks for any advice. __________________ Bernie

02-13-2003, 02:28 PM	#2
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,790	big block The 454 will fit and bolt in ,however the distributer cap is tight (with hei) and firewall clearance on drivers side valve cover is also tight. I don't think manifolds changed much,but those are tight as well. If you are doing a body lift, things will fit better.Good luck,go for the 454!!

02-13-2003, 03:16 PM	#3
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	In a 4X4, if you try to install a BB in the original engine location, the valve covers will hit the firewall. You have to either move the engine forward to the 2WD position, add a body lift, or both, depending on what kind of valve covers are on the motor. The Corvette manifolds might work out OK, since the original SB exhaust manifolds on a 4X4 of this era are virtually identical to Corvette manifolds except for the diameter of the tubes. If you move the engine forward though, the outlets of the manifolds might interfere with the crossmember. There are a few people on the board who have installed BB motors in 4X4s, so I am sure they will chime in to help. Also do a search on the subject. __________________ Tim

02-13-2003, 04:14 PM	#4
70 Jimmy aka Crusher, Crushergmc Join Date: Mar 2000 Location: Oregon Posts: 1,834	My 70 Jimmy in it's previous life as a 4x4 had a 454 in it in the rear position with some (not much) clearence for the HEI and th valve cover. . The difference it seems is that beefed up Small Block motor mounts were used. __________________ "KEEP IT DOWN!" 70 Jimmy 454 2wd 56 GMC Big Window "It's funny till someone gets hurt, then it's freakin' hilarious"

02-13-2003, 04:36 PM	#5
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,790	big block In addition to my first thread, i did the swap. My valve covers are from a corvette, i believe. The back corner is notched and dropped for a brake booster. The engine is sitting on the 350 motor mounts. The exhaust manifolds are from a 77 454 pickup. H ad to do a little grinding, but easy to do. I had to "adjust" the firewall with a hammer to get the hei wires to clear.I would suggest a mallory or unilite dist. to get more room. Also if you don't move the motor mounts, watch the wiring for the rear, as it runs behind that one valve cover.(found out the hard way, have new wires now)

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