Moving BBC forward, header clearance, firewall clearance? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

IGOR · 08-03-2011, 06:45 PM

So, I'm at the point in my build where hit a bit of a snag.

Putting an 8.1/4L80e/NP205 in my '72 K5 4x4

I am toying with moving 8.1 forward 1-2" to accommodate length of 4L80e as well as firewall clearance, but I'm worried about header interference.

I want to get the new headers from these guys: http://67-72chevytrucks.com/vboard/s...314836&page=11

Any recommendations from folks that have installed a BBC? (Keep in mind that the 8.1 engine mounts & header mount surfaces are identical to 454)

IGOR · 08-03-2011, 07:29 PM

FYI -

Found some good info in this thread:

http://67-72chevytrucks.com/vboard/s...FORWARD&page=5

turp mcspray · 08-03-2011, 09:37 PM

I put a 454/th400 in my 72 4x4. I moved the engine ahead 2" or 2 1/2". It worked out perfectly. The fan fit the factory 2wd shroud, and looked like a factory install. I notched the frame rails for my headers. I have seen bb swaps with manifolds, that needed frame notched for clearance. IMO moving the engine ahead is the best way to do a bb swap in a 4x4. I think any notching on the frame that you MAY have to do, is well worth it, for all the added room you will have between you engine and firewall.

AJs72K5 · 08-03-2011, 11:20 PM

You've seen everything I did to squeeze it into the factory K5 location. I don't think there's one answer that works for everyone.
Posted via Mobile Device

08-03-2011, 06:45 PM	#1
IGOR Registered User Join Date: Feb 2003 Location: Damascus, OR Posts: 260	Moving BBC forward, header clearance, firewall clearance? So, I'm at the point in my build where hit a bit of a snag. Putting an 8.1/4L80e/NP205 in my '72 K5 4x4 I am toying with moving 8.1 forward 1-2" to accommodate length of 4L80e as well as firewall clearance, but I'm worried about header interference. I want to get the new headers from these guys: http://67-72chevytrucks.com/vboard/s...314836&page=11 Any recommendations from folks that have installed a BBC? (Keep in mind that the 8.1 engine mounts & header mount surfaces are identical to 454) __________________ -Ben 1972 CST K5 - Undergoing frame off, 8.1/4L80E/NP205, 3/4 ton, 8" lift, currently a pile of parts that when assembled resemble a Blazer 1972 K10 - Rust Bucket, TBD 1976 C10 SWB, 350 / T350 My blazer build thread: https://ck5.com/forums/builds/72-k5-...17-update.410/

08-03-2011, 07:29 PM	#2
IGOR Registered User Join Date: Feb 2003 Location: Damascus, OR Posts: 260	Re: Moving BBC forward, header clearance, firewall clearance? FYI - Found some good info in this thread: http://67-72chevytrucks.com/vboard/s...FORWARD&page=5 __________________ -Ben 1972 CST K5 - Undergoing frame off, 8.1/4L80E/NP205, 3/4 ton, 8" lift, currently a pile of parts that when assembled resemble a Blazer 1972 K10 - Rust Bucket, TBD 1976 C10 SWB, 350 / T350 My blazer build thread: https://ck5.com/forums/builds/72-k5-...17-update.410/

08-03-2011, 09:37 PM	#3
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: Moving BBC forward, header clearance, firewall clearance? I put a 454/th400 in my 72 4x4. I moved the engine ahead 2" or 2 1/2". It worked out perfectly. The fan fit the factory 2wd shroud, and looked like a factory install. I notched the frame rails for my headers. I have seen bb swaps with manifolds, that needed frame notched for clearance. IMO moving the engine ahead is the best way to do a bb swap in a 4x4. I think any notching on the frame that you MAY have to do, is well worth it, for all the added room you will have between you engine and firewall. __________________ Turp Mcspray New life for an old 2wd, farm blazer http://67-72chevytrucks.com/vboard/s...d.php?t=505987 My Blazer build http://67-72chevytrucks.com/vboard/s...d.php?t=342299

08-03-2011, 11:20 PM	#4
AJs72K5 Registered User Join Date: Nov 2007 Location: South Tx Posts: 1,083	Re: Moving BBC forward, header clearance, firewall clearance? You've seen everything I did to squeeze it into the factory K5 location. I don't think there's one answer that works for everyone. Posted via Mobile Device __________________ - AJ Gray Matter Build - 1972 K5 with some stuff



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