Attn Yukon Jack?

[BOSS]

Hey there bud i know you have put a BBC into a 4x4 and was wondering what all you had to do to get it to fit?I think i read that you had to adjust the firewall a little,about how much and where?Will the regular mounts be ok on a 72 4x4?Any other advice that you could give me would be great.Thanx man...........James

[barn9]

He's trying to get the truck back from the "Snails Pace" body shop right now, and it isn't coming along as he had hoped. Yes, he did have to alter the firewall, etc. Hopefully he can get it home soon, and get back to the mechanical part of his ordeal. I'm jumping in here just to help keep this up where he will see it, and he can fill you in on the details. Everyone wish him luck, 'cause this has turned in to a bit of an ordeal.

[BOSS]

Thanx Barn TTT.

[Yukon Jack]

Has been a long project, that is for sure.

What I have learned in putting in a big block in my K20 is that for whatever reason some get the bb in with little to no modification and others have to do alot.

I have my bb in the small block location using my factory small block crossmember, towers and mounts. For me even with a 2" body lift I had major valve cover/firewall clearance problems on both sides of the engine. I stepped up to a 4" body lift as I could not easily move the engine forward at the body shop - though I do plan to drop the body lift back to 2" as soon as I can. Even with a 4" body lift I still had contact with the firewall. Attached is a pic which shows the modifications I had to do to get plenty of firewall clearance.

Some have to just massage the firewall a little, some have opted to move the engine forward. I don't know exactly how far you need to pull the engine forward but for me it looks like 1 1/2" to 2" would be enough.

Using the small block engine crossmember the oil pan clearance on my 1989 1 ton 454 was very close. I did shim the motor mounts slightly to give a little more clearance. An option is to use a later small block crossmember and mounts. This puts the crossmember in front of the engine. Also helps with header fitment.

I am using Dynomax Cermacoated headers, part number 86022, designed for the 67-87 BBC 2WD. The headers for 73-87 BBC 4WD would not work.

I did move the crossmember forward about 3/8" or so to give me better oil pan clearance and header clearance for the first header tube on the passenger side. Although I moved the crossmember forward, the location of the engine mounts stayed in the same location by adjusting the bolt hole used to secure the engine to the mount.

To make these headers fit I did not have to make any modifications to the driver's side other than I did have to go with a shorter oil filter as this engine has an oil cooler setup which put the larger oil filter in contact with the headers.

On the passenger side I had to remove a little bit of frame to give clearance for the first and second header tubes. I would guess I removed about 1/4". I also ended up grinding off a little bit of the engine crossmember tower as it was in contact with the bottom of the first header tube. In the end I had to use some spacers that I put between the engine and the engine mount bolts to raise the engine a bit on the passenger side and I also raised the drivers side by using spacers about half as big.

The above modifications have me comfortable with the clearance around the oil pan and passenger side headers.

Here are the dimension info on the Big Block vs. Small Block measurement differences:

Big Block
23.63" length from center motor mount hole to front of motor
7.68" height from center motor mount bolt to top of motor
22.96" wide

Small Block
21.78" length from center motor mount hole to front of motor
5.33" height from center motor mount bolt to top of motor
19.68" wide

The width and extra height are the problem.

I am going with a hydraulic clutch. I think working the linkage for the standard clutch setup would have been difficult with headers I am using.

It is all going to be worth it in the end but I can guarantee I won't be putting a big block in the K5.

Here is a web page I just made that gives the above info and a little more information about my swap. My big block swap into my 1969 K20

[Warbones]

I love that color. Awesome truck in the making! Good job.

[BOSS]

Thanx Yukon!Now i need to decide which would be easier for us,454 into a 4x4(72) or what would it take to put it into a 72 Super 2x4?Is it just the towers and mounts that are different in the 2 wheel drives?Thanx again for all of the help and you truck is looking sharp!!....James

[dubie]

I have seen a few 67-72 4x4's with a big block under the hood with no real mods. The engine was placed in the stock small block location and was on big block stands. Either way.....a big block kicks azz in a 4x4

[Yukon Jack]

I believe that the 2wd truck have the bb closer to the radiator than if it were a sb - someone else will have to confirm that though.

[big70chevy]

Looking real good Yukon! I hope when I get to that point on mine that I'm one of those few who don't have any clearance issues. I talked with a fellow last week from down around Louisville, Ky that told me that he just installed a 454 in his 72 with no problems. One of the lucky ones I guess.

[68cajun]

Yukon what color is the paint. I plan to paint my 68 silver and like the shade you have.

[Yukon Jack]

The color is based off of a GM Saturn metallic silver that was lightened and more metallic flake was added - really sparkles.