47-55.1 Help locating a 5.3 in '51 3600

[51 3600]

Been on this great forum for awhile but mostly looking, reading and learning. Now I'm at a point where I'm going to an outside shop to do work I have neither the skills nor equipment to do. They have skills and equipment but my project is not the norm for them so I'm seeking info to help in the process.

Objective is to install a LM7 5.3 engine from a '01 Tahoe along with 4L60e trans and 8.8 Exploder rear end with Jeep Wrangler leaf springs into my '51 3600 frame. Front suspension already installed is a Danforth crossmember with '01 Blazer suspension.

First task is installing engine mounts so I need help with proper positioning/locating engine and trans. I've seen a lot of pics here but can't find info as to where exactly that engine should sit (Pics attached show where engine is presently planned to sit). So my questions are:
1) Knowing engine bay is cramped in length, how far back can/should the engine sit in relation to radiator crossmember assuming use of electric fan?
2)Will fire wall have to be modified (tunnel) to accept trans?
3) How low can the engine sit, if possible, to avoid #2 above?
4) Does the original oil pan have to be replaced with another unit?
5) Other questions you know I should be asking but am too ignorant to do so.

Trying to keep ride height of truck close to original because I want to use it in my work so no lowering, no air ride, etc. Upgrading drivetrain so more practical on highway.

Thanks in advance for any info. Oh, I'm no mechanic so simple not too technical explanations would be appreciated.

[BigBird05]

It is best to place the cab on the frame to locate the engine. That will also tell you if you will need to cut up the wire wall and or the trans tunnel.

[BigBird05]

Only after you have mounted the engine will you know if the oil pan is sitting to low and will need replacing.

[51 3600]

Thanks BigBird, cab was attached to the frame but they removed it as the trans looked like it was going to require cutting into the fire wall seam. So moved the cab out of their way while positioning the engine.

Thought maybe the engine could be positioned lower to avoid that but don't know what other problems that would cause (pinion angle, oil pan, etc.)

If trans just barely hits cab, could cab be raised 1/2" or so? Hood and fender problems then?

[mongocanfly]

Definatly dont do it with the cab off..I know they removed it but have it in place....do yourself a favor and go ahead and reccess the firewall for engine clearance...itll be extremely tight if you dont..if floor need a tunnel do that after...I wouldnt raise the cab but make sure the mounts are solid and not sagging..

[65blackfleetside]

I agree with Mongo
Having just finished an AD with LS3 there is not much room front to back. I would go ahead and tunnel the cab floor and recess the firewall.

It will also help you with your accessories on the front of the motor and save you lots of $$ by having the option of running stock oem accessory brackets for: AC compressor, Power Steering pump and alternator IF you mount the engine with oil pan 2-3" above the frame crossmember. ( This will raise your transmission higher too so that's where the need for tunneling will come in)

Also shift the engine 1" to 1.5" off to favor passengers side. This will avoid extra work of having to build a heim joint with steering column.

[torchlight]

I don’t know if the frame is different on the 3600 but on my 53 3100, we were able to get a 5.3 LM7 and a 4L65E in there without cutting the cab. Might depend on your IFS crossmember though (I used Scott’s Hot Rods IFS). Also, I used Camaro/Firebird front drive brackets, which saved some room. CTS-V pulleys would be even better. Electric fan, of course. Used the standard 5.3L truck oil pan.

Should be some good info about my setup starting on this page (but read the next page after this one also):

http://67-72chevytrucks.com/vboard/s...=541111&page=4

[51 3600]

torchlight, thanks much for the post and link to your build thread. Just the info i was hoping for. Will have to read more of your build thread. BTW the 3100 and 3600 frames are identical from front to about the rear of the cab. 3600 frame straightens out from there rather than continuing the v shape. I may be asking you more questions as I progress. Beauty of a truck.

I appreciate the suggestions on altering the firewall and creating a tunnel. Really hoping not to have to do that as I would have to have someone else do that and budget is tight as it is.

Thanks all. Any other comments surely welcome.

[youngrodder]

Originally Posted by torchlight

I don’t know if the frame is different on the 3600 but on my 53 3100, we were able to get a 5.3 LM7 and a 4L65E in there without cutting the cab. Might depend on your IFS crossmember though (I used Scott’s Hot Rods IFS). Also, I used Camaro/Firebird front drive brackets, which saved some room. CTS-V pulleys would be even better. Electric fan, of course. Used the standard 5.3L truck oil pan.

Should be some good info about my setup starting on this page (but read the next page after this one also):

http://67-72chevytrucks.com/vboard/s...=541111&page=4

I'm running a Porterbuilt front drop member and I too fit an LS without cutting the floor or firewall in my 53 Suburban. I mocked up with a poly LS block and 4l60e trans to confirm fitment. I'm using an F-body oil pan and a Holley front drive. Your motor mounts will play a room in if you need to cut your cab as well.