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Big Block swap ???'s

T

Tommy

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Big Block swap ???\'s

I am swapping a big block into my 70 out of a 72. They cut the cross member to let the pan go below cross member onm the donor truck. Is there a way that you don't have to cut it? I don't mind fabbing a lower crossmember to clear the pan. Also the mounts in my truck(327), and the 427 mounts were busted. Has anyone else found a better mount? I plan to burn the rubber off, and make my own solid mount, and lift the engine up about an inch for better header to frame clearance.

Drive it Like You Hate It!
 
Re: Big Block swap ???\'s

I know many trucks used different towers to mount the bb but dont know about the k5. I would recommend you using a rubber or polyurethane mount rather then solid. it will be very shakey. I know someone on here has info on the swap though. i believe header clearance and firewall clearance is an issue.
 
Re: Big Block swap ???\'s

HoHoHo. Going to a Rat, eh? Well, don't make solid mounts. Not unless you want your teeth to chatter and your front spring mounts to crack. I have stock steel/rubbe rmade in india/bought at autozone for $17.00mounts in mine, and after 2 years, still no problem with them breaking.

No header clearance between the frame rails. I wish, but no go unless you cut the frame, or hand make headers.

Body lift is necessary to clear the HEI unless you take a hammer to the tub. It's a little heavier (about 128lbs more than a mouse) a bit longer(!!), hell of a lot wider too. It really fills up the engine compartment in the K5.

Harry
 
Re: Big Block swap ???\'s

Harry pretty much outlined any problems with the swap. I didn't have any problem with my pan clearing the crossmember, but it is dang close. The problem with trying to get the engine higher from the crossmember is that you'll then have the problem of valve covers, distributor hitting the firewall. I have a 3" body lift, and both the dist. and valvecovers are close to the firewall. New front springs will definitely be necessary. Harry, what do you use for exhaust: headers or a manifold. I've tried the Hedman Headers that don't fit (ha!), but it seems that shorties would fit fine.

1970 GMC Jimmy 502HO/SM465/NP205 doesn't run just yet!
 
Re: Big Block swap ???\'s

Well the motor came out of a 72 K5. It had headers, with minor notching of frame. I have a 3" body lift, so I figured since the other blazer fit, mine would fit better. I guess I will buy the mounts from carport here, they are $14, I just run solids in my 69Z, and figued they would be ok for the blazer. Thanks for the input guys.

Drive it Like You Hate It!
 
Re: Big Block swap ???\'s

Jim,

I'm running stock manifolds on mine. With a 454, I have not noticed too much difference in power between the manifolds and headers. I don't really rev it up much. I do find myself lugging it quite a bit. I also have a 2" body lift on mine to clear the HEI and since I have low valve covers on mine, no problem at the back.

HarryL
 
Re: Big Block swap ???\'s

454 w/HEI in mine and the valve covers and HEI don't hit but they are close enough to use a feeler gauge to measure the distance! I'll be moving it to the front holes which will probably mean a modified motor mount. Good Luck.

70 Jimmy, 454, 2wd
56 GMC, Big Window
 
Re: Big Block swap ???\'s

Hey guys..does someone sell a aftermarket header for these 454's that runs outside the frame or aint this doable,my plan was to dump my 78 454 into my 72k5 from my 86k5 after building it and it either needs new headers orI'll have to find a set of manifolds for it..

72K5 "PROJECT 40" BOGGERS (currently frame off)
86K5 454ci., 400/205,3/4ton 4.10s,4''susp.3"body,38.5 swamper sx
 
Re: Big Block swap ???\'s

Wrath,

Where did you get the TH400/NP205 combo?
I've also got a 454 in my 72K5 (from a 78 burb) hooked up to a Th350/205. I think I'm getting ready to blow up my th350 and am looking for something stronger....

Harry
 
Re: Big Block swap ???\'s

Harry, ok ,that part of my sig is wrong..I was gonna swap th 350 for 400 ...but after checking into it deeper..I found it was gonna cost way too much to adapt.I even went as far as buyin a 400 2x trans and was gonna swap output shafts so now I'm stuck with a trans I dont need ...Heres a question for you ..my th350 (79) off a 203 case ...will that mount to the 205 case?the 205 is a 72 and adaptor mount is still there...I'd also like to talk to ya about yer 454 in yer blazer but this is getting long so maybe I'll check back with ya later..thanx

72K5 "PROJECT 40" BOGGERS (currently frame off)
86K5 454ci., 400/205,3/4ton 4.10s,4''susp.3"body,38.5 swamper sx
 
Re: Big Block swap ???\'s

Wrath,

About your question th350/203 swap a 205 in place of the 203....I have not the faintest. I had a 350/203 combo, but broke it apart just to get the cast case for the 203. I wanted to make a 203/205 doubler but then I lifted it 8' instead.

I can send pics of the 454 if you need.

Harry
 
Re: Big Block swap ???\'s

Man! 8 feet!

1970 GMC Jimmy 502HO/SM465/NP205 doesn't run just yet!
 
Re: Big Block swap ???\'s

Well, you'd think it was lifted 8' trying to climb into it. I've got one of those plastic milk crates I stand on to climb in. I've got a rope tied to the crate so I can haul it in before shutting the door.

Harry
 
Re: Big Block swap ???\'s

Am I gonna be able to use the BB mounts from the 454 (1978)that came from burb to get into the 72k5..?

72K5 "PROJECT 40" BOGGERS (currently frame off)
86K5 454ci., 400/205,3/4ton 4.10s,4''susp.3"body,38.5 swamper sx
 
Re: Big Block swap ???\'s

On both trucks I'm working on now, the BB & SB have the same mounts.

Drive it Like You Hate It!
 
Re: Big Block swap ???\'s

Sorry, misread, both of mine are first gens.

Drive it Like You Hate It!
 
Re: Big Block swap ???\'s

In 69 they put in the 396, 70 - 72 they put in the 402's. My question is : Why didn't the distributor hit the fire wall and why didn't they notch out the crossmember? Was there a different crossmember or a ring spacer between the motor and tranny
These BB swaps should be easy! Right? They were already doing it from the factory.
This is just my .02 worth. I too plan on putting a 502 in my 72
 
Re: Big Block swap ???\'s

I would guess the distributor had room because it was a small points distributor, not HEI, as for the other I'm not sure.

Drive it Like You Hate It!
 
Re: Big Block swap ???\'s

I'm new to chevys. I just put a 350 into my jeep but i didn't use a HEI. I went with a MSD ignition. My mopars distributor was up front on my 383ci.
Is a HEI better than running a MSD system? I know it's cheaper running a HEI! What about performance?
 
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