L6 250 to V8 350 swap...how to keep dizzy off firewall - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tp85 · 11-27-2012, 08:18 PM

i've heard there may be another hole in the frame to shift the engine mounts forward a few inches. correct? or do the mounts get flipped?

then, with the 350 shifted forward, how do i mate up to the SM465 without moving the tranny and transfer case? is there a longer bellhousing?

or do most guys just have the V8 sit close to the firewall? opinions welcome!

thanks,
tom
72 blazer 4X4 250 SM465 NP205

airdale94 · 11-27-2012, 08:23 PM

You need v-8 motor mounts and a v-8 trans x-member. You will then need to lengthen the drive shaft. So much for chevy interchange.

Yes there are additional holes.

**special-K** · 11-28-2012, 07:40 AM

I'm not sure that's correct on 4wds. I have never seen this addressed with 4wds,but all V8 4wds have the motor back into the firewall. I'm 99.9% sure that all 4wds have the transmission & transfer case in the same location and the same length driveshafts with the same axle/trans/t-case combination. The only time I've changed driveshafts is going 1/2t to 3/4t or 3spd/Dana20 to TH350/NP205 and that only affected the rear shaft

tp85 · 11-28-2012, 11:11 AM

good points. shortening the front driveshaft would also be necessary if shifting the tranny w/engine.
i wonder if the v8 trans-member swap is limited to 2WDs?

Quote:

Originally Posted by special-K

I'm not sure that's correct on 4wds. I have never seen this addressed with 4wds,but all V8 4wds have the motor back into the firewall. I'm 99.9% sure that all 4wds have the transmission & transfer case in the same location and the same length driveshafts with the same axle/trans/t-case combination. The only time I've changed driveshafts is going 1/2t to 3/4t or 3spd/Dana20 to TH350/NP205 and that only affected the rear shaft

airdale94 · 11-28-2012, 04:16 PM

Quote:

Originally Posted by special-K

I'm not sure that's correct on 4wds. I have never seen this addressed with 4wds,but all V8 4wds have the motor back into the firewall. I'm 99.9% sure that all 4wds have the transmission & transfer case in the same location and the same length driveshafts with the same axle/trans/t-case combination. The only time I've changed driveshafts is going 1/2t to 3/4t or 3spd/Dana20 to TH350/NP205 and that only affected the rear shaft

Diddn't see that he was working on a 4X4 Blazer.

SS Tim · 11-28-2012, 06:01 PM

The holes should be in the frame. My understanding is the V-8 engine and trans. crossmembers go to the forward set of holes in K series applications. The pictures I have confirm this. The parts catalog indicates the crossmembers should be the same. Crawl under your truck and look around with a mirror (sounds like you haven't). Download your own parts manual and see what you come up with. Here are some pictures that might help some. However I haven't done this conversion nor know anyone that has. Can't even remember actually seeing a 250 I-6 Blazer.

69GWC · 11-28-2012, 06:28 PM

Mine came with a 6 and now has a 350, I dont see any signs of mine every being moved and my dizzy is pretty tight to the firewall.
Posted via Mobile Device

tp85 · 11-28-2012, 07:05 PM

i'll will check this out tonight and get some pix.

**special-K** · 11-28-2012, 08:54 PM

All V8s sit back tight to the firewall on 4wds. That's why they all have deep fan shrouds. A factory V8 4wd motor sits as tight to the firewall as a V8 swapped into a factory I-6 2wd when the mount towers are left alone. I've never done the swap. Just have had both I-6 and V8s from factory and didn't need to know.

PanelDeland · 11-28-2012, 09:00 PM

Not to be a smart a$$ but the dizzy is no problem with the 6.If you're gonna use it OR ,you need the torque,if you're gonna use it on the street,you wont need 4X4.JMO.

**WIDESIDE72** · 11-29-2012, 03:39 AM

Quote:

Originally Posted by SS Tim

The holes should be in the frame. My understanding is the V-8 engine and trans. crossmembers go to the forward set of holes in K series applications. The pictures I have confirm this. The parts catalog indicates the crossmembers should be the same. Crawl under your truck and look around with a mirror (sounds like you haven't). Download your own parts manual and see what you come up with. Here are some pictures that might help some. However I haven't done this conversion nor know anyone that has. Can't even remember actually seeing a 250 I-6 Blazer.

http://67-72chevytrucks.com/vboard/c...zer-2wd&cat=12

tp85 · 11-29-2012, 11:10 AM

great feedback, thanks. if i do the swap, the v8 will be in the normal position back close to the firewall. i have no huge compelling reason to put in the effort to shift the entire drivetrain forward.

BTW, the tranny crossmember does not seem to have an alternative/shifted forward mount location (i.e. additional OE frame holes) like the engine mounts.

tp85 · 11-29-2012, 11:19 AM

in the long long run, i think it may be the overall most economical path. not swimming in $, and need to either rebuild the 250 or swap.

Quote:

Originally Posted by PanelDeland

Not to be a smart a$$ but the dizzy is no problem with the 6.If you're gonna use it OR ,you need the torque,if you're gonna use it on the street,you wont need 4X4.JMO.

Davemotohead · 11-29-2012, 01:05 PM

Its my understanding the 4wds engine sit farther back in the engine compartment than 2wds in order to make room for the front diff and driveshaft/transfercase,,I had a 68 2wd and a 71 4wd and the engine in the 68 was farther forward by about 6 inches,,I believe that you could get a big block in the 67-72 2wds from the factory but only a 350 or small block 400 in the 4wds as the big block would not fit in the 4wds,,I managed to wedge a 396 in my 4wd 71 with some effort,,I had to use the 1 hump camaro oil pan and stock valve covers as the covers are a tight fit,,also had to dent the firewall to fit the HEI distributor in place,,very tight fit and a pain to work on,,if I were to do it again would section out the firewall for more clearance at the distributor for easyer access,,But all the trouble was worth it Cuzz its a Bruzer with the BB power!

11-27-2012, 08:18 PM	#1
tp85 Registered User Join Date: Mar 2002 Location: frederick, md Posts: 110	L6 250 to V8 350 swap...how to keep dizzy off firewall i've heard there may be another hole in the frame to shift the engine mounts forward a few inches. correct? or do the mounts get flipped? then, with the 350 shifted forward, how do i mate up to the SM465 without moving the tranny and transfer case? is there a longer bellhousing? or do most guys just have the V8 sit close to the firewall? opinions welcome! thanks, tom 72 blazer 4X4 250 SM465 NP205

11-27-2012, 08:23 PM	#2
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall You need v-8 motor mounts and a v-8 trans x-member. You will then need to lengthen the drive shaft. So much for chevy interchange. Yes there are additional holes. __________________ 68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). Last edited by airdale94; 11-27-2012 at 08:24 PM. Reason: add

11-28-2012, 07:40 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall I'm not sure that's correct on 4wds. I have never seen this addressed with 4wds,but all V8 4wds have the motor back into the firewall. I'm 99.9% sure that all 4wds have the transmission & transfer case in the same location and the same length driveshafts with the same axle/trans/t-case combination. The only time I've changed driveshafts is going 1/2t to 3/4t or 3spd/Dana20 to TH350/NP205 and that only affected the rear shaft __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

11-28-2012, 06:01 PM	#6
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,503	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall The holes should be in the frame. My understanding is the V-8 engine and trans. crossmembers go to the forward set of holes in K series applications. The pictures I have confirm this. The parts catalog indicates the crossmembers should be the same. Crawl under your truck and look around with a mirror (sounds like you haven't). Download your own parts manual and see what you come up with. Here are some pictures that might help some. However I haven't done this conversion nor know anyone that has. Can't even remember actually seeing a 250 I-6 Blazer. Attached Images __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

11-28-2012, 06:28 PM	#7
69GWC Registered User Join Date: Jun 2012 Posts: 1,089	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall Mine came with a 6 and now has a 350, I dont see any signs of mine every being moved and my dizzy is pretty tight to the firewall. Posted via Mobile Device

11-28-2012, 07:05 PM	#8
tp85 Registered User Join Date: Mar 2002 Location: frederick, md Posts: 110	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall i'll will check this out tonight and get some pix.

11-28-2012, 08:54 PM	#9
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall All V8s sit back tight to the firewall on 4wds. That's why they all have deep fan shrouds. A factory V8 4wd motor sits as tight to the firewall as a V8 swapped into a factory I-6 2wd when the mount towers are left alone. I've never done the swap. Just have had both I-6 and V8s from factory and didn't need to know. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

11-28-2012, 09:00 PM	#10
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall Not to be a smart a$$ but the dizzy is no problem with the 6.If you're gonna use it OR ,you need the torque,if you're gonna use it on the street,you wont need 4X4.JMO. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

11-29-2012, 11:10 AM	#12
tp85 Registered User Join Date: Mar 2002 Location: frederick, md Posts: 110	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall great feedback, thanks. if i do the swap, the v8 will be in the normal position back close to the firewall. i have no huge compelling reason to put in the effort to shift the entire drivetrain forward. BTW, the tranny crossmember does not seem to have an alternative/shifted forward mount location (i.e. additional OE frame holes) like the engine mounts.

11-29-2012, 01:05 PM	#14
Davemotohead Registered User Join Date: Sep 2011 Location: rosamond ca Posts: 130	Re: L6 250 to V8 350 swap...how to keep dizzy off firewall Its my understanding the 4wds engine sit farther back in the engine compartment than 2wds in order to make room for the front diff and driveshaft/transfercase,,I had a 68 2wd and a 71 4wd and the engine in the 68 was farther forward by about 6 inches,,I believe that you could get a big block in the 67-72 2wds from the factory but only a 350 or small block 400 in the 4wds as the big block would not fit in the 4wds,,I managed to wedge a 396 in my 4wd 71 with some effort,,I had to use the 1 hump camaro oil pan and stock valve covers as the covers are a tight fit,,also had to dent the firewall to fit the HEI distributor in place,,very tight fit and a pain to work on,,if I were to do it again would section out the firewall for more clearance at the distributor for easyer access,,But all the trouble was worth it Cuzz its a Bruzer with the BB power! Attached Images



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