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#1 |
Registered User
Join Date: Jul 2006
Location: Seattle
Posts: 56
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72 GMC - Engine hitting firewall...need advice
So I took the 350 out and I'm installing a 383 stroker. (We're talking about a 72 GMC 3/4T 4x4.) We finally got the engine built and installed, but it's barely touching the firewall. What should I do? It's the first time I've done this, and I'm not sure what the best option is. Should I move the firewall back? notch it out? move the engine forward and the tranny too? .... advice and pics of what to do would be very much appreciated. Hope you guys have a great x-mas.
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#2 |
Registered User
Join Date: Mar 2006
Location: USA
Posts: 21,020
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Re: 72 GMC - Engine hitting firewall...need advice
All 4x4's motors were close to hitting the firewall stock.Thats why big blocks in 4x4s have clearance problems.You could
(A) move engine crossmember/tranny/t case forward but that would mean you would have to get new driveshafts made (B) add a body lift (C) make some changes to the firewall to allow room. (D) If its the valve covers get different ones Hope this helps.Someone else might think of something to add that I forgot.Nice motor btw ![]() Merry Christmas Dustin Last edited by 1969k10stepside; 12-24-2006 at 03:01 PM. |
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#3 |
Registered User
Join Date: Dec 2004
Location: El paso, Tx.
Posts: 428
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Re: 72 GMC - Engine hitting firewall...need advice
Just like 1969K10stepside said body lift
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1969 Chevy C-10 350/700r4 |
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#4 |
Registered User
Join Date: Nov 2003
Location: Alexandria, VA
Posts: 1,534
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Re: 72 GMC - Engine hitting firewall...need advice
Where is it contacting the firewall? Is it the "tall" valve covers? I'm sure the 4X4 boys can help you out here...
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'72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction. ![]() ![]() ![]() |
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#5 |
Registered User
Join Date: Apr 2006
Location: MinneSNOWta
Posts: 1,381
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Re: 72 GMC - Engine hitting firewall...need advice
it looks to me, like the motor is mounted in the 6 cyl location.
I base this assumption on the location of the fuel pump versus the section of the frame that is bent up. this is exactly how my motor looks, and it is mounted in the 6cyl location.
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2003 GMC Sierra 1500 WT 1995 Nissan Hardbody 2016 Hyundai Veloster Turbo DC2 (SW/AW) Clyde W. Harvey USN "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery" Winston Churchill |
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#6 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: 72 GMC - Engine hitting firewall...need advice
it's a 4X4... it's supposed to be in the 6 cylinder location.
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#7 |
Registered User
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Location: Pahrump, NV
Posts: 1,079
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Re: 72 GMC - Engine hitting firewall...need advice
It looks like you are doing a super clean build and I think pulling the motor/tranny forward would be the cleanest move and best in the long run.
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#8 |
Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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Re: 72 GMC - Engine hitting firewall...need advice
Why does it being a 4X4 mean its in the 6cyl location? Just trying to learn here, not disputing...Were all of them mounted that way? I know my engine in the Blazer is close, but its the dizzy thats super close, not the valve covers.
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1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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#9 | |
Registered User
![]() Join Date: Nov 2006
Location: Pahrump, NV
Posts: 1,079
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Re: 72 GMC - Engine hitting firewall...need advice
Quote:
I had a 2 wheel drive small block mounted close to the firewall and a co-worker had the same truck but big block mounted closer to the radiator. So I always thought the big block made the differance in mounting but I'm sure I will be corrected. ![]() |
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#10 | |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: 72 GMC - Engine hitting firewall...need advice
Quote:
2 wheel drives had the inline mounted back there, but the small blocks and big blocks were pushed considerably forward. desertrat, your old 2 wheel drive you mention was assembled wrong. There should be something like 6 inches to the firewall from the back of the intake to the firewall on a 2 wheel drive. |
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#11 |
Registered User
Join Date: Jul 2006
Location: Seattle
Posts: 56
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Re: 72 GMC - Engine hitting firewall...need advice
thanks for all the suggestions and advice. I have another quetion for you. If we were to move the T-sec & tran forward say 3-4", how much would that affect the drive line in terms of balance when under extreme pressure such as towing a heavy trailer, or say getting unstuck (which is unlikely since I have another rig for playing in the mud)?
Also, what all is involved in moving everything forward? That does sound much easier than messing with the firewall, which I'd hate to do anyways. Last edited by ducmons; 12-25-2006 at 03:12 AM. |
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#12 |
Registered User
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Location: Pahrump, NV
Posts: 1,079
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Re: 72 GMC - Engine hitting firewall...need advice
It's possible the previous owner moved the motor back on my old 2x. I know the motor was not original.
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#13 |
Registered User
Join Date: Mar 2006
Location: USA
Posts: 21,020
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Re: 72 GMC - Engine hitting firewall...need advice
On my 69 4x4 the distributor cap was almost hitting the firewall on the 350.The 71 C/10 I had with a 350 had no clearance issues.
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#14 |
Registered User
Join Date: Dec 2006
Location: Glenpool OK
Posts: 255
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Re: 72 GMC - Engine hitting firewall...need advice
I was going to say the same thing about the 6-cyl location< dident know all the 4wd truck were like that. My msd distributor barely clears after a little hammer work on the top of the fire wall. I want to move the whole thing forward so I can run tall valve covers when I do some more engine work.
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#15 |
Back in the sticks
Join Date: Jan 2001
Location: Fordland, MO
Posts: 3,188
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Re: 72 GMC - Engine hitting firewall...need advice
Mine are the same 1969k10stepside. My 71 has no clearance issues with the motor in the original location, just had to move the crossmember for the 700R4. The Blazer I thought I put the motor in the same spot, but the original engine was disassembled when I bought it too. Also changed out the tranny on it as well. I didn't have to hammer the firewall, but the dizzy is touching. At least on of the plug wires is anyway.
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1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty |
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#16 |
Registered User
Join Date: Mar 2006
Location: USA
Posts: 21,020
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Re: 72 GMC - Engine hitting firewall...need advice
Pic time..
The pics are off my 71 K10 swb.It had a 292/sm465/np205 in it.I took pics of the holes the motor crossmember bolts too.There is several different holes.BTW,like the paint job? ![]() |
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#17 |
State of Confusion!
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Location: Gulfport, MS USA
Posts: 46,901
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Re: 72 GMC - Engine hitting firewall...need advice
I would massage the firewal, rather than move the engine forward. You may not be able to move the engine forward because of the front driveline. I belive that is why all the 4x4s were mounted in the rear position was to allow clearance fro the front drive train.
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Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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#18 |
SIX BANGER
Join Date: Sep 2005
Location: NC
Posts: 169
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Re: 72 GMC - Engine hitting firewall...need advice
massage the firewall would be the best
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http://www.cardomain.com/ride/2597018(NN) 1979 chevy truck swb 454 w turbo400 with buckets 1977 chevy truck swb soon to be 454 1976 chevy dually 454 1969 chevy truck six shooter |
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#19 |
Registered User
Join Date: Apr 2004
Location: N.E. MO
Posts: 1,749
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Re: 72 GMC - Engine hitting firewall...need advice
I'm in agreement with bowtie. ![]() I did mine with a ball peen hammer and another hammer to tap the ball peen with. (Sometimes it takes more than a tap... ![]()
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72 C20 4X4 454 4 speed 89 Trans Am (was) 305 TPI 700r4 93 C1500 2wd Extended cab 350 700r4 98 Sonoma (TPI outa the Trans Am) 03 Yamaha 660 Raptor 03/04 660 Raptor 07 700 Raptor 85 Honda Odyssey |
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#20 |
Registered User
Join Date: Apr 2006
Location: Bellflower
Posts: 79
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Re: 72 GMC - Engine hitting firewall...need advice
When i installed my new big block, the valve covers were lightly touching the firewall. I just used a ball peen hammer and started lightly tapping the area and just worked it in a little bit into a circle, it came out great. No heat, just tap it and work it until its smooth. I got mine back a good 1/2". Ill see if i cant get pics if i remember. If its lightly touching, i dont think its necessary to move the motor and trans forward. But thats up to you.
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#21 | |
Registered User
Join Date: Jul 2006
Location: Seattle
Posts: 56
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Re: 72 GMC - Engine hitting firewall...need advice
Quote:
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#22 |
Post Whore
![]() Join Date: Feb 2000
Location: Rose Hill, KS, USA
Posts: 12,684
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Re: 72 GMC - Engine hitting firewall...need advice
I'm a little confused on where you engine is touching the firewall. Your prior 350 and the 383 are the same physical side so that is what has me confused. I'm assuming it is touching at the valve covers as that is all that could really be different. Did you change to a different style motor mount?
Lots of people move the engine forward a bit when swapping to a bbc so you can go that route. You will increase the front driveshaft angle a bit and it might have to be shortened. You will also maybe need to have your rear driveshaft lengthened. Give specific info on where the contact is.
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1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14 |
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#23 |
Senior Member
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Location: Estherville, Iowa
Posts: 3,371
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Re: 72 GMC - Engine hitting firewall...need advice
New cab mounts may help, if they are sagging, you can gain some space that way.
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1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0 |
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#24 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: 72 GMC - Engine hitting firewall...need advice
Take the motor out (after you have marked the rubbing spots) and then rework the fire wall. There are ways to do it right and then there are ways that will just crap it up, so be careful of what you do and how you do it. Repainting the firewall is easier than rebuilding the qwwhole drive train. Make it as smooth as your engine and it will look great.
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#25 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: 72 GMC - Engine hitting firewall...need advice
sagging cab mounts could hinder the issue
tall valve covers could be the curlprit you could try loosening all the mounts, the motor mount to towers, towers to frame, tranny mounts... and slide the whole engine forward about a 1/2 an inch...maybe just a quarter inch. There's that much slop in everything. IIRC, the clam style later motor mounts jackl it up a hair maybe you could shim the tranny mounts and tilt it forward (or level it out a tad more acuratly) A combo of all this would probably do the truck. As for firewall mods, i would mark the offending area, jerk the engine out, cut that outlined area out, flip it around so it is inside out, and weld it in place. The shoe box guys call this bubleing the firewall, I plan on doing this in the one problem spot on my caddy swap. |
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