Big Block Motor Mount Question...? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**67 cst swb** · 01-28-2008, 06:18 AM

Can you use small block V-8 motor mounts to mount a Big Block... of course you would need to enlarge the hole, but is that do-able....?
I had posted earlier the question about the cab floor, I have now found out the friend of mine has a low hump cab, no mounts and no crossmembers...

So, I have small block V-8 mounts and a stock TH350 crossmember I can give him....

So, can you mount a Big Block/TH400, in small block towers (modify hole) and a stock TH350 crossmember in a stock low hump cab?

please, reply to this question before offering "better possibilities" Thanks...

Matt72blaze · 01-28-2008, 09:54 AM

i'll take the 1st question.... i used small block mounts on the 454 in my blazer. i'm not sure what hole you're talking about enlarging, i just bolted them on then bolted them to the towers.

not sure about the rest of your questions...sorry.

corn · 01-28-2008, 10:09 AM

My truck is a stock bb. I had a small block in it for a while & it now has the big block back in it. No problems at all. I have heard that you cant run manifolds with small towers though but I cant say. I had headers on both motors...

71 super · 01-29-2008, 12:45 AM

The crossmember is basically the same you will have to move it back a little further on the frame- the holes are there. You can use sb mounts but they require modification as corn stated. You will also need a frame bracket for the th400- different from th350 but the rod from column to shift pawl is the same length. You will also need a driveshaft due to length of 400. Some early 69/70 lwb trucks used low hump floors with bb so you don't need to cut the floor to make it fit, unless you just want to.

**clay68c10** · 01-29-2008, 02:22 AM

I think you'll have clearance problems. The BBC towers had a bigger (I think) hole compared to the SBC. They also have a pretty different shape, which is where you run into exhaust manifold clearance problems. Someone on here has a pic of them side by side. I've got a pic of some BBC ones I sold a while back so you can compare to the ones you have now:

The part at the top is where the most difference is, that big curved area is for the manifolds and they sit pretty close.

**clay68c10** · 01-29-2008, 02:27 AM

...I forgot to add:
The SBC rubber mounts will work fine with BBC towers, I didn't have to modify anything when I used those in the pics. Just put a big washer on the center bolt.
If you're going to change towers, it's worth using the 72 style. You get a LOT less vibration with those captive mounts.

71 super · 01-29-2008, 06:36 AM

Hey I know those mounts! Seems like there is a set identical to them on the shelf in the garage

Small block pads can be used as clay stated, but issues occur when exhaust is run with a bb on small block stands. I would look for corect stands and use sb pads instead of trimming or what ever on a set of sb stands.

**67 cst swb** · 01-30-2008, 01:58 PM

So, Big Block/TH400 going into a '68 low hump cab (originally a 307/3-speed on the column)

OK, so here are our current options...
Use the Small Block stands with Big Block Rubber Mounts on the Big Block engine, but must use headers as there is stock manifold issues... This Option is the cheapest, as Headers were in the plans already and we already have SB towers....

OR...

We thought of purchasing the Big Block 72-later style mounts from ECE

Either way... (am I understanding this correctly?)
We will need to find a TH400 crossmember or build a tubular one, as it is not the same as a stock TH350 crossmember... I thought a Auto crossmember was an Auto crossmember...
Also... my '67 (originally a 327/TH400) will it have the correct crossmember if TH350 & TH400 x-members are different???????

Sorry for all the questions.... I've never ran, nor had the desire to run a Big Block... It's the friend of mines project,... and yes I'm trying to get him on the board.

**67 cst swb** · 01-30-2008, 02:08 PM

Quote:

Originally Posted by 71 super

The crossmember is basically the same you will have to move it back a little further on the frame- the holes are there. You can use sb mounts but they require modification as corn stated. You will also need a frame bracket for the th400- different from th350 but the rod from column to shift pawl is the same length. You will also need a driveshaft due to length of 400. Some early 69/70 lwb trucks used low hump floors with bb so you don't need to cut the floor to make it fit, unless you just want to.

Ok, I re-read this... the X-member will work, but requires a different pivot point bracket for the linkage....
I did expect the driveshaft change already (plus we don't have one so we were having to have one made already)

corn · 01-30-2008, 02:10 PM

When I was swapping mine around, the threads on the drivers side mount were boogered up a little & I couldnt find a replacment at a parts store so I bought a 6cyl mount. One washer behind each bolt & it was good to go... When I put the 396 in my 84 GMC for a while I had header issues (clam shell motor mounts) but I never had any issues swapping big to small to big on the 69. I also used Chevelle headers on both motors with no problems...

**67 cst swb** · 01-30-2008, 02:18 PM

remind me to always stay with what I have... I've replaced 6 cyl with V-8's alot, but that was easy... get V-8 towers/mounts, Auto crossmember/Auto column & linkage/ have a driveshaft built.... and your done...
geez...all these Big Block differences tweeks my headache....

So, I'm going to suggest the ECE Big Block 72-later style mounts, then sell him my TH400 X-member (from my '67 327/TH400 truck, when I build it I'll be going TH350) and tell him we will still need a TH400 linkage pivot point bracket (My '67 might still have it, It should work right?)

RICKSRAT · 01-30-2008, 03:33 PM

67 CST if you use the small block stands the trans linkage will not line up. Also small block stands would require over 1/2 of the top of the stand to be cut away for the headers to fit. Have you looked at the performance online tubular mounts? If you use the BB stands I have a 1 piece driveshaft the correct length w/1330 yoke and Ujoints complete.I put a new 1350 Dennys nitrous ready in my '72 a few months back.

http://www.performanceonline.com/sto...cat=455&page=1

mechanicalman · 09-06-2014, 12:49 PM

Quote:

Originally Posted by 67 cst swb

Ok, I re-read this... the X-member will work, but requires a different pivot point bracket for the linkage....
I did expect the driveshaft change already (plus we don't have one so we were having to have one made already)

error

*Fitz* · 09-07-2014, 09:48 AM

Quote:

Originally Posted by 67 cst swb

Can you use small block V-8 motor mounts to mount a Big Block... ...

Big Block on small block frame stands and big block on big block frame stands:

dukkie · 04-14-2015, 07:48 PM

Who knows about fitting a 1999 LM7 5.3L into a 72 C20 with Big Block Stands?

**SOON2BLAZE** · 04-14-2015, 09:33 PM

Quote:

Originally Posted by RICKSRAT

67 CST if you use the small block stands the trans linkage will not line up. Also small block stands would require over 1/2 of the top of the stand to be cut away for the headers to fit. Have you looked at the performance online tubular mounts? If you use the BB stands I have a 1 piece driveshaft the correct length w/1330 yoke and Ujoints complete.I put a new 1350 Dennys nitrous ready in my '72 a few months back.

http://www.performanceonline.com/sto...cat=455&page=1

I'm using the POL mounts on my BB as well with the front engine mount frame holes and a factory trans cross member that uses the stock mounting holes. Quick, easy and when I bought mine I saved money getting new vs what factory BBC mounts were going for used in the for sale section.

01-28-2008, 06:18 AM	#1
67 cst swb Senior Member Join Date: Nov 2001 Location: Rapid City, SD Posts: 2,281	Big Block Motor Mount Question...? Can you use small block V-8 motor mounts to mount a Big Block... of course you would need to enlarge the hole, but is that do-able....? I had posted earlier the question about the cab floor, I have now found out the friend of mine has a low hump cab, no mounts and no crossmembers... So, I have small block V-8 mounts and a stock TH350 crossmember I can give him.... So, can you mount a Big Block/TH400, in small block towers (modify hole) and a stock TH350 crossmember in a stock low hump cab? please, reply to this question before offering "better possibilities" Thanks... __________________ My Trucks: 1967 Chevrolet Short Wide Box 327 TH350 9" w/3.90 gears paint will be White - Current Project 1967 Chevrolet Custom LWB 283 TH400 3.73 Posi, no-AC, no-PS, no-PB, bench-seat, small-window - mostly orig driver 1967 Chevrolet CST LWB originally a 327 TH400 3.73 Posi AC PS PB, had Buddy Buckets, Small Window - parts truck 1967 Chevrolet CST LWB, 283 MT 3.73 had Buddy Buckets, Panoramic Window - parts truck 2001 Chevrolet 3500 2WD Crew Cab Dually 8.1L Allison White 2002 Chevrolet 1500HD 4x4 Crew Cab 6.0L 4L80E Red

01-28-2008, 09:54 AM	#2
Matt72blaze Registered User Join Date: Sep 2007 Location: Wilmington, OH Posts: 60	Re: Big Block Motor Mount Question...? i'll take the 1st question.... i used small block mounts on the 454 in my blazer. i'm not sure what hole you're talking about enlarging, i just bolted them on then bolted them to the towers. not sure about the rest of your questions...sorry. __________________ 1970 C20 now a K30 1986 3+3 Dually

01-28-2008, 10:09 AM	#3
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Re: Big Block Motor Mount Question...? My truck is a stock bb. I had a small block in it for a while & it now has the big block back in it. No problems at all. I have heard that you cant run manifolds with small towers though but I cant say. I had headers on both motors...

01-29-2008, 12:45 AM	#4
71 super Registered User Join Date: Sep 2005 Location: Canton North carolina Posts: 3,078	Re: Big Block Motor Mount Question...? The crossmember is basically the same you will have to move it back a little further on the frame- the holes are there. You can use sb mounts but they require modification as corn stated. You will also need a frame bracket for the th400- different from th350 but the rod from column to shift pawl is the same length. You will also need a driveshaft due to length of 400. Some early 69/70 lwb trucks used low hump floors with bb so you don't need to cut the floor to make it fit, unless you just want to.

01-29-2008, 02:22 AM	#5
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,909	Re: Big Block Motor Mount Question...? I think you'll have clearance problems. The BBC towers had a bigger (I think) hole compared to the SBC. They also have a pretty different shape, which is where you run into exhaust manifold clearance problems. Someone on here has a pic of them side by side. I've got a pic of some BBC ones I sold a while back so you can compare to the ones you have now: The part at the top is where the most difference is, that big curved area is for the manifolds and they sit pretty close. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ Last edited by clay68c10; 01-29-2008 at 02:23 AM.

01-29-2008, 02:27 AM	#6
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,909	Re: Big Block Motor Mount Question...? ...I forgot to add: The SBC rubber mounts will work fine with BBC towers, I didn't have to modify anything when I used those in the pics. Just put a big washer on the center bolt. If you're going to change towers, it's worth using the 72 style. You get a LOT less vibration with those captive mounts. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

01-29-2008, 06:36 AM	#7
71 super Registered User Join Date: Sep 2005 Location: Canton North carolina Posts: 3,078	Re: Big Block Motor Mount Question...? Hey I know those mounts! Seems like there is a set identical to them on the shelf in the garage Small block pads can be used as clay stated, but issues occur when exhaust is run with a bb on small block stands. I would look for corect stands and use sb pads instead of trimming or what ever on a set of sb stands.

01-30-2008, 01:58 PM	#8
67 cst swb Senior Member Join Date: Nov 2001 Location: Rapid City, SD Posts: 2,281	Re: Big Block Motor Mount Question...? So, Big Block/TH400 going into a '68 low hump cab (originally a 307/3-speed on the column) OK, so here are our current options... Use the Small Block stands with Big Block Rubber Mounts on the Big Block engine, but must use headers as there is stock manifold issues... This Option is the cheapest, as Headers were in the plans already and we already have SB towers.... OR... We thought of purchasing the Big Block 72-later style mounts from ECE Either way... (am I understanding this correctly?) We will need to find a TH400 crossmember or build a tubular one, as it is not the same as a stock TH350 crossmember... I thought a Auto crossmember was an Auto crossmember... Also... my '67 (originally a 327/TH400) will it have the correct crossmember if TH350 & TH400 x-members are different??????? Sorry for all the questions.... I've never ran, nor had the desire to run a Big Block... It's the friend of mines project,... and yes I'm trying to get him on the board. __________________ My Trucks: 1967 Chevrolet Short Wide Box 327 TH350 9" w/3.90 gears paint will be White - Current Project 1967 Chevrolet Custom LWB 283 TH400 3.73 Posi, no-AC, no-PS, no-PB, bench-seat, small-window - mostly orig driver 1967 Chevrolet CST LWB originally a 327 TH400 3.73 Posi AC PS PB, had Buddy Buckets, Small Window - parts truck 1967 Chevrolet CST LWB, 283 MT 3.73 had Buddy Buckets, Panoramic Window - parts truck 2001 Chevrolet 3500 2WD Crew Cab Dually 8.1L Allison White 2002 Chevrolet 1500HD 4x4 Crew Cab 6.0L 4L80E Red Last edited by 67 cst swb; 01-30-2008 at 02:03 PM.

01-30-2008, 02:10 PM	#10
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Re: Big Block Motor Mount Question...? When I was swapping mine around, the threads on the drivers side mount were boogered up a little & I couldnt find a replacment at a parts store so I bought a 6cyl mount. One washer behind each bolt & it was good to go... When I put the 396 in my 84 GMC for a while I had header issues (clam shell motor mounts) but I never had any issues swapping big to small to big on the 69. I also used Chevelle headers on both motors with no problems...

01-30-2008, 02:18 PM	#11
67 cst swb Senior Member Join Date: Nov 2001 Location: Rapid City, SD Posts: 2,281	Re: Big Block Motor Mount Question...? remind me to always stay with what I have... I've replaced 6 cyl with V-8's alot, but that was easy... get V-8 towers/mounts, Auto crossmember/Auto column & linkage/ have a driveshaft built.... and your done... geez...all these Big Block differences tweeks my headache.... So, I'm going to suggest the ECE Big Block 72-later style mounts, then sell him my TH400 X-member (from my '67 327/TH400 truck, when I build it I'll be going TH350) and tell him we will still need a TH400 linkage pivot point bracket (My '67 might still have it, It should work right?) __________________ My Trucks: 1967 Chevrolet Short Wide Box 327 TH350 9" w/3.90 gears paint will be White - Current Project 1967 Chevrolet Custom LWB 283 TH400 3.73 Posi, no-AC, no-PS, no-PB, bench-seat, small-window - mostly orig driver 1967 Chevrolet CST LWB originally a 327 TH400 3.73 Posi AC PS PB, had Buddy Buckets, Small Window - parts truck 1967 Chevrolet CST LWB, 283 MT 3.73 had Buddy Buckets, Panoramic Window - parts truck 2001 Chevrolet 3500 2WD Crew Cab Dually 8.1L Allison White 2002 Chevrolet 1500HD 4x4 Crew Cab 6.0L 4L80E Red Last edited by 67 cst swb; 01-30-2008 at 02:18 PM.

01-30-2008, 03:33 PM	#12
RICKSRAT Registered User Join Date: Apr 2000 Location: LAKE JACKSON TEXAS Posts: 343	Re: Big Block Motor Mount Question...? 67 CST if you use the small block stands the trans linkage will not line up. Also small block stands would require over 1/2 of the top of the stand to be cut away for the headers to fit. Have you looked at the performance online tubular mounts? If you use the BB stands I have a 1 piece driveshaft the correct length w/1330 yoke and Ujoints complete.I put a new 1350 Dennys nitrous ready in my '72 a few months back. http://www.performanceonline.com/sto...cat=455&page=1 __________________ '72 SWB 3,600# Indigo Blue , Sunset Racing Pump Gas 582" 1,002hp / 833tq ,Transking 400 W/ Transbrake, Moser Dana 60 w/4.30 Old Motor: 60'. 1.43 1/8 6.58@104.64 1/4. 10.42@127.10 Nitrous: 60'. 1.28 1/8. 6.15@ 112.02 1/4. 9.75@ 136.32 Last edited by RICKSRAT; 01-30-2008 at 04:18 PM.

04-14-2015, 07:48 PM	#15
dukkie My Spoon Is Too Big Join Date: Mar 2010 Location: Magnolia Tx Posts: 457	Re: Big Block Motor Mount Question...? Who knows about fitting a 1999 LM7 5.3L into a 72 C20 with Big Block Stands? __________________ 1972 C20, 03-14-10 Build Thread 2000 Silverado 4.8L, 11-04-13 (Currently Parting) 1999 Silverado 5.3L, 07-07-14. (Engine Donor) 2015 Ram 05-20-15 (Daily Driver)



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