clamshell mount placement - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sammywells · 11-21-2019, 07:33 PM

Working on a 68 1/2 ton with 350 and Hei and a 700r4. Using the later clamshell mount. Brackets are from a c20. My question is where do i mount the brackets to the frame so the i have enough clearance with the hei and firewall. There are different holes in the frame but not sure which ones to use. Right now I just have a rolling chassis and want to mount the engine and want to make sure the engine doesn't hit the firewall when i put cab on. Transmission mount is already loose and can be moved.

GASoline71 · 11-21-2019, 09:40 PM

Are you referring to engine stands as the "C20 brackets"?

Gary

sammywells · 11-21-2019, 10:14 PM

Yes, engine stands from a c20

**HO455** · 11-21-2019, 10:39 PM

Here is how my 67 is mounted. The front holes pictured and not the best photo showing the distributor in relation to the firewall.

sammywells · 11-21-2019, 11:50 PM

HO455, is that a clamshell mount. Looks like the older style.

**Grumpy old man** · 11-22-2019, 12:22 AM

This picture might help , small block with a turbo 350 trans .

sammywells · 11-22-2019, 07:52 PM

yes that helps. thank you

sammywells · 11-23-2019, 03:34 PM

anyone else have any pics or measurements

KQQL IT · 11-23-2019, 06:00 PM

Old blues 74 c20 crossmember 454 with tons of hei clearance

sammywells · 11-23-2019, 06:00 PM

Ok i did find a post on here from roj2323 that had what i needed.

**MikeB** · 11-23-2019, 06:02 PM

On my 69, the rear set of holes on the frame are for 4WD trucks, the front set for 2WD. I have seen 67-68 2WD trucks use the rear set of holes, but I'm not sure they were all like that. I don't know what to tell you when using clam shells, because even my 69 C10 didn't use them.

Any movement fore or aft from the original location will require driveshaft lengthening or shortening, and may affect gear shift linkage and clutch linkage, if applicable. So make sure you keep it where it belongs. As for HEI clearance, my 69 had tons of clearance behind the HEI, but, again its 350 engine was mounted in the forward holes.

Also, it's important to make sure the engine has the correct driveline angle, and that your engine mounts put the radiator fan in the center of the fan shroud. Even when using an electric fan, I like to have the intake manifold carb pad level with the ground. Nothing looks sillier than an engine that's leaning forward. And even level is not ideal.

BTW, what was the original engine?

69 C10 small block mounts. 67-68 are probably the same.

sammywells · 11-23-2019, 06:05 PM

thanks for the pics.

sammywells · 11-23-2019, 06:07 PM

Mike B i'm using the 73 and later mounts. not sure what the original engine was as the truck had none in it.

tdangle · 11-23-2019, 07:08 PM

Interesting, can 73 up mounts be used on the earlier trucks. I assume you would just replace the frame mounted towers and new mounts. Correct?

sammywells · 11-23-2019, 07:43 PM

yes as far as i can tell u just replace with new frame stands. where it gets a little tricky for me is exactly where to bolt them so the engine will be in the correct spot. it would be easy if my cab was on the truck but it's not so i'm just trying to figure it all out, but i think i'm in the ball park. I know engine angle is also a factor.

**Getter-Done** · 11-23-2019, 07:56 PM

This thread may be a good help for you.

Link:http://67-72chevytrucks.com/vboard/s...ghlight=mounts

.

sammywells · 11-23-2019, 10:26 PM

yes, that's the post i found. Thanks

Greasey Harley · 11-24-2019, 01:43 PM

Couldn't this modification potentially throw off the driveline angles?

**MikeB** · 11-24-2019, 01:59 PM

SammyWells -- I suggest you create a new thread asking if there are HEI clearance issues with a small block mounted in the rear set of frame holes on a 67-68. I can't recall any issues on the this forum, and I'd bet at least half the 67-68 trucks have been upgraded to large cap HEIs.

**HO455** · 11-24-2019, 02:05 PM

Yes it could. On my Burban a 1/2" plate under the transmission mount changed the driveshaft angle by 1.5 degrees. The new engine mounts and the longer transmission (700r4) could make quite a change in the angle compared to the original set up. It definitely needs to be checked after installation with the truck loaded at normal ride height.

**HO455** · 11-24-2019, 02:30 PM

Quote:

Originally Posted by MikeB

SammyWells -- I suggest you create a new thread asking if there are HEI clearance issues with a small block mounted in the rear set of frame holes on a 67-68. I can't recall any issues on the this forum, and I'd bet at least half the 67-68 trucks have been upgraded to large cap HEIs.

I am not completely sure but I believe the back set of holes were used on K models and HEI clearance is tight on those with some trucks OK and others touching the firewall.
If SammyWells still needs a measurement I can get one from the core support to a cylinder head (on my 2wd Burban) which would be the same no matter which style of motor mounts you made use of.

sammywells · 11-24-2019, 03:56 PM

Looking at the top pic posted by grumpy old man the mount spans both sets of holes. And that engine has an HEI. I think i'll just have to get the engine over on the mounts and then take some measurements and check some angles. I should have the trans back this week and should be able to start checking things out.

KQQL IT · 11-24-2019, 04:52 PM

These holes are on both side of the rearward part of the motor mount bracket.

11-21-2019, 07:33 PM	#1
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	clamshell mount placement Working on a 68 1/2 ton with 350 and Hei and a 700r4. Using the later clamshell mount. Brackets are from a c20. My question is where do i mount the brackets to the frame so the i have enough clearance with the hei and firewall. There are different holes in the frame but not sure which ones to use. Right now I just have a rolling chassis and want to mount the engine and want to make sure the engine doesn't hit the firewall when i put cab on. Transmission mount is already loose and can be moved.

11-21-2019, 10:14 PM	#3
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement Yes, engine stands from a c20

11-21-2019, 10:39 PM	#4
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,350	Re: clamshell mount placement Here is how my 67 is mounted. The front holes pictured and not the best photo showing the distributor in relation to the firewall. Attached Images __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

11-21-2019, 11:50 PM	#5
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement HO455, is that a clamshell mount. Looks like the older style.

11-22-2019, 12:22 AM	#6
Grumpy old man Senior Member Join Date: Dec 2013 Location: Gods country East,Tn Posts: 8,545	Re: clamshell mount placement This picture might help , small block with a turbo 350 trans . Attached Images __________________ 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop

11-22-2019, 07:52 PM	#7
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement yes that helps. thank you

11-23-2019, 03:34 PM	#8
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement anyone else have any pics or measurements

11-23-2019, 06:00 PM	#9
KQQL IT At the body shop. Join Date: Aug 2009 Location: Land of fruits and nuts. Posts: 5,254	Re: clamshell mount placement Old blues 74 c20 crossmember 454 with tons of hei clearance Attached Images __________________ " That didnt make it any newer " " Dont antique the equipment "

11-23-2019, 06:00 PM	#10
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement Ok i did find a post on here from roj2323 that had what i needed.

11-23-2019, 06:02 PM	#11
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	Re: clamshell mount placement On my 69, the rear set of holes on the frame are for 4WD trucks, the front set for 2WD. I have seen 67-68 2WD trucks use the rear set of holes, but I'm not sure they were all like that. I don't know what to tell you when using clam shells, because even my 69 C10 didn't use them. Any movement fore or aft from the original location will require driveshaft lengthening or shortening, and may affect gear shift linkage and clutch linkage, if applicable. So make sure you keep it where it belongs. As for HEI clearance, my 69 had tons of clearance behind the HEI, but, again its 350 engine was mounted in the forward holes. Also, it's important to make sure the engine has the correct driveline angle, and that your engine mounts put the radiator fan in the center of the fan shroud. Even when using an electric fan, I like to have the intake manifold carb pad level with the ground. Nothing looks sillier than an engine that's leaning forward. And even level is not ideal. BTW, what was the original engine? 69 C10 small block mounts. 67-68 are probably the same. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

11-23-2019, 06:05 PM	#12
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement thanks for the pics.

11-23-2019, 06:07 PM	#13
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement Mike B i'm using the 73 and later mounts. not sure what the original engine was as the truck had none in it.

11-23-2019, 07:08 PM	#14
tdangle Registered User Join Date: Mar 2005 Location: Jurupa Valley, Ca Posts: 1,210	Re: clamshell mount placement Interesting, can 73 up mounts be used on the earlier trucks. I assume you would just replace the frame mounted towers and new mounts. Correct? __________________ Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC

11-23-2019, 07:43 PM	#15
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement yes as far as i can tell u just replace with new frame stands. where it gets a little tricky for me is exactly where to bolt them so the engine will be in the correct spot. it would be easy if my cab was on the truck but it's not so i'm just trying to figure it all out, but i think i'm in the ball park. I know engine angle is also a factor.

11-23-2019, 07:56 PM	#16
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 8,408	Re: clamshell mount placement This thread may be a good help for you. Link:http://67-72chevytrucks.com/vboard/s...ghlight=mounts . __________________ ________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build



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11-23-2019, 10:26 PM	#17
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement yes, that's the post i found. Thanks

11-24-2019, 01:43 PM	#18
Greasey Harley Registered User Join Date: May 2013 Location: Post Falls, ID Posts: 898	Re: clamshell mount placement Couldn't this modification potentially throw off the driveline angles?

11-24-2019, 01:59 PM	#19
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	Re: clamshell mount placement SammyWells -- I suggest you create a new thread asking if there are HEI clearance issues with a small block mounted in the rear set of frame holes on a 67-68. I can't recall any issues on the this forum, and I'd bet at least half the 67-68 trucks have been upgraded to large cap HEIs. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

11-24-2019, 02:05 PM	#20
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,350	Re: clamshell mount placement Yes it could. On my Burban a 1/2" plate under the transmission mount changed the driveshaft angle by 1.5 degrees. The new engine mounts and the longer transmission (700r4) could make quite a change in the angle compared to the original set up. It definitely needs to be checked after installation with the truck loaded at normal ride height. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

11-24-2019, 03:56 PM	#22
sammywells Registered User Join Date: Jun 2018 Location: Lucasville,oh Posts: 61	Re: clamshell mount placement Looking at the top pic posted by grumpy old man the mount spans both sets of holes. And that engine has an HEI. I think i'll just have to get the engine over on the mounts and then take some measurements and check some angles. I should have the trans back this week and should be able to start checking things out.

11-24-2019, 04:52 PM	#23
KQQL IT At the body shop. Join Date: Aug 2009 Location: Land of fruits and nuts. Posts: 5,254	Re: clamshell mount placement These holes are on both side of the rearward part of the motor mount bracket. Attached Images __________________ " That didnt make it any newer " " Dont antique the equipment "

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