3 speed to 4 speed and long water pump - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rdrdave · 11-22-2005, 06:47 PM

Starting Wed. I will be switching out the old 307 with the 3speed and putting my 350 with M21 into my 68 lwb. Does the frame already have the holes for the automatic crossmember or do I have to drill some, since it is a 3 speed and held on by the bellhousing. Also, I've read that my 350 long water pump will need an electric fan? Is this true. Is there that much a difference with the length when switching from a short to a long water pump system? Any help is greatly appreciated. I hope I don't find any bugs because this is my daily driver!

crazy longhorn · 11-22-2005, 07:04 PM

If you pulled a 307/3spd stick out of the truck, you can use the truck bell,& bolt the 350/ M21 in the same way factory did.....or if you prefer, you can use the auto crossmember under the 4spd(the holes are there in the frame). on the waterpump, yes it does sit really close to the rad in factory V8 sb position if using the later long pump. IMO, you would be better off using the pump/ pullies/ect from the 307, then the stock fan/shroud will fit properly. best of luck....

L

BubbaGreen · 11-22-2005, 10:38 PM

If you have a SBC w/long water pump....and serpentine set up!!!
The following works well: the sbc in the stock forward position
1.] 2 or 3-core radiator (smaller cradle mounts for the radiator tanks)
2.] Fan from an S-10, 1989
3.] Fan Clutch, 1990 suburban
4.] Fan shroud for a big block -or- gmc v6 67-72
This set up puts the thermal sensor of the fan clutch apprx 1~1.5 inches from the radiator coils. Using the v6 shroud puts the fan 2/3 into the shroud.
The S-10 fan is slightly smaller in diameter than the standard 350 fans. Its also a 5-blade fan that's offset to reduce fan noise. If anyone actually wants part numbers, i will attempt to dig them up. This makes for a very nice set up.

Jim_PA · 11-23-2005, 08:55 AM

I hope you have some steep rear end gears to go with the M21! -- First gear is pretty rough in the close ratio muncies. I had an M22 in a '68 camaro with 3:73's in the rear, and it was kind of a PITA pulling out in first gear.

crazy longhorn · 11-23-2005, 07:56 PM

Quote:

Originally Posted by Jim_PA

I hope you have some steep rear end gears to go with the M21! -- First gear is pretty rough in the close ratio muncies. I had an M22 in a '68 camaro with 3:73's in the rear, and it was kind of a PITA pulling out in first gear.

yea, that 1st gear being 2.20 does cause some clutch slip on the take off......with a 3.73 or 4.10 on a 28" tire that booger will flat go shifting through the gears tho.....I used to rev mine up & side step the clutch

L

Rdrdave · 11-24-2005, 12:06 AM

it has 3.08 gears still in the back with 275/60/15 rear tire. Going to switch to a 3.73 posi in a month or so. Need the holidays to pass. Hopefully "santa's girlfriend" will put one under the tree.

Rdrdave · 11-24-2005, 01:30 AM

oh it also is a Centerforce I clutch setup. I'm using the 621 bellhousing 11" clutch set up. Will i have to cut out the bellhousing mounting xmember or can I just leave it in place?

fastwillie 696969 · 11-24-2005, 03:00 AM

Leave In Place

Rdrdave · 11-24-2005, 09:57 PM

Well everyone, it's in! 350/m21 combo. Bolted engine and tranny together slid right in the first time and the motor mounts lined up on my first try. It's kind of difficult getting up and down so many times. I used the hoist and floor jack. I'm going to do the alternator conversion and finish up the wiring tomorrow. I got the wrong starter, nosecone was too big. My mistake asked for a k5 4 speed one. Should have asked for a chevelle or camaro SS one i guess. Sorry for the long post but I'm stoked that I actually got it done. The only bad part was that I had to do it alone. Being Thanksgiving everyone was busy and all but it's ok. Well, I'll add some pics of before and after. I still want to change some things but my daily driver has to get what it gets right now. Have a great and safe weekend. Pics to come. Happy Thanksgiving. Update...it's raining! no wiring today. hopefully tomorrow.

Well, got it started on the first try today. Everything is done! I'm dead tired though so it's sitting at mom's for tonight. I'll get back to it next week. Raiders football tomorrow and then relax the rest of the day to get ready for the grind. I will modify some of the wiring. Add a 30 amp fuse to the HEI, re-route some of the old wiring and clean up the compartment. I just needed it road worthy so I can get back and forth to work. I owe alot to the conversion of the 3 to 4 to this website. Everyone rocks here. Thanks a bunch. Anytime you are in the SF Bay Area don't hesitate to let me know. We'll spill a beer or two. Thanks.

11-22-2005, 06:47 PM	#1
Rdrdave Broke and still trying Join Date: Apr 2003 Location: Alameda, CA Posts: 562	3 speed to 4 speed and long water pump Starting Wed. I will be switching out the old 307 with the 3speed and putting my 350 with M21 into my 68 lwb. Does the frame already have the holes for the automatic crossmember or do I have to drill some, since it is a 3 speed and held on by the bellhousing. Also, I've read that my 350 long water pump will need an electric fan? Is this true. Is there that much a difference with the length when switching from a short to a long water pump system? Any help is greatly appreciated. I hope I don't find any bugs because this is my daily driver!

11-22-2005, 07:04 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Re: 3 speed to 4 speed and long water pump If you pulled a 307/3spd stick out of the truck, you can use the truck bell,& bolt the 350/ M21 in the same way factory did.....or if you prefer, you can use the auto crossmember under the 4spd(the holes are there in the frame). on the waterpump, yes it does sit really close to the rad in factory V8 sb position if using the later long pump. IMO, you would be better off using the pump/ pullies/ect from the 307, then the stock fan/shroud will fit properly. best of luck.... L __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

11-22-2005, 10:38 PM	#3
BubbaGreen Senior Member Join Date: Mar 2001 Location: Cedar Park, TX Posts: 686	Re: 3 speed to 4 speed and long water pump If you have a SBC w/long water pump....and serpentine set up!!! The following works well: the sbc in the stock forward position 1.] 2 or 3-core radiator (smaller cradle mounts for the radiator tanks) 2.] Fan from an S-10, 1989 3.] Fan Clutch, 1990 suburban 4.] Fan shroud for a big block -or- gmc v6 67-72 This set up puts the thermal sensor of the fan clutch apprx 1~1.5 inches from the radiator coils. Using the v6 shroud puts the fan 2/3 into the shroud. The S-10 fan is slightly smaller in diameter than the standard 350 fans. Its also a 5-blade fan that's offset to reduce fan noise. If anyone actually wants part numbers, i will attempt to dig them up. This makes for a very nice set up. __________________ 71 Chevy C-10 SWB Fleetside RamJet-350/4L60e & Compushift/3.73Posi See it at www.prismnet.com/~grzanich Last edited by BubbaGreen; 11-22-2005 at 10:39 PM.

11-23-2005, 08:55 AM	#4
Jim_PA Registered User Join Date: May 2005 Location: PA Posts: 2,696	Re: 3 speed to 4 speed and long water pump I hope you have some steep rear end gears to go with the M21! -- First gear is pretty rough in the close ratio muncies. I had an M22 in a '68 camaro with 3:73's in the rear, and it was kind of a PITA pulling out in first gear.

11-24-2005, 12:06 AM	#6
Rdrdave Broke and still trying Join Date: Apr 2003 Location: Alameda, CA Posts: 562	Re: 3 speed to 4 speed and long water pump it has 3.08 gears still in the back with 275/60/15 rear tire. Going to switch to a 3.73 posi in a month or so. Need the holidays to pass. Hopefully "santa's girlfriend" will put one under the tree.

11-24-2005, 01:30 AM	#7
Rdrdave Broke and still trying Join Date: Apr 2003 Location: Alameda, CA Posts: 562	Re: 3 speed to 4 speed and long water pump oh it also is a Centerforce I clutch setup. I'm using the 621 bellhousing 11" clutch set up. Will i have to cut out the bellhousing mounting xmember or can I just leave it in place?

11-24-2005, 03:00 AM	#8
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	Re: 3 speed to 4 speed and long water pump Leave In Place __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

11-24-2005, 09:57 PM	#9
Rdrdave Broke and still trying Join Date: Apr 2003 Location: Alameda, CA Posts: 562	Re: 3 speed to 4 speed and long water pump Well everyone, it's in! 350/m21 combo. Bolted engine and tranny together slid right in the first time and the motor mounts lined up on my first try. It's kind of difficult getting up and down so many times. I used the hoist and floor jack. I'm going to do the alternator conversion and finish up the wiring tomorrow. I got the wrong starter, nosecone was too big. My mistake asked for a k5 4 speed one. Should have asked for a chevelle or camaro SS one i guess. Sorry for the long post but I'm stoked that I actually got it done. The only bad part was that I had to do it alone. Being Thanksgiving everyone was busy and all but it's ok. Well, I'll add some pics of before and after. I still want to change some things but my daily driver has to get what it gets right now. Have a great and safe weekend. Pics to come. Happy Thanksgiving. Update...it's raining! no wiring today. hopefully tomorrow. Well, got it started on the first try today. Everything is done! I'm dead tired though so it's sitting at mom's for tonight. I'll get back to it next week. Raiders football tomorrow and then relax the rest of the day to get ready for the grind. I will modify some of the wiring. Add a 30 amp fuse to the HEI, re-route some of the old wiring and clean up the compartment. I just needed it road worthy so I can get back and forth to work. I owe alot to the conversion of the 3 to 4 to this website. Everyone rocks here. Thanks a bunch. Anytime you are in the SF Bay Area don't hesitate to let me know. We'll spill a beer or two. Thanks. Last edited by Rdrdave; 11-27-2005 at 01:36 AM.

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