350HO and 700R4 Uprgrade - The 1947 - Present Chevrolet & GMC Truck Message Board Network

JMac11 · 04-03-2006, 09:13 PM

Think I am going with this combo in my Blazer. 373 gears/31.5 tires. Anyone got a similar setup??? Have a 670 CFM Holley unit to put on a Edelbrock Airgap intake...

Might not get the AC rehabbed this summer

rigon4 · 04-04-2006, 01:36 AM

You will have to shorten drive rear shaft and add to front . i have a 87 k-10 425 hp 350, th350 with shift kit, np205, 4.11, with 33 inch tires and only got 4-7 mpg so i would go with the OD trans. I have 71 2wd blazer going to pull 350 out of 87 put a tpi setup on it with BW t-5 five speed.

ClassicStyle · 04-04-2006, 09:40 AM

that would be nice, i have a 350/350 combo in my 72, but the th350 is geared for highway. and i have a 305/700r4 combo in my 82. they get similiar MPG, but i lost all my fun down low in my 72.

-Cameron

Jason915 · 04-04-2006, 10:01 AM

You will like the low 1st gear in a 700R4 and the OD on the HWY, as long as you have 3.73's and lower then I would defiantly recommend a 700R4. The only thing I would advise you against is the RPM intake the are not for heavy trucks and the loss of low end torque is very noticeable. I ran one in my truck and it would really scream in the upper RPM's but even with 4.10's it didn't tow worth a crap unless it was 2500 RPM and higher. I switched to a EPS intake and 4x4 CompCam and that made a huge difference in low end power. I notice alot of people on this board are using the RPM intakes on big 4x4 trucks but believe me if you go off road and tow with your vehicle it is not the best choice, actually even Edelbrock don't recommend the RPM intakes for vehicles that weigh more than 3600 LBS, and there is a reason for that.

Musclerodz · 04-04-2006, 12:36 PM

Installin a LT-1 and 700r4 in mine. I decided to use a machined adapter rather than the advanced adapter output shaft. There has been some tranny pan clearance issues with the output shaft depending on your front yoke style.

Mike

Paul72 · 04-04-2006, 06:59 PM

The 700 is about 1.75" longer than the TH350. If you keep the 205 in the same place and move the engine forward, you can avoid the lengthening/shortening of the driveshafts. Check the FAQ section and search for 700R4 - lots of info on the swap.

Paul

13lazer · 04-11-2006, 12:05 AM

in my 1970 2 wheeler blazer, i'm running a 385 stroker small block with a 700r4 and 3:73's. i have 33's from my 4x4 that im gonna dump soon. it seems to lug the motor only when i hit the lock up toggle at 2500 rpm's. i have the 670 holley and a holley street dominator intake manifold. my old truck surprises alot of european performance cars in the $60k-$100k range when they cant pull away from me on the freeway. i have a set of 235 70 r15's that i think will solve the motor lugging issue. it should be running at maxi mum efficiency at that point. i recommend this upgrade for anyone who plans on driving their truck alot.

04-03-2006, 09:13 PM	#1
JMac11 Registered User Join Date: May 2005 Location: Tallahassee Fl Posts: 773	350HO and 700R4 Uprgrade Think I am going with this combo in my Blazer. 373 gears/31.5 tires. Anyone got a similar setup??? Have a 670 CFM Holley unit to put on a Edelbrock Airgap intake... Might not get the AC rehabbed this summer

04-04-2006, 01:36 AM	#2
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: 350HO and 700R4 Uprgrade You will have to shorten drive rear shaft and add to front . i have a 87 k-10 425 hp 350, th350 with shift kit, np205, 4.11, with 33 inch tires and only got 4-7 mpg so i would go with the OD trans. I have 71 2wd blazer going to pull 350 out of 87 put a tpi setup on it with BW t-5 five speed.

04-04-2006, 09:40 AM	#3
ClassicStyle Registered User Join Date: Aug 2005 Location: Scottsdale, AZ Posts: 215	Re: 350HO and 700R4 Uprgrade that would be nice, i have a 350/350 combo in my 72, but the th350 is geared for highway. and i have a 305/700r4 combo in my 82. they get similiar MPG, but i lost all my fun down low in my 72. -Cameron __________________ 1972 Dark blue, Cst, Highlander

04-04-2006, 10:01 AM	#4
Jason915 Registered User Join Date: Jan 2005 Location: Colorado Springs Posts: 693	Re: 350HO and 700R4 Uprgrade You will like the low 1st gear in a 700R4 and the OD on the HWY, as long as you have 3.73's and lower then I would defiantly recommend a 700R4. The only thing I would advise you against is the RPM intake the are not for heavy trucks and the loss of low end torque is very noticeable. I ran one in my truck and it would really scream in the upper RPM's but even with 4.10's it didn't tow worth a crap unless it was 2500 RPM and higher. I switched to a EPS intake and 4x4 CompCam and that made a huge difference in low end power. I notice alot of people on this board are using the RPM intakes on big 4x4 trucks but believe me if you go off road and tow with your vehicle it is not the best choice, actually even Edelbrock don't recommend the RPM intakes for vehicles that weigh more than 3600 LBS, and there is a reason for that. __________________ 1971 GMC K1500 SWB Fleetside, 4" skyjacker softride and, 14 Bolt FF, HD Dana 44 4.10's 1970 K5 TBI conversion lifted etc SOLD 1968 C20 camper truck SOLD “To ban guns because criminals use them is to tell the innocent and law-abiding that their rights and liberties depend not on their own conduct, but on the conduct of the guilty and the lawless.” Jeff Snyder

04-04-2006, 12:36 PM	#5
Musclerodz Senior Member Join Date: Aug 2005 Location: OKC, OK Posts: 2,364	Re: 350HO and 700R4 Uprgrade Installin a LT-1 and 700r4 in mine. I decided to use a machined adapter rather than the advanced adapter output shaft. There has been some tranny pan clearance issues with the output shaft depending on your front yoke style. Mike __________________ Mike Redpath

04-04-2006, 06:59 PM	#6
Paul72 Registered User Join Date: Sep 2003 Location: Waterloo, IA Posts: 1,147	Re: 350HO and 700R4 Uprgrade The 700 is about 1.75" longer than the TH350. If you keep the 205 in the same place and move the engine forward, you can avoid the lengthening/shortening of the driveshafts. Check the FAQ section and search for 700R4 - lots of info on the swap. Paul __________________ '72 Chevy K20 - 383/4sp/205 - SOLD after 41 years in the family Next project - K/5 Tahoe (71 Blazer on 99 Tahoe chassis) Build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=789958

04-11-2006, 12:05 AM	#7
13lazer 13lazers' blazers Join Date: Jul 2005 Location: San Pedro, CA Posts: 152	Re: 350HO and 700R4 Uprgrade in my 1970 2 wheeler blazer, i'm running a 385 stroker small block with a 700r4 and 3:73's. i have 33's from my 4x4 that im gonna dump soon. it seems to lug the motor only when i hit the lock up toggle at 2500 rpm's. i have the 670 holley and a holley street dominator intake manifold. my old truck surprises alot of european performance cars in the $60k-$100k range when they cant pull away from me on the freeway. i have a set of 235 70 r15's that i think will solve the motor lugging issue. it should be running at maxi mum efficiency at that point. i recommend this upgrade for anyone who plans on driving their truck alot.



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