Question about the 305. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Averix · 02-26-2010, 02:54 PM

Hey guys, I was curious if anyone knew how well those le9 305 motors held up and what kind of fuel efficiency I'd be looking at if I kept it, or is it simply better to swap to a 350? Its a 84 K10 with an as of yet unidentified rod style manual transmission, np208 transfer case and 3.42?(so I'm told) diff. The truck will mainly be used as a driver and occasional towing. Thanks!

1973GMC_1500 · 02-26-2010, 10:59 PM

If you're happy with the power and it does what you need it to do, just run the 305. If it gives up the ghost, swap in a 350. None of these older trucks are going to be too good on fuel (unless TBI). The 305 might give you 15-16 MPG with a q-jet. A 350 will usually be slightly worse, but not enough to worry about. Maybe 12-14.
If you have overdrive, that will help quite a bit.

spinem · 02-27-2010, 01:59 AM

Quote:

Originally Posted by 1973GMC_1500

If you're happy with the power and it does what you need it to do, just run the 305. If it gives up the ghost, swap in a 350. None of these older trucks are going to be too good on fuel (unless TBI). The 305 might give you 15-16 MPG with a q-jet. A 350 will usually be slightly worse, but not enough to worry about. Maybe 12-14.
If you have overdrive, that will help quite a bit.

Agreed^^^

also, parts are a little harder to find for that 305.... 350, pssh, dime a dozen.

bikes&bowties · 02-27-2010, 02:12 AM

everything but 2.02 heads and pistons interchange between a 305 and 350. as far as I know. there might be a couple other things. MAYBE

*C-10 simplex* · 02-27-2010, 01:20 PM

Cranks can't interchange unless rebalanced. 305 pistons are lighter than a 350's.

Averix · 02-27-2010, 10:06 PM

Thanks guys! Guess I'll just run it till it dies then... Probably alot easier on the pocket book then if I don't start building another engine for it now and worry about some of the other problems like the power steering hose that burst on me after taking it about 15 feet after replacing the calipers

02-26-2010, 02:54 PM	#1
Averix Registered User Join Date: Jan 2010 Location: Kindersley Saskatchewan Posts: 14	Question about the 305. Hey guys, I was curious if anyone knew how well those le9 305 motors held up and what kind of fuel efficiency I'd be looking at if I kept it, or is it simply better to swap to a 350? Its a 84 K10 with an as of yet unidentified rod style manual transmission, np208 transfer case and 3.42?(so I'm told) diff. The truck will mainly be used as a driver and occasional towing. Thanks!

02-26-2010, 10:59 PM	#2
1973GMC_1500 Registered User Join Date: Jan 2010 Location: Oran, IA Posts: 78	Re: Question about the 305. If you're happy with the power and it does what you need it to do, just run the 305. If it gives up the ghost, swap in a 350. None of these older trucks are going to be too good on fuel (unless TBI). The 305 might give you 15-16 MPG with a q-jet. A 350 will usually be slightly worse, but not enough to worry about. Maybe 12-14. If you have overdrive, that will help quite a bit. __________________ '87 GMC K2500 Factory 6.2 Diesel, 4 speed. Converted to 350 (has cracked block) converting back to 6.2 '82 [COLOR="Sienna"]Cadillac Coupe Deville 350 DIESEL '93 Chev S10 2.8L 5 speed '98 GMC K1500 Z71 ext cab shortbox 6.5 DIESEL '96 Ford F250 7.3 Powerstroke

02-27-2010, 02:12 AM	#4
bikes&bowties Registered User Join Date: May 2009 Location: Washington Posts: 663	Re: Question about the 305. everything but 2.02 heads and pistons interchange between a 305 and 350. as far as I know. there might be a couple other things. MAYBE

02-27-2010, 01:20 PM	#5
C-10 simplex Account Suspended Join Date: Dec 2008 Location: indisclosed Posts: 1,515	Re: Question about the 305. Cranks can't interchange unless rebalanced. 305 pistons are lighter than a 350's.

02-27-2010, 10:06 PM	#6
Averix Registered User Join Date: Jan 2010 Location: Kindersley Saskatchewan Posts: 14	Re: Question about the 305. Thanks guys! Guess I'll just run it till it dies then... Probably alot easier on the pocket book then if I don't start building another engine for it now and worry about some of the other problems like the power steering hose that burst on me after taking it about 15 feet after replacing the calipers



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