Thinking of swapping 355 for 305,307 or 283 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rscam · 03-02-2008, 08:14 AM

I have a 355 with about 320HP. Edelbrock 600 carb and 230/230 480/480 109LSA camshaft. I am thinking of taking it out and getting a 305 or 283/307. Something cheap and more drivable. The 355 is not very street friendly because of the cam and gas is so high. Would I benefit in the MPG area if I stepped down. I don't really care anymore how fast the truck is and a 305 will move it just fine and you can find them anywhere. I just want to drive it when I'm done with it. Is it worth the effort?

Arad68 · 03-02-2008, 08:38 AM

Have you considered a cam change, fuel injection and overdrive with taller gears?

I would use a 283 if you change the engine.

HavinSomeFun · 03-02-2008, 08:42 AM

if you do a cam change it will help and you will still have plenty of get up and go.

BurnoutNova · 03-02-2008, 08:46 AM

i dont think the cam you have is to radical, its a mild cam by todays standards. but dont get me wrong it IS much bigger than a stock cam.

try putting on a rebiult q-jet, the one in my 71 K10 gets about 13-15 MPG in town, and its got a factory L79 camshaft, not as big as yours but its .447"/.447" and has around 290* duration @ .050"

OR

take the money your gonna throw at your truck and buy a beater that gets decent gas mileage, you should be able to pick up a little 4 cyl truck or car and save some gas and not rack up mile on your truck.

*Billla* · 03-02-2008, 08:51 AM

A mild cam swap would be my recommendation, followed by headers and a dyno tune.

I expect you wouldn't see a SIGNIFICANT change by the reduction in CID but sticking with an SBC. If you were really looking to make a swap, a straight six would be a better choice.

BurnoutNova · 03-02-2008, 08:56 AM

i used to have a 76 nova with a 250 I6 and a th350... i dont know if it was a pos carbeurator, how it was tuned ect, but it got crappy gas mileage. i bet it was like 8-10 mpg.

i think any old heavy vehicle is doomed to poor gas mileage compared to the econo box 4 cylinders there are runnig around.

03-02-2008, 08:14 AM	#1
rscam Registered User Join Date: Nov 2005 Location: Monroe,Georgia Posts: 313	Thinking of swapping 355 for 305,307 or 283 I have a 355 with about 320HP. Edelbrock 600 carb and 230/230 480/480 109LSA camshaft. I am thinking of taking it out and getting a 305 or 283/307. Something cheap and more drivable. The 355 is not very street friendly because of the cam and gas is so high. Would I benefit in the MPG area if I stepped down. I don't really care anymore how fast the truck is and a 305 will move it just fine and you can find them anywhere. I just want to drive it when I'm done with it. Is it worth the effort?

03-02-2008, 08:38 AM	#2
Arad68 Trucks N Tranzams Join Date: Dec 2002 Location: North Las Vegas, Nevada Posts: 816	Re: Thinking of swapping 355 for 305,307 or 283 Have you considered a cam change, fuel injection and overdrive with taller gears? I would use a 283 if you change the engine. __________________ Don '68 Chevy LB 383 TH400/GV/373 posi '56 Chevy 4WD SWB '64 Chevy short stepside '79 Trans Am 455/TH2004R/12blt/4whldisc 95 Kia (Wifes car) 2002 S-10 extended cab pickup "God punishes small sins immediately"

03-02-2008, 08:42 AM	#3
HavinSomeFun Still Just Havin Some Fun! Join Date: Jun 2007 Location: Piedmont, Oklahoma Posts: 1,145	Re: Thinking of swapping 355 for 305,307 or 283 if you do a cam change it will help and you will still have plenty of get up and go. __________________ a green one with some stuff done to it....

03-02-2008, 08:46 AM	#4
BurnoutNova Registered User Join Date: Mar 2004 Location: CA Posts: 2,057	Re: Thinking of swapping 355 for 305,307 or 283 i dont think the cam you have is to radical, its a mild cam by todays standards. but dont get me wrong it IS much bigger than a stock cam. try putting on a rebiult q-jet, the one in my 71 K10 gets about 13-15 MPG in town, and its got a factory L79 camshaft, not as big as yours but its .447"/.447" and has around 290* duration @ .050" OR take the money your gonna throw at your truck and buy a beater that gets decent gas mileage, you should be able to pick up a little 4 cyl truck or car and save some gas and not rack up mile on your truck.

03-02-2008, 08:51 AM	#5
Billla Account Suspended Join Date: Sep 2005 Location: Monroe, WA Posts: 3,815	Re: Thinking of swapping 355 for 305,307 or 283 A mild cam swap would be my recommendation, followed by headers and a dyno tune. I expect you wouldn't see a SIGNIFICANT change by the reduction in CID but sticking with an SBC. If you were really looking to make a swap, a straight six would be a better choice. Last edited by Billla; 03-02-2008 at 08:51 AM.

03-02-2008, 08:56 AM	#6
BurnoutNova Registered User Join Date: Mar 2004 Location: CA Posts: 2,057	Re: Thinking of swapping 355 for 305,307 or 283 i used to have a 76 nova with a 250 I6 and a th350... i dont know if it was a pos carbeurator, how it was tuned ect, but it got crappy gas mileage. i bet it was like 8-10 mpg. i think any old heavy vehicle is doomed to poor gas mileage compared to the econo box 4 cylinders there are runnig around.



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