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#74555 03/09/2007 5:47 PM | Joined: Mar 2007 Posts: 4 Junior Member | | Junior Member Joined: Mar 2007 Posts: 4 | Can anyone tell me the bore x stroke of the 305-351-401-478 GMC V6 engines ? Were these 60 degree or 90 degree ? Were they all based on the same block ? How physically big were they, bore spacing, block deck height, weight ? | | |
#74556 03/09/2007 6:29 PM | Joined: Sep 2003 Posts: 2,384 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 2,384 | | | |
#74557 03/10/2007 1:54 AM | Joined: Jan 2007 Posts: 202 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2007 Posts: 202 | Heres' some numbers for you. The 305 has a bore of 4.25 x 3.58 stroke. The 351 has 4.56 x 3.58. The 401 is 4.87 x 3.58 the 478 is 5.125 x 3.86. These engines are about indestructable. Coffee can sized pistons on the last two almost. Not fuel efficient unless some headwork is done and proper gearing. The 305 and 351 with hwy gears are too bad on fuel and pull real well. If you put on an atomizer or a hydro unit it will help you get about 4 mpg more. I hope this will help you out. Henry | | |
#74558 03/10/2007 2:21 AM | Joined: Jan 2007 Posts: 202 Wrench Fetcher | | Wrench Fetcher Joined: Jan 2007 Posts: 202 | Gary534, I just wanted to add some info on those great engines. The compression ratio is usually 7.5:1. Pretty low. They were designed for more torque than hp. If you have the block decked to bring them up to 8.5 or 8.75:1 they will perform and still have a bunch or torque. I would keep it below 9:1 as they were mainly a pulling motor and tougher than nails. 500k miles is not unusual for them with todays oil. Could last even longer. Also I would machine the intake to take a square bore 500 cfm carb. They could use a 600 cfm but the smaller one would be more efficient with a spacer plate up to 2 inches. With some headwork and balancing it would be an awesome set up, gobs of power, and with tall gears not too bad on fuel, otherwise 10-14 mpg is all you would get. The bigger ones, well not too much for mileage but will pull almost anything including a semi down the road on a hook truck. My brother got 17 hwy with tall gears and a three speed manual on his 305 V6. The 351 would be more thirsty but no more than a 350 V8 if set up right. Just a few thoughts and suggestions. H. | | |
#74559 03/10/2007 5:25 PM | Joined: Mar 2007 Posts: 4 Junior Member | | Junior Member Joined: Mar 2007 Posts: 4 | Thank you very much, 64fleetside and Henry G. Really informative link, 64fleetside. | | |
#74560 03/13/2007 1:28 AM | Joined: Feb 2007 Posts: 8 Junior Member | | Junior Member Joined: Feb 2007 Posts: 8 | Not my thread, but really apreciate the v6 info. I have been to 6066 but Henry G really helped. I am pulling B UT SAVING a 351 for a future rat project.
Now I know what to do with it.
Thanks | | |
#74561 03/13/2007 1:35 AM | Joined: Mar 2001 Posts: 1,181 'Bolter | | 'Bolter Joined: Mar 2001 Posts: 1,181 | Gary,
The new truck I bought has the 305A. Here is what I plan to do to mine. Change out the intake to the 4 barrel one. Put in a Petronix dist/coil combo (get rid of the points) Change the rear end to a better gesr ratio. I'm now just really learning what to do to a truck NOW that I have one! Check out my webshots album on the restoration is you want.
Jake | | |
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