305 to 350 swap questions...

[Richard8971]

I know this might be better put in the 'engine and drive line' section, but I think the traffic is better here.

I think I am going to get a reman long block 350 for my truck. I currently have an 1983 305 in there right now. I will be getting a new water pump when I get the engine, but my question is, should I be able to swap the intake, oil pan, valve covers etc... over to the 350? My starter, alt and power steering pump are new.

I think I should be able too, but I wanted 2nd opinions on what will and what may not work...

Thanks!

Don

[72chevyk10]

as long as the 350 doesent have centerbolt heads you should be good!

or if both have/or not have, centerbolt heads...

[my67chevytruck]

should have no issues.... with the exception listed above... post pics of your progress....more power for your stepper

[mr48chev]

That is probably the easiest change over out there as both came in the same model trucks.

As 72ChevyK10 said the only possible issue might be if the engines have different style valve covers.

The only things that don't interchange well between these engines are the cylinder heads. The runners on the 305 heads are too small for a strong performing 350 and the bigger valves in some of the 350 heads are too large for the cylinder bore on the 305 blocks.

As for outside physical dimensions, and bolt hole and bracket tab locations they are identical.

[LOW DOUGH]

the only other thing i can think of is the pan. the 305 and 350 need to be the same year range. Your 305 is an 83 so you need a 350 up to 87 i think. In 88 they went diff pan and the center bolt valve covers (pan has diff rear seal and maybe front too). Also if it has center bolt covers it will have different bolt angles for the intake that bolt straight down insted of angled out to the sides.

Lets see some pics.

[Speedracer77]

Watch the starter. Some 305 starters have the bolts right beside each other, in line with the back of the block. 350's have the bolts offset, one closer to the bell housing than the other. not all blocks have all three holes tapped, and some blocks only have two of the three drilled.

[Speedracer77]

Tried to edit, it's not working out. So adding this:

As mentioned above the one piece rear seal pan is different from the two piece rear seal pan. One piece rear seal is mounted in an aluminum piece that bolts to the back of the block and started in, I believe '87. Two piece rear seal block the seal is built into the rear main cap. The center bolt valve cover heads with the different angle on the two center intake bolts on both sides of the intake (four changed holes in total) started being installed one year before the one piece seal block came out. I believe '86. So it is possible to have a two piece seal block with center bolt valve cover heads from the factory for that one year.

I have heard many time of people elongating the intake holes to use on old style intake with center bolt heads and having no problems with sealing, but for myself I would use the correct intake so that the head of the bolt seats properly on the flat of the intake.

[LOW DOUGH]

so, it sounds like you would want a long block up to 85.

I went with an 85. I had an 85 305 and went with an 85 350 and everything swaped over.

[Richard8971]

Sweet thanks guys. I will post pics in my build page when I get ready... hopefully in the next week or so.

Don