250 integrated head to a 305

[fred_e81]

First square so bare with me,

I have a 79 stepper with a 250 integrated head 3 on the tree converted to floor shifter by PO. I am having issues with it idling and stalling out when I put a load on it. I know these heads are garbage but, I have an opportunity to buy a 305 complete with accessories for $400 obo (engine is still in the vehicle to test out). My question is will the 305 mat to the 3 speed tranny that I have on it now? What exactly will be needed to perform the swap? Money is kind of an issue so getting a different tranny is out of the question for now. I bought the truck in October and I just want to enjoy it for now. Any help is greatly appreciated, thanks!

[cadillac_al]

I am doing a swap like this next month (250 to 350) and I assume the bell housing is the same. If not, I'm not worried because I have lots of spares. Worst case scenario is you might need a bell housing but I really doubt it. If your 250 is like mine was, the clutch is very very tiny. That won't live behind a 305. I converted to a 10.5" clutch years ago so I'm ready for the 350.

[greg64]

The 250 and 305/350 share the same bellhousing design. Your existing tranny will bolt right up to the 305. You may need a different flywheel, depending on the year of the 305.

One thing to check is how the clutch z-bar linkage is attached to the engine on the 250. The 305 may or may not have the necessary threaded boss.

You know, you may just need a carb rebuild on the 250. This is really easy if it is a single barrel Rochester. I'm a six cylinder guy, so I'm biased towards saving the six.

[fred_e81]

Thanks for the replies fellas! Good to know that they will match up to each other. Al, I am Going to take you advice on the clutch

Greg how will I know which flywheel I will need? Is there a certain number of teeth that I'm looking for?

As for the z bar linkage, if the 305 doesn't have the threaded boss should I discard that motor?

As for the carb, it's a Rochester Varajet 2. I was quoted about 270 for a full rebuild. The man who quoted me does pretty good work here in El Paso. He advised me to get another non integrated head and slap it on because the integrated head and that particular carb would be a headache to get running right.

Keep in mind I know nothing about these trucks. I'm coming over from the vintage Volkswagen side of the house.

I figured for a little more cash I can have a V8 and make it more appealing in the case I decide to sell it later in in the future.

Thanks again for all of the responses!

[73kay]

I had the 250 and 3ott, just installed a crate 350. Night and day torque. Granted my 250 was worn but it was a good motor. It just wouldn't die lol

I was able to reuse my flywheel from the 250 to the 350. Not too familiar with the 305.

I miss the straight six uniqueness but having cheap torque outta 350 has definitely made it a different truck especially on hills. What's your rear axle ratio? The six didn't like too high rpms. I have a 3.40 in my c10

[greg64]

Originally Posted by fred_e81

Greg how will I know which flywheel I will need? Is there a certain number of teeth that I'm looking for?

As for the z bar linkage, if the 305 doesn't have the threaded boss should I discard that motor?

What I'm thinking about with the flywheel is that all 250s had a two piece rear main seal, which is the larger bolt circle. The 305 could probably be either, depending on year. After 87 (from memory) the bolt circle is smaller and the 250 flywheel won't fit.

I wouldn't chuck the 305 because of the clutch boss, but it's something to check for.

You can swap from an integrated head to a non-integrated head. But I understand if that's not your thing. Good luck with the v8 swap.

[Bigstevex4]

Swapping a 350 for my 250 soon as it gets built. the vari jet is a POS no other carb will bolt up made an adapter plate put a 1 barrel on. runs pretty good little under carbed. putting the 305 will cost about half of what it cost to swap heads. on the 250 there scarce as hell in my area

[fred_e81]

Thanks for all of the input! Well, seems like the swap is gonna be a no go. I haven't gotten a reply on the motor.....probably to good to be true. Kind of bummed out my 12 and 6 year old boys as this is a father and sons project. Anyways, I do plan on upgrading in the future if I find one for the right price of course. Good to know the flywheel will work on a 350. Once again thanks for the help guys and my apologies for the late response.

[ultrahd4me]

Fred you can also check around for any boat salvage yards. The Mercruiser 4.1 is a GM 250 inline six. You can find them cheap with good heads, bigger cam, and the hard to find finned valve & side covers. I have found them for $200 complete with a cracked blocks from not being winterized. Good luck.

[Bigstevex4]

Originally Posted by ultrahd4me

Fred you can also check around for any boat salvage yards. The Mercruiser 4.1 is a GM 250 inline six. You can find them cheap with good heads, bigger cam, and the hard to find finned valve & side covers. I have found them for $200 complete with a cracked blocks from not being winterized. Good luck.

Wow that's cool as hell SD few boats but? I saw a adapter plate in an online catalog. for the irrigated head to adapt a 1 barrel. tried calling a couple boat places in Houston seemed a dead end. So made 1.

[fred_e81]

Wow, in a boat salvage yard, that's awesome! I'm going to try and look for one of those in the local classified because out here in southwest Texas their aren't too many lakes at least not here in El Paso.

Bigsteve, do you remember where you found that adapter plate for the integrated head to replace with a 1 barrel?

[fred_e81]

Wow, in a boat salvage yard, that's awesome! I'm going to try and look for one of those in the local classified because out here in southwest Texas their aren't too many lakes at least not here in El Paso.

Bigsteve, do you remember where you found that adapter plate for the integrated head to replace with a 1 barrel?