Is a 72 307 in a 79 C20 an easy swap?

[lap15]

First off, I am not an internal engine person and have never swapped a motor before, but I want to attempt it.
My 79 C20 has a bad 350 4BBL V8 with a newly rebuilt TH400. Someone is giving me a decent running 72 307 2BBL for free that's attached to a SM456. Can I use the 4BBL w-intake, PS, alt, and HEI from the 350 directly on the 307? Also can I just swap the flywheel for the flex plate since I'm keeping the TH400? What else am I going to need to do the swap besides engine hoist and stand?
Some other questions I have are: Will the HEI just slip into the 307 block and what about the wiring? What about motor mounts, do I use the ones from the 79 or from the 72? What about the pulley for the PS pump and alt, will they fit the 307? Finally, will the 79 exhaust manifolds work on the 72, because the driver side ram horn has a crack in it and can't be used in the swap. I am obviously doing this on the cheap and plan on using the 307 until it dies and hopefully by then I can rebuild the original 350 and install it again- so, I do not want to have to do any modifications. Thanks!

[i8tokyo]

This is an easy, straight forward swap. All your accessories should bolt on with no issues. You will need to reuse your exhaust manifolds so that's not an issue either. So far as what you'll need besides a hoist and stand, common hand tools, torque wrench and a friend to help go a long way. Good luck.

[mopar346]

Straight forward as started, but I wouldn't bother the 307 is a gutless wonder and you will be very disappointed. The 465 is a very popular tranny especially with the CJ crowd, I would try to trade it for a decent running 350, they are fairly common.

[WarBeard]

307 manifolds will bolt right onto a 350 with no problems?

[i8tokyo]

Originally Posted by motomech

307 manifolds will bolt right onto a 350 with no problems?

They'll bolt right on without an issue. The pre-1986 small blocks 262-400, all have the same bolt patterns. The 1987-95 have the bolt angles changed a little but can be modified to work. (Not my first choice but doable.)

[i8tokyo]

Originally Posted by i8tokyo

They'll bolt right on without an issue. The pre-1986 small blocks 262-400, all have the same bolt patterns. The 1987-95 have the bolt angles changed a little but can be modified to work. (Not my first choice but doable.)

What I should have said is the 1955-1986 small blocks are the same. The 1987-1995 are slightly different but can be modified.

[lap15]

What about the HEI? The 307 still has the points/coil ignition- I'm confused about swapping distributors. Also, will the 307's starter work on the 350's flex plate?

[i8tokyo]

Originally Posted by lap15

What about the HEI? The 307 still has the points/coil ignition- I'm confused about swapping distributors. Also, will the 307's starter work on the 350's flex plate?

The HEI distributor will slide right in. Just make sure you mark the position of the rotor when you pull the dist. out of the 307 and get the HEI's rotor in the same position when you install it. The starter should work as well, just compare the two as you swap your parts around.

[manimal]

The only differences between the 350 and the 307 is the bore and stroke. Everything else will interchange.....OH and the 307 can be made to run really good for cheap,and they are reliable. Just remember you have a truck,not a race car.

[mopar346]

maybe

[manimal]

not getting into that discussion. A 307 will run great with the same bolt ons that a 350 will.

[smashingchuck]

keep looking man. that 307 and 465 is going to be nothing but disapointing.

[mopar346]

Cubes rule, bore is too small to make any decent power, the factory heads are junk and I believe the cam is almost flat (kinding but small for sure). If memory serves the stroke is the same as a 350, boring would help some but I think the walls are too thin to do too much with them. It is also a 72 the first and worst of the low compression smog motors, although 307 may have always been that way.

But on topic he was talking about dropping it in on the cheap, not tricking it out. Although the intake off of his 350 will bolt right up but I think you end up with a bigger intake runner than the port in the head, not a good scenario. BUT I'm a Mopar guy so I could be wrong.

[manimal]

Originally Posted by mopar346

BUT I'm a Mopar guy so I could be wrong.

Now I understand!lol
Anyhow the 307 is a bore of 3.875 and a stroke of 3.25 and 350 heads w/1.94 intake valves will bolt on(I've done it),BUT you will lose power. If you are wnating any type of power from a 307,a small cam(.450/.460 lift) and 305 heads will really wake up the "lazy" 307.

[mopar346]

I don't disagree that you can make more out of a 307 than it's stock form but back to my original statement why bother. The OP is looking to make a straight stock swap and my best advice is don't cause he will be disappoointed. Yes, every small block head will bolt on any other, only the 400 will have heatign issues (something to do with steam holes not 100% sure). I am surprised a set of 305 heads would be an improvement unless maybe it was the early tune port injection head, I'm not familiar with them. Not doubting you just surprised.

OK, back to his question, yes it will fit without issue and can be done in a week end. I would still look to find a running 350 out of the bone yard or local, avoid the TBI engines cause there heads have very restrictive port design from what I understand. The vortecs are also very good although I think the intake and exhaust are different. I used a 93 4 bolt main roller block when I built my son's engine, if you can score one it will provide you with an excellent foundation for a future build. I still say if you are getting the 465 for free you can off it for a few hundred to help fund the replacement engine.

[manimal]

You're right, the 307 is not a 350 by any means. If the OP is expecting the power level of a 350 from a 307, then YES he will be disappointed. If he is just looking to get his rig back on the road, then the 307 is a great way to do it...especially for the cost.
The ONLY thing about 305 heads that help the 307 is it keeps the compression up a bit.

[lap15]

Thanks for all the feedback guys...but I really just need advise on replacing a motor.
I am pretty mechanically inclined, but have never done an engine swap before and want to take this opportunity to learn how to do it. I just want to be able to drive the truck while fixing it up and occasionally use it for hauling materials, hay and firewood. The truck is a '79 Scottsdale C20. I got it from an elderly farmer friend who bought it new. I paid $250 for it and it has 105,000 mi. The PO never used it hard, but didn't take care of it either- being the type of person who believed if it started and ran, then it didn't need anything. In the spring of 2008 he lost all forward speeds and had the TH400 rebuilt for $700. He put about another 900 miles on it when the engine failed (developed a knock in the lower end and totally lost oil pressure). He then parked it and bought a beater truck to use because he did not want to spend any more money on it. I came along in the fall and bought it as a parts truck, but after getting it home I noticed it was in great shape for the year and was 100% original because the PO did nothing to it. I stored it inside since then and am now itching to get it running again~but, funds are very limited, hence the super duper el-cheapo engine swap. Ultimately, I want to pull the 350, take it apart, find out what failed and attempt to rebuild it myself because I want to learn how to do all this stuff myself. The 307 is just a temporary fix to make the truck usable again until I can restore it the right way. Hope this clarifies things, keep the feedback coming!

[manimal]

Take the 350 out,and put the 307 in. Make sure the 307 has a LONG water pump(same as your 350)and all your brackets/pulleys and accessories will bolt right on. The flexplate is the same for the 307 to 350(both are internally balanced) You ca drop in your HEI distributor,set the timing and be on your way within a weekends time.

[tater502]

My 72 chevelle had a 307 and Im putting a 350 in it, from what Ive read I need to change out my frame mounts. Might want to measure just in case.

[lap15]

Yeah, I think the 307's motor mounts are different than the 350. That's why I wasn't sure if I had to use the ones on the 307 in the '79 truck.

[tater502]

Just did a little research. I have to bolt the 307 motor mounts to my 350, so you would use the 350 motor mounts for the 307.

[lap15]

Perfect! That was one of my major questions....thanks very much. Great help!

[manimal]

Use the mounts "for" the VEHICLE.

[lap15]

Makes sense...thanks!