1968 C25 307 to 350 Swap Advice
 

Hi guys,

Well, it happened. I was driving home from the lumber yard a couple of weeks ago and I blew the rear main seal. My original 307 seized up about a half mile from home. I got it towed home and it sat in the driveway for a couple of weeks, but now that I've gotten it into the garage I'd like to get it up and running again.

So I'm looking for some advice. I've never done an engine swap on one of these trucks, but I need to decide if I'm going to get my 307 rebuilt (and most likely machined to be a 350) or if I should just drive to Reno to get a new 350 from summit racing. I called my local machine shops and they're all going to be the same price. It will end up being ~$2,000 for a rebuilt 307 done by a machine shop, ~$2,000 if I do it myself (except for the machining), or ~$2,000 if I go buy a brand new 350 at summit racing in Reno. It's roughly a 2 hour drive for me to go pick it up, so it's not too far out of the way and I could go get it and have it home in the same day. I'll list my questions below.

https://www.summitracing.com/nv/part...aillocation=nv

1. Has anyone used the summit base model 350 crate engine they sell and was it easy to install? Was there anything you needed to do before dropping the engine in and running it? I know I'd have to add oil, the intake manifold, the alternator and water pump, and the carburetor and anything else I disconnect to remove the old engine.

2. Is there any reason I shouldn't just go and get the summit racing 350 crate engine?

3. When reinstalling the engine, is there anything else I should replace while I've got it out? I'm trying to do this on a budget, but as we all know it's a lot easier to do certain things when you've got the engine compartment wide open. I'm planning on doing a new alternator, water pump, and thermostat as of right now.

4. I called a local junk yard and he's got a '77 2 ton with a 350 in it that allegedly has 53k miles on it and I could have it for $500. I'm going to check it out on Monday. He said he drove it in there a few weeks back, so I'll ask to drive it and run a compression test. Anything else I should look at on the engine?

I'm just looking for advice and tips that anyone who has done this before might offer to a green owner of one of these trucks.

Thank you in advance!

Re: 1968 C25 307 to 350 Swap Advice
 

There is no way in :devil: I would rebuild a 307 over buying a GM crate 350! I have not personally used one of those engines a vehicle of my own, but I helped my dad install two of them in two different vehicles and they both are still going strong (20 years later!) and were easy to swap. Decent power and reliable. You're basically just doing a remove & replace, everything should bolt right back up. Good call on the water pump & thermostat. New spark plugs, distributor cap, rotor and maybe plug wires if they are questionable.

Not so sure I'd replace the alternator unless you were having issues with it before. They are easy to get to with the engine in place if you need to replace it down the road.

You should look at getting an oil priming tool to pump oil through the engine before starting it up and follow proper break in procedures since that engine uses a flat tappet cam.

Re: 1968 C25 307 to 350 Swap Advice
 

I would not build the 307. It will cost same or more than a 350 with no benefit. It is hard to beat a crate 350 for price. Nothing wrong with a used one for the right price, but I would want to get a 1-pc seal one ('87 up). They don't leak like the 2-piece ones do. With that you would need another intake as the heads for these have the 2 center bolts at a different angle. While it is out I would put a front seal in an automatic trans or a clutch in a manual unless they are very recent. So to me the crate 350 is the way to go. Do be sure you look at the pilot bushing in the back of the crank and take it out if you have an automatic.

Re: 1968 C25 307 to 350 Swap Advice
 

My crate 383 was oiled and cam worn , and dyno'd before it was sent to me

Re: 1968 C25 307 to 350 Swap Advice
 

Can you go into more detail about this? I read a little about this, but I wasn't sure I understood it. Is this basically just pumping oil through the engine and getting it into all the little nooks and crannies?

Do you have any advice on where I could read about "proper break in procedures?" I definitely don't want to screw this engine, especially if we go the crate engine route.

Thank you!

Re: 1968 C25 307 to 350 Swap Advice
 

Here's the procedures plus a lot of other info for crate engine installs....

-
I don’t know about anyone else but the engine I ordered from Jegs did not include break in instructions. I saved the instructions from my last 350ci 260hp crate engine so I thought I would post them in this thread. The normal disclaimers apply to this document such as no guarantee of accuracy, correctness, or omissions, and you use it at your own risk… All I can tell you is that I used these instructions for the crate engine I installed in my ’69 Suburban last summer and it worked great…. It also includes a lot of other useful info. Just print it out and hang it on the wall.

If anyone finds any errors please let me know and I will check them out.

Thanks,
LockDoc


------------------------------------------------
Initial Crate Engine Break In Procedure

The following form is the GM recommended crate engine start-up procedure with some minor changes made to it by Sallee Chevrolet. You can use this form for keeping track of your engine's break-in.

GM'S RECOMMENDED CRATE ENGINE START-UP PROCEDURE

Print this document out and check off numbers below when each step is completed.

1) Safety first! If the car is on the ground, be sure the emergency brake is set, the wheels are chocked, and the transmission cannot fall into gear. Next verify that all hoses are tight and that both the radiator and radiator over flow jar/tank are full and have been filled with the proper anti-freeze and water mix.
2) Before starting your engine for the first time, add one pint of engine oil supplement ( EOS¹) to the crankcase oil and then check the oil level. Once this has been done, prime the oil system with an oil pump primer tool. Make sure number 1 cylinder is on TDC compression stroke, and install the distributor.
3) Adjust the distributor timing roughly by hand for a quick start up and smoothest idle possible.
4) When the engine first starts, verify that the engine rpm is at a safe level and that the timing is set near or at 30° before top dead center (BTDC). Run the engine speed between 1,500 and 2,500 RPM's, varying the engine speed up and down with-in this range, to prevent overheating of the exhaust valves and the exhaust system. This should be done with no-load on the engine and for the first 30 minutes of operation.
5) After the first 30 minutes of the engine running, set the ignition timing according to the timing specifications. Now would be a good time to check thoroughly for leaks.
6) Adjust the carburetor settings, if necessary.
7) Drive the vehicle with varying speeds and loads on the engine for the first 30 miles. Be sure not to use a lot of throttle or high RPM.
8) Run five or six medium-throttle accelerations to about 3,800 RPM (55 to 60 MPH), then letting off in gear and coasting back down to 20 MPH.
9) Run a couple hard-throttle accelerations up to about 3,800 RPM (55 to 60 MPH), then letting off in gear and coasting back down to 20 MPH.
10) Change the oil and filter with recommended oil (10w30SG in most cases) and filter.
11) Drive the next 500 miles normally, without high RPM's (below 3,800 RPM), hard use, or extended periods of high loading.
12) Change oil and filter again.
13) Your engine is now ready for many happy cruising miles!

Note¹: EOS P/N 1052367 can be used any time during the life of the engine.
Technical Note: This procedure has been corrected and improved from the original GMPP procedure by Sallee Chevrolet.

Warning: Your engine will not be fully broke in until after at least 2,000 miles of driving have been put on it with normal organic oil.

Installation Parts You May Need
10147994 - Intake Gasket
12346192 - Silicon Sealant for Intake Gasket

Both of the following gaskets are needed for the fuel pump mounting plate:
10114141 - Fuel Pump Gasket
12560223 - Fuel Pump Mounting Plate Gasket

This would also be a good time to go to a chromed fuel pump block off plate or mounting plate if you are planning on adding chrome to your engine or you can just reuse your existing mounting or block off plate. Sallee Chevrolet can supply you with a chromed block off plate that has the Chevy Bow Tie on it as well as a chromed mechanical fuel pump and chromed fuel pump mounting plate if you plan on running a mechanical fuel pump.

You can use either a 1 quart or 3/4 quart oil filter with this engine.
25160561 - 1 Quart Oil Filter (ACDelco PF1218)
25324052 - 3/4 Quart Oil Filter (ACDelco PF454)

05613957 - Spark Plug (ACDelco R45TS) [Gap @ .035 for points distributor, .045 for HEI distributor]

Flexplates and Flywheels that can be used depending on your application:
00471598 - 14 inch diameter flexplate (automatic transmissions)
00471529 - 12.75 inch diameter flexplate (automatic transmissions)
03991469 - 14 inch diameter flywheel (manual transmissions)

Harmonic dampers that can be used:
06272221 - 6.75 inch harmonic damper
06272222 - 8 inch harmonic damper

Thermostats that can be used:
10207381 - 180°F Thermostat
12514334 - 195°F Thermostat
10105135 - Thermostat Gasket

Water pumps that can be used:
12522016 - Cast iron, long-leg style, water pump for 1969 through 1976 applications.
88894341 - Cast iron, Long-leg style, water pump for 1977 through 1987 applications.
12458926 - Cast iron, short-leg style, water pump for 1967 through 1972 pickups and cars up to 1968.
12458924 - Cast iron, short-leg style, water pump for 1971 through 1981 Corvettes.

--------------------------------------------------------------------------------

What to do after installation and initial break-in is completed.

1) Check oil level.
2) Check engine coolant for level and proper temperature protection for your location. Also check that the coolant is cycling properly and that the thermostat is opening when the engine warms up.
3) Check for leaks and retighten fan belts.
4) If you have installed an aluminum intake manifold, you must re-torque the intake bolts. Torque to 35 ft.-lbs. or tighten snuggly with a wrench, if no torque wrench is available or practical for your application.
5) If your engine has tubular exhaust headers, retighten the header bolts after the initial engine break-in to prevent leaks.

--------------------------------------------------------------------------------

Periodic Maintenance

1) Change engine oil and oil filter every 3,000 miles or every 3 months whichever comes first. At the time you are changing the oil, you should also inspect the air filter and the PCV filter. Replace these if dirty.
2) Do a monthly check of fluid levels and check for fluid leaks.
3) Do a monthly check of fan belt tension and condition.

--------------------------------------------------------------------------------

350ci/5.7L Engine Torque Specifications

Camshaft Sprocket Bolt/Screw - 18 ft.-lbs.
Connecting Rod Nut - .006 bolt stretch preferred 20 ft.-lbs + additional 55° (45 ft.-lbs. if no angle gauge available)
Crankshaft Balancer Bolt/Screw - 63 ft.-lbs.
Crankshaft Balancer Pulley - 35 ft.-lbs.
Crankshaft Bearing Cap Bolt/Screw and Stud - Inner: 70 ft.-lbs, Outer: 65 ft.-lbs.
Cylinder Head Bolt/Screw - 65 ft.-lbs.
Distributor Bolt/Screw - 25 ft.-lbs.
Drain Plug - 15 in.-lbs.
Engine Oil Gallery Plug - 15 ft.-lbs.
Engine front Cover Bolt/Screw - 75 in.-lbs.
Exhaust Manifold Stud and Bolt/Screw - 26 ft.-lbs.
Flywheel Bolt/Screw - 65-70 ft.-lbs.
Intake Manifold Bolt/Screw:
First Pass - 15 ft.-lbs.
Final Pass - 35 ft.-lbs.
Oil Filter Adapter Bolt/Screw - 17 ft.-lbs.
Oil Level Indicator Tube Bolt/Screw - 106 in.-lbs.
Oil Pan Assembly:
Corner Nut/Bolt/Screw - 15 ft.-lbs.
Side Rail Bolt/Screw - 165 in.-lbs.
Oil Pan Drain Plug - 15 ft.-lbs.
Oil Pump Bolt/Screw To Rear Crankshaft Bearing Cap - 66 ft.-lbs.
Oil Pump Cover Bolt/Screw - 80 in.-lbs.
Spark Plug (Tapered Seat) - 15 ft.-lbs.
Starter Motor Bolt/Screw - 35 ft.-lbs.
Valve Rocker Arm Cover Bolt/Screw - 25 in.-lbs.
Water Pump Bolt/Screw and Stud - 30 ft.-lbs.

LockDoc

Re: 1968 C25 307 to 350 Swap Advice
 

Summit sells an oil pump priming tool - it goes into the distributor hole, engages the oil pump shaft and you spin it with a handheld drill to pump oil through the engine's oil system before starting the engine for the first time. Just pick one up when you get the engine. There are many people who have successfully started engines without doing this, but the priming tool is cheap and it's just extra insurance.
http://www.summitracing.com/int/part...1010/overview/


I would thoroughly read all the paperwork that comes with the engine, especially in regard to installation specs & procedure and how it impacts warranty coverage so that IF something does go wrong, you may have recourse in the matter.

Looks like LockDoc has you covered!

Re: 1968 C25 307 to 350 Swap Advice
 

Best priming tool is a cut off old distributer,will get oil to the top end, where a regular priming tool will not,go for the summit 350, 307s are boat anchor,also while engine is out pull the torque converter out and replace front seal in trans, sure as sh$t the thing will leak after,lol.

Re: 1968 C25 307 to 350 Swap Advice
 

Wow, that's exactly what I was hoping for. Thank you for sharing that, LockDoc!

BossHogg69, that's really helpful. I can definitely handle the $20 cost if it adds a little extra assurance that it'll be well lubed before I start it up. Thanks again!

Re: 1968 C25 307 to 350 Swap Advice
 

I think the base 350, left completely stock, with a ~600CFM 4-barrel (or a Quadrajet set up right) will run so much better than the 307 you'll be surprised. I don't think it's possible to make a 350 out of a 307 unless you achieved some funky stroker combo. For the same cost the crate 350 is a no-brainer.

Re: 1968 C25 307 to 350 Swap Advice
 

So it looks like I'm going to go with the summit crate engine. I'll also buy the oil pump primer as BossHogg69 suggested. I've been having issues with my alternator, so I'll replace that (the previous owner bought the regulated model, but didn't install the regulator on it. It also wasn't connected to the battery when I bought the truck....) I'll also replace the water pump and thermostat. All plugs, plug wires, and hoses, as well as the distributor cap and rotor will be replaced.

Someone mentioned replacing the front transmission seal as well. Is that pretty easy to do when you've got the engine out? I'm all for replacing seals and gaskets when I'm right there, especially if it prolongs the time before I have to pull something big to fix a leak.

Is there anything else anybody would suggest that I do while I'm in there? I'm still fairly new to this world, so I just don't want to have a long list of "shoulda done thats..."

Re: 1968 C25 307 to 350 Swap Advice
 

Do you have a torque wrench, timing light, vacuum gauge, a bunch of tools and big house fan?
And you’ll need some break in oil. It has required zzdp in it.
And an engine hoist.
And a non drinking helper. No beer until it’s done and on the road.
Good luck!

Re: 1968 C25 307 to 350 Swap Advice
 

I'd get the crate motor --

I have an odd affinity for the 307 too --- its a nice engine for its intended purpose, but not worth throwing a lot of money at ----

Plus the bore size is not conducive to taking out to 4" (size needed for a 350, ) - and the stroke is too short.

People have told me they have successfully taken the bore to 4" though and it resulted in a large journal 327, which some think is kind of cool

Re: 1968 C25 307 to 350 Swap Advice
 

Jegs has a 350 on sale for $1799 with free shipping.

http://www.jegs.com/p/Chevrolet-Perf...67244/10002/-1

Re: 1968 C25 307 to 350 Swap Advice
 

Good call on the summit crate engine. And as for the swap it’s about as easy as it gets. By the time you do a few of them you’ll be able to swap engines so fast the old engine will still be warm on the ground and the new one will be running

Re: 1968 C25 307 to 350 Swap Advice
 

Chevy Orange engine paint if You don't like the black...Maybe detail the engine bay...Engine mounts!?

Re: 1968 C25 307 to 350 Swap Advice
 

I've got everything except for the break in oil. Do I need to put in 5 quarts of break in oil? Would you go the additive route or just get the pre-mixed stuff?

:bann: I just might have to order that today...

Re: 1968 C25 307 to 350 Swap Advice
 

I’d use the premix.
You know it’ll be good.

Also plan on heater hoses, vacuum hoses, rad hoses.

Do you have an automatic or standard tranny?

Re: 1968 C25 307 to 350 Swap Advice
 

I've got a standard 4-speed tranny. Gotta love that granny gear!

Re: 1968 C25 307 to 350 Swap Advice
 

Whichever motor you get, check the pilot bearing.
Here’s a better motor if you’re interested. You’ll need a different flywheel and possibly need an electric fuel pump to make it work.
This one has better compression, better heads, better cam, better rear main seal etc.
And a roller cam so no worries about cam break in.
https://www.summitracing.com/int/par...0283/overview/

Re: 1968 C25 307 to 350 Swap Advice
 

That's a 3/4 , 1 ton motor truck engine w/no fuelpump hole

Re: 1968 C25 307 to 350 Swap Advice
 

It is, isn’t it.
But there’s no stopping you or me using it. It’s got good parts. Especially the 4 bolt main. They do sell a 2 bolt main engine also if you want
Sure there’s a couple changes you might need, but overall a better deal than the other crate with 8.5 compression, no heads, flat tapper cam etc.
He likely will need to surface his flywheel so buying a new one won’t add much.
And depending on carb he might need a regulator so the electric pump isn’t much more.
It really boils down to want you need. I’d buy the roller block and have no worries if it was my first motor swap.
Too many pluses in the roller motor to not consider it.

Re: 1968 C25 307 to 350 Swap Advice
 

One more thing that I always do with those base crate 350's: Replace the cheap valve cover gaskets and oil pan gaskets with FEL-PRO perma-dry gaskets (blue rubber), as well as the rear main seal with a FEL-PRO and install it correctly, or they will start leaking within weeks. Gen.I 350's have a bad rep about leaking rear mains (rightfully so) but FEL-PRO took care of that with their perma-dry gaskets , in my opinion. I have installed several over the last few years in different engines and they are still bone dry. I know it's a little more work, but worth it, imo. The people here on the board can help you with how to install it the right way and it's pretty straight forward with the engine on the stand.

Re: 1968 C25 307 to 350 Swap Advice
 

I agree, I'm a big fan of that engine, especially the heads and roller cam. But it wouldn't be a straight forward swap.

Re: 1968 C25 307 to 350 Swap Advice
 

:agree: