Affordable engine replacement?

[rich weyand]

I'd go with the 3.42 ratio. The 3.78, even with my 31" tires, is pretty high in revs at 80. With 29" tires, a 3.42 would work great.

G80 posi in the rear while you're at it.

The stock 350 is a good engine, and there are advantages to starting with everything all new. Put a cam in when the warranty is expired.

 

[DarthKnight84]

Good lord this is a lot of information to take in! Thank you gents!


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[MikeB]

I thought I had the stock 305 in my 83 c10, turns out I have a 1969 307 backed by a 700r4 and I assume the stock 3.08 gears. I'm not looking for a race engine, but I want something that gets up and goes when I want it to. It's my daily driver and will be for the foreseeable future. Right now everything runs and drives fine, but I'd like to start to upgrade it. Do I start with my engine and work back or start with gears and work forward?

If the engine runs fine, but you want more performance, here's what I suggest:

If you don't have dual exhaust with performance mufflers, start there. 2.5" pipes would be great, but 2.25" are fine for a 307.

Check your ignition timing to make sure you have at least 10-12 degrees advance at idle (with vacuum advance plugged). And then make sure advance increases with RPMs. If advance is 10 degrees or less at idle, feel free to rotate the distributor CCW to get 12-14 degrees. Then reconnect the vacuum advance and go drive it, and listen for pinging under full throttle and light acceleration. If you hear anything, then back off the advance a little. Also verify that vacuum advance is working. Advance should jump 10 or more degrees when you reconnect the carb manifold vacuum port to the distributor. There are better ways to do this, but the above will serve as a basic starting point.

Also a 307 will really like 3.73 gears, and will be happy on the highway with the OD trans and lockup converter, unless the truck has very tall or very short tires. Are you sure the truck has 3.08 gears? My 82 C10 came with the default 2.73 gears behind a 250 six, and I think 2.56 was standard for the 305. Talk about lack of acceleration!

Finally, you should consider headers if your engine currently has cast iron log-type manifolds.

If you still want more power, well, inches are everything!

 

[DarthKnight84]

If the engine runs fine, but you want more performance, here's what I suggest:

If you don't have dual exhaust with performance mufflers, start there. 2.5" pipes would be great, but 2.25" are fine for a 307.

Check your ignition timing to make sure you have at least 10-12 degrees advance at idle (with vacuum advance plugged). And then make sure advance increases with RPMs. If advance is 10 degrees or less at idle, feel free to rotate the distributor CCW to get 12-14 degrees. Then reconnect the vacuum advance and go drive it, and listen for pinging under full throttle and light acceleration. If you hear anything, then back off the advance a little. Also verify that vacuum advance is working. Advance should jump 10 or more degrees when you reconnect the carb manifold vacuum port to the distributor. There are better ways to do this, but the above will serve as a basic starting point.

Also a 307 will really like 3.73 gears, and will be happy on the highway with the OD trans and lockup converter, unless the truck has very tall or very short tires. Are you sure the truck has 3.08 gears? My 82 C10 came with the default 2.73 gears behind a 250 six, and I think 2.56 was standard for the 305. Talk about lack of acceleration!

Finally, you should consider headers if your engine currently has cast iron log-type manifolds.

If you still want more power, well, inches are everything!

Thanks man. I don't have dual exhaust or headers right now.

I'll have to look at the ignition timing. Right now it has the old style distributor.

It currently has stock rims and tires. If I change the rim size (eventually I will) I plan to keep the overall size of rim and tire combo the same. So bigger rims and smaller tires than what I have now.

This seems to be the best budget performance idea so far. I really appreciate you all taking the time to help out a newbie.



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[Georgeb]

I ran a 307 as a temporary engine for a bit in a 71 C10. I was running duel exhaust, a stock HEI and the stock 2bbl carb. 3.73 gears an 28" tires backed by a saginaw 4 speed with a floor shifter. I think I was around 12 deg initial advance. That was a spunky lil motor and I was very impressed with how it performed.

 

[DarthKnight84]

I ran a 307 as a temporary engine for a bit in a 71 C10. I was running duel exhaust, a stock HEI and the stock 2bbl carb. 3.73 gears an 28" tires backed by a saginaw 4 speed with a floor shifter. I think I was around 12 deg initial advance. That was a spunky lil motor and I was very impressed with how it performed.

Well now that's two votes for keeping my 307 for now. I guess that's what I'm doing until I can save up for something really nice! Thanks fellas!


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[Green79Scottsdale]

The stock 350 is a good engine, and there are advantages to starting with everything all new. Put a cam in when the warranty is expired.

While a cam is going in, replace the head gaskets with some .015 thick ones. Every bit of compression helps at that level!

 

[Pender1]

Wow, this thread has really taken off since I left.

To update my situation, insurance is totaling my truck out. I paid $1K for it and put about $2500 into it. They are going to give me $4K after my deductible and salvage fee, so I suddenly have enough money to buy an engine and a few other things I've been wanting to do after I get it back on the road.

I'm leaning towards the $1500 long block and Comp cams cam from the git go. The dream is to slap a set of 1 tons under it in the distant future, but there is much to do before then.

If budget isn't a constraint, is there a better cam than the 12-235-2 if the goal is torque while still being drivable?

 

[rich weyand]

If budget isn't a constraint, is there a better cam than the 12-235-2 if the goal is torque while still being drivable?

Nope. Seam Murphy at Sean Murphy Induction (SMI) turned me on to that cam. He had it written down as the cam to go to in that engine for a truck. And he would know. He said it's the closest you can get to a ZZ4 without doing a ZZ4.

 

[Pender1]

Nope. Seam Murphy at Sean Murphy Induction (SMI) turned me on to that cam. He had it written down as the cam to go to in that engine for a truck. And he would know. He said it's the closest you can get to a ZZ4 without doing a ZZ4.

What's a ZZ4?

 

[74 Shortbed]

What's a ZZ4?

Here ya go..

http://www.gmhorsepower.com/350-ZZ4-Turn-Key.php

 

[rich weyand]

What's a ZZ4?

Google is your friend:
https://www.google.com/#q=zz4

 

[DarthKnight84]

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I have this sitting on the shelf and my wife just gave me the go ahead for $200-$300 budget. What should I get first? I was informed this might be a little too much of an intake for what I'm trying to accomplish. What one should I get and what should I pair it with to stay on budget? Should I start with new hei first?


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[1987 GMC Jimmy]

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I have this sitting on the shelf and my wife just gave me the go ahead for $200-$300 budget. What should I get first? I was informed this might be a little too much of an intake for what I'm trying to accomplish. What one should I get and what should I pair it with to stay on budget? Should I start with new hei first?


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From what I understand, that's a "racing intake." Also, the manufacturer recommends not using them on trucks or vans. Also x 2, they recommend a 600-800 CFM carburetor, which is too much for that 307. I would ask $180 for it and try to get as much as you can. I think the Edelbrock intakes are the most popular, and I would get an Edelbrock 2101 intake and match a Quadrajet to it. It's a damn shame you missed the one on here because that was a good deal. It'd be the easiest to get either a divorce choke or an electric choke one so it's automatic. If you're turned off by the Quadrajet, just get an intake that corresponds to the carb you have now. If it's an Edelbrock, it'd be a 2701. If it's a Holley, the latter may work. I'm not sure if you'll need an adapter for the 2701, but I know it'll work on the 2101 with an adapter. With the money you potentially make off that intake, you can get your preferred intake. And then you still have your budget. I would probably use it to do your HEI and your camshaft. If you do it cheaply, you can probably get these for $180 - $200. You'll still have a hundred. I'm really hoping you'll say it's a Quadrajet, and you want to keep it because I think there's a lot more thought in the design than its aftermarket contemporaries, and I feel like there's a lot of performance to be generated from stock. Anyways, I would use the leftover to venture into your carburetor plans unless there's a shiny, functional carb already there.

 

[DarthKnight84]

From what I understand, that's a "racing intake." Also, the manufacturer recommends not using them on trucks or vans. Also x 2, they recommend a 600-800 CFM carburetor, which is too much for that 307. I would ask $180 for it and try to get as much as you can. I think the Edelbrock intakes are the most popular, and I would get an Edelbrock 2101 intake and match a Quadrajet to it. It's a damn shame you missed the one on here because that was a good deal. It'd be the easiest to get either a divorce choke or an electric choke one so it's automatic. If you're turned off by the Quadrajet, just get an intake that corresponds to the carb you have now. If it's an Edelbrock, it'd be a 2701. If it's a Holley, the latter may work. I'm not sure if you'll need an adapter for the 2701, but I know it'll work on the 2101 with an adapter. With the money you potentially make off that intake, you can get your preferred intake. And then you still have your budget. I would probably use it to do your HEI and your camshaft. If you do it cheaply, you can probably get these for $180 - $200. You'll still have a hundred. I'm really hoping you'll say it's a Quadrajet, and you want to keep it because I think there's a lot more thought in the design than its aftermarket contemporaries, and I feel like there's a lot of performance to be generated from stock. Anyways, I would use the leftover to venture into your carburetor plans unless there's a shiny, functional carb already there.

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Found this



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