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I just got a 78 nova as my first car. It has a 250 inline six engine in it and I'm trying to give it some more pep. I wasn't able to sell my parents on a 350 but I convinced them that a 305 would be a decent medium. Aside from getting the engine I was wondering what else I would need to do to the car to do the swap. Stuff like new front shock or be***** up the rear end. Would any of that be necessary? I just need to know what I'm getting myself into.
 

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Honestly I wouldn't bother but if you must you can bolt it right on in without changing much. You have to move the motor mounts (the frame is already drilled for it.) and new exhaust. With a weezy 305 your cooling system will be fine if your radiator is ok now. You won't need to replace the front springs.
 

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If you are stuck on getting a 305, look for a early 90's roller motor. They breath well and love a Performer RPM and 500cfm carb, with headers!

Leave the suspension alone and save for some new rear gears next. (determine what you have first - jack up the rearend, put car in neutral, have a friend help you count rotation of pinion - rotate both rear tires in same direction at same speed, count pinion turns - if it goes around 3.5 times, its' a 3:50 gear, if it goes round just over 4 turns, its most likely 4:11, if it goes round 2.75 times, it's a 2:75 gear) You will love some 3:50 to 3:73 gears for the street. Later you can get an overdrive to help with gas mileage.

The 6 cyl transmission should work, just be easy on it cause you will be pushing more HP, but possibly not more torque - those 6's are torquey motors! If it sat up for a long time, then it may want a rebuild. What kind is it? Auto or standard???? Either way you will need a flywheel.

For this change you will need to bend the fuel line to mate with the carb - use short sections of rubber fuel line if needed to make the connections. Make sure you put in a new filter.

Mark you wires before you remove the engine so you know where they will go on the new engine (alternator, a/c, distributor, water temp, oil temp (maybe), carb choke)

Most of all, post lots of pics of your progress so everyone can help! HAVE FUN!!!
 

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Thanks for the info! The cars an automatic and the engine is a new crate engine a local shop is selling, so there isnt a donor vehicle, if that makes a difference.
 

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Is it a long block (with heads) or short block (without heads)?
Does it include the intake manifold?

You will need to purchase some exhaust manifolds, might as well get headers! Use copper gaskets or the dead soft aluminum ones...they won't leak.
You will likely need a water pump, pulleys, alternator brackets, power steering pump brackets, belts, hoses, plugs and wires, distributor, cap and rotor, and an intake and carburetor along wtih an air cleaner. You may be able to use your carbs throttle cable/rod setup but it may need a new bracket to mount to the intake. Also need a fan to bolt to the water pump. Don't forget a starter.

You can find most of this stuff at a wrecking yard, except for headers, intake, carb. Then take it to an exhaust shop to weld in new exhaust pipes and mufflers.
 

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The engine is mostly complete minus water pump and carb. It has an intake, distributor and headers.
 

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The 305 isn't a bad engine. Seems a lot of people think it is though. "Weezy"? Don't let em discourage you. I have a new 305 in my 84 c10 truck and it has plenty of power. I've got a later 1 piece rear main 305 roller block on my engine stand right now that I am planning to build and put in my 64. Not everyone can have a 350.
Probably the only thing I can think of that you will definately have to get right would be the engine mounts. If I remeber right there are two different engine brackets that bolt to the block sides that attach to the mounts on the frame. The V8 frame mounts, GM part number 459021, are universal through all the chevrolet car lines ( B,A,G,F and X). Your frame already has the V8 location holes drilled to bolt these on. The steel V8 engine brackets from 73-88 differ in length. There is a longer bracket ( number 334601) used on B body cars and all other 73 and later GM cars use the shorter bracket ( number 334970) which is the one you need.
Also, make sure the headers will fit your vehicle application. There are many differnt types out there. Get the brand and part number off them and check that info on a website or catalog to determine what chassis they are made for. If they are not for your particular car, you may be able to have the shop remove them and come down on the cost of the engine. no sense in paying for somthing you can't use. u should be able to find the other parts like pullies, front engine brackets for power steering, etc at your local salvage yard. Find out more about the engine such as what camshaft it has in it. that basically determines how it is going to run. As far as gears, I would not go beyond 3.36 for an everyday driver. Go to deeper gears and those RPMs will leave the engine screaming on the highway and doesn't help MPGs. If this is your first time doing this and your first car, I'll give you some advice. Do not fall into the trap of thinking bigger or more is better. especially for a street car. You want a dependable driver with reasonable MPGs. Be conservative on your parts selection and you'll never go wrong. If you want a race car, build a 2nd car.
 

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I did an 250 to 305 swap in my 74 Omega years ago, and well ... I would advise you to change the front springs/shocks.

I pulled a 305 out of a 85 Parisienne, and turns out I didn't have to adjust or move the motor mounts. I did use the calm-shell (brackets) from the Parisienne and it turned out my motor sat a little lower then it should of.

Thus, having a soft front suspension ... made for alot of cringing moments when hitting potholes or a bumpy road. Finally got around to changing the springs/shocks about 3 years later.

Just my 2 cents ... Good luck with your wrenching!

If you have a moment, check out this link of my engine swap: http://oldsomega.ca/slomega/2006omegaengineswappics1.html
 

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The torque converter is 250 I-6 specific. It will have a higher stall speed than a V8 converter has (it also is a bolt on to the 305/350 flywheel). This will help with the launch until a different set of gears is in place. My guess on the car is that it will have eith 2.56 or 2.73 gears in an open 7.5. Not exactly the strongest rearend, but was used for years.

Common swap is the 8.5 rear from a Trans Am or Z/28. This should get you at least a 3.42 or 3.73 gear & maybe posi if your lucky. You will also want to look at a set of multileaf rear springs (HD or police units for a 4th gen Nova). Be sure to check out all the bushings for rot (hey, it's an old car).

But seriously, be sure the car stays reliable. Your folks don't want lawn art in front of the house. Also, the more low key it looks, the better they will like the car. Last tip: Soak every bolt with penitrating oil now. Will make life easier when doing the swap.

Jim
 

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The torque converter is 250 I-6 specific. It will have a higher stall speed than a V8 converter has (it also is a bolt on to the 305/350 flywheel). This will help with the launch until a different set of gears is in place.


Jim
I think you might be confusing the TH350 converters with the powerglide converters. The 6 cyl powerglide converters had a higher stall speed than the V8 counterparts. And drag racers back in the day would use the 6 cyl powerglide converters as you describe. However, I believe the stock TH350 converters were all the same between the 6 cyls and V8s during the 70's. To check this, go to an auto parts store website and cross check part numbers and applications. I went to O'reilly's web site and checked on stock replacement torque converters for a 78 Nova with a 305 V8 with TH350 auto and a seperate check on a 78 Nova with a 250 6cy with TH350 auto. The converter part numbers for both applications were the same.
 

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Discussion Starter #11
Thanks for all the information everyone! I got all the info I need. All I gotta do now is get the parts and put them all together.
 
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