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Old 03-20-2017, 06:55 AM
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Junkyard 305 Chevy rebuild

Hello, I built a 383 chevy last year to replace the original junkyard 305 that came with the car. However, have another car I'd like to put the 305 in since I have it laying around.

It's an electronic carbed engine but I will run a regular carburetor once it goes in the other car. I have a few questions however.

1. The cam was worn out so I'd like some advice on what cam to choose? Can I use some stock 350 cam I have? Budget is to be kept very small.
(I have a new set of pistons that will never get used, new bearings and gaskets though)

2. Could I gain some more "performance" out of the 305 heads by doing a bit of porting and polishing? I ported the stock heads for my 383 with positive results but not sure how much material there is in the runners on these heads? I have lots of time and will not change these heads.

3. How much reliable (as in at least 5000 miles without grenading) horsepower can a stock 305 bottom end take if one were to slap a turbo on it?
Just wondering...I read about "the grenade" at the turboforums but those kinds of numbers are a bit out of my comfort zone.

Thanks

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Old 03-20-2017, 07:45 AM
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Thanks for answering, yeah I know the heads are basically useless but I have them and so therefore they are free. Valves and seats looked ok so will not spend any money on them. I am not really that interested in driving cars compared to working on them...
I'd rather spend 30 hours porting a set of useless free heads than spend a couple of hundred on another set of old used heads and just slapping them on gaining 25hp compared to some ported stock ones.

Will have to think about the turbo and see if I could find a decent carburetor to modify for blow-through. Just a bit of boost to reach 300-350hp for the fun of building it.

Quote:
Originally Posted by hcompton View Post
The 305 can be built but for me i would not waste my time.

The heads can be a big deal. They often have very small valves that restrict flow. Porting will help a lot there is only so much metal that can come out since the valves are not large enough to support much more. Should not be hard to port out.

Here is an article that suggest cam and other parts to make it a better performance motor.

343hp 305


Turbo would not be a bad idea but engines that are choke off from poor flow will get hot ar from the turbo and often dont make a ton of hp with poor flowing heads only so much can be done. Still should put down 300-350 hp on it.

Best heads for this build that are cheap are the corvette aluminum 113 heads. they are right size chambers for compression and should also help build a lot of hp with there better flowing ports and larger valves. 2.02 heads wont fit the 305.

350 cam is fine its all the same wont make much power with the stock cam. tho. it needs all the help it can get.

Now add in the turbo a set of 113 heads and some port work. along with a good cam and it should make close to 400 hp. Maybe a touch more.

As for strength well there is none and no real way to fix it cheaply. Since the rods and pistons are very light if you upgrade them to 350 parts the engine will need a full balance to survive. so i would consider the 350 hp range pretty mch max for the stock bottom end. It could live a while at that power level.
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Old 03-20-2017, 10:48 AM
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Quote:
Originally Posted by Jeb383 View Post
Hello, I built a 383 chevy last year to replace the original junkyard 305 that came with the car. However, have another car I'd like to put the 305 in since I have it laying around.

It's an electronic carbed engine but I will run a regular carburetor once it goes in the other car. I have a few questions however.

1. The cam was worn out so I'd like some advice on what cam to choose? Can I use some stock 350 cam I have? Budget is to be kept very small.
(I have a new set of pistons that will never get used, new bearings and gaskets though)

2. Could I gain some more "performance" out of the 305 heads by doing a bit of porting and polishing? I ported the stock heads for my 383 with positive results but not sure how much material there is in the runners on these heads? I have lots of time and will not change these heads.

3. How much reliable (as in at least 5000 miles without grenading) horsepower can a stock 305 bottom end take if one were to slap a turbo on it?
Just wondering...I read about "the grenade" at the turboforums but those kinds of numbers are a bit out of my comfort zone.

Thanks

Grocery getter 305s and 350s got the same cam.


Would need the head casting number to see if anything useful can be done. So 305 heads respond to porting and larger valves some not so much.


Turbo's are expensive toys not just the turbo but all the plumbing and controls that go with it. Unless you have a set up just laying around this quickly gets outside the realm of inexpensive.


Bogie
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Old 03-20-2017, 01:06 PM
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Very popular and budget friendly: https://www.summitracing.com/parts/sum-k1102/reviews/
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Old 03-20-2017, 01:39 PM
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Thanks for answering.

Will take a look at the casting numbers in a day or two when I am at the garage.

The turbo route would of course mean a step up in the budget department.
Should have most things necessary though except a blow-off valve and some decent piping. Need to check the size and condition of the turbos I have somewhere also.
Probably not going to happen though. Maybe at some point, we'll see.

Quote:
Originally Posted by BogiesAnnex1 View Post
Grocery getter 305s and 350s got the same cam.


Would need the head casting number to see if anything useful can be done. So 305 heads respond to porting and larger valves some not so much.


Turbo's are expensive toys not just the turbo but all the plumbing and controls that go with it. Unless you have a set up just laying around this quickly gets outside the realm of inexpensive.


Bogie
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Old 03-20-2017, 03:57 PM
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Testing the limits of a 305" with nitrous:


Cheap turboing:

Cheap Turbos From eBay On A 350 Small Block Engine - Hot Rod Network

Testing turbo limits of a 351W:

How to Push a Junkyard 351 Windsor Past 1,000 HP! - Big-Bang 351W
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