302 - 306

Stopsign32v · Jul 31, 2008

I would highly......very highly suggest you go with the 331/347 combo I listed for you. Deck the block at 0 and run flat top pistons. With a 331 decked to 0, flat top pistons, and a 60cc chambered head you should be right at 10.1:1.

Forget the damn 306!!!!!!!!

5spd GT · Jul 31, 2008

Stopsign32 - A 306 is a cheaper option.

There are pros and cons to each.

A camshaft plays an often overlooked role to compression and octane rated needing.

Stopsign32v · Jul 31, 2008

5spd GT said:
Stopsign32 - A 306 is a cheaper option.

There are pros and cons to each.

Ofcourse it is a cheaper option. But for basically $500 more than what his 306 will cost what other mod could you do to the car for the same amount of money that will give the same performance all the time as a 331 or 347?

Also what are the pros and cons?

LxVert · Aug 1, 2008

I want to do a 331 or a 347 but as of right now that extra 500 would break the bank, I was figuring that this cheap 306 build would hold me over until I'm out of school. Once I'm done with school and dont have to worry about sending in a $10,000 check every semester I'm going to build up a nice stoker motor out of my other block.

Stopsign32v · Aug 1, 2008

Well then get a set of flat top pistons with valve reliefs in them, deck the block at 0, and figure out what you need to mill your heads to to get 10.1:1 compression. Somewhere around 56cc I'd guess.

NIKwoaC · Aug 1, 2008

5spd GT said:
Stopsign32 - A 306 is a cheaper option.

There are pros and cons to each.

A camshaft plays an often overlooked role to compression and octane rated needing.

Right. However, dynamic compression ratio, though important, I think is beyond the scope of this thread. But if boost was ever introduced, a different cam and altered ignition timing could be looked at. But I don't know if getting that deep into power making on boost makes any sense if the foundation starts with hypereutectic pistons... Like he said, right now its all about getting the car back on the road for cheap.

5spd GT · Aug 1, 2008

I have a 10.5:1 engine I daily drive and it runs great at 89 octane, and I have ran 87 octane.

This was with a camshaft for a 9.2-9.4:1 engine.

You could run a 10.8:1 static compression engine (BDC divided TDC volume) and have no issues with 89 octane. You could run a 9.5:1 static compression engine (BDC divided TDC volume) and have issues with 93 octane.

The camshaft is big. The intake valve closing point ABDC becomes key here.

By the way, I was speaking on N/A terms, not boost as was mentioned.

LxVert · Aug 13, 2008

So when I had been going back and forth with the machine shop they said if they could get them in my price range they would get a set of forged pistons for me, other wise it was going to be hypers. Well I never remembered to ask the other day when I picked up the motor what pistons they got. The pistons that came in the box were Speed Pro pistons, how can I tell just by looking at them wether they are forged or hypers?
The machine shop is a small mom and pop kinda place and they are closed for the next 2 weeks for vaca so I can't call them up to ask.

NIKwoaC · Aug 14, 2008

I doubt there is any real distinct difference in the appearance of material between the two different pistons. Your best bet would be to have markings on the pistons or part numbers from the boxes they came in. Do some homework online and see if you can find any info from the part numbers. If not, I'd say give Speed Pro a call.

backfocus · Aug 14, 2008

Ofcourse it is a cheaper option. But for basically $500 more than what his 306 will cost what other mod could you do to the car for the same amount of money that will give the same performance all the time as a 331 or 347?

More like a $1000 buy the time you also add a balancer and new flywheel, along with getting it all balanced. LxVert as stated early your best bet for your stated budget is the 306. As far as the pistons forged or hypers, many times it will have forged stamped on the pistons, but some manufacturers may not, the best way is to look up the number or call Speed Pro. They were very helpful to me when I was trying to identify some pistons, they no longer made.

As 5sp stated the cam is where you can make your motor better. You might want to look into a custom cam, so you could get the powerband you want and really setup the combo to work together. Although you will be above the $1000 dollars of your budget, as a custom will run around $300 and up, plus new lifters etc. but it would help you get to most out of your small cube combo. Just a thought!

NIKwoaC · Aug 14, 2008

Some people will argue this, but the stock 5.0 cam is actually pretty decent in a street motor with stockish heads. I've seen N/A motor build-ups where the cam wasn't installed and dynoed until the heads and intake had already been, and the motor only saw 15 more hp at the flywheel with the aftermarket cam over the stock one. I say just get the car moving then save money for big mods down the road.

backfocus · Aug 14, 2008

For some reason I was thinking he already non-stock heads and intake, but after reading, its all stock, so no on the cam, as NikwoaC stated it won't yield you enough yet. I would only suggest it if you were changing heads and intake both. The stock cam is a fairly good cam what the component it had from the factory.

If your goal is to just get it back to running you are on the right track.

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