Piston selection for about 10:1 compr.

[D.Hearne]

Shouldn't be any intake fitment problems after milling an 8.229 deck block. The mill will bring it down to what it would be on any other 302 block.

 

[Tim65GT]

by SoCalCruising:
Since you will be decking the block, you will be changing the mounting position of the intake - the intake will sit higher on the heads than with the original deck height. So, when you have the heads on during mock-up, mount the intake with a gasket and torque to about 15 ft/lbs. Check the clearance between the block end rails and the intake surface. There is a chance that the intake will mount flush (no space between block end rails and intake). If this is the case, you must have the intake milled.

Many of us use silicone to seal the end rails and this is especially good if the clearance you have is small (e.g., <0.100"). The cork gasket may sit too proud and not allow the intake to seal against the head if you have little clearance and use the cork gasket. If you have lots of clearance, you can use the cork, plus some silicone to get a good seal.

Ideally, you will mock up the shortblock with at least four pistons - one at each corner. Measure the piston-to-deck height at each corner. This is a good idea because the deck may not be square (i.e., not perfectly parallel to and equidistant from the crank mains). You will want to find the shortest piston-to-deck measurement, tell the machine shop how much you want removed from that height, and then tell them you want the decks squared up on that dimension. Frankly, a zero deck is great, but asking for 0.005" will allow a fudge factor and not affect compression very much

Wow, Thanks for the detailed tips!

I know decking the block or heads affects the Intake mounting, and I'll use your info when I put it together.

AFR 165s and 185s have standard exhaust and intake port positions and bolt patterns, so any header and intake made for the factory head will work. Just be careful when tightening the header bolts into that soft aluminum

What? No steel inserts? I thought I was getting top of the line stuff.

it will ruin your day if you strip a bolt hole.

Even more so on brand new $1400 heads!

I'm sure a torque spec sheet comes with 'em, huh? Does it say if you can use thread lock on the header bolts? I've heard copper plus high temp silicone sealer also helps to prevent header leaks.

 

[SoCalCruising]

I didn't see a spec. Maybe there's one one their website. I tighten by feel. I get it snug and with enough torque to seal the header - and, yes, I use high temp/copper sealer. Edelbrock heads are the only aluminum heads I know of that come with helicoils in place. Oh well, AFRs make more power. Try tio use a header bolt (length) that gets as much thread as possible into the hole without bottoming out. That's about all you can do.

D.Hearne is correct in that there SHOULD not be an issue with your intake given the piston you want use and the current deck height. However, it is always good to check, and should be a routine part of your mock-up process.

 

[Hack]

In regards to piston weight... it's the same as other reciprocating parts. The piston has to stop and start during every stroke F=MA, so the lower the mass of the piston, the lower the force required to stop/start the piston. If you are building a motor to rev very high, lighter parts are preferred so that the rod bolts and cylinder walls can handle the stress. There are always trade offs - lighter parts cost more. They may be more fragile as well.

 

[D.Hearne]

I'm sure a torque spec sheet comes with 'em, huh? Does it say if you can use thread lock on the header bolts?

Just me, but thread locking compound on steel bolts in aluminum heads is a bad way to avoid having to retorque your header bolts. Leave em long enough and you WILL need thread inserts after you remove the bolts a few years later. All the bolts that go into any parts that are aluminum I assemble get a dose of anti-seeze compound on the threads.

 

[Tim65GT]

D.Hearne:

Just me, but thread locking compound on steel bolts in aluminum heads is a bad way to avoid having to retorque your header bolts. Leave em long enough and you WILL need thread inserts after you remove the bolts a few years later. All the bolts that go into any parts that are aluminum I assemble get a dose of anti-seeze compound on the threads.

Good call. I use the antisieze in aluminum too. I read about the thread locking compound somewhere, and that's why I asked. I won't use it. Thanks.

I'm used to checking for loose bolts on a '78 Harley

 

[302 coupe]

I know a place where you can get better heads, with better hardware, properly "set up" for a better price. AFR makes a good head, but not the best, even for the price.

 

[Tim65GT]

302 coupe
I know a place where you can get better heads, with better hardware, properly "set up" for a better price. AFR makes a good head, but not the best, even for the price.

Well....?