Who has AFR 165's and a 10:5:1 compression 306 or there about? Daily driver?

5spd GT · Dec 9, 2005

Well I have had some recent engine trouble and I really need to do a rebuild in my opinion. I have 164k on the ticker anyways. What did it take for you to run a higher compression with your AFR's and a rebuilt 302 (306). I want something streetable that makes more power.

What makes the higher compression "less streetable". How does your car react. I am very picky (as most know) and I don't want something that will cause problems...

What are the cons of going more compression (staying N/A)...?

Thanks for the suggestions

I will be going with Probe pistons most likely.

So what did it take to run that compression? milling? decking? My cam is quite on the big side for p-v clearance so I hope to not run into that problem...will see...

bluevenom867 · Dec 9, 2005

Higher compression is better on the street (well,to a point).More power and torque though out the band.

Usualy its in the pistons having a slight dome,and a slightly thiner head gasket,but also,a larger bore (.030 over) give you a little more.Only mill the heads if you really want to have some serious compression,even if you got 64cc chambers or what ever the AFR's are,you can easily get a piston to raise the compression to 10.5/11:1.

Only "con" would be if you ever put crap gas in you would be in trouble....

soontobefastfox · Dec 9, 2005

10:5:1-11:1 is the highest I would go on the street because you are going to have to run high octane fuel so it doesnt ping. My dad's stroked 351w takes racing fuel and its got a 10:5:1. Its streetable, but gas is was is going to hit you.

5spd GT · Dec 9, 2005

I have access to 93 octane. I don't want to run any higher octane than that.

I have the 58cc AFR's. I need to have pistons that will clear the cam. I know my factory ones clear somehow but not by much. I need an aftermarket piston that has better relief for the valves but doesn't drop compression. I would need to deck the block I'm assuming but that drops p-v clearance and so does milling...grr...just seeing what others got.

Thanks for the replies!

lwtchlx · Dec 9, 2005

how would boring the motor .030 raise compression? when you do that arent you increasing the size of the cylinder bore? so wouldnt that lower compression if you were to using the same size pistons? i thought it was when you stroke a motor you raise the compression b/c it forces the piston up farther in the cylinder bore.

5spd GT · Dec 9, 2005

lwtchlx said:
how would boring the motor .030 raise compression? when you do that arent you increasing the size of the cylinder bore? so wouldnt that lower compression if you were to using the same size pistons? i thought it was when you stroke a motor you raise the compression b/c it forces the piston up farther in the cylinder bore.

Right, good point but boring an engine also helps quenching I believe and maybe that is what bluevenom87 has in mind in someway

I had/have that same thought...

5.0 HOtrain · Dec 9, 2005

Somewhat off you're topic, but not really, I run 11.25:1 in the 418 on 93 octane pump gas with no real problems.
mike.

5spd GT · Dec 9, 2005

5.0HOTrain - That isn't to offtopic...but what do you mean "no real problems"

This car is driven everyday in every situation and I want something that won't cause any "exhausted" grief...

So what setup would I need to do?

mat50ho · Dec 9, 2005

I have a similar combo and my compression ratio is 10.4 to 1.
I have no problems as long as I run 92 octane. With the tune or with out.

Btw probe piston might not clear your cam. They would not clear mine.. I had to go with ross pistons Part # 82006.

Grn92LX · Dec 9, 2005

5spd GT said:
I have access to 93 octane. I don't want to run any higher octane than that.

I have the 58cc AFR's. I need to have pistons that will clear the cam. I know my factory ones clear somehow but not by much. I need an aftermarket piston that has better relief for the valves but doesn't drop compression. I would need to deck the block I'm assuming but that drops p-v clearance and so does milling...grr...just seeing what others got.

Thanks for the replies!

Milling and decking will effect your p to v clearance but with the probe slugs you need not worry at all. Boring an engine has zero effect on quench. Quench is the distance between the top of the piston to the head deck. So for example if you have a zero deck block and a .039" gasket, your quench would be .039" which is what mine is. I would zero deck your block which will add compression and give you a nice tight quench assuming you use a .039" or so gasket. The only problem with milling and decking is it can make the manifold not line up good with the head so you'd have to have a shop mill the manifold if needed. I think I need to do that on mine but its way too cold to pull my motor apart now.

You should be able to get around 10.5:1 with a zero deck block, your 58cc afr's, a .039" gasket and a probe flat top.

I run 11.045:1 compression with full timing advance (34* total) on 93 pump gas with no issues. No issues either in hot summer days. The combination of more power a much higher compression did make my car run a little hotter but not overheating hot.

mat50ho, how could a probe slug not clear your tiny cam and small valve?? I have plenty of clearance with bigger valves, MUCH bigger cam, milled heads (appx .035") and 0 deck block.

Blk91stang · Dec 9, 2005

soontobefastfox said:
10:5:1-11:1 is the highest I would go on the street because you are going to have to run high octane fuel so it doesnt ping. My dad's stroked 351w takes racing fuel and its got a 10:5:1. Its streetable, but gas is was is going to hit you.

Wow! I have a 351w running 12.5-12.75 compression on the street topped off with 150shot of NOS, all on 93 octane. Timing is pulled a little but never ever heard the car ping (I've went through 3 stock starters before going to a Mean Green for $360 )

The disadvantages to high compression are more heat generated, harder on the starter, and running 93 octane gas all the time.

Of course with only 10.5:1 compression you shouldnt have any of these problems. 11:1 and up is when you will have to worry about those problems.

Shave em to 58cc and have some fun with the added torque and gas mileage!!

bluevenom867 · Dec 9, 2005

lwtchlx said:
how would boring the motor .030 raise compression? when you do that arent you increasing the size of the cylinder bore? so wouldnt that lower compression if you were to using the same size pistons? i thought it was when you stroke a motor you raise the compression b/c it forces the piston up farther in the cylinder bore.

I have proven this piont befor...increasing the bore will draw in more air,and allows it to draw in air faster too,as it unsdrouds the valves.

And more air will give you more compression.

And the whole concept of "stroking" a motor is to get more air and fuel in it.

5spd GT · Dec 9, 2005

mat50ho said:
I have a similar combo and my compression ratio is 10.4 to 1.
I have no problems as long as I run 92 octane. With the tune or with out.

Btw probe piston might not clear your cam. They would not clear mine.. I had to go with ross pistons Part # 82006.

Thanks for the reply...would you mind shooting me a PM on the specs of your cam. Thanks

10.4 to 1 sounds good to me...

5spd GT · Dec 9, 2005

Grn92LX said:
Milling and decking will effect your p to v clearance but with the probe slugs you need not worry at all. Boring an engine has zero effect on quench. Quench is the distance between the top of the piston to the head deck. So for example if you have a zero deck block and a .039" gasket, your quench would be .039" which is what mine is. I would zero deck your block which will add compression and give you a nice tight quench assuming you use a .039" or so gasket. The only problem with milling and decking is it can make the manifold not line up good with the head so you'd have to have a shop mill the manifold if needed. I think I need to do that on mine but its way too cold to pull my motor apart now.

You should be able to get around 10.5:1 with a zero deck block, your 58cc afr's, a .039" gasket and a probe flat top.

I run 11.045:1 compression with full timing advance (34* total) on 93 pump gas with no issues. No issues either in hot summer days. The combination of more power a much higher compression did make my car run a little hotter but not overheating hot.

mat50ho, how could a probe slug not clear your tiny cam and small valve?? I have plenty of clearance with bigger valves, MUCH bigger cam, milled heads (appx .035") and 0 deck block.

Your summers a bit different than mine.

You didn't really have it done in the summer as much.

Unless you know his cam how do you know your "much bigger". You very well could know though. Also, you have TW heads. The valve angle is different which allows you to run the "bigger valve".

I might just try to see what compression I can get without milling the heads. I'm going to definatly converse with Rick and Ed a bit on this...and see where I stand

Oh and running 93 octane isn't a problem, I have been doing that since I have had the car (advanced timing).

Grn92LX · Dec 9, 2005

5spd GT said:
Your summers a bit different than mine.

You didn't really have it done in the summer as much.

Unless you know his cam how do you know your "much bigger". You very well could know though. Also, you have TW heads. The valve angle is different which allows you to run the "bigger valve".

I might just try to see what compression I can get without milling the heads. I'm going to definatly converse with Rick and Ed a bit on this...and see where I stand

Oh and running 93 octane isn't a problem, I have been doing that since I have had the car (advanced timing).

Yeah it probably gets a little hotter where you are. I had my motor running for the entire summer minus 2 weeks. I recieved the shortblock 6/24/05, finished building it and had it running around 4th of July time. So yeah, pretty much the entire summer

You should not need to mill your heads to reach your desired compression but the fact that you over heated this motor a few times, you warped the heads for sure and they need a minimum of a clean up mill.

Probe slugs have inline and a TW style relief on them. So the valve angle doesn't mean a thing since its not like comparing it to a stock piston. It has its own relief unlike a stock piston.

Think of your dead motor in a postive way. Dont worry about the money, think of how its time to make more power and build a fresh engine

5spd GT · Dec 10, 2005

Grn92LX said:
Yeah it probably gets a little hotter where you are. I had my motor running for the entire summer minus 2 weeks. I recieved the shortblock 6/24/05, finished building it and had it running around 4th of July time. So yeah, pretty much the entire summer

You should not need to mill your heads to reach your desired compression but the fact that you over heated this motor a few times, you warped the heads for sure and they need a minimum of a clean up mill.

Probe slugs have inline and a TW style relief on them. So the valve angle doesn't mean a thing since its not like comparing it to a stock piston. It has its own relief unlike a stock piston.

Think of your dead motor in a postive way. Dont worry about the money, think of how its time to make more power and build a fresh engine

My dead engine runs It just runs hots. I have the same oil pressure I did and all...just runs hot officially...

I wasn't trying to compare the probes to stock. Just saying the valve approach angle on the TW's are more forgiving. Stock piston could be used as an example.

Aluminum heads are fairly resistant from what I understand...I doubt the damage will be that bad. I will check them...

I'm going to do a fairly basic rebuild. Pistons/bore/rings/bearings/clean up crank probably/clean/balance. I'm just worried about compression right now and clearance.

I don't want to get a combo together and find out that it hits That would not be cool...

ninjacoupe · Dec 10, 2005

lwtchlx said:
how would boring the motor .030 raise compression? when you do that arent you increasing the size of the cylinder bore? so wouldnt that lower compression if you were to using the same size pistons? i thought it was when you stroke a motor you raise the compression b/c it forces the piston up farther in the cylinder bore.

Going to an overbore increases your compression ratio by increasing your displacement at bdc. Your chamber remains the same size at tdc. Bigger cylinder being compressed into the same size chamber= higher ratio

Hissing Cobra · Dec 10, 2005

I hope you get your engine up and running as quickly as possible. Why is it continuously overheating? Is your radiator old, plugged, corroded, etc...etc...etc...?

Anyway, I have a 306 with 10:8:1 compression and the 58 cc AFR 185's. To get that compression ratio, I used Keith Black domed hyperutectic pistons and the block has been decked.

Though not a daily driver, it could be. It runs fine on 93 octane with no detonation whatsoever and I haven't had one single problem since I put it on the road almost two years ago. I've never tried 91 or 92 octane because I didn't want to have to worry about knocking/pinging. Therefore, I began using 93 octane with my first fill up.

Good luck!

5spd GT · Dec 10, 2005

Hissing Cobra - Thanks for the encouragement!

ninjacoupe - I really don't understand it though. If your trying to put the same amount of air in a bigger area (bored cylinder - assuming same type piston) the pressure inside the cylinder will decrease. Pressure (as an example) equals compression. So compression should decrease right?

I think it is more in the piston design and the bore doesn't increase but rather decrease...it just seems more logical. Same air amount in bigger area equals less compression (less psi).

ninjacoupe · Dec 10, 2005

5spd GT said:
ninjacoupe - I really don't understand it though. If your trying to put the same amount of air in a bigger area (bored cylinder - assuming same type piston) the pressure inside the cylinder will decrease. Pressure (as an example) equals compression. So compression should decrease right?

Your not trying to put the same amount of air in the bigger area. Your going to pull in more air with a bigger bore. I'm not talking valveshrouding just volume. A bigger bore has a bigger volume, the bigger volume will create a bigger vaccuum. The point is that when the piston is at the bottom of the bore you have a larger amount of air. A 306 at bdc has more volume than a 302 at bdc. About .5 cubic inches worth of volume per cylinder.

Your static compression ratio is the ratio of volume when a piston is at BDC to its volume at TDC or BDC:TDC after simplification it is expressed as 10:1 or 11:1 or 9.5:1 or whatever:1 if you increase volume at bdc ie overbore or a larger stroke you increase one side of the ratio.

Piston design has a minimal impact at BDC but will greatly impact the chamber size at tdc. Thus changing the other side of the equation.

Who has AFR 165's and a 10:5:1 compression 306 or there about? Daily driver?

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