What is the truth about stock compression in 302s by year

I have seen many lists that show how the compression on stock 302 mavericks have changed from year to year, mostly going down as the fuel economy became more important.

I have 1974, EGR-equipped 302 Maverick, and have heard that my compression is somewhere between 7.5:1 and 8.5:1. Most saying 8:1.

What is it really?

Also, I had a head job last year, and talked to the guy who machined them. He said he took of .008, maybe .010. Will this even give me a 0.1:1 increase in compression?

When I rebuild, will I have to mill the top of the block at all, or just swap out pistons and rods to get compression up to 10:1? How high can I go and still use 92 octane pump gas? How much improvement will Edelbrock Victor Jr. head give me (in compression)? Would smaller chambers increase it?

Lots of questions...Need to know

 

I run 92 octane in my 289 it has a 10:1 cr. It doesn't like anything less.

 

The compression ratio in a 1974 model 302 is 8:1. This is due to dished pistons. A set of flat-top pistons can rais your compression ratio to 9 or 10:1. The combustion chamber size is 58-60 CCs..

 

Is the dish in the pistons there for any reason, other than to reduce compression?

Also, since it is easy to get to the pistons, can I fill the dish in and make them flat, with some kind of bonding compound that can withstand heat (ever hear of Belzona?)?

Sounds like I need to replace the pistons...

 

A bit of modeling clay, set up for an hour then sprayed with heavy duty hairspray should fill them in as long as you stay away from nitrous...LOL..Do NOT try to fill in the pistons! Yes, a new set is in order if your desire is to raise the cmpression..

 

I was thinking play-doh with 3 minutes of hair dryer...

Actually, when I worked in machine shops, we used an "epoxy" type of compound called Belzona. When it hardened, it was very heat resistant, nearly impossible to sand/grind, etc. We used it to replace lost metal in centrifugal vacuum pumps and compressors. It cost something like $600 per quart, and was indestructible. Of course, for $600 I could do some serious upgrades to the engine. And wouldn't have "indestructible" chunks flying around in my cylinders and eating up my valves.

 

You would never want to try something like that with pistons. Just buy new ones for around $150. Your idea whould throw the balance off as well as add weight. You want your pistons to be light-weight and the rotating assembly to be balanced for minimum vibration.

The purpose of the "dish" is to lower the compression ratio for use with lower octane gasoline, and for lower emissions...

 

Emissions? What's that? I live in Texas, and anything older than 1978 gets no emissions test. Give me power, or give me death!

Any suggestions on piston/rod combos?

 

Use the Rods you already have. They are forged and plenty strong. There are many places you can get new pistons. Try P.A.W. for one...

 

Really, use the old rods? If I would have known that, I would have rebuilt the engine a while ago, since new rods seem to jump the price up quickly.

Any suggestions on pistons? What will give me 10 or 10.5:1, lightweight, etc? What "features" am I looking for?

I have seen many with semicircular indentations where the valves are, longer and shorter pistons, different ring setups, things like that. I drive this car on weekends, sometimes to work (just to show off) and on the drag strip 3-4 times a year, just for test-and-tune. I would like 350 HP, more if it happens on accident, by the time I am done building.

Any suggestions would be greatly appreciated.

 

I would like 350 HP...

You're gonna need more than new pistons if you want that kind of power out of a 302.

 

You'll need aftermarket heads and a hellacious cam...

 

HEADS< heads r good heads r grrreat. i like my roush 180's very much. (world products a.k.a. windsor jr.)(bought mine assembled for 400 a piece). i should have gotten a bigger cam, but ohwell.:evilsmile

 

How are the edelbrock heads? Are they just someone else's heads with an "Edelbrock" stamped on it, and an extra $100 stamped on the price tag?

 

dont know squat about edlebrock heads, but i feel safe in assuming that they are edl's own design. I don't like aluminum. my roush 180's are good bang for buck in my book. lower cc = higher CR. if i recall edl heads are higher cc. roush 180=1.94in 1.6exh 58cc 180cc in runner. roush 200=2.02in 1.60exh 64cc 200cc in runner. edl 1.90or2.02 in 1.6exh 60cc 170cc in runner. I VOTE roush/windsor jr 180 (world products)(no funky exhaust manifold reqd)(dual bolt pattern exh flange)