The number one performance killer on the 302 (and 289) is the tiny exhaust ports. They started out too small in the 289, and later got worse with the introduction of smog equipment. You must port-match these openings to your exhaust manifolds/headers, even if you leave the 2V carb and stock manifolds on. If you upgrade, with 4V, cam, or headers, a large part of the potential increase is wasted, due to these restrictive openings. You don't have to go deeply into the port as in a full porting job (except for removing the smog bump), just clean the outer part of the opening, as shown here. The results will feel like you put in a better cam.
This is a "before" picture. The shaded area needs to be removed. The nose-shaped bump in the port should also be removed.
I'm getting my original 302 rebuilt right now as a 331 by a local performance shop. I forgot to look at the block casting when I removed it - I'm meeting up with the builders in a week or so and I'll try to check out the block casting to see if I have anything special. Great thread!
If you are talking about a pre-roller cam 302, the best you can hope for is D1ZM-6015-AA "Hecho en Mexico".
I know that earlier 302 blocks, 1967-1975 (?) had a thicker wall casting, but is it true that they also had a higher nickel content? I've read this in a few places. I know the "Hecho en Mexico" block supposedly has an even higher nickel content, but do the early blocks have more nickel than the later blocks? Or is it just the thicker walls that make these a tiny bit special?
The earlier blocks have no more nickel than the latest ones did. There was a time in the mid 70's to mid 80's where Ford decreased the iron content of a block, but with the introduction of the E6SE block, that all came to a halt. I don't have the weights for the earlier blocks, but The late 70's D8VE block weighed 136 lbs. The 80-84 blocks weigh in at 118-120 lbs, then with the addition of the taller roller tappet bores in the 85 block, weight went up to 122 lbs, then 4 more pounds were added in the decks and bore bottoms starting with the E6Se block (126 lbs) More nickel = increased tooling costs due to the harder iron. Not something done with regular production blocks.
Hmm, haven't seen any mention of the engine balance change. All small-block Windsor engines are externally-balanced, relying on the correct flywheel and matching crankshaft damper. 289s and 302s up 'til 1980 (I think) had a 28 oz.-in. imbalance, while later engines used a 50 oz-in imbalance. Make sure you keep flexplates/flywheels and dampers matched appropriately; damaging vibration can result from a parts-matching error.
What spark plugs do you guys run in the 302? My 302 is a built up new roller cam block with edelbrock heads and 4 barrel. If more info is needed let me know. And the 302 needed a 50 oz. harmonic balancer and flexplate. TIA sparx
