Old style heads on newer motor

by WyldeBill66 Sat Dec 15, 2012 7:11 pm

I asked this question on another site, but got no answer so I thought I'd try it here. I have a 75 Chevelle with an 87 crate 350. Can you use the pre-87 style heads on this block? Aluminum heads for the older style are a lot cheaper than the center bolt 87 and later heads. I want to raise the compression up a bit from the stock 8.5:1, so I wanted the smaller chambers, plus the better flow and weight savings would be nice too.

I hope someone out there can answer my question. Thanks in advance

Bill

by Brainstain Sat Dec 15, 2012 7:38 pm

The simple answer is yes. I don't know how well they would work though. To really make a decision you would need flow numbers for both sets.

by WyldeBill66 Sat Dec 15, 2012 7:50 pm

I'm talking about Edelbrock heads with 64cc chambers and better flowing of course. They are under $1000, while the later ones are about $1300 to $1400. I think I could get a new set of valve covers for less than the difference and be worth it for the improvement in performance.

To go a different direction, what is good performance head work go for? Porting and the like for street performance duty. The current heads already have 1.94 valves stock.

Thanks

by dynchel Sat Dec 15, 2012 7:56 pm

I did the old 305heads on a 350 trick and i'll tell you what it woke my car up. Now my engine is the original, and I got a set of #416 ho heads off a 84 Monte Carlo but for the $400.00 (appx total) it was a really good bang for the buck. Lots of tire burning power. The heads I got were 58cc chambers compared to the 76cc stickers I took off. Just my two cents.

by WyldeBill66 Sat Dec 15, 2012 8:08 pm

Oh yeah...I forgot about that. What kind of flow numbers do those heads have. Obviously they'd bump the compression, but what size are the valves and intake and exhaust runners?

My stock heads are 74 or 76cc's too.

by Brainstain Sat Dec 15, 2012 8:18 pm

Head work depends on what you have done and whether it's CNC or manual work. To have my LS heads cnc milled, ported, polished and a 5 angle valve job with new seats and guides comes right at about $950 and they're bench flowed. If I were you I would go with the 305 heads and have work done to those.

by dynchel Sat Dec 15, 2012 8:22 pm

Valves are 1.88 if i remember correctly . If you google 305 heads on a 350 this is the head everyone recommends. I got mine for free and spent $350.00 to get them inspected, cleaned, one valve replaced and a 3 angle valve job. A gasket set from napa was very cheap. I dont have any flow numbers but i can vouch for the results.

by 77mali Sat Dec 15, 2012 8:51 pm

If you're looking to spend a little money, why not go with a vortec upgrade?
Of course you'd need a vortec intake as well but they're not too much money. The airflow is a big improvement over the previous design with the cross-over & they're made by all the top manufacturers both in aluminum & iron. I had my block rebuilt recently and am still putting it together but If I recall correctly, the compression ratio is 9.5:1 with this design so it's not too radical. They're iron heads & they are 170cc intake runner, 64cc combustion chamber, straight plug design @1.940" intake/1.500" exhaust valves.

My motor had 305 heads ("swirl" style casting) on a 350 w/ 4"standard bore when I got the car. I have a feeling that's was why I had a blown head gasket & a crack in between 2 cylinders. There are 2 or 3 types of 305 heads out there that are used for the purpose of enhancing low end torque. If you go that route- do your research. There is alot of debate out there about this swap.

by pila Sun Dec 16, 2012 12:20 am

The combo with the older type heads, 64 CC chambers etc, will sort of depend on the piston design, flat tops (?) or dished ?? 64 CC chambers on flat-top pistons may end up being too high CR for what you want. Some research, and calling some tech lines might be a good idea.
305 heads will jack up the CR alright, but the small valves & ports aren't gonna add much in the way of power. I've done all that stuff, and determined it wasn't worth even the labor involved. It's a matter of choice of course...

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Old style heads on newer motor

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