I've got a pair of new aluminum heads to go on my 302, with each of the heads came a pack of five black-steel top-hat bushes, these fit into the head bolt holes. Each head had ten bolts, only five bushes are supplied with each head, the supplier says this is correct. From what I can gather online they are 1/2" to 7/16" adaptors, do I only need five per head, if so, which bolts use them?
(http://www.torquedup.co.uk/forum/imagehosting/usr_images/1/4/8/148_588e6495a1706.jpg)
(http://www.torquedup.co.uk/forum/imagehosting/usr_images/1/4/8/148_588e64948b49f.jpg)
(http://www.torquedup.co.uk/forum/imagehosting/usr_images/1/4/8/148_588e649354abf.jpg)
I don't have the answer why they say only five per head. Putting 351W heads on the earlier engines was common and all the ones I have seen used 10 on each head. There are a few suppliers. I don't like the idea of the head bolt gouging the aluminum on the other five.
https://www.alexsparts.com/head-bolt-reducer-bushings-adapter-used-for-mounting-351w-heads-onto-289-302-blocks-1-2-to-7-16-head-bolt-bushings/
I'm sure Summit and those type people have them also.
Most aftermarket heads use 1/2" head bolts. The bushings would be used with your stock 7/16" head bolts. I not sure why there wouldn't be 10 per head though.
302 uses a 7/16" bolt and 351 uses 1/2" bolts. After market heads sometimes drill the holes 7/16 and some manufacturers drill them 1/2. Mine were 7/16 and I drilled them so they would fit the 351. I don't understand why all holes don't have bushings or at least a good washer. I have ARP head bolts and they come with heavy washers for all the bolts. A head bolt note: 351 head bolt holes are blind and need no sealer, the lower 5 holes on a 302 and 'wet' and need sealer.
Thanks, it makes no sense why there's only five with each head, I need to put an order into Summit so I'll order 10 more.
Silly question, but don't you have any speed shops in England? Or is it they just don't have American car supplies?
Quote from: gasman826 on 2017-01-29 17:12
302 uses a 7/16" bolt and 351 uses 1/2" bolts. After market heads sometimes drill the holes 7/16 and some manufacturers drill them 1/2. Mine were 7/16 and I drilled them so they would fit the 351. I don't understand why all holes don't have bushings or at least a good washer. I have ARP head bolts and they come with heavy washers for all the bolts. A head bolt note: 351 head bolt holes are blind and need no sealer, the lower 5 holes on a 302 and 'wet' and need sealer.
Actually, only later 5.0L blocks had "wet" lower head bolt holes in the block. On the 331 in my Fairmont drag car, I originally used a 1990 5.0L hyd. roller block, when I went to freshen the engine at the end of the 2015 race season, we discovered that the block has several cracks in the main webbing, so I needed another block. I found a 1974 302 block, and we used that, its been working great for 2 seasons now. In addition to having blind head bolt holes, it also has a bit more material in the bottom end. You are correct about the head bolt sizing on 302 vs 351W blocks and heads, and that many aftermarket blocks use the larger 1/2" head bolts. I have AFR 185 aluminum heads on my 331, and they have the steel reducing bushings on all the head bolts. The steel bushings will prevent galling that would otherwise occur with steel head bolts on a much softer aluminum head. Certainly a pain in the butt for our British member that he only got 1/2 a set.