Im using a set of 351w heads on my 302. The 302 head bolts are smaller than the 351 bolt and they say to use spacers to take up the difference. My question is are they really needed since the dowl pins in the block center the head and the bolt still will be tightening down just the same. Thanks.
. an even better thing to do is the stepped shoulder head bolts for this application. arp etc sells them. im sorry off hand i dont have th epart numbers but they work great . and the washers work too i just prefer the stepped bolt set up.
You don't have to use the step washers, but the heads on the 7/16" bolts are a tad smaller than the 1/2's the 351's use. The washers just help spread the load on the perimeter of the bolt holes.
The other option is to have the holes in the block drilled out and tapped to 1/2. Then just use the 351 head bolts. The stepped head bolts are the ticket though.
You can do the head bolts as mentioned, but I would think they are more expensive than the washers. I dunno for sure though. I have a set of Edelbrock shoulder type washers. I don't recall what they cost, but they were inexpensive. They aren't a must... plenty of folks have just bolted the heads down with original bolts, but I would imagine the thicker bolts or washers are a bit of an improvement.
I'll be trying to put 351 heads on my 302 as well. Is there anything else that needs to be done to the engine or heads? Anything else installed? or is the only problem thats in the way, the head bolts?
To do it absolutely correct, all you need is the fatter bolts with no washers, or stock bolts with hardend washers. Personally, I think that to install 351w heads on a 302 without porting the heads is a huge waste of time. The best 351w heads (69-74) have bigger ports and valves at first glance, but the exhaust is choked so badly that there is almost no gain. There is a HUGE lump of solid iron protruding into each exhaust port. At least remove that lump, if you do nothing else. Just taking out the lump is supposed to make 34 hp, no other changes. (I don't know if the 34 hp was on a 351 with the lump removed, or 302, but either way that is huge.) Fully ported 69-74 heads have been shown to flow better than many aftermarket heads.
Oh, and folks considering 351w heads on a 302... take note. 69-74 heads are your only option for a 302 unless you want to lose massive amounts of power! The later heads have ports/valves that are same size or smaller than stock 302, AND they have huge combustion chambers that will drop your compression ratio several points. (75-76 heads are close to early heads, but have internal AIR pump plumbing that clogs up the works.)
So basically just droppin on the 351w heads onto a 302 without anything else just bone stock is a complete waste of time?
If you have the wrong heads. The 'right' heads are good, but don't do much if left 100% stock. The larger ports and valves are beneficial, but then the big lump of iron in the ports, added to a slight drop in compression, pretty much make them a 'wash'. Even if they are good for 10 hp after all that I mentioned, it's alot of work and expense for 10 hp IMO... that is what I was getting at.
