As the title says ide like some help with this. I bought an 82 z a while back and was talkin to the guy i got it from about the carb and manifold he put on it when he tells me it has double hump heads which honestly means nothing to me since this isn't 1970. But from what ive read they are worthless on a 305 did they make them for 305s? Or do i have ebay supplies on my motor?

 

Sell those things to someone building a period motor and buy some real heads! Don't bother buying anything specific for a 305, just buy what will fit a 350 so you can swap it out later.

 

Well i want to keep the 305 its the original motor and i dont need a car much faster than this one its gotten me in enough trouble as it is. What would you recommend putting on it?

 

It's got camel humps, and different carb + intake. That's pretty much half the motor, wouldn't worry too much about 'original' anymore. If you don't need any better performance, what's wrong with what you've got? Is it running bad?

 

Agreed. Most of the value in the "originality" of your motor is the heads and induction system. Those are long gone, just rock what you've got.

Double humps are going to be a little low on the compression for you, but if its fast enough for you, then dont worry about it. Buying 305 specific heads wont really get you anywhere you want to be. Just enjoy it as is.

 

Well I've got all of the parts or atleast I thought I did but after finding out double hump heads don't come on 305 motors I can't say that now
But it runs awesome I've out ran more than enough cars and they are always shocked when I tell them it's just a 305. But it does only have 106,000 miles on the body and around 30,000 on the motor so its not fair against old mustangs with way more miles and a TON of money in them. But I was just in sure why some one would put them on the motor if they were not helpful guess I need to call the guy that built it and ask him what they came off of.

 

Its probably faster because most people who dont know better end up with the garbage awful 70s heads that we always steer people away from here. In comparison to those, the double humps are very good, and that's why they have the reputation they do. Modern heads are far superior.

If you're racing a bunch of people stuck in 1977 the double humps will be pretty quick.

If you're gonna tear it all apart and tear it down, I'd suggest you get some cheap 416 heads and do some minor portwork to them if they need a valve job. Dont open up the port, just smooth transitions inside them. With a big cam a 305 with those heads can put out over 300hp. You probably wouldnt want to go that big on the cam, but chances are it may already have an upgraded cam.

But since ith as been rebuilt, we dont know if the heads were shaved, if the pistons are domed, if they're flat tops, what the cam is, etc. All I can tell you is that anything with double humps isnt going to be all that great, but it can definitely be servicable. There's room for improvement but you could do a whole lot worse.

 

I'm going to have to disagree with something I saw in the thread. In my opinion, the most "valuable" part of his motor in terms of originality of the vehicle would be the block as the VIN is stamped into it. The heads and other pieces can be replaced with careful selection from the JYs by just being careful of the dates. Nobody would be able to prove they weren't the originals, just that they'd been removed and reinstalled, unless they started stamping VINs into the heads. Just sayin.

 

Thanks guys y'all have been a ton of help. I guess I really need to start digging through my paperwork and see if I can find out what was done to the motor because I really don't know. I'm still new to the whole keeping one car thing normally I get bored with in a couple years and flip it but this one I with be with me for a while

 

If you'd like to swap those out you can sell them to a period collector or restorer for a decent chunk of change. You can then buy a lower cost head from RHS, EQ, Dart, etc. Most manufacturers have low buck lines.

If you'd like to stick with the 305 then you're going to need to pay attention to the valves. I believe anything larger than a 1.94 intake (correct me if I'm wrong someone) will require the bore to be notched to clear it.

 

Ok so as for them not having an accessory hole what does that mean? Are we talking a/c or what?

 

Oh now, that's a little unfair. I wouldn't even say that cast iron L98 heads from the late 80's are really any better than a set of 041s, other than maybe a bit more compression. As to flowing, I believe the 041s will respond to modification better and hence flow better in the end. In my opinion, you had to wait for vortec heads to get anything significantly better than what the factory was making in 1969. At least if you want to bolt them to a GEN1 block.

 

Those are the holes drilled and tapped into the ends of the heads. They are where accessory (alt and ac) brackets typically bolt. You really need these holes to be present. Regardless of what you may be thinking, there are "double hump" equivalents like the 041 that do have accessory holes, they just don't actually have the two little hump casting marks. They have triangles.

 

There's more to it than just, "drilled"...

In the heads without them, there's nothing to drill INTO. The outer layer of the heads right there is just a shell about 1/8" (2 threads of the right size bolt) thick, and on the other side, there's water. All that the casting is good for right there, is to keep the water from falling out. Furthermore, the outer surface of the casting isn't flat or parallel/perpendicular, and isn't in the correct plane.

In the heads WITH the holes, there's a big thick deep boss cast in behind the surface, such that the hole can be about ¾" deep, and it's BLIND (doesn't hit water). There's a boss on the outside that is machined flat, and to a controlled dimension, such that it's in the same plane as the rest of the acc'y bolt holes on the front of the block, so that brackets can bolt up to all of them and lay flat.

Without that, you can't have "accessories", like .... an alternator; let alone power steering or A/C.

The bolt holes were introduced in 69. Heads from before that, including the most numerous of the double-humps (461 casting), don't have them, as well as some of the over-the-counter ones like 291. Heads from 69 up, including 041, 186, 462, and over-the-counter 492 and 292, DO have them.

Problem of course is, you can find 461s all day long, CHEEEEEP; because nobody wants them any more, because they don't fit any cars made since 69. The others are a bit less plentiful and more $$$$ because they're actually useful for something.

But regardless, you can get better heads in the aftermarket today than those could ever possibly be made into, for about the same money as taking a "free" set of DHs and working them up. By the time you mill & drill the stud bosses for screw-ins, drill the slots out to allow the use of guide plates, cut the spring pockets to allow decent springs, replace the 40-yr-old guides, cut the seats for bigger valves (usually you end up having to completely cut them out and install seat inserts), and buy all the hardware (valves, springs, guide plates, keepers, shims, seals, ....), and do enough porting work to make ANY of it worthwhile, you'll have around $750 in them BARE MINIMUM, and depending on how much porting you pay for, could easily exceed that. If you have to buy the castings you'll have even more tied up in them. But, you can buy aftermarket heads that will run circles around them, with all that already there, for around $1000.

HHHhhhhhmmmmmmmmmmmmmm.... ,,, ....... ,, ....... tough choice here. 40-yr-old stock heads for $900ish, or brand-new replacement ones that DRAMATICALLY outperform them for $1000??? {sofa makes weighing motions with his hands} I'm really struggling here... what do I do? Let me step outside and consult my financial adviser, this is just too complex for me. I'll let you know what he says.

 

Well since the heads are on the car I will leve them be for now. I would how ever like to find out what they are, I have an alternator and power steering and a/c but it's laying in the shed so I'm thinking they may nit be dhs then. Is the only way to know for sure to pull the valve covers? If so putting them back on as easy as replacing the gasket?

 

Since we're being pedantic and all. Sorry I didn't elaborate on the accessory holes more for the OP. You obviously could have "accessories" such as alternator and power steering on cars equipped with the hole-less heads, you just had to have the right brackets, intake and accessories to make it work.

Porting isn't free, unless you do it yourself, so I don't think that it fair to assume the old heads need porting and the newer L98 heads don't. I believe the 041 heads to be just as good as L98 heads when each is in stock form.

Of course you can buy much better heads today for reasonable money, but in 1990 that really wasn't all that true, especially if you were expecting to buy something production from GM. I was just commenting to make the point that better heads were allot longer in coming than after 1977.

 

Problem was, on the "hole-less" heads, the accessories can't be in the same place (duh); and the places that they were in with the bracket systems they came with, won't fit in these cars. Little details go wrong, like, the PS pump hits the PS gear, and the alt is on the wrong side. (for a 82 anyway) Plus you have to use a short WP and the 60s brackets.

I don't mean to be "pedantic"; problem is, every time somebody says "there's no blot holes", the first thing the guy looking to buy the "cheeep" DHs says is, "I'll just drill em"; and then some hilljack pipes in about how he did that and cut the bolts off to just the right length (so they quit bottoming out on the opposite surface of the water jacket) and put sealer on the bolt threads and stacked washers under the brackets, and drove the car all the way around the block and it's still working!! what's the problem? Just trying to prevent the inevitable before we get to it.

I agree, the cast-iron L98 heads are roughly equivalent in stock form to the DHs; or for that matter, effort for effort. But, they're MUCH better quality castings to begin with, MUCH better precision in the sand molds and whatnot, which makes the finished product "better" in other ways. But the problem remains the same; whether DHs or any other stock heads, the days of lovingly working up those precious "good" stock castings are long gone. CNC casting has pretty much made all that obsolete.

 

I hear you. I could be mistaken, but I thought there were also castings made that have the right bosses (or whatever you want to call them) to drill and tap. And yeah, CNC has changed everything. I've got a set of 041s in the garage, all ready to go about 15 years ago before I stuck them in the garage. 1.94 valves and bronze guides that were still doing ok. Not much room to take off the faces anymore though. They've been shaved a couple times in their previous life. They did the job in my old '69 camaro though with flat tops and a mediumish cam.