This is continuation of another thread but I thought it might spark more discussion if posted separately.
I've been doing some research lately on 350 builds. Wondering if anyone has experience with using the higher compression small valve heads on a 350 and with what result?
The heads won't have clearance issues like big valve heads and would seem to be a great option. Common castings would be the #46, #18, #48, 1970 #16, and 1968 #15. I see a lot of these for sale fairly cheap. The 400 and 455 guys want big valves so these heads are kind of in limbo. But for a 350 build?
One issue might be too much compression but several ways to bring that down to higher octane pump gas levels without much issue.
All the open chamber high compression heads were from '68, '69, & '70. So, that limits your choices to heads from these 3 years. I have never seen any open chamber high compression small valve screw-in stud heads. But, that doesn't mean they don't exist.
If you look thru the head info at this first link, you'll see that it shows that some '69 428 engines came with both #16 & #46 heads, which had small valves & screw-in studs. I don't know if this info is correct or not. Online info differs, and we all know that not all online info is accurate.
If you can't find any heads with small valves & screw-in studs, I'd say the cheapest way to get some would be to find some good #15 #16, #17, #46, or #47 small valve cores, and have the screw-in stud conversion done. Only other choice I see is to use big valve heads & cylinder chamfers in the block.
One option might be to find some of these heads that have already been set up, with the screw-in studs. You might find some for a reasonable price, over on the PY forum.
(2) Go with a Butler stroker assembly. Then you can buy some of the late '73 or '74 #46 heads, and run a Voodoo 262 cam. Should make a real spunky pump gas engine.
Wondering why nobody says... Wow great idea. Get some old high comp small valve heads for practically nothing cause nobody wants them, spend $750 at the machine shop, throw them on and rip it up? My experience is that if nobody says that there is a very good reason. What reason?
I would think that any second hand 40 year old heads are going to make a trip to the machine shop anyway so pressed in studs could be easily resolved. Like everything else it cost money but doesn't come near the cost of aluminum heads. Also I have this sort of odd nostalgic side that says if it isn't going to be original it should at least be era appropriate. Somehow helps me justify things like taking off my steel wheels and hub caps and putting on some Rally IIs. So using 1969 heads on my 1969 feels right.
I've been playing with compression numbers and the calculators. Lord knows if I did it correctly but seems like with the #16 small valve heads and bored 30 over I would be working down from somewhere near 10.5 in order to get to pump gas. That might be a good reason?
Can't really comment on the small valve heads, mine were big valves. But my compression ratio was at 9.8 to 1 (on my 350) and it ran fine. No knocking or pinging, though it had fully polished chambers.
-=>Lee<=- Due to budget constraints the "light at the end of the tunnel" has been turned off!
"...Wondering why nobody says... Wow great idea. Get some old high comp small valve heads for practically nothing cause nobody wants them, spend $750 at the machine shop, throw them on and rip it up? My experience is that if nobody says that there is a very good reason. What reason?
I would think that any second hand 40 year old heads are going to make a trip to the machine shop anyway so pressed in studs could be easily resolved..."
(1) I wouldn't say "nobody wants 'em", since there are lots of guys who have used the #17 & #47 heads, on performance builds.
(2) I'm not sure that you can get ALL the GOOD QUALITY parts & machine work necessary for a high performance head job, for $750. I'm guessing $200 for the ARP conversion studs + labor for proper installation. The holes must be tapped correctly. Then the bottom of the studs must be ground down and properly finished, since it is said that they are too long, as produced. Machine shops don't give away free labor.
Then, if you plan to do a lot of driving, most say you need to have hardened valve seats installed, for use with unleaded gas.(Many say the seats are not needed.)
Most say it's better to buy one piece stainless valves, which add to the price. Some say it's just fine to use the old factory 2-piece valves, if you're gonna use a small cam and stock strength valve springs.
Most say it's best to use the good valve stem seals, which fit around the valve guides. The guides must be machined for these seals, in most cases. Then they'll charge for for doing a "multi-angle valve job".
There are additional charges for cleaning, and any surface machining done. If you have much cut off the chamber side, to increase compression, they need to cut an equal amount off the intake port side, in order to maintain proper intake manifold fit.
If you can buy some GOOD cores for $200, add that to the cost.
And that does not include any type of porting or gasket matching you may want done. So, MANY have spent MORE than $1000, when transforming these low performance heads into high performance heads.
(3) If you really search for 'em, you can sometimes find some good heads that somebody else has already spent the $$$$ on, and save a few hundred bucks. You can usually find most anything you want over on the PY site. There are usually some guys switching over to alum heads, who have their iron heads up for sale, to help pay for the alum heads.
(4) BUT, if you wanna start from scratch, with the old small valve press-in stud heads, and have 'em built correctly, AND have the $$$$ to pay for it, then by all means, DO IT ! That way you'll know exactly what you have, and won't be using somebody else's old used stuff, that they didn't want any more.
I suppose what I'm trying to say is that you have options. But, the decision is all yours, as to exactly which way to go with your build.
"...with the #16 small valve heads and bored 30 over I would be working down from somewhere near 10.5 in order to get to pump gas.
Looks like the #16 heads had 78cc chambers. That won't get anywhere close to 10.5 CR, on a .030 over 350. I plugged in some numbers & get just over 9:1 CR. It depends on the EXACT size of the chambers, head gasket used, valve reliefs of pistons used, final deck height, etc.
"...Wondering why nobody says... Wow great idea. Get some old high comp small valve heads for practically nothing cause nobody wants them, spend $750 at the machine shop, throw them on and rip it up? My experience is that if nobody says that there is a very good reason. What reason?
I've done it to a set of #47 heads. And will be doing a set of small valve #16 heads. It's an expensive hobby and there's no way around it. Come to think of it everything in life is expensive. If your going to rebuild any set of heads with new valves,springs,keepers...etc price is going to be close if it's a big valve head or small valve head. Cost difference between valves is minimal. Installing screw in studs isn't a deal breaker $100- $180 depending on what the machine shops labor rate is. So if the final cost to do all this is around $800- $1000 is that terrible? I don't think so. And especially if all is done correctly you have a set of heads that will last another 40 years.
All really good thoughts and true. But I wasn't referring to built small valve heads, although that is certain a legit option. I want the high compression small valve heads that are also built. I already have basic small valve heads on the car. I could just take mine to the shop I guess. Drop $1000 and probably see a decent gain.
As for the expected compression. I used the 1969 46 heads at 68 cc. Admittedly I didn't do it correctly. I like the numbers oldsskol got way better.
I have a 69 vert. with the 350 that was rebuilt at some point before I purchased the car. Car came with a two barrel than a four barrel was added, also the cam was change. The compression on the engine is running around 170 per cylinder. The 46 heads are still on the motor. But deal is I have no idea what was done on the inside. I can only guess it was a complete rebuild. They had installed a edelbrock 650 that was not setup the right way, I changed the jets out to a smaller set, which the motor thank me for doing. I'm happy with the way it runs, It's not a race car by any means. I may be able to do more tuning, but for me it's a cruiser. On the highway it feels happy running around 80.
If the #46 heads on your 350 are 1969 than this would be the build i'm looking at. Those would be small valve high compression heads advertised at 68cc. But #46 heads are not that simple. Info I founds says one has pressed studs and the other has screw. The mid 70s #46 heads used on 350s had small valves. They were smog heads, some pressed some screw.. In true Pontiac style of course the 1974 #46 heads had big valves. Would it have been so hard to use a different number?
"... I wasn't referring to built small valve heads, although that is certain a legit option. I want the high compression small valve heads that are also built..."
I guess I'm confused. Is there a difference in " built small valve heads " and small valve heads that are also built ".
Or is the "high compression" part what you are emphasizing ?
As mentioned, you can not know EXACTLY what your combustion chamber size is, without measuring the chambers. Can't go by online info, or what was advertised years ago. And it don't take a really big cut to reduce the chamber size of a low '70's cc head, down to an upper 60's cc chamber size.
I assume you are saying that you wanna start with some 68cc #46 heads, hopefully with screw-in studs. If so, I wish you luck finding some.
I guess it all comes out the same if the heads flow and work. I was thinking "high compression" small valve heads. I found 2 different sets on CL within a sunday drive of western MA. 1967 #143, 1966 #093 today! For the record none were 46! LOL Thanks for all the input.
Not familiar with those older heads, and never fooled with any 389 or 326 stuff. I assume that the #093's are closed chamber. Some '67 heads were also closed chamber.
I think the valve angle was different, on pre-'67 heads. ??? Engines which came with the different valve angle, had valve reliefs in a slightly different location. As the cam gets bigger, and the valves get closer to the pistons, for whatever reason, valve size & angle, as well as valve relief location, come into play, for determining valve to piston clearance.
I read about one 350 build that used closed chamber 326 heads. Don't remember the head number or size of cam used. But, it ran pretty good. It was probably quite common for guys to use 326 heads, to increase the CR.
I personally would prefer to use open chamber heads, with the later valve angle.
As mentioned, you can not know EXACTLY what your combustion chamber size is, without measuring the chambers. Can't go by online info, or what was advertised years ago. And it don't take a really big cut to reduce the chamber size of a low '70's cc head, down to an upper 60's cc chamber size.
I would strongly agree with this. I've built lots of engines (from many manufacturers) and advertised numbers are rarely what you actually find when get out your tools and measure. You're using 45+ year old parts, you rarely know what has been done to them in that time, as well as the fact that the manufacturing process was not that precise to start with.
As someone said earlier, too many variables. You need to measure chamber size, piston deck height, valve reliefs, head gasket thickness, even cylinder eyebrows can add to chamber size.
-=>Lee<=- Due to budget constraints the "light at the end of the tunnel" has been turned off!
