Ahhh the camel hump...camel back...double hump ....double bump....fuelie.....known by a number of names and casting numbers, this GM head is either coveted or despised. with the introduction of the vortec heads, the camel hump is becoming a once again popular choice for a hot little small block mill, and in my opinion is the head of choice for a screamin small journal mill. I am not going to try and cover all the variations and styles that were made , but concentrate on the ones most likely to be found at the swap meet or the local paper. And try and cover some things to look for while checking out that "just rebuilt " piece. known mainly by the last 3 digits of their casting number, the most common ones to be found will be the 461 462 186 291 492. the ones I am going to cover here are the 461 and the 462 and also the 291...the 492 is not as common but still found, it was the factory replacement for the camel hump and is virtually the exact same as the 462 casting ...in fact most of the heads are the same configuration as the 462 casting except for the 461. what i like most about the head is the fact that it flows OK out of the box, around 160 on the intake....can be made to flow much better with a little work...will except most any intake manifold that you can throw at it, and will also accept a whole slew of spring and retainer packages to custom tailor to any cam. the vortec while still a popular choice, has limited spring options ...and while having a newer burn combustion chamber, is still limited to lift and flow parameters....as well as limited intake choices. There are some new ones hitting the market all the time , but in my opinion if building a older style motor they just don't cut it. most of the write ups you read about them any more are in mags where you turn the page and there is a big ad selling said heads. I classify the head with the craze that surrounded the use of the 305 casting in circle track motors, the small combustion chamber instantly bumped up the compression in a stock rules class....the intake tract didnt flow worth a crap, but it was an easy and cheap way to boost compression. any way...enough of my .02....lets look at some heads. here are a few that have I have been working with as of late..... the first thing I look at when I go to look at a set is what size valves do they have?....they will have either a 1.94/1.5 or a 2.02/1.6 valve set....either factory or machined afterward....a lot of the 1.94's that have had multiple or bad valve grinds, end up gettin cut bigger for the 2.02. in some very rare instances where a drag racer has had them, they could have a 2.05 intake, but it will be very rare to see this the 1.94/ 1.5 will have a definite area between the valves that you can plainly see the 2.02/1.6 will look like the valves are touching....virtually no area visible between them.....when you see this you know that you have the big valves the next thing to look at is what shape the valves and seats are in if the valves are sunken down into the valve seats, they have either been ground to much or to deep , or have pounded the seats down......the problem with sunken seats , are that they create all different valve stem heights.....especially if someone has been over agressive with the valve grinder.. here is an example of sunken valves and then using a straight edge on the valve stem you can see the difference in the heights what you would like to see are the valves sitting up, where you can actually see the valve edge or margin above the seat area. next I look at the valve springs, have they been modified? and to what extent. a stock set up will have cast iron guides and valve springs with oil shields installed. they should have a small O ring style valve stem seal on the valve stem.......the oil shield is to help control the amount of oil the the O ring has to deal with...insureing enough oil gets to the valve guide ,but not to much the springs will look like this most times when a valve job is done the valve guides are changed to either a thin bronze liner or a new thick wall bronze guide is installed.... a lot of times a positive type valve stem seal is installed when this is done...I do not like to see the positive type seal used if the stock oil shields are gonna be reused, you are not going to get the proper amount of oil to the valve guide by using this combination if you are gonna use the postive type seal you should go to an after market retainer at least. next thing to look at is the rocker stud set up . It will be stock pressed in stud..... pressed in stud that has been pinned...... tapped for a screw in stud...... .tapped and machined for a guide plate and screw in stud. I dont have any pictures of pinned studs....it really isn't done much any more...the first pic is a pressed in stud. You can see the boss the stud sits on is tapered at the top. in the next pic you can see where the boss has been machined to flatten it off and give a little more surface area then drilled and tapped finally the last pic you can see the boss has been milled down to accept the thickness of the guide plate and screw in stud. it's nice to at least have the screw in stud for a performance application. a couple of other things I want to touch on briefly, if you are running the 2.02 valves and the valve area of the combustion chamber has not been unshrouded , you are more than likely flowing worse than of you had the 1.94 valves...there is nothing wrong with the 1.94 in a hot little street motor....you can usually pick these up cheaper , because everyone wants the 2.02. most of the ones that I find at swaps and what not have been done by racers that have moved up to a better head for their paticular class...they want to get little money back out of them . but in most cases they have had excellent machine work done......and you can get it at a fraction of the cost.....walk by the guys with the 600.00 dollar core heads ...matching corvette numbers,,, yada yada yada, these heads are not getting those kind of prices any more... lets go find a set of heads........
I picked up this set of 291's the other day,, they had the 2.02 valves and the chambers had been unshrouded....they had fresh comp cam springs and retainers and had also been cut for screw in studs and plates I diassembled them and checked them over...they had hardened exhaust seats and everything looked good, spring heights are even, studs are machined straight. the fellow I bought them from had took them off his 383 stroker, they just were not enough head for it.he gave me the name of the machine shop that had done the work, everything looked good so I brought them home and opened them up, checked the seat runout, guides etc they have had a little pocket porting done,valves unshrouded, everything looked good so a little elbow grease and I had them cleaned up, these prolly have 4 or 5 hrs run time at most , and are everything the seller said they were. after checking spring pressures and valve seats, a little more cleanup I shot them with a little chevy orange VHT they started to look so good I rolled them over and installed the Glenn Hayes/Federal Mogul sponsored roller tip rocker arms..... and there you have it . the 2006 HAMB DRAGS raffle engine heads 291 casting 2.02/1.6 stainless valves pc seals comp springs/ retainers/ locks bronze valve guides screw in studs guide plates pocket ported roller tip rockers these things cost us less than ONE vortec head, and this is not a rare deal , but i believe the 4th set that I have picked up this year, and a couple I passed on at the last swap, cause I just didnt need them...., oh I have walked by some junk to find them but keep your eyes and ears open and I am sure you will run across a set just as nice. Fred
Running the risk of sounding like I'm preaching to the choir, the only other thing I would do to prep those heads would be to deburr them with a wire wheel on an electric drill. I've owned a lotta' "double humpers", & I highly recommend them if for no other reason, the fact that they "breathe" so well! My 2 cents only.
Great Tech! Thanks RACEFAB. I have a question about hardened seats. I'm unsure if my heads have them. Should I be adding lead to the gas?
Thanks Fred. Glad to see you're still on the tech series. What has to be done in order to run the new style oil seal? Any machine work?
What a cool compilation of information! The winner of the engine will have a great resource of information on its build up! RACEFAB - you don't know how much your time is appreciated! I know I don't say a couple of words to people often enough so here goes... THANK YOU!!!
I have run this style head since the late 70's. On my own personel stuff I have never had hardened exhaust seats installed. I use to add a little lead additive every fifth tank or so, but a lot of times would forget about it...I never saw any ill effects later on when I pulled them apart. I leave it up to the individual, if they are gonna feel more comfy with them , by all means install them. If they are happy with adding the additive . go for it. without knowing, and it if it worries you, I would toss a little additive in there once in awhile. Fred
I have heard that the race fuel still contains lead and it can be added and ran through just like the additive. I don't know if this is true or not but at 5 bucks a gallon, it's not much more than 7-11 gas....
you can get them to fit over the stock guide boss, but they should be tailored to the spring package.... if the springs require a smaller diameter seal, or the lift of the cam requires the top to be cut down so there is no retainer hitting the top of the guide issues, then they will have to be machined for that application. Fred
On the hardened seats thing, it depends on the way you use the engine, also. If it's in a heavy car or truck where the engine has to work hard and that will see a lot of miles, the seats will be more likely to get hammered, and hard seats might be a good idea. For a light car that won't get too many miles on it, it shouldn't be a problem to run the heads without hard seats.
This is very, very, helpful. Thanks. I'm intent on putting a new motor together to replace my 283 eventually and the advice in this post is going to help me select and find the heads I need.
Thanks Fred! Great stuff. These heads were the "only way to go" back in the day - plentiful and resonably priced, yet surrounded by the usual clueless lore and mis-information that is so often part of "hot-rod tech" at bench-racing sessions. I'm the first to admit being guilty of using the "double-humpers" without really knowing the facts - or necessarily doing the right thing. Thanks much for the "refresher course" and straight scoop on these classic performance parts. My first head-porting job was on a set of "camels" - and laughable, I'm sure - as far as performance gains went (they looked cool though! - LOL). How about some of your down-to-earth advice regarding "home" porting work (i.e., port matching, general "clean-up", etc.) for these heads? Is there much worthwhile a person can do on his own - or is it best to rely on the pros all the way? P.S. Where can you get the "lead additive" that some of the posts here mention?
Geeezzz....another bellybutton SBC post ...I love it ! Thanks RACEFAB, a great tech post and great info.... CC
Great info, can you shed some light on what is different about the 461 "X" heads, as apposed to the normal 461 castings?
Great post Fred. I purchased a set of 462 at the Feb swap in Puyallup. 2.02/1.60, triple springs, reworked runners, 7/16 studs, the works. A racer had pulled 'em off his race motor in favor of a set of aluminum heads and I got a good deal on 'em. I took the heads to a machine shop for more street friendly springs to be installed and I changed the studs. I'm into them for very little $$$$.
Fred thanks for the Tech, the pictures really help. And thanks again for helping find my set of heads. Joe
Hey Fred, I haven't worked at a machine shop, or even had any machine work done in YEARS, so I don't know what shops are charging these days; So here are a couple of questions... If you had more than one set of heads you wanted to "hook up" (cut for studs/guideplates, cut for PC seals, maybe bigger spring seats, etc), would you be further ahead to purchase the cutters and do it yourself? Would it be worth picking up the stuff to put in bronze liners, or are full guides the way to go? If you're fortunate enough to have a mill, is there any reason a home machinist couldn't tackle the "closer-tolerance" jobs, such as replacing guides and hogging bowls for larger valves? You can pick up a used seat grinder set for $100-$200 on Egay; while it's not as consistent as something like a serdi, is there any reason that it wouldn't be great for a home workshop? When I was working in a machine shop, I preferred the stone setup for my own heads, because I had more control over the widths of the individual angles, as well as being able to dress stones to different angles to get exatly the radii I wanted Is this still considered a "good" setup for unshrouding valves, or is there a better way now? It seems to me that for about $600 or so you could purchase most of the tools necessary to hot rod a set of SBC heads... how many heads would you have to do to offset the initial investment? If it makes any difference in how you answer my questions, I was an ASE certified auto engine machinist; but I let it expire, because there's MUCH more money to be had poking holes in people! Thanks! Steve
A buddy of mine just got some Camel Humps that end in the number 46 They do not have the "1" on the end... What are they? Sam.
what is the threshold that requires roller tip rockers? I have a pair of World Products SPII heads and a medium lift Comp cam on a 383ci SBC, my machine shop suggest stamped rockers would be fine on the street so that's what I went with. TZ
any reason these heads (461,462,186,291,492) will not fit on a 265 block?? if they will not what should i be looking for?? thanks for the info, great post
They will all fit but your comp ratio will be in the crapper. Trust me......I found out the hard way.
I just saw a old Nickey chevy ad at a car show listing some of these heads for 36 buxbrand new ! I wonder what these things cost now?
Great post. I'm going to check my double humbers for numbers. Just had them redone too. Wish I had of waited a bit....would have had more educated questions...Thanks.
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