I have a set of heads casting numbers as 333882. Then I bought me a set of 3917291 double hump heads. Can you tell me the difference between the two. They are both 1.94 and 1.50 valves. With the double hump how big can I go with the valves? 202,205,208? I was just wondering. Im just now starting my s10 v8 with a 355 with trw forged pistons flat top 10.5:1. 291, 64cc double hump heads,victor jr intake,holley 750 double pumper,mallory igntion and distributor with rev box, roller rockers,3800 stall, 10 inch 8.5 rear end with 4.56 gears. B&M quick silver slap shifter. Just going to have a little fun. Its a 91 short bed. Street/Strip.

correct me if im wrong but i think the biggest intake they came with was the 2.02 which was popular with corvettes back in the day.

 

so the just to 2.02 and a 1.60? And how about the flow between the both?

 

If I were you, I'd sell both sets and buy a pair of Vortecs,

 

Im just gonna stick with the 291s. My 99 z71 prolly has vortec heads tho lol. With the vortec you have to have a vortec intake manifold so Im going in this one direction.

 

Between those two, the 882's are junk, the 291's are the only ones worth rebuilding.

You can fit a 2.05"/1.6" combo, but it makes them real thin between the two valves and very prone to cracking. 2.05"/1.55" fits better, but it will take a lot of port work to realize much of a gain over the 2.02" valve, the stock intake port is too small for a 2.02" valve from the get-go if big power is your goal and 2.05" just makes this more pronounced, needs lots of metal removal.

882 head is a 76cc smogger head, 291 is 64cc closed chamber head. The closed chamber shape produces on average 20 ft.lbs more torque just from the better chamber shape, not even including the compression ratio gain.

The only good 882 head is a smelted down 882 head, used to make some other cast iron piece

Vortecs are indeed better, but the 291's are decent, use them if you got 'em.

 

Problem with the 291's is they are forty+ years old.

I am doing a typical set right now. The customer paid $250.00 for them. They need valve job, guides, seats, mill, head bolt holes repaired plus he wanted 2.02-1.60 valves, screw in studs, guides cut for seals and clearance.

Thats better than $800.00 in a pair of $250.00 junk heads..

 

Hoping!!!

Im hoping to run in the low 8s in the 8th and still drive on the road. Thats my plan but anything faster is great also. Im going to build the 291s. It should be pretty fast anyway as Im having it built by John Phillips. Hes a very talented builder. And Tranny builder. Cant wait to see what it will do.

 

I like the 291. To get the most out of them learn to port and polish and open the exaust ports up and 2.02 will work good with a 1.6 exhaust. Make sure if you get yhe valves a lil larger they deshroud the valves or you could be hurting the set up by shrouding the valve. Just trying to help with my 2 cents

 

Ok thanks for all your info guys. What do I port and do I just gasket match? And that being on intake to head? And how do you know your heads and intake match?

 

amazing. bobcrman just said that he is doing $800 worth of work on a 40 year old set of heads. Old combustion chamber shape. Set of Vortecs from junk yard, $200. New springs, rocker studs, guide plates, what, $300? Vortec manifold on ebay, $200. $700 total for heads that will outflow the 291's, have a modern combustion chamber, and are worth an easy 40 HP gain over the 291s in STOCK FORM. Why in the world would you let an intake manifold get in the way of doing the smart thing? Don't get it.

 

yeah gasket match the intake and open up the exhaust to mtach your gaskets which should match your headers for the most from your system.What do you mean does your intake match your heads? the 291's take the old style intake where the intake bolts in the middle go in at a angle and not striaght down. I think i said that right. For your setup whats your cam of choice and rpm range desired?

 

Yes vortecs are better but a good set of camels will flow good for him if that is all he has. Look up porting and polishing on youtube. Buy a kit from summit. If nothing else you could learn something new and have the kit for other projects

 

Ridiculous advice, sorry to be so blunt. Pick up a porting kit and do the 291's and make them flow like Vortecs????? First time porting and with no flow bench? Not going to happen. Sure, camel humps can make good power but no where near a Vortec without $800 worth of porting.

Again, the fact that he doesn't have a vortec manifold seems to be the deciding factor. As my post indicated, he can do the vortecs for a lot less overall and have a way better head.

 

882's make good scrap weight, 291's are good for restorations.

Sell both sets and get some Vortec heads and an intake to work with them. You'll be dollars and horsepower ahead in the long run.



Larry

 

That's what I was getting at to begin with, :thumbup:

 

There is a little bit more to running Vortec heads than just picking up an intake.

You have to use guide plates especially made for vortec heads or run self aligning rocker arms.

They need screw in studs installed, by a machine shop.

Depending on the springs you want/need to run, the spring pockets might need to be opened up.

The valve guides will possibly need to be cut for seals.

A set of aftermarket valve covers will be needed, maybe tall depending on the rockers you use.

The valve pockets just under the valve needs to be opened up to get full benefit of the far superior design of the head.

Is all that worth it? YES! Don't waste money on the old stuff unless you are restoring.

In my opinion, even with all the above, the money you will end up spending on the 291 heads will be more than you would spend on a Vortec setup. And be hp/tq up.

Did anyone mention the 291s will need all new hard seats?

 

There must be an echo in here. LOL Exactly what I am saying. I have pocket ported 041 heads on my engine. As soon as I can, I will be switching to production Vortecs or picking up some of the Bowtie Vortecs. Just not smart to put a bunch of $$$ into old heads unless you are bound to use them by racing association rules or, like said, you are doing a numbers correct restoration.

 

There is a little bit more to running Vortec heads than just picking up an intake.

You have to use guide plates especially made for vortec heads or run self aligning rocker arms.

They need screw in studs installed, by a machine shop.

Depending on the springs you want/need to run, the spring pockets might need to be opened up.

The valve guides will possibly need to be cut for seals.

A set of aftermarket valve covers will be needed, maybe tall depending on the rockers you use.

The valve pockets just under the valve needs to be opened up to get full benefit of the far superior design of the head.

Is all that worth it? YES! Don't waste money on the old stuff unless you are restoring.

In my opinion, even with all the above, the money you will end up spending on the 291 heads will be more than you would spend on a Vortec setup. And be hp/tq up.

Did anyone mention the 291s will need all new hard seats?

Just grab the stock valve covers and self-aligning rocker arms to go with the heads. I bought OEM covers for mine, used, for $25. New OEM GM self-aligning rockers are $60. Valve spring change, about $75.

 

I heard these heads are a lot heavier than newer ones. What is the max 291's can be milled? What is the largest valves you can run? With enough work they may work better than vortecs depending on the application?

 

as others have said. The biggest size you really wanna go is 2.02 and the amount of money and the work involved in developing the 291 head is more oney and effort when a simple ride to the junkyard and geta set of vortecs they will out flow the 291s. Yes 291s can flow good. But it will take alot of moneya and time.

 

... With enough work they may work better than vortecs depending on the application?

The problem is, unless you can do all the porting, and probably the machine work as well, you'll never come out ahead on the hp per $$ comparison.
Between the high swirl chambers and the flow of the Vortecs, the 291s just don't stand a chance in that comparison. :mwink:

 

The biggest size you really wanna go is 2.02

What is the biggest valve size that you can go though? And still have room for a proper valve job.


I agree Vortecs are a lot easier to make power with out of the box, but i can't see how these heads instantly turned to **** after the Vortecs came out. For a LONG time they were great; now they're not as great as some others but can't they still make some power when in the hands of the right person? I know a lot of classes don't allow Vortecs- then what?

 

Problem with the 291's is they are forty+ years old.

I am doing a typical set right now. The customer paid $250.00 for them. They need valve job, guides, seats, mill, head bolt holes repaired plus he wanted 2.02-1.60 valves, screw in studs, guides cut for seals and clearance.

Thats better than $800.00 in a pair of $250.00 junk heads..

For that kind of price, I'll junk the heads and get brand new alum heads for the same price.
800+250 = $1050

 

C'mon. At one time cast iron log exhaust manifolds were the norm. Then somebody developed headers.

At one time, vacuum tubes were the norm, then transistors came out.

Yeah, the Vortecs turned the 291's to sh$t just like that in an apples to apples, punch for dollar spent. Turbolover, you seem to be missing the point here. Vortecs = More flow, more HP, more torque, less timing required to run vs. spending big bucks for porting old design heads with a disadvantageous combustion chambe just to MATCH what the vortecs will give you.

 

I agree the vortecs are better I just don't think 291's are useless. They put cars into the 10's twenty years ago I don't know why they can't do even better today. Comparing a set of track prepped 291's to stock vortecs my money is on the racing heads. And track takeoffs are fairly common at times thanks to them going to better heads. Unfortunately no one has done extensive testing on a comparison like this, at least that I know of.