Whats the difference in these heads??? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-08-2010, 06:38 PM
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Whats the difference in these heads???

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.

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Old 08-08-2010, 06:43 PM
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Quote:
Originally Posted by TGCheeseman
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.
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Old 08-08-2010, 07:00 PM
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so the just to 2.02 and a 1.60? And how about the flow between the both?
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Old 08-08-2010, 07:16 PM
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If I were you, I'd sell both sets and buy a pair of Vortecs,
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Old 08-08-2010, 07:20 PM
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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.
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Old 08-08-2010, 07:48 PM
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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.
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Old 08-08-2010, 08:08 PM
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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..
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Old 08-08-2010, 08:17 PM
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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.
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Old 08-08-2010, 08:28 PM
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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
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Old 08-08-2010, 08:34 PM
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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?
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Old 08-08-2010, 08:40 PM
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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.
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Old 08-08-2010, 08:41 PM
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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?
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Old 08-08-2010, 08:45 PM
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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
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Old 08-09-2010, 06:43 AM
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1.21 giga-watts???!!!!
 
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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.
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Old 08-09-2010, 08:47 AM
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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
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