Motor and head combination. - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 05-13-2015, 08:44 PM Thread Starter
 
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Motor and head combination.

I have a chance to pick up a 400 motor with 094 heads. I can't remember the block casting number but it ended in 988. The motor was 1971. I believe the heads to be from a 1966 326. The motor needs cleaned but is standard bore and in great shape. Any opinions on this combo?
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post #2 of 7 (permalink) Old 05-13-2015, 09:33 PM
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094 (326) heads aren't going to be the best for a 400. They've got the smaller valves, and probably will result in too much compression for pump gas. If they're 94 (and not 094) heads, then they're from a 71 350. Still not going to have the 'good' valve sizes but with 96 cc (nominal) chambers you shouldn't have to worry about the compression aspect.

Regardless of the heads, if the rest of the engine is 'good' and you can get it at a good price, I wouldn't hesitate.

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post #3 of 7 (permalink) Old 05-13-2015, 10:41 PM
 
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Yeah, the 481988 blocks are the good 400 blocks that were used from '71 thru early '75. They also have 5-motor mount bolt holes on each side so that they can be used with either 2 or 3 bolt mounts.
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Last edited by oldskool; 05-13-2015 at 10:53 PM.
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post #4 of 7 (permalink) Old 05-15-2015, 11:08 AM Thread Starter
 
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Bear, they are definitely 094 heads stamped on them. What heads would you recommend? This is a pontiac guy and he may have other options. I am trading a 327 for it so cost isn't much of an issue except rebuild cost. The block is stamped 481988 and looks to be in great shape except for some surface rust.
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post #5 of 7 (permalink) Old 05-16-2015, 11:31 AM
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If you want to run cast iron heads, Google up "Pontiac Head Codes" to get a list of sites that have information. Two things you want to pay attention to: Valve sizes and combustion chamber volume. The big valve size is 2.11" on the intake, 1.77" on the exhaust and most of those heads also will have screw-in (vs. pressed in) rocker studs. Problem though is that "most" of those iron heads will also have 72cc chambers and on an otherwise 100% stock 400 with factory specs, is going to result in too much compression for todays gas, so you'd want to use pistons with "some" dish in them (exact volume determined by other details of the engine build). "Good" iron Pontiac heads are getting harder to find these days though, and unless you find a pair of later model (71 or later) heads that also meet the above criteria you'll have an additional concern over exhaust valve seats. In 71 with the advent of unleaded fuel, manufacturers had to begin building heads with hardened-exhaust valve seats to make them live without lead (which helped protect the seats from getting 'hammered' so much that they receded into the head) under extreme use. There are two schools of thought on this now. One says you always need hardened seats no matter what, the other says that unless you're pulling trailers or doing something else that always puts heavy loads like that on the engine, you'll be ok with non-hardened seats on unleaded fuel. I happen to belong to the second group, but I wanted to mention it so that you can make up your own mind about that.

The 'easy' answer is to go with a set of aftermarket aluminum heads. They all have hardened seats, are available in chamber sizes such that compression won't be a concern, and (because they're aluminum) you can get away with a little more compression than you can with iron. The down side of course is the cost, and to do it right (in my opinion) the cost is more than just the initial purchase. The 'right' way is to buy the heads bare (no valves, no springs, etc) and then have a "head guy" you trust finish them out for you while also treating them to whatever porting work suits your needs (and your bank account). I say this because the 'ready to run' heads all use the cheapest available parts (valves, springs, other hardware) which I wouldn't recommend using, so why not put a little extra into them while you're at it? That's what I did with the Edelbrock heads I'm running on my car. Out of the box they're set up for 2.11 intakes and 1.66 exhausts. I had Dave Wilcox of CVMS build and port mine, and not only did he open up the valves (2.194 intakes and 1.77 exhausts), the "basic entry level" port work he did on them is gorgeous.









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post #6 of 7 (permalink) Old 05-16-2015, 09:15 PM Thread Starter
 
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Thanks Bear. Great info. The pics are great too. I don't know how you ever get to knowing all this, but you never fail to impress.
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post #7 of 7 (permalink) Old 05-16-2015, 10:27 PM
 
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Low Budget Option

If you don't have $3000 or so for a set of new alum heads with all the trimmings, there are cheaper alternatives. If you are just building a street car, you probably are not shooting for 500hp +.

If you would settle for a 400 with about 350hp, you can use the cheaper 6x heads. A good pair of cores run about $200. Then you can have a GOOD machine shop rig 'em up with stainless valves, and a good 3 angle valve job. Don't need any porting or 1.77 exhaust valves.

The 6x heads already have hardened seats, so as long as you don't let the machine shop talk you into 1.77 exhaust valves, they'll be fine with unleaded pump gas. But if they cut the seats for 1.77 valves, there is a possibility that they could cut thru the hardened part and into softer metal.

With these heads, you can either shave some off the chamber and intake side of the heads, to increase compression, and retain good intake fit. Or you can just surface the heads, and use thin Cometic head gaskets to raise the CR. And then run one of the steep ramp cams, like the Lunati Voodoo series. These cams increase cylinder pressure, and raise what is referred to as dynamic compression, in otherwise low compression engines.

So, I figure you can make somewhere between 325 & 350hp with about 8.5 or so CR. If you cut the heads down a bit more, use thin gaskets, and zero deck the block, to get the CR up to around 9-9.25 CR, you can easily make between 350-375hp, with the correct combo of parts.

Now if you want over 400hp and 500ft lbs of torque, for some tire smokin power, you can go with a 4.25 stroker assembly from Butler.

http://www.jbp-pontiac.com/products/...s.html#461_467

Or, if you don't have access to a good Pontiac machine shop, you can buy either a 400, 455, or 400 block 4.25" stroker, crate motor, with 6x heads, for between 4000 & $5000 or so, from Len Williams. The entire 400 engine is not much more than a good set of ported alum heads. And he can add forged rods and other stuff, if you prefer. The 455 with an Eagle crank and rods is only $4500 + shipping.

400 Long Block

455 Long Block

455 Short Block
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