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Iron D-Port Heads All iron d-port heads, flow number and performance results

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Old 02-17-13, 02:55PM   #1
Gtogtx
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Default 142's or 143's

I'm putting together a '67 400 for my Catalina. It's not going to be anything fancy at most I'll put in a RA III cam. I have a set of 142 heads at about 8.6 compression and the 10.25 143's. It will be a 3 speed manual with 3.08 gears. I'm going to make the slug a daily driver and wondered which heads would be better. I will upgrade to a 4bbl intake as soon as I can find a stocker. Will be topped with a 600 Edelbrock. Anyone have an idea of which head would be peppy without pinging to death? I have a 4-5 minute commute to work and 93 octane readily available
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Old 02-17-13, 08:22PM   #2
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Definitely go with 143's the more compression the merry. The 400 with the 3.75 storke can Tolerate more compression. I ran our 400 ci with 10.75 comperssion with Absolutely no problems on 93 octane.
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Old 02-17-13, 08:30PM   #3
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The better head is the 6x-4 they came on 400 GP and some Firebirds. Those are the heads the Supper Stock guys go with, its one of the best big chamber heads, and has and exellent port better then most of the D-port iron heads, for runing a low compression 400 motor. If your not crazy about getting the most out of it then just stick with the 143's.
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Old 03-03-13, 05:07AM   #4
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Default Use 350 6X-4 castings

The 6X-4 heads were used on the 350 engines and have smaller chambers than the 6X used on the 400 engines.
By milling the heads & using flat top pistons with single valve reliefs and getting the pistons reasonably close to "zero deck" can get the compression to a "safe" 9/ 9.5:1.Careful cam selection is required.
The cam will actually determine the running or dynamic compression ratio the engine actually sees at certain rpms. Spark adv. curve will have to be adjusted to suit gearing, weight and operating range.

Push much past that compression range on today's "pump grade" motorfuels.
10:1 , 10.25:1 & points higher using stock cast iron heads without using a computerized engine management system is a crapshoot at best.Mandatory
big radiator, & trans cooler to keep operating temps from spiking.

An aluminum aftermarket head would be safer to attempt upper 9.75 to 10.5 static compression ratios. The aluminum is more forgiving that way because it dissipates heat faster.

Catalina is a heavy car and will have more of a tendency to Ping under load than a lighter car with the same or larger numerical ratio would.
I had a '63 Bonneville that did not like anything less than 98/96 octane gasoline. It was at 10.25:1 static . Large valve 1963 389 closed chamber heads w/600 cfm carter & stock cam for the 325 hp engine for that year.
It was a detonator 8 on lower octane gasolines.

Item of note: the federally mandated gasohols (e-85/e-15) actually have a slightly higher octane rating because of the alcohol in them.
However that does not translate into more power.
Alcohol does not make as much btu heat per pound as gasoline does but will resist detonation slightly better at higher compression ratios.
That may save your bacon if the compression ratio is a few points too high.
The trade off is Gasohols make less power per pound of fuel burned when used directly in engines that were originally designed to run expressly on real gasoline.
Mileage and power will suffer.

This happens even to late model electronic fuel injected cars & trucks.
I have a neighbor that owns a new Chevy truck and he said when he runs a tank full of E-15 fuel the thing is down on power & mileage.
He tows his desert toys with it and notices the difference on the mountain grades under load.

My current car uses a 400 @.030 over w/6x-4 heads that were milled .060
It runs on California 91 octane gasoline and has plenty of power.No pinging, no detonation,no dieseling / run on at shutdown.
Currently using a 2.73 gear. Lower 1st & 2nd planetary ratios to compensate that and still have 1:1 3rd and cruise economy.
Use an RP Quadra Jet , Carter Thermoquad or new Street Demon carb .
They work well if using a stock cast iron spread bore manifold.
Q jet & TQ will handle 750 to 800 cfm ,Street demon is avail in 650 & (now) 750 cfm.
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Old 08-18-13, 11:43AM   #5
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I've now picked up a '69 stock intake with the correct Q-jet to put on the car. But I'm starting to wonder about not going a little more aggressive since a few things changed at home. I'm wanting to keep the 143's and I'm using the 67 front water pump timing cover etc. I want the engine to look pretty much stock but I think I'm going to step up the cam a little. I know the rear gears need to go up and I'm saving for something around 3.70 to 3.90. I'm also hunting for a reasonable 4-speed but for now the 3-speed is the ticket. As far as the 143's does anyone have a spring recommendation in order to step up to a cam in the .480-.510 lift area? .510 is at the high side for what I would run but I like leaving a safety net. I'm going to minimum gasket match the heads to the intake, smooth out any sharp edges in the chambers, and if the budget allows look into adding bigger valves. I'm not going too crazy but after looking around other than the occasional resto GTO there are not any feisty Pontiac powered Pontiacs around. There is a '72 Ventura but it's running a big CU SBC that is pretty mean and is set up for 1/8 mile. Racing fuel is available so I'm not worried about occasionally dumping a few gallons in to be safe. I had a comp Magnum 292 in a 400 at one time but the combo wasn't well thought out and it was disappointing
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Old 08-18-13, 12:24PM   #6
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You can find a set of heads already done for what the cost would be to do the 143's
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Old 09-11-13, 01:35PM   #7
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the big valve hi-po Pontiac heads have become very affordable again during this present recession, car parts are a buyer's market. Before I'd invest and bolt on a pair of low-perf pressed-stud 142 or 143 heads, I'd buy a pair of big valve 400-428-455 heads instead. In the long run it's a better investment. Even if you put all big valves, seats, machining, porting into the 142/143 heads, in the end they wouldn't be worth diddley on resale.

you can get casting 62 and 16 heads at a pretty good price, I'd get those.
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