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Old 09-14-2009, 08:24 PM
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anybody wanna give advice on pontiac 400 build?

well i got a 1979 trans am i bought it for dirt cheap and its rust free needs a paint job, the guy said the motor ran awesome 5 years ago last time he drove it i towed it home and putt a batt on it no go tried a breaker bar on the crank bolt to turn it over no go,its seized but it hasnt had a air cleaner on it for 5 years and was sitting in the elements, so i was asking for it, im pulling it out tomorow, i got a good idea of what im gonna do but want expert advice so feel free to critisize or offer suggestions i really want to car to turn the high 13s is that acheivable and i want to be able to burn some good rubber from a dead stop without and use of a break on normal street tires

its got a edlebrock carb offenhauser intake accell super hei distributor and wires, its got a serperate tranny cooler, its a 1974 motor 400 ci i looked up the numbers and its got 6x heads so i know its been all tooken apart before if i recall right 6x heads werent available till 1975 its got the 3.23 posi gears

im gonna get new pistons rings all that good stuff, i got the jim hand book and im gonna try to lightly port the heads myself going by what the book says i read that its good for almost 50 hp or send it to butler performance for 500 bucks theyll do that, since the heads are good for 7.6 to 1 compression im probabaly gonna get domed pistons and shave the heads a little to try to get around 9 or 9.5 compression, i was thinking about the summit Summit SUM-K2801 cam i am assuming i should build off the torque with the pontiac engine
my dad used to have alot of cool cars when he was younger he said the fastest car that he ever had that was bone stock was a 1970 ram air 3 trans am, that summit cam is similar to the pontiac ra3 068 cam grind and with similar compression it should perform about the same since the 6x heads flow just as good acording to flow charts and if there ported a little theyll flow signifigantly better 50hp worth butler performance says,

if i have my fresh pontiac 400 with 9-1 compression and the 6x heads lightly ported/cleaned up the offenhauser intake, summit 2801 cam, edlebrock carb, acell super hei and wires, and a set of hooker headers going into 2.5 inch true dual exhaust without cats and 3.23 gears will i be able to burn a respectable amount of rubber from a dead stop and when i get some good tires on it maybe turn high 13s?? if not give me some suggestions what will get me to my goal without breaking my bank,thanks for any help
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Old 09-14-2009, 10:10 PM
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Everything sounds good except for two things. Domed pistons would be a bad move, with the large fully machined combustion chamber that Pontiac uses trying to push the limits on compression ratio(if this is to be a pump gas engine) is a really bad move. I would consider 9:1 to be the limit, this isn't an SBC we are talking here, have to treat compression on this engine like you would on a BBC because of the large chamber. Zero deck with a flat top. mill the head a little, and then accept what you get from it.

The 068 cam (or a close copy)is badly outdated, might have been the shizzit in 1970 when leaded good gas was available, but there are much better grinds from Kaufmann or Butler, or a custom cam grinder of your choice. You are likely giving up 35 hp by using it, possibly more.

3.23 gears would be a pretty good gear to also allow highway use, pair them up with a 200-2400 stall converter and it should really scoot.

Modern Performer intakes are better than the Offenhauser but it will get you by if it isn't that terrible Dual Port split runner junker.
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Old 09-15-2009, 08:17 AM
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hotrod on spike tv did a pontiac 400 build last week. use headers, 6x heads, mild cam (220 degree range), q jet, performer intake. I think it made 310hp and 410 ftlbs . I didn't watch it so close so please recheck the facts.
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Old 09-15-2009, 08:35 AM
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yea i was gonna get a slight dome to try to get around 9-1 or 9.5-1 so i didnt have to cut the heads and zero deck the block because its gonna need new pistons because it will need to be bored, i have the jim hand book i think with zero decking the block and cutting 12ccs off the 6xs ill be around 9.2-1 compression if i remember right using a head gasket he recommends, the summit grind is a bit more modern then the the old 068 but i know what your saying,
what gets me is in jim hands books he uses relativley large camshafts like here ill list a combo out of there i was thinking about doing they recommend 3.23-3.55 gearing and a 2700 stall

expected quarter mile mid 12s to 13s depending on gearing,head porting, rocker arm ratio, carb/intake. basically a stock rebuilt 400 with a crower cam 229/239 duration at .050 480/501 lift with 1.5 rockers, 108 lsa, pontiac heads ported to flow 240cfm/200cfm @ 600
doesnt that seem like alot of cam for a pontiac 400? is that what its gonna take to run 13s?

300 horsepower just sounds so little at the flywheel,thats what turned me off about that build the torque sounds awesome though it was 400 lbs at like 3300 rpm yea i watched that i wrote everything down they used a howards cam with 214/224 duration, but i do have a 1978 400 4 spd thats all stock and it pulls really good for being 220hp id say it be a low 15 second machine all stock and smogged out
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Old 09-15-2009, 08:54 AM
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sounds like a good cam (229/239) for a 4 speed, 3.23 gear, 400cid combo. and yes, 9 to 9.5:1 cr will also be a good match.

what do the heads flow at 0.500"? this will be a good number to have sense the cam lifts to around .500" (not 0.600)

bowl smoothing (under the valve) is easy hp. smooth the transition between the valve seat and port for easy flow increase. This is the low hanging fruit in the head porting world.

1/4 mile times depend greatly on traction and gearing. Mid 12's to 13's can be run with trap speeds as low as 100 mph and as high as 120.

a 3800 pound car will need 300hp to run 100 mph in the 1/4 mile and 510hp to run 120 mph. With good traction, a 300hp car can run a lower et than a 500hp car with bad traction.

limited slip differential, sticky tires, low gears, stiff rear springs and soft fronts springs will allow for good traction and low ets.

It would be hard for me to build a 400 when a 455 is the same size block.
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Old 09-15-2009, 09:27 AM
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oh this one isnt a 4spd its a auto i was just saying i have a 78 4spd thats alright for being bone stock, well the light porting butler performance offers will flow about 240-250 cfm they say but they dont say at .500 or .600 but its safe to say at least 220-230 at 500 lift then, compared to stock they flow 163 at .500,

yea if i had a 455 itd be being built but i got the 400 so thats the one getting built hah, im trying to keep on a real cheap budget here so buying a 455 is out of the question would cost more then i plan on spending on my whole 400 probably hah and itd still have to be rebuilt, and i gotta justify spending the 2 grand or so on the rebuild by having it be able to roast the tires from a dead stock without the brake and kissing the 13s
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Old 09-15-2009, 09:47 AM
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sorry, missed the stall comment (2700 stall).

cam maybe a little on the big side. I would drop one cam size. say, knock off 6 to 8 degrees.

163 cfm is really bad. this will limit hp to 320hp. getting ported heads is a good idea.

what carb are you planning to use?

good point on the 455 versus 400 budget. good luck with your build.
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Old 09-15-2009, 09:51 AM
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its got a edlebrock carb on there right now not sure what cfm probabaly a 600 or 750, but a carb is a cheap and easy thing to change its probabaly shot anyway, yea the head porting i think will make a big difference theres some videos out there and i have a book on porting 6x heads i might just give it a try i got a bunch of 6x heads and 400 so it might be a good skill to attempt to learn,
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Old 09-15-2009, 10:12 AM
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I recently did a similar build for a customer, or the lower end at least.
I think he must have read a pontiac performance magazine or something prior to bringing the thing to me, because he was dead set on needing 9.5:1 compression. To accomplish that, I zero decked the block (can't remember how much now, but used basic silvolite pistons), and the heads on these pontiacs are just begging to be milled a large amount, it almost appears from the factory that they are built with that in mind. At any rate, I believe it took about .080" off the heads to get the desired CC's and compression ratio, and that should not be a problem on these durable 6x heads.
He was going to port his own heads and pick his cam, but I did a basic lower end build, fresh crank, bearings, cam bearings, and about the only real upgrade was to put ARP bolts in the rods and resize them.
It's in the same car as yours, and he's quite happy with it now. Runs on premium pump gas and has more power than he can hook up on DOT tires and leaf springs.
I would HIGHLY recommend the ARP bolts on the rods, and keep the RPM's below 6000 if you're planning a similar build.
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Old 09-15-2009, 10:22 AM
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If you pursue porting here are thing I'velearned-

Get yoursel a cheap grinder from Harbor Freight and a rheostat, its a cheap combo that will easily get you through all the heads an amateur will get to.

Buy your other supplies from Cylinder Head Abrasives. They carry top notch stuff at great prices- chinese crap off ebay is cheaper but doesn't come close ot the quality.

If you only buy one carbide burr make it a 3/8 double cut tree with a round nose on a 4" shank- you can take care of a LOT with that one carbide bit. Use the 6" shank white stones from CHA for finishing your intake runners and as middle work on your exhaust runners. Plan on using about 2 per head. Polish your exhaust up to a near mirror shine and just finish your intake runners with 60 grit cartridge rolls (1/2" will get you through 90% of that).

The porting kits are nice, but don't really give you enough of what you need, you're best off buying your supplies on your own terms, unless you get a great deal on a kit.
And crossbuffs look neat- and that's about all they do.

Always wear safety glasses, and a paper dust mask is nice for when you get the cartride rolls out. Make sure you have a good lighting source, a solid work bench, and a comfortable chair- you'll be there for 20 hours.
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Old 09-15-2009, 10:55 AM
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yea its gonna get arp bolts for sure and most likely 5140 forged rods since there a cheap 240 dollar upgrade and itll cost 100 at least to recondition the factory rods so it only makes sense, the car will never go past 6000 for sure depending on what cam i get id bet itll never see 5800, i got lots of harbor frieght grinders and stuff in the garage already but ill need to buy the stuff you suggested, well im 19 and im laid off from the railroad so i got nothing but time.

plaintoast how much did you charge to do the bottom end??? im curious how much its gonnna run me didnt bring the engine to the machine shop yet

anyone use the xe268 or xe274 in a pontiac 400?? im playing around with camquest just wondering if anyone has real world experience with those cams or similar cams in the 400
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Old 09-15-2009, 11:15 AM
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I believe the customers bill on that one was about $1800.
That was hot tank, magnafluxing, boring and honing, decking
the block, installing cam bearings, freshly turned crank, ARP rod bolts
and all the rod work, new pistons, rings, gasket set, oil pump, timing set and
heavily milling the heads, as well as assembling to that point. I can't guarantee the prices will be the same but shouldn't be too far off since you are fairly close to me. One thing I forgot to mention, those heads have non-adjustable rockers, so you will either need to convert them, or get the correct length pushrods for it once you have the cam and lifters in. My memory isn't always the best, but it seems to me this guy found some -.094" pushrods and that worked out perfectly for him. Kind of an odd size, + and - .100" is more normal and should work too.
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Old 09-15-2009, 07:57 PM
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Okay after reading the above posts since you have Jim Hands book read it throughly. The 5140's are a better choice than trying to rework the stock rods. Also use forged pistons (flat tops) and zero deck the block 9.5:1 is not too much compression for pump gas on Pontiac's and very doable. First you need to determine if you have 6X-8 or 6X-4 heads. If you have the 8's then first you need to determine whether they are for a 400 or a 455 as the chamber sizes are different. If they are 4's then they should be 92cc's and can be taken to the desired chamber size of 85cc's by milling only around .040. Also if you read closely what Jim says about camshaft selection pay close attention to how Jim tells about how lobe separation has an effect on dynamic compression and how that varies from static compression. Also ditch the Performer intake and Edelbrock carb in favor of a stock 68-71 iron intake and Q-jet carb. Separate the water crossover from the intake to aid in correct port alignment with the heads. Porting the heads will help in overall power and torque well beyond the bogus show on Hot Rod TV. While alot of people prefer the Comp XE grinds contact Bullet Cams for a recommendation on a cam, either off the shelf or have them grind you one of their Ultradynes. Also work your distributor to where you achive total timing of around 34-36 degrees all in by around 2600rpm. As far a converter go by the camshaft recommendation and use headers with a primary tube diameter of 1 3/4 inches and I would recommend a Pypes system of 2 1/2 inch with either Walker Dynamax Turbos or a set of Pypes Race Pros. And there is nothing wrong with a factory 068 cam, still one of the finest cams there is and will pull very well to 5200 and will work very well with your 3.23 gears.
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Old 09-16-2009, 08:13 AM
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also, use oil additive with any flat tappet cam.

www.zddplus.com
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Old 09-16-2009, 08:36 AM
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C10454 that is not necessary if you do a break in using Shell Rotella as it has the additives that is missing from other oils today, with the exception of Valvoline Racing oil which also the additives.
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