Pontiac 6X Heads, Advice Needed (pontiac masters)

[Buryingthesun]

I Have a Pontiac 400 block im going to start building, stamp code is 481988 (71-74 block) I have a set of 1968 6X-8 heads. With some forged internals, a nice bump stick and general Pontiac machine work should I be able to run pump gas and make 500hp? Should I do some elaborate porting on the 6X heads? have access to a highly advanced machine shop.

[Tom Welch]

The 6x-8 heads are low compression heads, they will work good on a 400 engine if prepped properly, larger exhaust valves, port work, etc. 500 hp is a pretty stout 400 cid pontiac motor. I would play to the pontiac engines strength, which is torque. 500 lb ft of torque is doable. 500 hp will be a challenge for a street engine. Contact Jim Butler, Kauffman racing, Central Virginia Machine Shop. These 3 have a solid reputation as far as I know concerning Pontiac engines.

[Takid455]

500 from a pontiac 400 will require some effort. Stock crank will be fine. upgrade rest. Can the heads and get a set of aluminum ones. By the time you get iron heads ported and what not, you wont be too far off cost wise from a set of aluminum units which will still flow better out of the box. You can run around 11:1 and be OK w/ 93 w/ AL heads. A nice roller cam set up and mid rise intake will be on the list. Keep in mind most BOP engines are torque motors vs high HP & 'low ' torque like chevys.

[tazzz25906112]

Hell I have stroker cranks, heads, blocks (400 & 455), early 70's carbs (570, 263, 564 etc) and they are all supposed to be worth the big money.... problem is there is ""No Money"" in a Pontiac motors after it is built... Don't waste time, build an LS.

If you think I'm joking,,,, $8,000 buys my fully dressed $22,000 455 stroked to 473 with CV-1 canted valve heads topped of with a full Jesel Roller shaft system, Holley fuel injection, March pullies and custom headers that fit 73 TA... Best part is you can hear it run too....

[72blackbird]

500 from a pontiac 400 will require some effort. Stock crank will be fine. upgrade rest. Can the heads and get a set of aluminum ones. By the time you get iron heads ported and what not, you wont be too far off cost wise from a set of aluminum units which will still flow better out of the box. You can run around 11:1 and be OK w/ 93 w/ AL heads. A nice roller cam set up and mid rise intake will be on the list. Keep in mind most BOP engines are torque motors vs high HP & 'low ' torque like chevys.

X2. Porting Pontiac iron heads is only worth the effort if you are concerned about an OEM appearance and want 60-80% of the performance you can get out of a set of aluminum heads. The cost of having iron heads ported professionally vs. getting a set of stock aluminum heads make aluminum heads a better option in terms performance results. But it is possible to reach 500 hp with ported 6x heads and a roller cam- HPP did a build a few years ago and did it with a carb. It's common to see over 500 hp with stock e-heads or KRE's with a HFT (hydraulic flat tappet cam) on a 461 or 455- go over to Performance years forum and you should be able to dig up a few recipes in the street section.

Geno

[MonzaRacer]

to the LSx booster, give it up. So many people talk about LSx making so much power, for cheap, well after having figured EVEN a stock LSx swap with a carb would cost a minimum of $5000 average. After buying ignition, carbed intake, CUSTOM headers, accessories etc.
After all that its STILL a stock LSx.
6X heads, swap in some swirl polished valves, basic polish job and 3 to 5 angle valve job and matched ports and a Pontiac can push well over 500 lb ft of torque, MUCH more useful over 500 HP. keep the cam choice reasonable and as said before, use forged rods and pistons and some good ARP fasteners. And it can be done much cheaper as a good old fashion HEI can light it off over $800 worth of MSD parts.
Headers can be added easily as general off the shelf units work fine on Pontiacs that arent built to RPM.
Regular aluminum intakes and your choice of carbs can be used, from Qjets to dominators.
It doesnt take cubic dollars to build a Poncho, but to install an LSx in most anything its not stock too,,,well cough up the cash.
Always rememebr for a Pontiac its low end air flow that makes the torque.

[Skip Fix]

Unless the 6x-8s are massively ported(close to breakthough) and you run more compression and cam you aren't going to make 500 HP with a 400.They have a hughe 98-101cc chamber-plug that into a compression ratio caclulator like at Wallace Racing. Unless you plan on boosting it then talk to Luhn Performance they have soem mild high HP boosted Pontiac motors.
NA stroker motor in the 400 block maybe. To get there you are going to need way more airflow out of some aftermarket alumiunum heads regardless.

[paul s.]

I like the website here! Pretty good information.

Interesting comments regarding people's views of the Pontiac engine. I see a couple of names here that know Pontiacs and they tend to give some pretty good information. I do believe I have something to add here even though I am getting here kinda late...

To the O.P., like some others have stated; ditch the 6x heads, they can be -8's or -4's, it doesn't matter. In my opinion, there are just too many battles to fight. Low compression and lack of airflow are performance KILLERS! The Pontiac 400 is an internal combustion engine just like any other out there with restrictive cylinder heads. Therefore it will respond to an increase in compression and airflow... just like any other tall deck engine with a long rod.

500hp out of a 400 with good cylinder heads is a piece of cake, generally speaking, it will just take a little more rpm than a 455 if built with conventional valvetrain parts and a moderate lift flat tappet or roller cam. An aggressive solid roller can really get it done at lower rpm but you're starting to hang it out there.

I also respectfully disagree on the amount of camshaft it will take to make that power. As far as duration and lift is concerned, if a 455 can make 500hp with E-heads and a 230 @.050 flat tappet, then a 400 can as well. Will it use the same I/C or lobe family? Hmm.

I would not try to cam a 400 with a 1.77 rod/ratio and a 3.75" stroke the EXACT same way I would a 1.57 rod ratio, 4.21" stroke engine since you KNOW it will take more rpm. There are so much more to cams than duration.

Pontiacs are only low rpm torque engines if you build them that way.

[pitts64]

I agree with Paul....

[Mr_Roboto]

Heads need to go. As said 500HP will be a real battle on them, and with a lot of compromises. Even the flow of the "high performance" variants of the Pontiac heads don't really flow that great much less the smog heads that people have come to like pretty much for their accessories (The screw in studs, hardened exhaust seats and 6 bolts for headers.) If I were going to start with production heads it would be earlier ones due to the fact they have combustion chambers you don't need pop ups to get optimum compression with.

I'm in a really interesting place though process wise with my 350 Pontiac, it just seems like a challenging engine to make power with unless you're tossing a bunch of aftermarket parts at it. Really thinking the pair of Grand National turbos I have hanging around is my best bet to making real power with it over all.

[dobie6982]

Mr. Roboto, Its a little tricky to get awesome power out of the 350. I do know you have to notch the cylinder walls to clear the valves from the E-heads. They also make a stroker kit for the 350. Try Jim Butler. I have many parts from him. A truly great guy to do business with.

[paul s.]

Heads need to go. As said 500HP will be a real battle on them, and with a lot of compromises. Even the flow of the "high performance" variants of the Pontiac heads don't really flow that great much less the smog heads that people have come to like pretty much for their accessories (The screw in studs, hardened exhaust seats and 6 bolts for headers.) If I were going to start with production heads it would be earlier ones due to the fact they have combustion chambers you don't need pop ups to get optimum compression with.

I'm in a really interesting place though process wise with my 350 Pontiac, it just seems like a challenging engine to make power with unless you're tossing a bunch of aftermarket parts at it. Really thinking the pair of Grand National turbos I have hanging around is my best bet to making real power with it over all.

How much power are you looking to make?

[Nicks67GTO]

A while back I thought of building a 400 with Kauffman heads and an RPM intake. I emailed SD performance for a recommendation. He told me with his 290cfm Kauffman heads, RPM intake, 230/[email protected] stump puller hydraulic roller and 10:1 compression I should expect a docile 525+ hp and 500+ ft lbs and a fat broad tq curve. Im still considering it over the larger 455 as that is plenty to get the job done and im sure it would MPG much much better. Like was said above.... an HEI can fire it off because you wont eclipse 6000 RPM you'll have a fat tq curve and youll have a traditional Pontiac engine which IMO is way cooler than any LSX.

[Nicks67GTO]

Hell I have stroker cranks, heads, blocks (400 & 455), early 70's carbs (570, 263, 564 etc) and they are all supposed to be worth the big money.... problem is there is ""No Money"" in a Pontiac motors after it is built... Don't waste time, build an LS.

If you think I'm joking,,,, $8,000 buys my fully dressed $22,000 455 stroked to 473 with CV-1 canted valve heads topped of with a full Jesel Roller shaft system, Holley fuel injection, March pullies and custom headers that fit 73 TA... Best part is you can hear it run too....

Im going to respectfully disagree. This is kind of an extreme example and lets be honest... theres no money is any used engine. I just sold a SBC that I had 7K into for $2200 bucks and it only had 10-15K miles on it. Have you offered that engine up on PY yet? I would think it would get snatched in a heartbeat @ $8000 expecially if it was built by a reputable shop. The CV1 setup alone is rediculously expensive and the Jesel rockers are big$ too. What does that engine make for power just out of curiosity? My rule of thumb is up to 600hp or so a Pontiac is about like building a BBC. Over that it gets pretty niche and very pricey and youre into aftermarket IA2 block territory. A standard 500-550hp street Poncho isnt that bad to build anymore and from everything ive seen theres nothing cheap about LSX anything. They are very nice setups but they are not "cheap" Im pretty sure the rule of thumb for the forged stroker 290cfm, old faithful hydraulic roller, 468" Pontiac setup is about 10K built and out the door from a good shop. Not that bad considering the streetability 14" vacum and 550hp and 600 ft lbs.

[Mr_Roboto]

How much power are you looking to make?

I would think on a 1971 engine like mine would be around 400hp fly with 10 psi and ligh mods. No not huge but that would probably be an intake/carb, turbo headers and valve springs.

Mr. Roboto, Its a little tricky to get awesome power out of the 350. I do know you have to notch the cylinder walls to clear the valves from the E-heads. They also make a stroker kit for the 350. Try Jim Butler. I have many parts from him. A truly great guy to do business with.

Nothing huge about the bore notching. Pontiac did the ho engines that way. Was more concerned about shooting an armasteel rod through the block wall spinning enough to even use ported irons on a 350. Everyone seems to think revving one of these is no go.

[72blackbird]

Funny you guys are talking about 350 Pontiacs- there's a thread on Performance Years forum debating over which engine would make for a stronger build, a 350P or a 400 using a lightweight 500557 400 block. Having both I can tell you the 350P is definitely the stronger block, and capable of supporting 600 hp with just the addition of ARP main studs to a 2-bolt block. Getting even close to that number is another story.

But getting 400 hp from a 350P is pretty straightforward these days- a set of stock KRE's ordered with slightly smaller valves than stock (2.07/1.66), a HFT in the 280/288 advertised degree range, headers and 2 1/2" exhaust, a decent set of forged rods, cast pistons w/ valve reliefs, and the stock crank (rotating assembly balanced of course) will do it- I would be surprised if it didn't make at least 425 hp. No stroker kit is needed, but if you run one it will also make around 400 hp with ported iron heads. Go with 290-300 cfm ported aluminum heads and I'll bet you'll see 450 hp. The chamfering the block will also definitely help unshroud the valves and provide critical valve-to-block clearance. And as far as revving goes, as long as your oil clearances are good, the assembly is balanced, you have forged rods, and heads that flow, you will not only be able to rev the 350P happily to 6500, but it will make 400+ hp well before then and make that characteristic big, broad Pontiac torque curve that we all love.

Geno

[Nicks67GTO]

Why anyone would build a 350 pontiac over a 400 pontiac is beyond me. 350p = smaller bore, same 3.75" stroke of a 400. Youre simply leaving power on the table with the small bore. If youre starting from scratch you can find good 400 blocks for 1-200 bucks and the cost will be the same either way. Im not leaving 50 cubes on the table for 100 bucks.

[paul s.]

I would think on a 1971 engine like mine would be around 400hp fly with 10 psi and ligh mods. No not huge but that would probably be an intake/carb, turbo headers and valve springs.



Nothing huge about the bore notching. Pontiac did the ho engines that way. Was more concerned about shooting an armasteel rod through the block wall spinning enough to even use ported irons on a 350. Everyone seems to think revving one of these is no go.

Were you specifically looking to add some boost because a 350P is just like any other internal combustion engine.... with a very small bore. I would consider some aftermarket aluminum heads (I'm fond of the Edelbrocks) for the increased comrpression ratio. 11:1 with that small bore would be a piece of cake on premium pump gas... 10.5 if you want to fudge it. Add a mild solid flat tappet or if you really want to let it eat put a mild roller in there. I agree with 'Blackbird, that would be a fun build but if the right guy was doing it, it wouldn't stop at 450hp.

BTW, it will have smaller, lighter pistons than any other modern pontiac out there, don't be afraid to rev it.

[paul s.]

Why anyone would build a 350 pontiac over a 400 pontiac is beyond me. 350p = smaller bore, same 3.75" stroke of a 400. Youre simply leaving power on the table with the small bore. If youre starting from scratch you can find good 400 blocks for 1-200 bucks and the cost will be the same either way. Im not leaving 50 cubes on the table for 100 bucks.

Generally speaking, for anything under 400hp, why not go smaller? I could see a smaller, higher reving engine for a guy with a 1st gen 'bird and a 6 speed. No it wouldn't be the fastest, but it would be fun.

I agree if MORE output is the goal then more cubes are always a good idea. But for a good running, SOMEWHAT fuel efficient cruiser.... I say go for it with a smaller engine.

[Mr_Roboto]

Were you specifically looking to add some boost because a 350P is just like any other internal combustion engine.... with a very small bore. I would consider some aftermarket aluminum heads (I'm fond of the Edelbrocks) for the increased comrpression ratio. 11:1 with that small bore would be a piece of cake on premium pump gas... 10.5 if you want to fudge it. Add a mild solid flat tappet or if you really want to let it eat put a mild roller in there. I agree with 'Blackbird, that would be a fun build but if the right guy was doing it, it wouldn't stop at 450hp.

BTW, it will have smaller, lighter pistons than any other modern pontiac out there, don't be afraid to rev it.

I was more referring to a stock long block 350P. To start with you're not really talking "shelf" pistons in a "good light weight forging." All I found was cast, not too surprised at that since it seems most "odd ball" engines are that way. This means you're on the hook for a few pistons if you ever need a replacement, and that you're looking at custom lead time too if you want forged not to mention the extra cost (which isn't horrid considering.) On the flip side though anyone ever rev the snot out of one of these using a set of cast slugs and decent rods?

One of the guys on Turbo Mustangs a long time ago was running low 11s/high 10s in a 3800lb car with a stock rebuild fully cast 455. It ran mid 10s using ARP rod bolts and prepped Armasteel rods. While I wouldn't expect the same results out of a 350, I wouldn't expect it to be a slouch either. If it puked it would simply be a matter of building a 400 up, throwing a slightly larger set of turbos on then letting it do what it does best except with better breathing and 50 more CID.