I am in the planning stages for my 400 HO build. I don't need or want a fire-breather, but a good running, powerful, fairly stock engine. I have a Q-Jet available, and the stock intake, but I also have an Edlebrock intake and carb - I think the Performer series - also available. I was thinking of a mild cam upgrade also, as my wife likes a rough idle . What upgrades are recommended besides the hardened valve seat inserts? Do the valves need to be replaced also? What rods and rings? Thanks!

Does the engine need a complete rebuild? Stock intack and Q-Jet are your best carbs for the car unless you go high end new tech.

068 Cam is stock with a 400 HO. You have to look at adjusting your cam for pumped gas. Find a Pontiac engine builder. The guys can
recommend someone close to you.

Need to plan what your intend to the car will be when your done.
Street rod, Track racer, driver etc.

How much HP?
CAM?
tranny, Auto, Std?
rear end gears??

Recommendations will depend on several things. Need more info.

Like:

(1) Is your engine original numbers matching, and if so, do you wanna keep it that way, including the heads ?

(2) Or, is it OK if it just looks sort of original ?

(3) Aprox how many miles per year will it be driven ?

(4) What is your total budget for the entire engine build ?


A few options:

(1) If your engine is original numbers matching, I'd store it, for possible future resale of your car.

(2) But, if it is not original, I'd use the block for the rebuild. If you don't care about numbers matching, I'd go with 6x-4 heads, or 5c-4 heads, or even late '73 or '74 #46 heads. My choice would be the 6x-4 heads. If your budget will allow, I'd go with 2.11/1.66 one piece stainless valves. If you go with the larger 1.77 exhaust valves, it is said that you need hardened valve seat inserts.

(3) The cheapest decent pistons are the Speed Pro L2262F forged pistons, in the oversize you need. The Ebay price is about $320. Less than $400 with rings.

(4) Better pistons are the Auto Tec brand. They are lighter, use the modern, thinner ring sets, will produce slightly more compression. But, I think one of the biggest advantages is the fact that they will relocate the pin holes, in order to position the top of the pistons closer to the block deck. This will reduce machine shop costs, by requiring less material to be machined off the decks, in order to achieve the desired near zero deck height. Total shipped price is a little over $500. Rings not included.

(5) Most nowadays don't recommend using the 40+ year old cast rods. The cheapest forged Pontiac rods are the RPM 5140 I-beams. But, for only about $100 more, the RPM H-beams are a much better value. They come in either floating or press-pin versions, for $400 shipped. Some say it costs over $200 to rebuild cast rods, with new ARP bolts. I think the RPM H-beams are the best rod value.

(6) The compression ratio for this combo will be somewhere in the middle 8's. So, a Voodoo 262 cam may be about the best cam choice, for what you have described.

http://www.lunatipower.com/Product.aspx?id=1775

(7) The cheapest decent lifters I know of are the $59 lifters sold by Paul Spotts, on Ebay.

(8) Crower sells some "Cam Saver" lifters, which supply extra oil to the cam lobes. Some Pontiac guys recommend ONLY Hylift Johnson "R" lifters.

(9) 3 valve spring possibilities are: either of the springs sold on Ebay by Paul Spotts, or Comp Cams 988-16 springs, or Crower 68404-16. The stock replacement Spotts springs are the cheapest. The Crower springs are the highest. If the engine won't go past 5000rpm, the cheaper Spotts springs or the CC 988-16 springs may be OK. But, if you plan to rev over 5000 rpm often, the stronger Spotts or the Crower springs will be better.

(10) If you wanna go with some of the early, big valve heads, like #16, #62, #48, #12, or #13, most recommend hardened seats, at least on the exhausts. Might also need dish pistons, to reduce compression, for pump gas use, unless you wanna mix in some race gas or a good octane booster, like Torco Accelerator.

Well hey, there are a LOT of different recipes for a Pontiac street engine, These are just a few ideas.

Thanks Gus. My car is similar to yours, but is a 67 with the Rally wheels - same color. It is also a very nice car, and I just want to get it back to about the original HP - 325 or so, with a little rougher idle. Mainly a Sunday "Lets go get ice cream!" kind of car, and the occasional show. It is show worthy... The replacement engine does need to be gone through, as it has been sitting for 15 years on my buddy's engine stand and only turns over for about 600 degrees of rotation - then it stops dead. Only a couple of valves move, so I imagine a timing gear issue and a valve is hitting a piston. I haven't taken it apart, so I am not sure yet if I need to replace the pistons, but probably. I've got a 4 speed in it with a .355 posi rear end.

"...The replacement engine does need to be gone through..."


Need to make a positive ID on the block & heads.

(1) What is the casting number of the block ?

(2) What heads are on it ? That's the number cast over the center exhaust ports.

The most common 400 block around nowadays is the "557" block. If the block you mentioned has a casting number which ends with 557, I wouldn't spend a penny rebuilding it. Those blocks have weak main webs which have resulted in many web failures. Some brag about how much power they have made with these blocks, without any problems. But, others had had failures in near stock rebuilds. No reason to take a chance IMO.

Most agree that the 481988 block is the best, commonly available, all around choice for a stock block engine build. They have the thicker main webs, and have 5 motor mount bolt holes, so that they can be used in most any Pontiac chassis. They were used in '71 thru early '75 models.

Thanks oldskool.

YT engine code, casting number 9786133 (no transfer lug, 3 freeze plugs), and 670 heads. From everything I can find, it's a 1967 325 HP 400, 10.75:1 compression ratio, 2.11 intake valves and 1.77 exhaust valves. The YT code is the correct code for the car (it was originally an automatic), but unfortunately it is not the original engine. I am planning on only putting ~2000 miles per year, but am planning on putting in the hardened seats anyway. My machinist is working cheap, as he owes me... I plan on replacing the rods, but I don't want to back down to the mid 8's for the compression ratio. Is 91 octane pump gas OK with the 10.75:1 or will I run into detonation? There is 110 available at the pump in my area due to the close proximity to Road America, but the cost is triple the 91 octane. Like I said, I don't need it to be fire-breather, but I want it to sound good, and perform well on the street. Mama doesn't let me get into the throttle much, but she's not always with me .

Will definitely need dish pistons in order to get by with 91 octane.

The cheapest dish pistons will probably be having the machine shop machine a dish in the SP L2262F pistons.

Next cheapest will probably be Icon brand dish pistons, bought from CNC-Motorsports. Their price is $500 + shipping.

The next best price, and my choice, are the Auto Tec brand pistons. I think they charge around $150 to cut the dish. But again, you can get a custom pin height, in order to reduce the amount needed to be machined off the block decks. Will only need enuff cut to square up the decks.Then order the pin height you need to achieve zero or near zero deck height.

With zero deck height, you can use the thicker & cheaper 8518PT head gaskets, and have only a .045 quench distance. Many say .035-.040 is better. The more expensive Fel Pro 1016 gaskets are only .039 thick. This will give a slightly smaller quench height, and raise the CR slightly.

I've read that the 670 heads are more detonation prone than the '68-up open chambered heads. So, it might be a good idea to build with no more than 9:1 CR, I think the chambers can be opened up some. But that adds to the cost of building the heads.

If you get the compression up between 9:1 & 9.5:1, you can use a cam with more adv duration.

The smallest cam I'd consider is a Summit 2801. A Summit 2802 will give you more idle lope & upper rpm power. The Lunati 10510312 & Crower 60916 fit between the 2801 & 2802. The biggest cam I'd consider is a Crower 60243. A Crane 283951 fits between the 2802 & 60243. Just barely above the 60243 is the Howard's 410051-14.

If you have the chambers opened up, you can probably use the Voodoo 262.

Some still prefer the 068 cam. But that cam has a smooth idle and just barely over .400 lift.

So back in the day, when the engine was new, with 10.75:1 compression ratio, the TEL in the fuel reduced the knock tendency that much? Reducing the quench area - I thought that was more an emissions reduction technique than anything. Does that effect the knock or performance also?

Yes.

Lower quench distance reduces chance of detonation, and improves performance.

Most Pontiac engines came with an .023 or more deck height. But, pump gas was much better back then.

The major emissions reduction items were unleaded gas & catalytic converters.

And, in the mid & late '70's there were lots of internal carb restrictions & calibrations designed to reduce emissions.

I think it was in '81 when the carb's fuel/air mixture began to be electronically controlled, for emissions purposes.

You can have the pushrod holes elongated to work with 1.65 rockers to go with that 068 camshaft. That should give you about .450 lift.

I have a .030 over 400 engine with 670 heads on it, TRW's replacement for stock flat top pistons and 460 lift. It runs very well and very strong, but it would never tolerate 91 octane. If you plan to use pump gas you may want to get larger chambered heads rather than machine the 670s (as they are still sought after and do run well.) As mentioned, if you do use the 670s and plan to use pump gas, get dished pistons. Or, if you don't drive it every day and you don't mind the mixing you can use octane booster. Mine runs exellent and has great throttle response with the high compression. I love it, and have no problems. I also use octane booster for way less $ than the racing fuel. However, I mix it exactly the same each time I fuel so I never have to change the timing.

Any thoughts on running E85? 105 octane at less than the cost of regular 87 octane no lead...

I'll start a new thread for this...

Keep is stock. I would recommend Butler performance for your parts. I sourced everything for my 400 HO and my 389 Tri-power engine from butler.

Agree with Gus68, keep it stock with maybe a nice medium sized cam. (Around 450 -460 lift or so with a bit of extra duration and about 112 separation.) Avoid all the mods by just running a consistent mix of octain booster. Check the head charts, 670s are one of the best heads for a moderate cam. Either way you go, would suggest hardened valve seats. IMHO
Best of luck!