Is that the numbers matching block for the car? If so I would hands down say go back with the 400. Numbers matching cars are getting fewer every day. A stock 70 made 350hp and 445 ft lbs of torque.

Probably a little more information would make answering the question a little easier. Such as what is your intent for the car daily driver? weekend cruiser? are you going to keep it forever? do you plan on selling it?

If you plan on selling it the 400 would the way to go because it will have more appeal and bring more money especially if numbers matching. If it is numbers matching and you decided not to go back stock be sure to keep all of the parts because someone else someday may want to return it back to stock.

The most important thing to remember is that it is YOUR car so do what makes YOU happy. Enjoy the car. :cheers

 

Of course, it's your car, your cash, and you're the only one who gets to make the decision on how you spend it.

Having said that, though.... PLEASE don't put that "Chevy" motor in it! :willy:

For your perusal, here is a link to the dyno sheet for my YS 400 that I built for my 69 GTO. These are real-world results,

In the interest of full disclosure, due to a 0.035 overbore and a 4.250 stroke crank, it's no longer a 400 - it's now a 461. Please especially notice the torque numbers and the rpm where they occurred. I built this engine myself using readily available parts, from a plan that I put together with the assistance of Jim Lehart at Central Virginia Machine Services.

Depending on how much you want to invest (on a set of aluminum heads, for instance) you can easily build your 400 to be even quite a bit stronger than mine. Jim is a great source for helping you put together a plan to meet your goals. I'd also be willing to share my parts list with you.

Bear

 

I can't vouch for the dependability and reliability of the LSX....but I can for the 400. My '67 YS code 400 has 243,000 miles on it and is going strong. I rebuilt it at 173,000, but actually it only needed a timing chain and valve job.I've driven this car (in my avatar) cross-country numerous times, with good economy and reliablility. It always starts, runs well, and gets me there...and I've put over 120,000 miles on it myself. What is your definition of reliable?? Check out the other forums....there's one guy running a 2 bolt main 400 block with splayed caps added who's been using it for 3 years at the track....1600 HP. Many, many more are building cost-effective 440 or 461 inchers out of these engines using readily available parts. Fun to drive, and wheel-lifting power. The '67-'72 Pontiac blocks are a high nickel content block, and are rugged as heck. Built right, they will run STRONG. Why downgrade to a "better" motor?

 

Bear, thanks for posting. There it is on the Dyno sheet. Real PONTIAC power for a Pontiac!!

 

Thanks for your posts and video. I gotta get the 400 checked out and make sure its not cracked or anything from setting. Not sure how longs its been setting and if it ever had water freeze in it.

 

You have the number matching engine for your car, that's a no brainer.. 10 years from now most muscle cars will be converted over to LS motors or later motors, original motors will become less common. Keep this one number matching, if you want to put a LS in something, do it in the Lemans as your next project.

 

Looks like Im gonna go 400! Might try to put a fuel injection setup on it or something. Not sure but 400 it is.

 

You have chosen wisely, Grasshopper.....

Let me make a couple recommendations to you, first, these two books:
"How to Build a Max Performance Pontiac V8"
"How to Rebuild and Modify Rochester Quadrajet Carburetors"

And also this shop:
Jim Lehart - Central Virginia Machine Services.

The first book, despite the title, is really more about building strong STREET motors instead of "max performance" race motors, but it's still the best all-inclusive reference out there. The information in it is a little dated now. That's why I recommended Jim Lehart. He's the guy who actually wrote the section in that book about 'building your short block', and he's up to date on all the current thinking about building very strong Pontiac engines using the parts and technology that are available today, and not around when that book was first written. Dave Wilcox, one of *the* best head porters in the business also works out of Jim's shop. If you want to get everything out of your heads that's there to be gotten, Dave's your man to do it.

Finally, in case you didn't already know about them, there are a couple more forums you might want to check out. I'm listing them in order of my preference as far as getting good, reliable information:
Pontiac Street Performance
Pontiac Zone
Performance Years

The first is more oriented towards building street engines. The second is more towards building all-out race engines. You'll find many of the same people on all three forums, including Jim Lehart (who usually goes by the moniker "Mr. PBody"), and Cliff Ruggles. The last forum is the largest and most active, but they also sell the most advertising and have their own line of restoration parts and supplies so always remember to filter any recommendations you get through that awareness. On any forum you'll run into people who are very opinionated and can be a little closed-minded about anything different from their own ideas ---- just like real life. Always filter everything you hear through your own good sense, and if you get into a topic where you feel like you "don't know enough" don't be afraid to aske people explain the 'why' to you and spend some time on self-education. After awhile you'll start to get a feeling for who you can trust and who's just trying to either blow smoke or live vicariously by telling you how to spend YOUR money. There are some folks who have "history" between them that's not always out in the open, too, and sometimes that leads to some bashing that may or may not have any basis in reality. When you see someone bashing someone else, take that into consideration. I guess what I'm trying to say, is don't put your money into anything until it makes sense to you and you've got a reasonable expectation of how it's going to turn out.

One last recommendation. When I started planning my 461 I licensed a copy of Performance Trends Engine Analyzer. I found it to be a valuable tool for comparing different options (cams, heads, intake, carb, headers, etc.) to compare the relative effect they'd have. It can be a little daunting to get accurate measurements for input into the program, but the effort pays off. In my case, the actual dyno sheet tracked very closely to the program's predictions but I look at that as 'gravy'. The real value for me was answering questions like, "will this cam be better than that cam?", "will this cam/compression ratio get me too close to detonation?", "what size header tubes will work the best with this cam?", "where's peak torque going to be with this combination and what stall rpm converter will I need to take advantage of it?", etc.

Have fun!!!

Bear

 

10 years from now, our landscape will look like a scene out of "Mad Max" and "Road Warrior". The North Koreans will have nuked our defenseless A$$ into oblivion, and we'll be running ANYTHING to get from one bunker to the next!!! Seriously, with more support than ever to keep these cars on the road, I doubt "most" will be converted to late model power. I know mine never will! Gotta go...I'm running low on dogfood.....

 

Well I am definitely the minority here, putting the LS1 motor into the 65. but the original motor was not an option. plus I love the looks on peoples faces when they ask to see under the hood

 

Hey crusty, it's your money and your car. As long as you're happy with the result then you don't owe anyone any explanations. :cool

Bear

 

I'm not offending anyones LS build, I would LOVE an LS in my car. I was saying he has the right engine for the car.. It's an apples/oranges debate, original or restomod. I love both, but with the trend to restomod, many will do it. Orbit is doing a frame off on a real 70 GTO and has the original motor, and has a 71 Lemans, so time for 2 projects, gotta think ahead! Free style the Lemans and original the 70 GTO
Geeteeohhguy, I hate that you think the world is ending... If it is I'm building the mad max car and I will be ready to go.. Hell, I'd build the mad max car if the world wasn't ending, that car is cool.:cheers

 

Well I think I am gonna retain the number matching 400 as long as it is buildable. Then I might just take all the parts I have left over and build a bondo bucket out of that and restomod it.

 

too bad you cant see #s below 3100. i would like to see how early it is making at least 400lb-ft. cool engine, how much money do you think it would take to duplicate it?

 

I've got all the receipts so I could add it up, but I may not want to know!

The one component that would be difficult to duplicate exactly would be the heads, because they are real 69 GTO round port Ram Air IV's. I bought them many years ago, back before all the aluminum heads came out, and I really wanted to use them because of the 'cool' factor. In terms of power though, a good set of aluminum Edelbrocks or even the D-ports would probably make more torque/power. I really had to jump through some hoops to get the compression down to 9.46:1 with these heads.

Here's a parts list:
Eagle cast crank (3" main, 4.250 stroke, "BBC" rod journal size) and Eagle h-beam forged steel rods, 6.800" length
KB/ICON IC-967 forged pistons, additional dish cut for a total dish volume of 22 cc's.
Comp Cams solid roller cam. 236/242 intake/exhaust duration at .050, .377/.381 lobe lift, 110 degree LSA, installed at 106 degrees intake centerline
Pontiac #722 heads, 72cc chambers, heat riser passages plugged with aluminum, mild port job (282 cfm intake flow / 166 cfm exhaust flow at .600 valve lift)
Scorpion 1.65:1 roller rockers
Comp Cams "Endurex" solid roller lifters, pushrods, titanium retainers, superlocks, and rocker stud girdle.
Comp Cams billet 9-way adjustable timing set (cam installed 4 degrees advanced as per Comp Cams specs)
Howards Cams double valve springs (1.9" installed height, 175# seat pressure, 440# pressure at .700 lift)
Melling high pressure oil pump, Milodon main stud kit and windage tray, Nitemare performance oil pump plate, cam plate, oil pump drive shaft, and rear main seal
Milodon high flow alumimum water pump
Proform HEI ignition
Factory cast iron intake, port matched to gaskets and heads, water crossover cut and separated from the intake.
Service replacement 455 SD Quadrajet
Doug Thorley D-567 headers
Cometic head gaskets, .075 compressed thickness
RobbMc mechanical fuel pump and mini starter
SFI-rated harmonic balancer and flex plate
Milodon 'kick out' oil pan
I also went to extra effort to retain the use of the factory valve covers even though I'm running roller rockers and a stud girdle. I'm using some tall spacers, painted engine color. My goal was to be able to tell the casual observer, "yeah, it's the 400 that came in the car - nothing special" and get away with it ----- until they hear it run.
They really aren't that noticeable unless you're really paying attention.

The additional piston dish and the thicker head gaskets were compromises I had to make in order to reach the compression ratio I needed for 93 octane. I also didn't 'zero deck' the block because I really needed that extra bit of clearance volume that the .011 deck height gave me. These changes definitely have a negative effect on piston/head "quench" and thus combustion efficiency and flame travel --- but I had to do it to make sure I don't have detonation problems. Even with that, the motor still seems to be happiest at 32 degrees total advance so maybe I didn't hurt combustion efficiency too bad.

Running 87 cc chambers and flat tops would almost assuredly make a better running engine than mine, because you'd have both good quench and reasonable compression.

As far as machine work, I had the block align honed to straighten the main bores, bored (with a torque plate) to plus .035 for the pistons, "just enough" cut off the decks and heads to make sure they were square and flat, and a good 3-angle valve job done on the heads. I installed oil-restrictors in the lifter bores myself. Since I'm running solids, I don't need much oil to the lifters so that oil is better used if redirected to the crank and rods.

I don't know the torque output below 3100, but Engine Analyzer, the program I used to help design the motor, estimates 409 lb.ft. at 2300 rpm, 452 lb. ft. at 2700 rpm. That's probably not far off.

Bear

 

Nice build there Bear. Execellent example of pure Pontiac Power. Op, you could replicate his strong shortblock (with a little tamer cam, lol) and run some mild ported D-port heads and have a nice stout torque motor.

 

2300! :cool

that engine is definitely a testimony for the stock intake and q-jet. whats the reason for cutting off the water crossover?

 

If you cut the crossover away from the intake, then you can remove and re-install the intake without having to open up the cooling system. I still USE the crossover, it's just no longer attached to the intake.

I've got another intake manifold I might want to play with from time to time. I dyno tested it too, and although it didn't make as much torque down low as the factory one did, nor did it make quite a much peak power, the torque above 5600 didn't fall off quite as sharply so the power "held on" longer at higher RPM's. If I can't get this thing to hook, then I might try the other manifold to soften up the low end a little bit and run slightly higher rpm to see if that results in better et's.

Bear