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Discussion Starter · #1 ·
Hey,

I bought my 68 Gto about 10 years ago and it was in sad shape and I restored it back to factory paint and made is presentable. The car had its original 400 pulled out and I retrieved it with the purchase. I later discovered it had internal damage that was not repairable. The 400 that is in it was probably from a low horsepower car, I assume it’s around 200 hp (it has no get up). I have since then put disc brakes on the front and did suspension work up front. The car runs and drives pretty smooth now but I would like to get it up to snuff and have about 450ish HP. I was hoping to get a recipe to build it up to that. I am mildly experienced with working on cars and I have lots of resources to help along the way. I will consult a local machine shop for the block. I have low compression in cylinder #6 so I assume I need a hone at the very least. I have the stock heads that came off the original motor but that is it. The seller gave me a camshaft and lifters but they don’t suggest what they are on the box. I appreciate any help I can get with the car. She looks pretty now but she does not have the vroom vroom that I know she should. I know I won’t know the shape of the block or what year it was manufactured until I pull it and read the casting codes. I’d like to keep the build under 4K, doing the work besides machining myself I hope that is feasible. Thanks.
 

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Hey,

I bought my 68 Gto about 10 years ago and it was in sad shape and I restored it back to factory paint and made is presentable. The car had its original 400 pulled out and I retrieved it with the purchase. I later discovered it had internal damage that was not repairable. The 400 that is in it was probably from a low horsepower car, I assume it’s around 200 hp (it has no get up). I have since then put disc brakes on the front and did suspension work up front. The car runs and drives pretty smooth now but I would like to get it up to snuff and have about 450ish HP. I was hoping to get a recipe to build it up to that. I am mildly experienced with working on cars and I have lots of resources to help along the way. I will consult a local machine shop for the block. I have low compression in cylinder #6 so I assume I need a hone at the very least. I have the stock heads that came off the original motor but that is it. The seller gave me a camshaft and lifters but they don’t suggest what they are on the box. I appreciate any help I can get with the car. She looks pretty now but she does not have the vroom vroom that I know she should. I know I won’t know the shape of the block or what year it was manufactured until I pull it and read the casting codes. I’d like to keep the build under 4K, doing the work besides machining myself I hope that is feasible. Thanks.

You will be hard pressed to get 450 HP for under 4K - think closer to 6K.

To keep it closer to 4K, just do a mild/stock rebuild. The heads are important. If you have a low HP set of heads with press-in studs and small valves, forget any big HP numbers. So knowing what heads you have can dictate some of the HP level. Camshaft selection is next, BUT, playing into this will be compression ratio. Do you want to run pump gas or are planning to run race gas? If you gotta have that kind of HP, you are looking at a stroker kit and aluminum heads - that's 4K right there.

That said, plenty of engine builds posted here if you use the search feature above. More info is needed in general. With 450HP, I'd suggest upgrades on the trans and the 10-bolt may have to go and a 12-bolt or 9" Ford swapped in. So bigger HP means heavier drivetrain components as well.

Pontiac engines are not inexpensive to rebuild - Chevies are. (y)
 

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Discussion Starter · #3 ·
I’d like to run it on pump gas. Would a stroker kit be something worth looking into? I was planning on doing something with the rear end. It’s a single trac and I don’t know the gear ratio. I assume it has a shift kit in it because it Chirps the rear passenger tire on WOT. If I could afford a first gen camero I would be a Chevy guy. I have a 79 trans am and that’s another disaster on my hands.
 

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Stroker kits are great solutions for the price, if you have the price. Turning a 400 into a 461 is a great way to really wake one up. I did that to my numbers-matching '69 and it's now an honest 11-second car at the track and still drivable "anywhere". It can get expensive and snowball on you though, because once you pump up the torque you'll start finding every other weak link - probably starting with the factory 10 bolt rear. I anticipated all that and did my best to build the whole car including better cooling, better oiling, a Moser 9" rear, 4-wheel disc brakes powered by a hydroboost system, much higher capacity alternator (to drive those big electric cooling fans), and greatly strengthened TH400. It sure wasn't cheap, but it sure is fun.


Bear
 

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I'm building exactly what you're talking about now. I agree with Jim. No way to make 450 HP for $4k. Even 6 may be ambitious right now. I ordered all my parts last summer and the prices have gone way up since last year. If you have a low hp year engine (4X stamped on the heads?) the heads need to go or will need some port work. My recommendation would be to try and spread out the cost. If the car is running now, keep it that way until you have everything lined up to do the build. Figure it's mid April now. If you start taking the engine apart now, you won't be back on the road before the snow flies next winter. Better to have an under powered GTO on the road than one that's up on stands all summer.

Take time and do your homework. Make sure you have the funds to build exactly what you want. This is going to be an expensive project either way, so why not make it exactly how you want it.
 

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Discussion Starter · #7 ·
That’s a great point!
I might look into tackling the rear end this summer. I’ll look into 12 bolt 3.73 gears. I had them in my last car and it seemed like a nice balance of street and highway capability. I’ll post a pic and codes stamped on the stock heads that are in my dad’s basement later today.
 

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If you're not used to Pontiac torque, you may find that 3.73 is both too aggressive and unneeded. I have 3.50's in my 9", and even those are a little much. 70 mph is clocking about 3200 rpm with the Nitro drag radials I run full time on the car. Unless it's on the track and I warm them up first, the car will still spin them all the way through 1st and 2nd gear on the asphalt the runs across the front of our property. This ain't no chevy you're dealing with ;)

Bear
 

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Discussion Starter · #9 ·
Haha it was a Chevy. This build is more or less inspired from my buddy that took me for a ride in his 70 GTO, bone stock besides a carb. The torque is what impressed me. One thing at a time; once I start considering parts I’ll check in with you all and get some insight If I’m on the right track. Thanks guys.
 

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There are affordable ways to build a 1hp per cubic inch old school engine. I know that you said 450hp, but if you can live with less than ideal highway rpms, you can make up the fun with numerically higher gears in the rear-end and, maybe, a higher stall convertor. I will be looking to put a different rear in my 67 during its upcoming build and considering the 3.55's to keep the tires from getting so wide that they look out of place. I don't want a tire smoker, but a good launch and use of power. Heck, the 3.36's may be where I land.

Most 1hp per cubic inch lower budget recipes call for these basics...

91-93 octane fuel to utilize a higher compression ratio by using the right head and piston combo,
headers and easy flowing exhaust,
poor-man's gasket matching/porting on the intake & heads, and
a street strip cam.

Note: Roller rockers are a nice affordable addition to the 1hp/ci build and a lack of belt driven accessories helps out when trying to get those last few horse out.

Most of the power, in my limited opinion, comes from the higher compression, but with that you need the in and out flows to cooperate to get the full benefit. Meaning the cam, intake, heads, and exhaust all need to be matched nicely.

With that said, surpassing the 1hp per cubic inch build with a larger cam, bigger carb, & aluminum heads usually means that your engine starts to get away from being steet-able and it's longevity suffers. Keeping mind I said an "affordable old school engine". With today's computer controlled engine technology, much more hp can be created and still remain pleasant to drive as a daily driver (or weekend cruiser).

The limiting factor is budget. The next logical step if funds can be stretched is to stroke it and bump up the head and intake (Like Jim said). This allows the 1hp per cube rule of thumb to be kept in tact, but is more money. Then EFI can be added to really get it up there....more money. At some point (which I will not find myself at - I'm just to old school), you might as well buy a wrecked high HP computer controlled vehicle and swap the drivetrain and go complete resto-mod....makes me cringe, but there are some fantastic examples of this out there.

I have built a few of these 1hp/cube motors and really like where they land. Fun to drive, not necessary a street drag racer, but affordable and on the more simple side. Did I actually get a hp/cube...I don't know, but they sound good, drive good, and don't self-destruct (usually - lol).
 

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Discussion Starter · #11 ·
I’m going to see what kind of funds I can set aside for the build this year. I was looking at the engine that is currently in my Gto and I’m having trouble identifying what size and year it is. The center of the head just has a “5” stamped on it and the front of the block has “180987 YC” and the back says “50055” I was researching Pontiac blocks and I thought a letter would be in front of the numbers suggesting the month followed by year of production. Any thoughts?
 

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I found myself needing a new motor for my '65 GTO when my nothing special 455 developed a rod knock the first summer I bought the car and couldn't believe the prices so kept hunting around and found the deal of a lifetime on Ebay for a Butler 461 that was dynoed but never installed from a guy who decided to go bigger. It all checked out with Butler and he had the build sheets and dyno info I was more than leery spending that much on Ebay but it had everything from carb to flywheel to MSD ignition to water pump even a stand for 7500.00 with 475 HP! So there out there just be cautious and try and see it in person, but sorry to say you're not getting 450 HP for under 7000.00 in a Pontiac but then again it's no Cheby. Here's one link I found and I'm trying to insert others but I'm better with cars than computers.
 

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Also the guys are right....450HP needs a good rear end, drive shaft, trans, suspension, tires, cooling, and seat belts! I have a 3:42 gear and wouldn't want any higher as I'm spinning 2500 rpm @ 60 mph with 28" tires but I have a 4 speed with a 2:99 first gear....Pontiac = torque (y)
 

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1971 GTO resto mod. Modified 428 HO, 4 sp (built by midwest muncie) Dana 60, 3.55 rear
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Goat,
Code YC was used many different years.. The 500557 were blocks used in the 70's either 400 or 455.. A few 350's also.
as for the heads having a "5" on the center port.. Could be a 5C which were 1975 heads. See below from the Wallace racing web site.

142218

Also,
this may help;
How to identify Pontiac engine blocks | Hagerty Media
 

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I’m going to see what kind of funds I can set aside for the build this year. I was looking at the engine that is currently in my Gto and I’m having trouble identifying what size and year it is. The center of the head just has a “5” stamped on it and the front of the block has “180987 YC” and the back says “50055” I was researching Pontiac blocks and I thought a letter would be in front of the numbers suggesting the month followed by year of production. Any thoughts?
If that is a 500557 cast block, end your 450HP goal right now. That is a late 1970's block and is a weak block - weak main caps/lower block mains. My be good up to 400HP, but even then, I would not invest a dime into it. HP ratings were low at that time, so Pontiac saved money by paring weight from the engine and this made it weak for any kind of high performance use. Pontiac recast the earlier blocks for the Trans-Am because these blocks did not hold up so well with the type of use these cars got.
 

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The 557 block was a 400 block, never a 455 or a 350 as was mentioned. No 350 or 455 blocks were cast with a number 500577
Jim is correct and I concur. Keep your build at or below 400 horse on the 557 block due to slightly weaker main saddles
Still will make a nice street motor and run on pump gas if you get your "recipie" together correctly.
Personally I would freshen it up, stock, and run a Q jet. use a comp cams extreme energy cam to help it along. It would run decent for cheap. You can take time and build a nastier engine then while still enjoying the car, then do a weekend swap once the killer power plant is hatched.
Which heads are on that thing?
 

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The 557 block was a 400 block, never a 455 or a 350 as was mentioned. No 350 or 455 blocks were cast with a number 500577
Jim is correct and I concur. Keep your build at or below 400 horse on the 557 block due to slightly weaker main saddles
Still will make a nice street motor and run on pump gas if you get your "recipie" together correctly.
Personally I would freshen it up, stock, and run a Q jet. use a comp cams extreme energy cam to help it along. It would run decent for cheap. You can take time and build a nastier engine then while still enjoying the car, then do a weekend swap once the killer power plant is hatched.
Which heads are on that thing?
Thanks for the correction LA.. I got ahead of myself.. what I meant and should have read before I posted is that code YC engines were 400, 455 and some 350's.. My bad.
 
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