# ??? 455 build???



## SWOOSH (Sep 20, 2008)

What is a good way to rebuild a 1972 Y4 455 ? Most hp! For the least money. Looking for atleast 425 hp.


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## JustAl (Mar 20, 2010)

I'll start but others will clime in, which is good. First to consider is the condition of the engine, a complete rebuild is probably in order. 425 HP is not too high a goal but rebuild details make all the difference. A good machinist with the ability to to do things right is the first step in the process. Lots of money has gone down the hole on work not done properly. That said, overbore with new pistons, reconditioned rods with good rod bolts, but if the money is there new forged rods is a good investment, Pontiac rods are the weakest link and of course new bearings. Balancing the assembly is a given. At some point looking into a complete rotating assembly from a major Pontiac rebuilder may be a good option, as sometimes the kit approach is cheaper in the long run, plus they are all new parts. Y4 code indicates a 220HP auto trans engine, low compression, not the best cylinder heads (if original) for higher performance, pressed in rocker arm studs and smaller valves. There are some decent iron heads that will give good performance and still yield compression ratios around 9.5:1 which is the limit with pump gas. If I recall 96 and 7k3 head codes have the bigger valves and don't breath too bad, both came off 400CI engine in the earlier 70's. Some 6X heads are also and option, with age all will require rebuild. Take a look at COMP Cams, they have several grinds that make good power with street manners. A good dual plane intake (Performer/RPM?) and a realistic carb and some ignition upgrades and you are on the way. Hey...where is MR. P. when we need him ??


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## SWOOSH (Sep 20, 2008)

Thanks Al, I just left an email at MrPbody's shop. Maybe he will come out from behind the curtain (OZ!). I have never built an engine. How much would this cost approx? Thanks for replying.


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## JustAl (Mar 20, 2010)

GOOD machine shop work isn't and shouldn't be cheap. If you deliver an engine stripped of internals expect to spend $700.00 for all the block prep and machining (ouch), your area might be cheaper. Now saying you go with the rotating assembly, which will run around $1400.00, add to this a cam,lifters, manifold, wow this ain't good. This isn't including the work needed on the cylinder heads. Building a good quality engine isn't cheap, but going your homework and using quality labor and parts will give you great results and peace of mind on a budget. Do it right the first time, you'll never regret it. For what it's worth I recently built a 455, now 467, Edelbrock heads/manifold, good rotating kit, Comp custom grind hydraulic roller cam, MSD ignition. I'm probaby into this for well over $9000.00 but I've spread it over a few years. Your goal of 425 HP should come much cheaper. These Pontiacs are torque happy engines, feels great on the street. Best of luck. I'm sure others will give some advice as well.


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## Mr. P-Body (Jan 20, 2011)

Swoosh,

Looked at my e-mails. Which one ARE you? - I get lots... 

What AL says is pretty accurate. The '72 has less-than-optimum cylinder heads, but is a decent block and crank. We can "work with it". 

Jim


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## SDGoat619 (Mar 21, 2011)

I have a XA block out of a 73 with 4x heads and edelbrock intake and carb, custom headers and dual exhaust. I have no clue as to the internals of the motor as this was the way I bought the car. The engine was rebuild by a pontiac guy so I have to trust that the rest would be in vain if not built from the ground up. What should I do next to the engine look for better heads ??


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## Mr. P-Body (Jan 20, 2011)

The '72 heads are missing the outboard bolt holes for the exhaust. Difficult to get good headers to seal up and "stay". Other than that, they're pretty much the same as all the other large chamber d-ports. 4X, 6X would both be good choices to start with. It's commonly misconceived the 6X-4 is "better". It simply has a 4 CC smaller chamber. On a 455, that is NOT a good thing. The 96 CCs (-8) are just "right" for a pump-gas friendly engine. Same is true of the 4Xs. I believe the 7H code is the most desired, but don't "quote" me. Measure the chambers.

As for the d-port iron heads, the main concern is chamber volume. Once porting begins, they "all look alike"...

Good connecting rods are paramount. The stock rods were inadequate when "new", and are now going on 40-plus years old. Verify the type of rods in there now.

A place "to start".

Jim


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## SWOOSH (Sep 20, 2008)

*#16 gto heads*

I am looking at a set of GTO heads.date code ko37.Supposed to be Ram Air. Would these be a good choice for the 72 455? What if it has to be bored .06 over? All these choices of heads is hard to decifer. I look at date codes and on some web sites it says one thing and something differant on another. Whew! This engine stuff is tuff!


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## thelarester (Dec 18, 2010)

Remember that if you use a pair of cylinder heads prior to 1970 on a post-1970 engine, the estimated compression will be above what is typically used for an engine running pump gas. This is the scenario that I was in with my 1972 455 YC block with 1968 "16" heads. With this configuration I needed to run a dished piston to bring the compression back down to under 9.5:1. My machinist recommended a Keith Black dished forged piston, which is what we went with. My build with all of the required machine work (and it needed everything!) totaled $4,500 for the longblock without any bolt-ons.


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## SWOOSH (Sep 20, 2008)

If I am reading all this right I need heads from the 70's,400 engine. Heads like 96,7k3,4x, 6x. What cc should I be looking for?


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## Thumpin455 (Feb 17, 2010)

I have a couple sets of 6X and a set of 7K3 out in York Ne. I might be coming back there first week of May, since I am running small chamber heads with lots of compression on E85 I dont need the low compression stuff. The difference between 8:1 and 9.5:1 is marginal for power, but makes a big difference in how much octane you need. If you want to run pump gas, dont worry about it so much, just use a set of 71 or later D ports from a 400 that are in good shape.

If you need them sooner I might be able to have a friend of mine pull them off next time he drives up from Geneva.


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## SWOOSH (Sep 20, 2008)

I am not in a hurry.I can wait. Will any of these heads give me the 9.5:1 Available octane? How much for the heads? Are they rebuilt already?


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## Thumpin455 (Feb 17, 2010)

Not rebuilt, they are still bolted to the engines, or sitting around in my dads shed. Send me a PM with your phone number and we can work things out when I get back.


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## SWOOSH (Sep 20, 2008)

Thanks! Thumpin.


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## Thumpin455 (Feb 17, 2010)

You're welcome, we will get you going with a fun engine, one way or another.


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## Instg8ter (Sep 28, 2010)

the 6x-4's should put you right around 9.5:1 on the 455


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## SWOOSH (Sep 20, 2008)

Is that enough for E85?


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