360 hp 455

[Jd 63]

I have this old 455 motor in my uncles bonneville it’s a yh block with 15 heads on it 

 is it worth pulling and putting in a trans am or would a 400 be the better choice 

  

Edited March 22, 2019 by Jd 63 (see edit history)

[padgett]

If that is a '70 455, they had weak cranks. Later ones (X code) are much better. 400 is better than any 455 before the 455HO.

[Pfeil]

I have a 70 YH 360 hp 455 that used to have 15 heads. I put it in a 69 LeMans that I built for Grand Touring in 1992. Grand touring is road racing, so we are talking about hammering the engine for long sustained operation. Originally the engine had roughly 75 K on it. When I pulled it apart the walls had to be cleaned up by .030 but the crank was perfect and all was needed was polishing. The high velocity #15 heads might have been a good performer in a Bonneville on the street, however I had a problem with detonation, so after many mixings of LL105 Aviation fuel I decided to deep port blend a set of 7K3 heads for lower compression for use with a RA4 intake. The 7K3's are big valve heads. Those heads really woke up that engine, all the while still using a 068 hydraulic cam.

With the bottom end checked for straightness a polished stock crank, rods, new flattops and a CRITICAL balance of the rotating assy. A melling 80 psi pump and a trap door oil pan for high G loads to keep the oil where it's supposed to be The engine has never given me any problems. Drag racing this car which has a stiff negative roll suspension I was very surprised with the results with this T400 with stock converter with a ten bolt 3.23 Safety track went 12.46 at 113mph at sea level. And the car weighs 4050, so you figure the hp. The track is where the funs begins. I like the shorter tracks where speed can't get way away  from you but I must say at 135mph and climbing all I feel it's telling me is faster - faster.

 Since I moved and at now at 5,000 feet I don't get the chance to see that kind of speed because there are no tracks close to my house and the places where there is a track are for most of the year in the 100 degree range.

YH 455 reliable? as reliable as you want to make it and treat it. FYI, special ordered the car new Dec 1968, Re-did the engine body and paint in 92, took 3rd place in POCI semi modified National Convention. I drive it about once a month for my doctor approved endorphin enhancer.

  

   

[Jd 63]

Nice car. 

 Thankyou very much for the info it was very helpful

[pont35cpe]

11 hours ago, padgett said:

If that is a '70 455, they had weak cranks. Later ones (X code) are much better. 400 is better than any 455 before the 455HO.

Pagett, where is this "X code" located? Thank you, Tom

[padgett]

Sorry brane fade. The "Z" code 455 engines were the interesting ones (455SD). 71-72 455HO was also a good engine. I agree the 70 can be built to be reliable (80 psi oil pump as on the SD, carefully inspected crank) but like the 67 Camaro SS350, the stock 70 455 Pontiac had excessive crank failures in service. Also AFAIR the 7K3 was a '72 400 head and only had three bolts holding the exhaust manifold to the head. I liked the 6 bolt 6X low compression, hardened seat head better but is personal choice.

[Xander Wildeisen]

My dads 1937 Terraplane had a 1970 455 Buick engine. Never raced, just a stock rebuild. No problems, except when you would stomp on the gas pedal. A popping/bang sound would come from the gas tank.  Because of the large amount of fuel leaving the gas tank, it caused the tank sides to flex inward due to the vacuum created in the tank from the high volume of gas being removed.

[Pfeil]

1 hour ago, padgett said:

Sorry brane fade. The "Z" code 455 engines were the interesting ones (455SD). 71-72 455HO was also a good engine. I agree the 70 can be built to be reliable (80 psi oil pump as on the SD, carefully inspected crank) but like the 67 Camaro SS350, the stock 70 455 Pontiac had excessive crank failures in service. Also AFAIR the 7K3 was a '72 400 head and only had three bolts holding the exhaust manifold to the head. I liked the 6 bolt 6X low compression, hardened seat head better but is personal choice.

 

 The 7K3 is a great head. They are easily modified in the home/ shop by drilling and tapping the blank bosses in the head for the rest of the exhaust studs ( even using Ra3 and 4 iron headers you are missing studs from the factory!.) RA3 can be made to accept five exhaust manifold bolts as I have done. Also 7K3's use 3/8  pressed in rocker studs which you extract and drill and tap for 7/16 rocker studs. These larger studs allow for the use of 1.65 rockers instead of the standard 1.50 rockers. You can use 1.65 rockers on a 3/8 bottle neck pressed in stud but I have heard they break easily.

 

The bottom end is what Padgett is really concerned about, but with a seasoned crank / block I wouldn't and didn't have a problem, also at a reasonable price there are New Pontiac Blocks/ cranks / heads out there being made. When I did my engine that availability wasn't there. Today I would use a New 428 crank for a better B/S ratio, but for the street a 455 crank works fine.

 Just remember Pontiac 455 or all REAL Pontiac V-8 engines are not Chevrolet Buick or Oldsmobile they are all different and respond to things differently. The 455 Pontiac is designed to move a heavy car to speed. It's design parameters of air flow ( with special note directed at 30 degree intakes instead of the usual 45 degree , camshafts,  cylinder bore and stroke ratio are to be a engine that runs best between 1200 Rpm to 5,200 Max rpm. spinning it faster doesn't make more h.p. but stresses it beyond it's ability to return to it's shape and waste h.p. That engine ( and all traditional Pontiac V-8's)  makes it's power in torque , not rpm. From 1500 to 4400 is where it's magic ( and it's 500+ ft. lbs. of torque live) is.

Remember ALL Real Pontiac engines are NOT BIG Blocks, nor are they small block, they are a MEDIUM block. Do you know the  general dimensions of the block never changed from 1955's 287, the bore spacing is the same. Realize this; the 455 connecting rod is the same length, journal diameter, piston pin height as a 287. All the engines with the same rod dimension from 287, 317, 347, 370, 389, 336, 326, 350 (  really a 355) 400, 421, 428 ( really a 427) and 455 ( really a 456) and the "Indy 4" Tempest 4 cylinder.  ( with the exception of the 301-265 which is a short deck version of the same) You show me any other GM engine family that has so much commonality that allowed it to last through three decades. When that engine died, Pontiac itself died.  

[Jd 63]

Thankyou so much for all the info

[Guest]

There's no replacement for displacement. 

[padgett]

To put in perspective, I would trust a Jim Butler 455 (or larger) to do whatever he said it would, with the proper prep (and a SD oil pump) they will last. However I also remember constant crank failures in 70 Bonnes when I was in Flint those years and a significant redesign in oiling for '71. I forget when they started using steel timing gears instead of phenolic ('72 ?) but was also an issue.

 

Yes they used the same block forever but that was not a plus, the narrow bore centers meant to achieve 455 (marketing move) it was necessary to  make it undersquare with a 4.15" bore and a 4.21" stroke. Meanwhile Buick came out with a new engine in the '60s and their 455 had a 3.9" stroke with much lower stresses at high RPM. Meanwhile the Chev 454 had a 4" stroke but the Olds 455 was even more at 4.25" (I always thought the Olds 350 was a better engine and almost bought a Rallye 350 but was told there would be a 4 month wait for 4-speed/posi/AC so bought a '70 Buick GS instead (partly because of the short stroke 455). Won a lot of autocrosses with that car.

[Pfeil]

1 hour ago, padgett said:

To put in perspective, I would trust a Jim Butler 455 (or larger) to do whatever he said it would, with the proper prep (and a SD oil pump) they will last. However I also remember constant crank failures in 70 Bonnes when I was in Flint those years and a significant redesign in oiling for '71. I forget when they started using steel timing gears instead of phenolic ('72 ?) but was also an issue.

 

Yes they used the same block forever but that was not a plus, the narrow bore centers meant to achieve 455 (marketing move) it was necessary to  make it undersquare with a 4.15" bore and a 4.21" stroke. Meanwhile Buick came out with a new engine in the '60s and their 455 had a 3.9" stroke with much lower stresses at high RPM. Meanwhile the Chev 454 had a 4" stroke but the Olds 455 was even more at 4.25" (I always thought the Olds 350 was a better engine and almost bought a Rallye 350 but was told there would be a 4 month wait for 4-speed/posi/AC so bought a '70 Buick GS instead (partly because of the short stroke 455). Won a lot of autocrosses with that car.

I have the 70 455 in the car, two 455 spares one a 73 short block and one complete 1975. They all have those plastic cam sprockets along with Cadillac all the way up to 500 cu.in and down the other side in 425, 368. Olds too. Even the Ford FE high rise 427 -425hp engine came with plastic camshaft gears. The 455 in my LeMans is a double roller with three keyways on the crank sprocket. Pontiac like 3 degrees advance over the stock straight up. What really tears up these plastic gears are the stick shift cars which with upshifting and downshifting pull that chain back and forth and plus with age/heat that plastic gets hard and brittle....and then the old jump!  

The short deck Gen 2 Olds is a great engine, there is another short deck to play with besides the 330 -350 and that is the 403. It is a big bore with the 330 short stroke. It can rev with that Bore / stroke ratio and big valves can be added. It's only draw back is in a road racing / endurance application it has problems with burning pistons because of it's Siamese bores with no full jacket cooling, but for the street and drag racing they are great. The tall deck 400 and especially the 425 are my favorite BB Olds.   

Edited March 23, 2019 by Pfeil (see edit history)

[EmTee]

19 hours ago, Pfeil said:

When that engine died, Pontiac itself died.

Amen. 

[Jd 63]

The olds and Buick 455 were mentioned how do they compare to the 455 Pontiac 

[Pfeil]

4 hours ago, Jd 63 said:

The olds and Buick 455 were mentioned how do they compare to the 455 Pontiac 

Architecture. I would suggest you get some books to read about them because the real differences would take a book to explain here. And in the General Forum it's just a forum general in nature and geared to simple question and answer and really not directed to race cars or hot rods or Grand Touring cars. Even the technical section ( where the post should have been in the first place ) can't get into the detail you are now asking for. 

[rocketraider]

I always thought 428 was as large as the Pontiac block should ever have been taken, but after Olds went to 455 ci in 1968 Buick and Pontiac had to follow.  I likewise think the Olds 425 and Buick 430 were better engines than either Division's 455, but cars were getting heavier and more strangled with emissions, so displacement had to make up for that.

 

Biggest complaint I had with the Pontiac 455 is they tended to run hot and the two I had were murderous on starters. But in an F-body I'd lean to the 400.

[padgett]

And don't forget the Chev 430/465/495 CID (4.44" bore, special aluminum block)

[Jd 63]

Wow I have received so much good information

  I’ve been thinking on what to do with my 455 Pontiac and here’s what I’ve come up with 

 take my 455 put a high volume oil pump on it change the 15 heads out to a 6x heads which a friend has ready to go and put a rev limiter on the car set at 4600 the rest of the engine would be stock, 

im not taking this to the track to race a quarter mile just wanting a fun 81 trans am evening cruiser 

  I can do this economical or I can sell it and build up a 400 that I also have which would cost more to do, 

[Pfeil]

4 hours ago, Jd 63 said:

Wow I have received so much good information

  I’ve been thinking on what to do with my 455 Pontiac and here’s what I’ve come up with 

 take my 455 put a high volume oil pump on it change the 15 heads out to a 6x heads which a friend has ready to go and put a rev limiter on the car set at 4600 the rest of the engine would be stock, 

im not taking this to the track to race a quarter mile just wanting a fun 81 trans am evening cruiser 

  I can do this economical or I can sell it and build up a 400 that I also have which would cost more to do, 

 

AND Now some more information;

The 455 will be the best choice, One thing you need to make sure is; 1976 6X head  is a open chamber head, and it is cast for the 350, (really a 355 if you do the math), 400, and 455-ALL in DIFFERENT chamber volumes. If you choose the 455 6X head your compression ratio will be 7.6 to one and will not make much power. ( that compression ratio was decided on by the factory to help with two things. 1, protection of exhaust seats and 2, lowering combustion chamber temperatures to prevent detonation and lower NOX emissions. You will need to make sure your friend is giving you the 400 Cu. in. 6X head and it is the ONLY one that should be used in a performance application. The 7K3 400 heads on my 455 give me roughly 9.6 to one compression with stock flat top pistons and it has a 96cc open chamber with 2.11 intake valves and 1.77 exhaust valves. The 400 6X head is a open chamber head with 101cc chamber and 2.11 intake valves, and SMALLER 1.66 exhaust valves and your compression is going to be around 9.0 to one.     

[Pfeil]

19 hours ago, rocketraider said:

I always thought 428 was as large as the Pontiac block should ever have been taken, but after Olds went to 455 ci in 1968 Buick and Pontiac had to follow.  I likewise think the Olds 425 and Buick 430 were better engines than either Division's 455, but cars were getting heavier and more strangled with emissions, so displacement had to make up for that.

 

Biggest complaint I had with the Pontiac 455 is they tended to run hot and the two I had were murderous on starters. But in an F-body I'd lean to the 400.

In the late 40's when the Pontiac V-8 was being developed NOBODY ever dreamed a engine, a production engine would ever be that large-especially a mid priced car. Pontiac's architecture AGE is about the same age as the Buick nail head, but with MORE advances, like it's independent ball pivot rocker arm valve train ( which Ed Cole at Chevrolet stole) and it's reverse cooled cooling system ( which was changed to conventional equa flow cooling in 1960). Thin wall casting techniques ( which Chevrolet also copied ).

Remember this; the Pontiac V-8 was ready for the 1953 Pontiac. 53-54 Pontiac frame, chassis and steering are ready for this block. It was BUICK division that cried to the corporation to HOLD Pontiac back for two years because they didn't want any publicity and competition for their new 1953 Nailhead.

So this Pontiac engine from 287, 316.6, 347, 370, 389, 336, 326, 350 a (355), 421, 428 a ( 427), 455 a (456) and short deck version of 301 and 265 made it through three decades is a example of fine engineering with lots of forethought in mind.

How many different generations of Cadillac? Buick? Olds? Chevrolet? How many Pontiac? 1!

                                      

Edited March 25, 2019 by Pfeil (see edit history)

[Pfeil]

Special note on the 400 cu in 6X head. Because of the lower compression than your original # 15 head at 10:00 to one you will probably be making less horsepower than with the #15 heads. 

Edited March 26, 2019 by Pfeil (see edit history)