My friend out of state can get me a 455 from a 1975 full size. Is this a good year or would I be better off with an older one? Any known issues with this year of 455?
Other than being a smog engine and having less than desirable heads, there's nothing wrong with it. Maybe depends more on what you plan to do with it?
The 1975-76 455's had a bit more beef to the block. The heads were open chamber so the compression was down around 7.9:1 or so. If you want to make big power, you'll need better heads.
This isn't quite true(unless Larry is discounting all cast iron factory heads in his statement?), closed chamber BBB factory heads vs. open chamber BBB factory heads, the open chamber heads have close to the same flow potential when ported than an earlier ported set. The main problem with the later 455 engines is the amount the pistons are in the hole. With the earlier 455 engines having fully dished pistons they didn't have any quench worth talking about so they might as well been open chamber heads on them. Now if you match the earlier heads with pistons with a corresponding quench pad to the head's chamber quench pad you can run more compression and the engine will be less detonation sensitive. But if fully dished pistons are used, then there's not much difference to using the opened chamber heads except for being able to get the compression up as easy as the smaller chamber of the closed chamber heads. On the other hand if flat top pistons are used then you can't get the compression down enough to be able to run the engine on pump gas with the closed chamber heads but with the open chamber heads the compression can be low enough to run pump gas. In conclusion, if you plan on just running factory cast iron heads with no plans to upgrade to aftermarket aluminum heads in the future then the open chamber heads with flat top pistons can be built to be a good runner. But if there are plans to upgrade or even start off with aluminum heads then a piston with a quench pad with an inverted dome would be a good idea. If you use a full dished piston(the dish shape is a complete circle) then it would be pointless to buy closed chamber heads to use because with that kind of piston it would cancel out any benefits they would have except for helping to raise compression, if that's the case choosing a cam with a faster IVC rate would make the lower compression work out better with the open chamber heads. If the plan is to run the factory built low end then the '75 might not be the best choice, but a great choice as a core to rebuild. So,........... what is actually the plan for this engine if acquired anyway? Answer this question and you can get a better answer to your original question. :eek2: Derek
Good info Derek. Yeah, I have a feeling that Gary just wants to drop a 455 in as is. He can always upgrade it in the future.
Good post Derek. I would have posted something similar but you beat me to it. The later blocks/engines are actually more desirable, if you plan on a budget-friendly, mild engine. Without that quench platform, open/closed heads don't really matter much other than the later ('75, '76) heads having an open chamber help with exhaust evacuation and emissions, which is why they went to this design prior to discontinuing the engine altogether. One thing of particular interest is that since the combustion chamber is so large, compression needs to be a bit lower (no matter which heads you use) when considering no quench platform, for detonation resistance. As a 'rule of thumb' (and this is used loosely), keeping DCR about .25-.5:1 point lower than what it would be on a Buick 350 is a safe goal. This is to say that instead of aiming for 7.5-8:1 DCR on a Buick 350 (which has an open chamber, albeit considerably smaller), aim for 7-7.5:1 on a non-quench big block. It won't be quite as efficient, but will still make tons of power by virtue of the fact that it has 105 more cubes. There's lots more to consider than just this of course, but it's something to think about. It's always best to play things on the safe side when there are so many dynamic variables that could alter/affect an engine's ability to reliably function in the real world with day-to-day driving. My 2c.
For a stock/mild build, the block doesn't have to be too perfect on the cylinder wall thickness and lifter bores when considering block core shift. If the engine made it all this time as is, chances are it'll be just fine for a rebuild without going much more radical than factory settings. Full-on racing is another story, of course. If I'm not mistaken, the later blocks had better oiling than the earlier blocks, so there'd be less work needed (if any) to factory oiling when considering a stock/mild rebuild. If I'm mistaken on this, someone please correct me so no one gets misinformed. In my mind, the later 455's would be perfect candidates for mild, budget-friendly street engines. The heads and less than perfect blocks (core shift wise) are less desirable (or outright rejected) by the racing community, and so could be had for less money for sure.
I appreciate the info in this thread. Thanks guys. I have a question though---what do folks around here consider to be a "mild" build? Less than 450 HP???
Yes youre feeling is right. I just want to drop a 455 into my LeSabre (who doesn't?) as is. The 455 has 8k actual miles according to the seller but I found out yesterday from my friend that the seller wants 1000 for it which is out of my price range. It is still in the car and runs strong. Also of interest is that the valve covers are painted blue. Was that the original color in 1975? I thought that was odd and would surely indicate that it is not original.
Just to be precise, 75 blocks are a one year only metallic teal blue, the color is not reproduced closest is an AMC blue Very late 75 and 76 blocks are GM corporate blue
/prattle on The term 'mild' is subjective, much like exhaust note 'loud' or 'quiet', etc. What may be mild to one person may be moderate or even fairly radical to another, and vice-versa. When I say 'mild', I'm referring to an engine that doesn't have much else done to it over factory specs (internally), with a smooth idle, good vacuum, and very little else done to it other than some head cleanup and a gentle cam profile. Somewhere in the range of around 375 hp and 525 ft. lbs. (give or take a few numbers), all coming in before 5,000 RPM is something I'd consider to be mild on a Buick 455 standard head engine using factory manifolds, burning run-of-the-mill premium pump gas found anywhere ranging from 91-93 octane. Forget the book numbers, they're misleading and were used for insurance/advertising. You can get a 455 to turn 450 hp (at less than 5,500 RPM) fairly easy with headers, mild cam, and around 7.5:1 DCR. Some here say their 500+ hp mills are 'mild'--and would be, considering what all can be done to one to make way more power than even this. So I guess it's all according to interpretation. This is the primary appeal to the big blocks--you can accidentally make power with them without even trying, vs lots of money and effort to spin a small block to the RPMs it takes to compare HP wise, and even then won't compare torque wise unless you force more air into it. Once you feel the sensation of 525 ft. lbs. and 375 hp on tap, it's difficult to go back to 375 ft. lbs. and 300 hp, unless you're looking for a few more MPG out of it. Pros and cons are everywhere. I loved my Buick 350's, but even the strongest one didn't hold a candle to the high comp 455 I ran in front of an ST300. The 350 could be argued to have a better block design (more rugged) vs the thin walled 455's, but if you build a 455 mild, the block is plenty strong enough to hold up. You only get into problems when you start dealing with higher-end racing goals. But for a super fun street machine, it's hard to beat a good running 455 with street gears--and you don't have to spend a small fortune to get it there. It's also way lighter than all the other big blocks ever produced, so putting one in a car that originally came equipped with a small block doesn't affect handling all that bad. A 1,000 dollars for a low-mileage good running 455 is a lot more than what I used to pay pulling them out of wrecked Electras back in the 80's, but times have changed. BBB aren't growing on trees anymore. Even the lowly factory assembled 1975 455 produced around 300 hp and 450 ft. lbs. (if you measured it gross and not net), which is a lot more than the 230 hp and 350 ft. lb. low comp Buick 350 it would be replacing, and would burn regular grade 85-87 octane pump fuel all day long. What's not to love about that? :grin: If the engine runs with no issues and is low miles, all accessories came with the engine and it would be a basic bolt-in swap over in a early 70's B body car, 1,000 bucks is getting off light when you start adding up money it would take to beef up the existing engine to approach what that 455 has right off the factory line (torque wise, anyway), or finding a 455 core to build. Just basic machine work and good pistons would easily eat up 1,000 bucks, not including anything else or the labor to assemble it. A stock low comp 455 in that era will give out of breath somewhere between 4,000-4,500 RPM, but from idle-4,000 RPM it's pretty stout. Perfect for a 4,500 lb. car, and will certainly move it around better than the 350-2 it came with! /prattle off
will do! and Gary Farmer, what you have described is exactly what I want. 550lb ft all done by 4000 rpm, strictly for cruising and short sprints.
Chris Scaling or Jeff Strube needs to chime on the Heads. I know on simple cam change, you can increase rpm range but not by much and horsepower will go up. Personally, I would increase the compression ratio and put a KB cam in it. This would a nice alternative.
Hi Gary Farmer, Thanks for your reply. Nice to know. I suppose I would consider "mild" to be about the same as you said. Of course, for so many of us mild often becomes a quest for moderate, which becomes.............??!! But hey, therein lies the fun of it.:3gears:
X2, I've never seen anybody else say that, but you are correct:grin: The 76's were a solid medium ugly blue. The '75 only color was actually nice looking:TU:
Yes, that would be my description of a mild 455. 375 HP is certainly attainable at 5200-5500 RPM, 525 ft. lbs. might be a bit optimistic. To get to 450 HP, you will need something more than stock untouched heads. Some porting to iron heads or out of the box aluminum heads, and you will need to spin it to more than 5000 RPM. That isn't a realistic expectation for a 455 you are going to buy for 300.00 on Craig's List. Most of the engines you pick up on Craig's List or elsewhere are going to be cores that need a rebuild. IMO, 1000.00 is not a bad price if the engine runs smooth and is quiet. Something you can drop in and run as is. Then you can make improvements as funds allow. This is a pretty interesting read, http://www.v8buick.com/showthread.php?183826-The-quot-Sneaky-500-HP-quot-motor&highlight=
Optimistic, maybe. Many sit around 500 ft. lbs. give or take, but I saw a very mild 455 push 380 hp and 530 ft. lbs. through manifolds, and it didn't have to spin over 5,000 RPM to get it. Yep. Again, rounded figures. '450' hp isn't difficult to obtain with a 455 using headers, good compression, and a moderate cam. Some head work will certainly make the goal easier to reach. Yeah, he may have made a typo saying 550 ft. lbs. and meant 450, since no one mentioned 550, but did mention 450? Just a guess. 1,000 dollars is a good price for something you KNOW runs and can get the accessories for, making it a direct bolt in swap on that car. My earlier 'guestimation' of 300 hp and 450 ft. lbs. is a bit off too...more like around 275 hp and 460 ft. lbs., if the conversion from net to gross is to be believed, and isn't too unrealistic. Still way more power than the 350-2 it would be replacing. Thanks Larry for your input!
