Alright, I joined a Buick 350 Performance Group which is pretty awesome on FB. I scored some parts for my 70 skylark for free! ( person passed them forward). Now just as in any place it is a free for all when it comes to knowledge, people ask questions and people get answers. Some people swear they are correct even when being presented with other facts. That makes me return to the real deal ground zero of knowledge I have always looked up to here @ V8buick sooo I ask you knowledgable gents. What was the compression ratio for the 1970 Buick 350 2bbl? I have yet to check the block code but my car is a 70 skylark custom. I found a page on Teambuick forums that shows it @ 9.0:1 and it states the info was compiled from service manuals. The people posting were saying I have an 8.5 and that they been rebuilding them etc it has potential etc. Which I agree and do understand after all this isn't my 1st Buick, but Iwant to settle it and feel happy I might have a 9.0:1 engine. FB Post question From Random people "Outside of the Intake and cam, is there any difference between the 2 and 4bbl engine of the same year? "Do these 350s come in both 2 and 4 bolt mains like Chevys? Sorry, I'm completely new to Buick and also returning to the old car hobby after about a 20 year absence... Basically having to re learn many things." Responses "There is no 4 bolt mains, 68-70 4 barrel engines if original are rated at 10.2 compression, 9.25 actual compression. Otherwise any engine 68-74 is 8.2 compression. 75-80 is 7.7 compression. Cam is same for 2 barrel and 4 barrel. 73 and up has better cap screw rodssome 72 heads up to 80 have different coolant passages, so they can’t be bolted on to early blocks without drilling and plugging the extra holes. . 68-69 the rockers are oiled thru the head passage. 70-80 rockers are different, and they are oiled thru lifters and hollow pushrods. There are no hi compression heads. All the same size." "Chances are only if someone changed Pistons to higher compression . The only difference between the 70 2 barrel and the 71 is the head gasket which is .025 thinner on the 70. If you blueprinted engine you could get 9.0. It would require the original head gasket and about .040 decked off block." I mean I can always rebuild it with the 10.25:1 pistons a nice TA CAM and port the heads buttttt that is in the future. Regardless I am happy with my 350. Sounds healthy and no leaks Thanks Guys
Your 1970 2 barrel engine is rated at 9:1 compression however it is closer to 8.5:1 I would say... maybe 8.7:1 max
Keep in mind that even if you use "10.25:1" pistons your actual compression ratio will still be about 10:1 because of the deck height and how the piston sits below the surface. When building a performance engine the deck height is taken into account and either milled or custom pistons added to fine tune the compression ratio.
Got it, So technically a nice can swap should wake it up more without having to raise the the CR and worry about pinging? lastly what would you say is the target sweet spot for a rebuild? If I order the Pistons .
This is Great Info! Thanks I never realized or have looked into this before. I will also be reading up on your Power timing Thread as a refresher again since I will be setting the timing on the 350
To keep it simple here are some basic suggestions... 1. Keep the engine at about 9:1 and use a mild cam like a TA-212 2. Raise the compression to about 10:1 and use something like a 284 cam If you use 10:1 with a small cam the dynamic compression may be too high causing detonation issues... If you use a big cam with 9:1 compression the dynamic compression will be too low causing lack of power. It is all about matching up the whole combo from vehicle weight, gearing, carb, intake, head flow, compression, cam etc. The most common mistake I see is people using too large of a cam without enough compression to match. The other problem is that without major mods there is not a ton of potential for raising the RPM range of a 350. Stock they peak in HP at about 4000. Add a Ta 212 cam and they peak at about 5500 rpm without giving up and low rpm torque. Add a huge cam and the rpm peak may raise to 5700 rpm but it's not worth the loss in torque the big cam gives. So the sweet spot for a low $ upgrade is about 9:1 and a 212 cam, with the right settings on the carb and timing it will be much stronger than stock.
Makes a lot of sense thanks for this. I know I have to get rid of my Poston Intake and the Edelbrock sitting on top of it. I actually have been looking into the 212 cam and keeping the stock bottom end since it appears to be super clean and possibly rebuilt. 212 Cam, new lifters, pushrods, double roller timing chain, & an oil pressure regulator, Mechanical advance kit (springs) and Larry's timing are on my list. So far the car appears to be happy but I feel I am leaving some power on the table. I removed the mechanical fan and purchased a higher end SPAL fan to help cool it and an aluminum radiator as well as a new 180 thermostat and water pump. The stock radiator needed a flush but figured I can upgrade the cooling system and free up parasitic HP loss to help my engine's cause. The reason I was looking @ the CR more closing and wondering was becasue I was researching the CAMS on TA & you pretty much exlpained it perfectly. I am going to go with the 212. I know the bigger cams mention 9:1 but I now understand it more clearly with the Dynamic Compression Ratio article Larry suggested. Thanks Guys!
