make sure you order at least one other adj. pushrod as you will need it to find out what length pushrods to order.. Also if the deck of the block have not been squared then you might as well check a cylinder on all 4 corners so that you know what to order... Most decks are not square to the crank.
Very interesting the specs on that 212 350 cam. The specs on it are different than the catalog shows, which makes the cam even better than I thought. .454/.456 @1.55, (218/230 @.050 remains the same as catalog info) 280/285 advertised. This puts the compression that can be used with this cam higher than previously thought, which makes it more compatible with the 10:1 pistons rather than using low comp pistons and shaving the block and heads to hell and back to get it to 9.5:1 compression. Static compression @ 8:1 dynamic is 10.14:1. This changes things dramatically from the catalog info of 265/280 advertised duration specs. The ratio between intake and exhaust is about 5%, which is about what the ratio would be with mild port work on the heads and stock valves (using the 1.55 exhaust valves), so the flow matches the cam. Match the compression as closely to the cam specs as you can and you'll have a very efficiently running performance engine. :TU: Using TA's cast 350 pistons @ .030 overbore (calculated 12 cc dish) and getting the deck height to .015 with 58cc heads and .040 gasket, you'd have 10.05:1 compression. TA's pistons sit .020 in the hole on an untouched block, so you'd only need to shave off .005 from the deck. OR, you could mill out the casting nubs in the head chamber to get 60ish cc chambers and mill .015 off for a .005 deck height if quench bugged you that much...though this would make valve-piston clearance more of an issue. Sweet. And before anyone goes on about quench, the Buick 350's quench is practically non-existant anyway even at zero deck, so F it. The open chamber design allows for a more evenly distributed burn so quench isn't really needed as much, IMO.
Thanks Sean for the tip about checking the pushrod length at each corner of the block, i'll order a few more adjustable pushrods. Gary, nice analysis of the cr with the specs of that cam. Before doing any polishing and porting, i measured the piston depth in the block (.058) and cc'd the heads (50cc) and calculated a static cr of 8.7:1. Shaving .060 off the heads should add 1.5, but we also ground off those casting nubs when polishing the combustion chambers so we gained a few cc's in the head. Should end up at close to 10.1, but we will remeasure the heads when they come back from the shop. This has been a good learning experience for my son and i. He often will thank me for "letting" him help me........geez, he put almost as many hours into the dissassembly and headwork as i have!!!
Well I've been a bit busy....unfortunately none of it car related. Heads look good. Have you done any measurements on them? Not quite sure what nubs you are referring to ..... you were looking at the side w/o the heat stove. so now my question to you......did you grind them down and did it leave a hole....sounds vaguely familiar doesn't it? Started working on the second head and it is easier than the first. I just hope I don't get complacent and not as careful as I was on the first. So you used an electric drill? So what did you do wrong to warrant that punishment? :laugh: I did go back and grind the machining bump (used for indexing if i remember correctly) and polished it accordingly. Did you plug the exhaust crossovers? If so what did you use? Were you measuring anything as you go? caliper gauges? or am I that picky? I keep thinking of things after i close this...did you polish the throat of the intake runners or did you leave it rough? Have heard that it should be left a bit rough to better atomize the air/fuel mix but am not sure how true it is. Scott
Hey Scott..........no, haven't been taking any measurements, good idea though. And no, we left the nubs there in the exhaust ports. When we put a probe down the bolt hole, and then laid it along side of the exhaust port, we saw that we would have left a hole there had we ground the nub off. So, we just polished it up. Yes, going to plug the exhaust crossovers with freeze plugs. And no, we didn't polish the throats of the intake runners, but we did remove any casting seams, bumps and junk. Yeah, the electric drill was a grin, glad that part is over. Got her done though............your pic of that chamber looks really good!!!
I ran some numbers on the compression ratio and I ended up using a dish CC of 24 CC to get 8.76:1 with a 50CC head. If you CC'd the heads you should also be able to CC the deck. Bring #1 around to TDC and seal off the ring land with Vaseline so the liquid doesn't run past the rings. With the actual deck CC you can get an exact compression ratio calculation. Any way you look at it with .060" head mill you will make the chamber about 11.5 CC smaller. Of course all the polishing in the chamber will make that number smaller. Assuming you get 10 CC smaller you'll be up to 9:7:1. That cam should really like it. I ran a real 10:1 in my 455 with the 212 and it ran great. Something else to consider is to get the 50CC chambers you have now the heads probably were milled .030" already. 58 CC would be more normal for a 350 head I believe. That being said make sure you take some measurements after the heads are bolted on to see how much the intake is sitting up. You'll probably have to take .060" off each side of the intake(more if the heads were already milled) to get it to sit right. Normally I'd take it off the head but I don't think you can safely take .060" off the intake side of the head. I've been running adjustable pushrods on most of my engines for years and it is IMO the best way(short of adjustable rockers) because each valve can be adjusted exactly. However in your case if you take that much off the heads you may bottom out the pushrod adjustment before they are slightly loose. Something to consider before ordering anything.
24.74 cc is the dish volume on low compression pistons from Summit, one of two sets available. Higher compression available with 10.13 cc dish volume, and each have 1.805 and 1.835 CH respectively. This puts the low comp pistons .070 in the hole and the high comp pistons .040 in the hole on an untouched block, leaving plenty of room for truing up the block deck and getting the compression where you want it. TA's pistons are about the same dish cc as the Summit high comp pistons, but have a 1.86 CH, putting them .020 in the hole, leaving less room for cleanup, but good if your block doesn't need much since it'll allow you to get away with not shaving the intake side of your heads and possibly using shorter pushrods. 50 cc heads indicates that they've already been shaved a bit, and since I think he doesn't want to pull the block and do anything to the lower end of the engine, leaves him with having to use the low comp pistons in there with their existing deck height and to just mill more off the heads, which will be pushed to the limits I think with how much can be milled off them. Shaving off .060 more off the heads will put them at probably around 35 cc...give or take.
Steve, I would have used some Rotary Files instead of Burrs. They make the Job go a lot faster. :spank: If I went to the Tool Crib at Buick and asked for a Rotary File this is what I'd get. I never knew what a Burr was until I joined The Board. It said right on the package Rotary File. But I guess they go by a lot of different names. I used an 18V Battery Drill and a couple of Die Grinders. Just depending on what I was grinding on. You Your Heads look Great. It must be fun with you and your son doing this together. My Son has no intrest in this kinda stuff. He isn't very Mechanical. He can only go so far but that's it. Does a nice job on his Bike tho. Keep up the good work Man. :TU: PONCH
Thanks No Lift for similar CR calculation, and my machinist said the same thing about not being sure how he could safely mill the intake side of the head. Will mock up the heads and manifold to the block when i get the heads back and see how much to take off the intake. We'll take off a little at a time. I am ordering an adjustable pushrod so i can measure for a set of the right length. Also, i have 1.65 roller rockers so i can adjust the lash to a light preload for each lifter. Gary, you're right about the block. I didn't want to pull it so i did a leakdown test before we started this. As i recall the readings were all near 15% +/-1. Thanks Ponch, i'm excited about how the heads turned out. Your son appreciates your time with him, no matter what you do together.
Steve, with a .040 head gasket, .058 in the hole and 24 cc piston dish, you're going to want your head cc's to be around 37 or 38 to get very close to, or slightly over 10:1 and be within the safe zone on that cam for premium pump fuel. I'd shoot for 38. You'll be in a safer zone at 9.93:1. You've put a lot of work into those heads, and if you were to ever rebuild the bottom end, you'd have to use low comp pistons again with a lower CH and mill back down to .058, which is doable with a .070 DH. Keep up the good work and I'll look forward to reading more about how you progress on this project. :TU:
Well that's what I thought too when I read how much he was planning on taking off of them, but he said his machinist said it could be done I guess. They're already sitting at 50cc so he's had about .030 taken off of them already, or someone has. It'll be borderline for sure. Probably won't be able to take that much off intake side of heads to match them, so he'll have to scalp the intake manifold as well... Yeah 58cc factory from what I understand. He's got some work in the heads already with porting. If it were me, I'd be refreshing the bottom end as well and having the deck milled and leave the heads as they are at 50cc. Putting them at 38cc means the only pistons usable now will be low compression pistons if a rebuild is done with new pistons. Which is ok. I know there's a ton you can shave off the deck and still be safe. Quite a bit of room to play with.
if you already have engine out just pull rods, press on higher comp pistons, get a hone and clean up cylinders instead of all that milling and fitting intake . brian just got 3.0 pistons from summit racing for around 250 and they are flattops. would be the best way to go since you aready pulled engine out
Thanks Gents for all the good input............that's what i appreciate about this site. It's the quantity of good information and help that encouraged me to start this top end build project. While i'm waiting for my parts and the machinist, my son and i are cleaning gasket surfaces and stuff. Hopefully we'll have more to post soon. Thanks again!
Back from a business trip to China, there's no place like home......and, all my parts came in while i was gone! My son has been cleaning gasket surfaces while i was gone. Picked up the heads from the machine shope before i left, looking very nice. Did a mock up with the heads, intake manifold and old gaskets, bolt holes were almost 1/16th of an inch low. On my way to the airport for the china trip i dropped off the intake at the machinist for him to mill .040 off. Picked it up this week on my way home from the airport and fitted it last night, very nice. Today we are taking the heads back to the machinist for the multi-angle valve grind, hardened exhaust seats, knurl the valve guides and assemble. Getting closer.......
The heads are still at the machinist for the valve grind and other and assembly...........but in the meantime, here's a pic of the heads freshly milled from a few weeks ago..........
if you dont mind me asking whats your machine shop charging for this? im in the process of porting my heads and hope to be sending them into the shop soon, but would like to get an idea of the price..
Hi Brian, no problem asking...........i've been keeping a log of parts cost and labor cost, it's home on my workbench. I'll get it to you tomorrow.
