When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Sorry for the noob questions but is there anyway to raise the compression ratio on a 72, 350 motor without changing the pistons, don't have a ton of money so I couldn't dive that deep into the block, maybe some head work, if I can or can't raise the compression would mark be able to do cam that would help the car a little stock or with head work? currently all I have done to it is add headers and duel exhaust but it just needs a little more go, would adding a performer intake and a new carb help me out or would that hurt the compression due to the thicker gaskets.
Thanks Joe, too bad. Can I get a little better Cam in the motor or is it about as good as gets on a stock motor, and would an aftermarket intake and carb help out all all thanks..
You could go a bit larger on the cam, but you have to be careful that you don't go too far. Check with Mark to see what he recommends.
Intake and carb will not really gain you any performance increase over the factory setup.
The best bang for the buck is lower rear gears. I did that twice back in the 80s (2.56 to 3.08, then 3.08 to 3.55) and each time it felt like a new engine with more horsepower.
The best bang for the buck is lower rear gears. I did that twice back in the 80s (2.56 to 3.08, then 3.08 to 3.55) and each time it felt like a new engine with more horsepower.
Yep. Go for this first. Otherwise, headers, roller rockers, cam, and intake are your options. You COULD cut the heads BUT you'll need to consider the head gasket you're removing is .017" and a typical replacement is .042". I would leave the heads alone if you're not gonna do a rebuild.
Joe, hate to argue but I have yet to see a set of 68-72 heads be less than 68cc.
Op- you might try a set of 65-67 330 heads, they’re already in the low 60’s typically. Then you can mill from there.
Cam will depend on what your final comp and rear gear ratio are.
Last edited by cutlassefi; July 7th, 2019 at 12:27 PM.
I have 7A heads on it now, will getting those heads done help with the compression or is it just a waste of money, the rear gear atm is a 2.73 and plan on keeping that. So honestly its probably gonna stay a low compression engine and would like to no if a cam swap is even gonna help thanks.. just dont wanna toss to much at this motor while im using it, when I have more money I will find another 350 to do slowly as funds permit.
Last edited by skyhigh; July 7th, 2019 at 12:15 PM.
'Course if you go to an overdrive transmission, you could then get a 3.90 rear, and in conjunction with the lower 1st gear, that would really provide a fun factor!
Joe, hate to argue but I have yet to see a set of 68-72 heads be less than 68cc.
Op- you might try a set of 65-67 330 heads, they’re already in the low 60’s typically. Then you can mill from there.
Cam will depend on what your final comp and rear gear ratio are.
64cc is the blueprint spec. As you know, Olds heads are typically cast larger than the blueprint spec. The problem as noted above is that unless the OP sources steel shim head gaskets, he's going to lose about half a point with the FelPro blue gaskets.
You can get a cam with around 204º intake duration @ .050" lift that will perk the engine up. I always liked the Crane 260 cam as it has a nice lift for the amount of duration compared to some other brands:
I’d stick with something that’s closer to a single pattern. It’ll retain more cyl pressure that way.
Joe- Yes he’ll lose a bit with the thicker gasket but if he uses a .027 or so aftermarket gasket he can minimize that and take advantage or the smaller chambers.
thanks for the info, would a cam like that and a bigger gear wake it up some, maybe a 3.08..
I'd go 3.42. More dig on the street and still tolerable on the freeway, as long as you're not going on any really long trips. And give some consideration to an overdrive trans -- that's having your cake and eating it too.
Thanks guys. The biggest i think i can go is up to a 3.23 with my carrier so i will talk to monz and see if he can get me what i need or get it from summit. Then in the fall i will talk to cutlassefi for a custom cam for the low compression with those gears and do those 2 changes over the winter. That should get me by while i save up some money for another engine build. Next spring should be a little more fun with those changes.
Ok, Mark hooked me up and the cam is on the way, I got cam, springs, lifters. Cam is 208/214@.050 with .460/.476 lift. I also got the Cloyes street billet true roller timing set 9-3513X9 from summit, after the cam arrives I will be booking an appointment with my installer I think all i need left to do is get a intake gasket, water pump gasket, but I might as well probably change the water pump.
Well I will have to wait till next week, the mechanic has had the car for 3 days, timing chain is in, the cam in and break in done, water pump in. The issue he says there's a stutter on idle, but not while driving, he thinks the #2 cylinder is the issue, the header pipes are like 300 degrees but #2 is 180 for some reason? He going to do a compression test on num 2. Took 3 water pumps to get the right one, apparently the 1970 was the right one, and he also told me he couldn't use the springs mark sent without the need to shave the heads down? He used the old springs and said the cam should have like 110 lbs and the old springs tested at 105 so it would be ok.. Do you guys think this sounds right. I could never get the block num to check, I wonder if its a 70 block with 72 heads?
All 1972-earlier heads have virtually the same chamber size, in the 60-64 cc range. It wouldn't matter if you had 1972 heads, 70 heads, or 65 heads, the result would be the same. The only difference is the size of the dish in the piston. 70-earlier pistons will have smaller dishes (and thus higher CR) than 71-later pistons.
he also told me he couldn't use the springs mark sent without the need to shave the heads down? He used the old springs and said the cam should have like 110 lbs and the old springs tested at 105 so it would be ok.. Do you guys think this sounds right?
No, doesn’t make sense. Shaving the heads has nothing to do with the valve springs. Ask him to explain that better if you would.
No, doesn’t make sense. Shaving the heads has nothing to do with the valve springs. Ask him to explain that better if you would.
yeah I will ask on Monday, he was like they would be tight, I don't want to take the heads off etc, shave the heads, basically told me a bunch of stuff and I cannot question theses statements because I have no idea whats needs to be done, I must say I don't no **** about motors, It a reason why I pay good money out to have things done, he was recommended from lots of classic car guys here in town, now I'm left to wonder all weekend why he told me the car is not idling right. I hope its not the case of me having sucker written on my forehead cause I'm not mechanically inclined.
Here a quote from another friend of mine who asked his friend lol, so when I see the mechanic on Monday do insist the new springs be installed, is all this talk BS?
Quote:
"Sometimes in order to change the springs on the olds heads depending on the head and motor - the head need to be machined or shaved in order to make the new springs fit properly"
Either we’re getting the terminology wrong or they’re all full of bs.
The spring diameter is right, as well as the spec’d installed height. At the very most he may have had to shim them, but they should’ve fit.
Last edited by cutlassefi; February 29th, 2020 at 02:19 PM.
Thanks Mark I will insist it get done, probably just didn't want to remove the heads is what I'm thinking, I just hope another issue didn't pop up with cylinder #2, who can say, maybe its a broken spring.. but I will will go in to see him monday, last week I was busy at work so I couldnt get in there during work hours
Wow guys I really feel dumb taking the car to this guy, it runs worse now than it did before he got it. The cam really doesn't sound any more different than the one pulled. Never did get my springs installed, his reasoning is the springs are to big he told me, 2 thousands 2 big? he would have had to shave the pockets down? I doubt Mark would have sent me the wrong springs, he got the cam for me and knew I had 7a heads lol. The car had such a high idle on the way home is was scary hearing that, especially at a light while stopped, I mean crazy high, I put it in park and revved it up and that wouldn't bring it down so obviously putting the car back in drive was violent on the transmission. the worse part of all is the thick dark blue smoke coming out of both tail pipes blinding the drivers behind me and the smell, I will post the bill to show what was done in hopes you guys can help me figure out what the hell he did to my car. Sorry the attachment not so clear, Is the oil getting into my exhaust possibly from the intake gasket not being done right or do you guys think the new cam maybe screwed the valves and that how oil getting in. Do the heads need to be rebuilt.
Last edited by skyhigh; March 3rd, 2020 at 03:26 PM.
High idle and blowing blue smoke likely mean a vacuum leak that's sucking in oil. Maybe the intake manifold isn't sealing against the heads.
X2, exactly what I was thinking.
And unless they sent the wrong springs or were boxed incorrectly, they should’ve worked. My car still has the original 7a heads so I know what spring works.
One more point, you won’t hear this cam really no matter what. I explained that early on. Your low compression severely limited your options. I did the best I could with what I had to work with.
But with that said, you need to take it somewhere else. This guy ain’t the sharpest knife in the drawer.
I wish you the best of luck, I’ll help any way I can.
Thanks fellas I appreciate the advice. I will have to save some more money in case I need to rebuild the heads and take the car to the original place I was going to bring it. I hope its just a vacuum leak and a new gasket to fix it, My friend wants me to get it to his place this weekend and first check the timing, then do a leak down test before I bring it anywhere and spend anymore money lol. He wants to look at the fuel color with the fuel line off the carb and squirt it into a bottle cause maybe its the pump diaphragm, his dad wants to look at the valve springs, thinks maybe one broke. So I will take them up on the offer and if nothing else learn a few things about how old motors work, they are chevy guys though lol.
Here is a 3 min video I took, now the car has a whine and not to mention I had to get rid of my cloths, my wife said I stunk something fierce, you can see at the end of the video how fast the smoke build up when i put the car back in the garage, the wind outside really didnt show the true nature.
We did the compression test, so do theses numbers tell me its the valve seals? I only had a box to write on lol. I pulled the fuel line and the gas had no oil in it. The plugs didn't look to saturated, there was oil in the tail pipe tips, my friends thinks i need to order valve seals.
Last edited by skyhigh; March 6th, 2020 at 07:29 PM.
We did the compression test, so do theses numbers tell me its the valve seals? I only had a box to write on lol. I pulled the fuel line and the gas had no oil in it. The plugs didn't look to saturated, there was oil in the tail pipe tips, my friends thinks i need to order valve seals.
Great pic and easy to read. I don't know about pressure needed, but they are all pretty close. I was thinking smoke at start up was valve seals. A cloud of smoke all the time makes me think you have worn valve guides. Maybe valve seals will fix it, but don't be surprised if you need valve guide repairs.
Another thing..........DON'T look for oil in the gas line.........LOOK and SMELL for gasoline in the crank case oil.
Good luck.
Thanks for the tip, today were gonna get a timing light on it, check the vacuum, and then we can go from there, mark I took a pic of the box of springs that were sent, are these the right height for 7a heads. oh and should i see any of the valley pan gasket sticking out of the intake, up near the valve cover area, I will get a pic of that when I get back today. Is there a name brand or type of valve seals, valve guides etc you guys prefer.
Valley pan, eh? Yes part of it is exposed, I think near the middle intake ports. And I wonder if the pan sealing ridges got compromised during installation and that is this problem. These are one time use and they have to be positioned correctly before lowering the intake manifold onto the engine.
July 7th, 2019, 08:31 AM
I think all i need left to do is get a intake gasket, water pump gasket, but I might as well probably change the water pump.
