| Slant Six Forum https://slantsix.org/forum/ |
|
| Cam and head choice https://slantsix.org/forum/viewtopic.php?t=59941 |
Page 1 of 3 |
| Author: | bigcasey123 [ Mon Jul 25, 2016 2:30 pm ] |
| Post subject: | Cam and head choice |
Hello everyone So I have a 1969 dart 225. I would like to make it a really nice street car. But I'm in high school and this will also be my daily driver. I have a few upgrades done to it already The brakes were completely redone New gas tank and fuel line Electronic ignition (distributor rebuild kit) New plugs and wires 2 bbl carb w/ adapter (1 bbl stock manifold) New starter I am also getting a new super 6 2 bbl intake. I already have it lined up. I am soon going to purchase dutra duals as well and put on dual 2" exhaust So after all of those upgrades I think next I will put in a mild cam/valve springs. And I may rebuild the head and consider milling/porting it and putting in oversized valve. I would like some advice on this. I would like some cam suggestions and if you think I should mill the head to increase the cr. And if I should port it and put in bigger valves or not. Maybe the porting and valves are overkill for a 2bbl I don't really know. Thanks for the help |
|
| Author: | DusterIdiot [ Mon Jul 25, 2016 3:22 pm ] |
| Post subject: | I would... |
Personally, if I had to make a shoestring budget 225 mod on a stock bottom end, I would do the following: You are going 2 barrel manifold and either BBD or a Holley 350 cfm... I would save the money and go this route... Save the dutra duals and cost/weight of the pipes until you can afford a ground up hi-po engine... you will get the same performance out of the stocker engine by going with the single 2 1/4" exhaust... Change the compression to be 9:1, or a smidge more... (need to pull engine and measure to make sure you aren't short...). Leave the stock valves and and seats have them reground to make sure they seat right and the seats aren't /sunk or shot... (the reason being...if you aren't going to over bore the engine the O/S valves might get shrouded, and compromise breathing.... do a street port, clean up the ports, open them a little, and work on the restrictions in the port... don't go hog wild in there, or the port velocity will suffer.... Most likely you will need a new set of springs (It used to be you could go to a junkyard and get a bucket full of used ones for cheap, and test them and get one good set to get you by...that's not a possibility anymore...) Cam choice would be an OCG 818 or an 819 depending on your final compression ratio... (have it ground 4 degrees advanced...we would need to check to see what center line will get you the best DCR and torque characteristics, once we know the measurements on the engine while it is apart). I have had no problem getting better than stock performance and solid driveability out of that combination... that will leave you with a fairly reliable combination with more 'pep' (especially with your rear gear combo)... so you won't be without your car for a few months when you have the money to put together the hi-compression overbored, O/S valve ported head, high duration/high lift cam, stall convertor, dual pipes, etc... etc... etc... With this combo you can then step up to the 4 barrel and duals and not change the engine....then you will have all your 'goodies' and then switch to the hi-po engine.... Just something to think about without costing you a couple thousand... (the headwork will be the biggest cost- it will be about 50/50 between the cost of doing the valve job and new springs and the large cut on the head to get the compression...).most late 60's 225's have the pistons down in the bore about .175, and a Fel pro gasket is going to add back about .039 after you cut on the head... I did this on my '67 and the chambers had more volume than the late heads (even my '74 drool tube head), so it took a very generous cut to make it all work out correctly. Just things to think about. |
|
| Author: | bigcasey123 [ Mon Jul 25, 2016 3:34 pm ] |
| Post subject: | |
Thanks for the advice. I do have a Holley 350cfm carb right now and it works great. The only problem with your plan is that I would like to keep the engine in the car. I've heard of people doing cam swaps without pulling it. And I could take off the head But I really would like to try to keep it up and running. Plus the engine only has 50,000 miles on it so it's pretty solid as is. |
|
| Author: | Badvert65 [ Mon Jul 25, 2016 4:52 pm ] |
| Post subject: | |
Quote: Change the compression to be 9:1, or a smidge more... (need to pull engine and measure to make sure you aren't short...).
What he said. Your biggest bang for the buck would be bumping the compression ratio up to 9 or 9 1/2 :1. If you do nothing else, do that.
|
|
| Author: | bigcasey123 [ Mon Jul 25, 2016 4:59 pm ] |
| Post subject: | |
Okay sounds good. Is it possible to achieve that just by milling the head and getting a thinner head gasket or would I have to mill the block as well. How many thousandths can you mill off the head? I was guessing from what I've heard 60-100 but what do I know |
|
| Author: | Badvert65 [ Mon Jul 25, 2016 5:10 pm ] |
| Post subject: | |
Best to measure to determine how much to shave. I had a head shaved 0.080 inch and got around 9.23:1 compression. I measured my head and block to determine those numbers. You can guess at it, but it isn't that difficult to measure. |
|
| Author: | bigcasey123 [ Mon Jul 25, 2016 5:24 pm ] |
| Post subject: | |
Is it a bad idea to measure the deck clearance while the engine is in the car. And my other bad idea is to check the compression with a compression tester while the engine is together and then measure the head CCs and then find out what the deck clearance is |
|
| Author: | Badvert65 [ Mon Jul 25, 2016 6:30 pm ] |
| Post subject: | |
The hardest part about pulling the head (besides lifting the dang thing over the fender) is unbolting the intake/exhaust. If you only want to shave the head (leaving the block in the car) you should just pull the head and measure your combustion chamber cc's and the piston/deck height. Both can be done with simple or inexpensive tools. I measured the chamber on a 73 slant and it has 57 cc. The deck height is 0.157. Using the on line calculators, this gives me an 8.1 compression ratio. Shaving .080 would give me 9.25 compression ratio. If I measured only 50 cc combustion chamber, I would have started with 8.75 compression, shaving .080 would bring the compression to 10.1. So, you can see how important it is to measure first. |
|
| Author: | bigcasey123 [ Mon Jul 25, 2016 6:41 pm ] |
| Post subject: | |
Okay that doesn't sound too bad. What should my cr goal be for the cams that were recommended to me |
|
| Author: | Badvert65 [ Mon Jul 25, 2016 6:58 pm ] |
| Post subject: | |
Quote: Okay that doesn't sound too bad. What should my cr goal be for the cams that were recommended to me
Probably best to check with the cam manufacturer, see what they recommend.
|
|
| Author: | bigcasey123 [ Mon Jul 25, 2016 7:03 pm ] |
| Post subject: | |
Is 9:1 a safe estimate |
|
| Author: | Dart270 [ Mon Jul 25, 2016 8:44 pm ] |
| Post subject: | |
9:1 would work well with the bigger cam suggested (819). Personally, I would not use the 818 cam since it is too close to stock. You will want to recurve your distributor to stop pinging and get best power, idle quality, and mileage. Lou |
|
| Author: | DusterIdiot [ Mon Jul 25, 2016 8:48 pm ] |
| Post subject: | Er... |
Quote: Probably best to check with the cam manufacturer, see what they recommend.
OCG does such a wide variety of work they can make some recommendations but aren't 100% in the know, but those of us on the board who have done a number of builds in various flavors can tell you where to bat ( 818 is similar in "flavor" to the Comp cam 252, and 819 is similar to the comp cam 264....) 818 and a super six build with all he has listed on the board if done right and sticks to a SCR from 9:1 to 9.3:1should get his Dart in the 17-18 sec. 1/4 mile and still allow for good mileage if he recurves the distributor.... (considering a stock points 225 late 60's Dart bats in the 20-21 second range... that's a big improvement and you will definitely feel it). 819 would be warranted if he in the 9.2-9.4:1 range... and he opens up the LSA to a 108... the high lift will work if he takes the time to port the head a bit... I have driven 2 cars with the Comp 264 and it was not as dazzling or been as low end torquey as the 252 was.... Once you can get some hard measurements, it will be easy to plug the variables into one of the online calculators, or one of us can do it for you and give some phasing options.... (some of us have been dialing in the dyno program with real world data for a while and can plug the build in and ball park the potential of the engine as well...) |
|
| Author: | bigcasey123 [ Tue Jul 26, 2016 3:45 am ] |
| Post subject: | |
Hey thank you so much for the help. I think my goal for compression is 9.2-9.4 like you said. I like the idea of the 819 just bc of a little more power and if I take the head off to mill it I know a guy who can port it for me. I'd like to see my dart in the 16s and hopefully someday in the 15s but I know those are lofty goals but I have quite a few upgrades left 
|
|
| Author: | Rick Covalt [ Tue Jul 26, 2016 1:04 pm ] |
| Post subject: | |
I am running the 819 cam in my truck, which probably weighs 5-600 pounds more than your Dart. It ran a 17.50 with the 3.55 rear back in May. You should be able to drop into the 16's fairly easily. I think the higher CR is a big help with my truck. Sorry I can't tell you what it is because I lost all my paperwork and my memory fails me. But I have 170-175# cranking pressure and I have to runs 93 all the time. But it runs sweet, and is still better than stock motor on mileage. Rick |
|
| Page 1 of 3 | All times are UTC-07:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|