About .120" off the head and .150" off the block should get you close.
.180 is stock deck height. 
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| Advice Please!! https://www.slantsix.org/forum/viewtopic.php?t=4675 |
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| Author: | Jason Kobos [ Sat Dec 21, 2002 7:34 am ] |
| Post subject: | Advice Please!! |
Hey guys, I need some help. I currently am unaware of the dimensions of the camshaft that I am running at this time. I did however measure the lift and it's around .510 on both exh. and int. The point I am getting at is that I need another camshaft for just the strip, but I am unaware of what I should get. The short block is the only thing that I have not rebuilt on the car since it was built before by somebody else, so it is the last thing that I have to learn. So, I need some advice on what type and size of cam to get or acquire. Here's my current combo. 225 +30 overbore, balanced bottom end, totally gone through head including 1.84int, and 1.50ext. valves plus about 30 hours of porting and polishing, 460 f@#$ big block triple springs, stock valve train(for now), msd 6A, clifford intake, holly 390, accel ss coil, accel 8mm wires, Nos cheater system, 904 with 3500 stall, 8 3/4 with detroit locker and 4.10 gears, car weighs 2700#'s approx with me, and 28x9x15 ET Drags. Well thats it guys, I just need some help and advice as to what cam to get or have made. I just need something bigger and better. Also I need it to be catered to the nitrous system. I am running a 150 shot for now, but once the bottom end is built I will be running a 210 shot. Thanks for all the help. |
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| Author: | Charrlie_S [ Sat Dec 21, 2002 8:17 am ] |
| Post subject: | |
Jason, Your best bet , is to call several cam companies. Give them your car and engine specs, and let them make a recommendation. One word of warning, the slant six cam has two intersecting holes drilled in the rear cam journal, for valve train oil metering. Make sure these holes are in any cam you get. Several people have gotten cams without these holes, and did not notice it until after the cams were installed. |
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| Author: | Doctor Dodge [ Sat Dec 21, 2002 8:17 am ] |
| Post subject: | Important Information Needed... |
The thing you need to figure-out is the compression ratio of this engine. Two values need to be found: 1) The static or calculated compression ratio. This is the easy one but take measurements and be accurate. 2) The "cranking compression" or cylinder pressure, the cam profile and the cam phasing (advance) has a big influence on this value. This is hard to determine with-out the actual cam and engine parts to "mock-up". The "trick" to cam selection is to match the cam with the intended use. (and compression ratio) This sounds like a race engine for WOT to a 6000- 6500 redline. You want a cam that will "come-on" as soon as possible but carry 6500 RPM If you are planning to run good fuel (race gas) then shoot for 180 - 200 psi of cranking compression. If its a "pump gas" engine, 160 to 180 psi is about all you can give it. DD |
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| Author: | Jason Kobos [ Sat Dec 21, 2002 6:00 pm ] |
| Post subject: | |
Hey Charlie, Doc, thanks for the responses. I really appreciate the help. I will perform both pieces of advice once I have the head bolted back on, still polishing bowls(never ending). Hey Doc, what did you mean by the line, this is hard to determine without the actual cam and engine parts to mock up? Oh, the compression is 10.5 to 1, or atleast I was told. And I run 110 race gas. Again I will let you guys know what the actual cranking compression is once I get it running by Wend. Jason. |
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| Author: | Charrlie_S [ Sun Dec 22, 2002 4:17 pm ] |
| Post subject: | |
Jason, While you have the head off, CC the combustion chambers, measure the deck hight, measure the gasket thickness. Then you can calculate the actual compression ratio. You will no longer have to guess, based on "what you were told", you will know for sure. |
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| Author: | Jason Kobos [ Sun Dec 22, 2002 5:32 pm ] |
| Post subject: | |
Hey Charlie, thanks for the help. After I noticed your response, I went to the garage and measured the deck height and the felpro head gasket. The deck height is 180 thou at tdc, and the gasket is 36 thou. Can you gestimate the compression with a stock 67 head(I am unaware of the stock head cc's), since my 68 head is trash, I need to know how much material to cut off of this new head to try and get around 11.5 or 12 to 1. Thanks buddy. Jason. |
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| Author: | slantzilla [ Sun Dec 22, 2002 6:36 pm ] |
| Post subject: | |
About .120" off the head and .150" off the block should get you close. .180 is stock deck height.
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| Author: | Jason Kobos [ Mon Dec 23, 2002 5:35 am ] |
| Post subject: | |
Thanks slant. However I have a problem. I am only doing the head right now. I don't plan on pulling the bottom end untill I blow it. Which may be awhile, or next season. So, what could I do to just the head in the mean time? Thanks, Jason. |
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| Author: | Dart270 [ Wed Dec 25, 2002 10:14 pm ] |
| Post subject: | ummm |
Actually the stock spec deck height is 0.140", but I've seen some that were more. My '68 Dart has that spec and 0.100"/0.200" angle mill on the head, equivalent of about 0.140" flat mill (less on intake side), and it has 10.6-10.8:1 comp (head cc'd and deck and composition gasket measured). I would say you need to mill some off the block (0.070"-0.100") to get 12:1. A steel shim head gasket will get you a little more comp too (try Year One). You could go to 0.120"/0.220" angle mill on the head, although I don't know how far you can push it. Lou |
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| Author: | Jason Kobos [ Thu Dec 26, 2002 4:15 pm ] |
| Post subject: | |
Well, found out that the motor has stock compression, 8.4 and the cam is Comp cam #642414(found old receipt of work done). Specs are dur. at .050='s 220, adv dur.='s 264, lobe separation is 110, and the gross lift is .440 both int. and ext. The moral of this little story is to NEVER trust anybodys work unless you see it with your own eyes. So today I had .130 thou taken off of head, and I will try and get shim gasket. Hey dart270 since I took .130 thou off head and my deck height is the same as yours, I should have about 10.7 - 10.8-1 with a steel shim gasket, right? Thanks for help. Jason. P.s. Hey charlie, when do want the motor, and what do you have up for offer? |
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| Author: | Charrlie_S [ Fri Dec 27, 2002 2:12 pm ] |
| Post subject: | |
Hey, guess who has some shim gaskets in stock? I am not going to have a day off work untill Sat Jan 4th, except for New Years Day. PS.your cam is very close to mine. |
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| Author: | Jason Kobos [ Fri Dec 27, 2002 4:17 pm ] |
| Post subject: | Interesting! |
Hey charlie, how about one gasket for 6 spark plug tubes? I have to work new years day, but I will see about the 4th. Take care, Jason. |
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