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Wich cam
https://slantsix.org/forum/viewtopic.php?t=41013		 Page 1 of 2
Author:  D-100/6 [ Mon Jul 12, 2010 7:09 pm ]
Post subject:  Wich cam
Its a stock 80 / with an a833od. Its getting an aussie 4bbl, 390 holley and a hooker header. I dont know what cam to get. I missed out on a cheap one on ebay that was said would be good for what I have. Will get a full rebuild when funds are available later but Want it streetable as I live 25 miles from my home town(also where work will be when I find a job) and its interstate the whole way. Also what forged pistons do you run or would cast be fine? Dont really have a preferance of what times are expected. Thanks
Author:  Joshie225 [ Mon Jul 12, 2010 7:53 pm ]
Post subject: 
Is this for your turbo build?
Author:  D-100/6 [ Mon Jul 12, 2010 8:16 pm ]
Post subject: 
No thats why there are 2 posts
Author:  Joshie225 [ Mon Jul 12, 2010 8:44 pm ]
Post subject: 
Quote:
No thats why there are 2 posts
OK, still need more info on the engine combination. Compression ratio especially.
Author:  D-100/6 [ Tue Jul 13, 2010 5:19 am ]
Post subject: 
First sentance says it all. STOCK 80 225 /6
Author:  D-100/6 [ Tue Jul 13, 2010 5:21 am ]
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When I rebuild it way down the road Id like under 10 for comp but thats later.
Author:  Joshie225 [ Tue Jul 13, 2010 7:30 am ]
Post subject: 
Quote:
First sentance says it all. STOCK 80 225 /6
Sure, but then you started listing all the non-stock stuff you're going to hang on the motor and are asking about a cam. When you tear down the motor you'll have to measure the piston to deck clearance and combustion chamber volume so we can calculate the compression ratio and recommend a suitable camshaft. If you are not going to raise the compression ratio the cam will be very mild as you can put a big cam in a low compression engine without killing torque. With a heavy vehicle like yours and the widely spaced gear ratios of the A833OD you need a strong and wide torque curve.
Author:  D-100/6 [ Tue Jul 13, 2010 10:29 am ]
Post subject: 
It is stock. The other stuff is bolt on and hasnt been put on yet. If it was a higher comp ratio or had been rebuilt I would have stated so. Just wanting to know what cam would work with what its getting now if thats more clear. What cam will work with the boltons is getting. Thanks
Author:  maxracer21 [ Tue Jul 13, 2010 10:56 am ]
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Try an RV cam w/ a super six set up ............2bbl carb and larger exhaust. You just don't have the compression to support the 4 bbl. Hope this helps some.
MaX
Author:  Joshie225 [ Tue Jul 13, 2010 10:57 am ]
Post subject: 
With that heavy vehicle, wide ratio transmission, an untouched stock head and a compression ratio that is likely less than 8:1 I would leave the stock cam in place. Make sure the timing chain is in good shape and the cam timing is correct. If you are interested in raising the compression ratio then a little more cam/valve duration could be tolerated. Porting the head and installing larger valves will help performance a lot.
Author:  D-100/6 [ Tue Jul 13, 2010 12:07 pm ]
Post subject: 
I have a few overhaul parts that will be put on ie timing chain and gaskets. Not doing a 2bbl. If the 4bbl is to much Ill get a 2bbl adapter for the 4bbl and run a 318 carb. Thanks
Author:  ceej [ Tue Jul 13, 2010 12:25 pm ]
Post subject: 
Having the head cut doesn't cost very much. With your headers and 4bbl, I'd really consider bumping the compression up in the 9:1 range. You'll be a lot happier.

A 60cc horse syringe and an old CD case cover are all you need for measuring CC's. Put an old spark plug in the head, smear vasoline or grease on the head around the combustion chamber, drill a couple holes in the CD case plastic, stick it down to the pre-greased head. fill the 60cc syringe to 60cc with water, inject the water into the chamber through one of the holes in the cd case cover, and burp the water out till it's full. Subtract whats left in the syringe.
Measure from the deck down to the top of the piston. Determine if there is an overbore, and if you like, verify your stroke.
Check back in here with your numbers. We can help you compute current compression, then help you determine how much to cut off the head to get your compression where you want it if you need help with it.

I think I spent about $40 to have a head cut the last time. I cut an improved chamber head 0.090" for 9:1 on my wife's over-bore engine.

With 9:1, Erson's RV15M, The RV15M RDP, or even a 260ish degree cam will work pretty well with the solid lifter top end and your 4bbl setup. There are grinds in the 270/260 RDP and larger, but for a street driven pickup they may be a bit much.

:D

CJ
Author:  D-100/6 [ Tue Jul 13, 2010 1:58 pm ]
Post subject: 
Im not pulling the head any time soon. I have another 80 /6 that I can have that head worked over and keep this one running. and maybe build the other motor aswell so itll just be out of comission fo a short time later. Im pretty sure its never been apart at all. Im not working at the moment and dont want to tear into it without having the funds to get going. Its not driven at the moment. I cant tune a carb so it wont run rite. The carb I pulled of had a studder that got slightly worse. My wifes cousin had rebuilt it(carb) short time before I got it and said he couldnt get more than 10mpg. I dont pay attention to milage as my daily driver is a 76 3/4 318 granny 4spd with a non working fuel guage and speedo/odo. Id like to take it to the track with a 1bbl first. Plan to swap carbs again and see if itll stay running. I rebuilt the carb on it now so guess I suck at it. Plus it was my first.
Author:  Doc [ Tue Jul 13, 2010 2:08 pm ]
Post subject: 
Quote:
I'm not pulling the head any time soon...
On a 1975 - 80 SL6, you will have to pull the head to change the cam, the lifters are "trapped" under the head.
DD
Author:  D-100/6 [ Tue Jul 13, 2010 3:56 pm ]
Post subject: 
Oh now doesnt that suck for me. Well. I gues I get the 1bbl figured out and worry about a cam later :( The most Ive done to a slant was change a fuel pump and swap a carb and tune up. Ive pulled a head but didnt pay attention. Would it be best to through parts and $$ at the 67-8 slant I have than? Or should I save that one for the turbo build? Like I said I have another 80 / and might be able to get a 78 / with trans from a stepside. Glad Im a member here.
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