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Old 06-18-2006, 09:40 AM
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Compression estimate, cam suggestion

With a 30 350 and flattops with the valve reliefs on one side, 76cc heads that have been milled .014 ( according to machinist) I'll probably run a thinner head gasket to try and pump it up a little more also.

The heads are fresh rebuilds with bronze valve guides and 1.94/1.50 valves

Plan on putting this in my S10 with a power glide and 3200 converter, I think it has 4.11's in the stock rear which probably won't hold up long. Looking for a solid cam to run in it now, any suggestions?

I'm saving up for the 49cc Dart iron eagles in the Speedway motors catalog and a victor Jr intake but that will take a while.

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Old 06-18-2006, 02:06 PM
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280/288 244/252@.050 .518/.536 106 lash .024/.024 and you want to shift at 6000, this cam will work well with the dart heads as well, just add 1.6 rockers and it should pull to 6500.

I would do some portwork on the exhaust side of the heads, as well as good freeflowing exhaust and 1 5/8 longtube headers min.. the 4.10's are fine..



2wld4u
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Old 06-19-2006, 05:46 AM
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engine

With out knowing the exact numbers it's only a guess but your engine will be around a 9.2:1 static compression....

The above cam is to big for that engine.... You will need to change cams when you swap the heads for the best results.... If you just want to get it running i would install a 230@.050 hyd cam for now to run with your current combo, then when you switch to the new heads up-date the cam then...


IMO


Keith
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Old 06-19-2006, 10:11 AM
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It is really hard to get an accurate compression calculation without knowing how much of a reduction in volume the chamber experienced with the milling. At 76cc's, and a .045 quench, I came up with 9:1. 9.2:1 would be as good as any guess that I could come up with taking the .014" mill into consideration. At that compression I would not go with a cam above mid 230's at .050 duration. You also need to take into consideration the fact that your heads probably only have a 150cc-160cc runner. having a matched setup is vital to a motor that performs well. A head of that size will probably be done be around 5500 RPM max on a 350. Going with a cam that is supposed to make power to 7000 RPM would be counter productive. I think a cam like the XE274H would be the best bet for these heads (230 236 @.050 .490 lift 1800-6000 RPM) realizing that you also have a 3200 stall. It is still probably a hair large for the heads, but that should not be the end of the world, they are still relatively close to each other.

Oops, I just realized that you were after a solid cam, in that case, I would do something like the xs268s (230 236 @.050 .488 .501 lift 1600-6000 rpm)

Adam
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Old 06-19-2006, 01:27 PM
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well it just happens I did a 355 a month ago just like this one, it was .060 350 flat tops with 4 reliefs and not the best chevy 386 castings( why? thats what he had), I gasket matched the entries, installed 2.02x1.60 valves, some bowl work , and used the same cam, and it went into a S-10, he wasnt really happy because the first time he got on it he grenaded the rear end, same 4.11 gears, but he did have a th350 and a B&M 3200 stall.. to each his own but I know what works.. now if idle quality is a main concern this cam may be a tad bit radical, as Idle quality was not an issue...

Dont want to get anything started but I do practice what I preach and if It didnt work I wouldnt have recomended it.. and to be honest I was surprised that the cam needed to have that much duration to make power @6000 with those heads, and yes we flow'ed em.. now if your RPM celling is 5000-5500 yes a smaller cam would be the best choice...


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Old 06-19-2006, 01:49 PM
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I agree that with larger valves and port work, as long as he is at 9.5:1-10:1 compression that a larger cam would work well and make more power. For the price of that though, I think he may be better off saving up for an aftermarket set of heads. I could be wrong, but i just seems like a missmatch having a 244@.050 cam with a 255cc runner? Am I wrong?

Adam

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Old 06-19-2006, 02:35 PM
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Thanks for all the replies, I was bidding on the pistons on e bay but didn't win
but this is still the combination I'm going to start with. I guess I don't NEED a solid cam but I've never ran one and I'm curious, just want to try one. I'm still not sure If I'm going to put plates on the truck or not so street ability isn't a real concern. According to the advertisement the 49cc heads should make over 12 to 1 with flat tops. So I don't want to run dome pistons.

The block is a 4 bolt gm replacement, one piece rear main with the provisions for a roller cam. It has a fresh 30 over bore and the crank is 10/10. I'm trying to fly under the radar of my wife and buy this stuff off ebay a little at a time. I still need the conversion kit for the v8 swap so I'm not in a hurry.
Just trying to get the parts together.

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Old 06-19-2006, 05:45 PM
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The problem is that you are talking about two very different motors. The one with the heads that you currently have is going to be better suited as a nice performance street motor. With 9.5:1 compression and a stock head, you are not going to get a real performer no matter whan cam you use. On the other hand, with 12+:1 compression , you can run something like a 215cc head and a much larger cam. Then, you will be talking about some serious power. I would buy a cheap flat tappet cam now and then another one when you get the new heads. Solid cams will make more power, but then you have to adjust them.

Adam
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Old 06-20-2006, 05:41 AM
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cam

I too would not post an answer with out doing the job first...

True that cam might work with a 9.2:1 engine but it's not the right cam... big difference...

Real light cars and cars with big rear gears will mask the problems with running cams that are to big...

Take that s-10 you just installed that cam in and race it, race it every weekend for a month untill you are sure you have agood idea what it runs, then install a cam with 10 degrees less duration @.050 and then race it again,,,

tell us what the results are...

I have seen it time and time again on the dyno and at the track where over cam'd cars are always faster with a smaller cam...

I just built a small block chevy with 10.0:1 and a 230@.050 hyd cam that made 526 hp and 550 ft/lbs......

keith
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Old 06-20-2006, 10:00 AM
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[QUOTE=k-star]I too would not post an answer with out doing the job first...

True that cam might work with a 9.2:1 engine but it's not the right cam... big difference...

Real light cars and cars with big rear gears will mask the problems with running cams that are to big...

Take that s-10 you just installed that cam in and race it, race it every weekend for a month untill you are sure you have agood idea what it runs, then install a cam with 10 degrees less duration @.050 and then race it again,,,

tell us what the results are...

I have seen it time and time again on the dyno and at the track where over cam'd cars are always faster with a smaller cam...

I just built a small block chevy with 10.0:1 and a 230@.050 hyd cam that made 526 hp and 550 ft/lbs......

keith[/QUOTE

I just built a small block chevy with 10.0:1 and a 230@.050 hyd cam that made 526 hp and 550 ft/lbs...... what does that have to do with a 9:1 350? unless you used the same heads? Thats misleading, at the most with 230* with the heads mentioned, he'd be lucky to get 350hp..


the 350 I just finished ran 8.0@82 mph N/a 1/8 mile @ 2000 feet and your telling me a smaller cam would make it faster?


2wld4u
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Old 06-20-2006, 11:08 AM
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It's called an example... It has nothing to do directly with his engine, but to show trends....

what was the 60' time with that 8.0 pass???

Yes if that engine is really a 9.2:1 350 then everything else being the same it would be quicker, (lower ET)

Keith
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Old 06-20-2006, 03:11 PM
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I don't want to start a fued here, and I agree that a cam change will be in order when I switch heads. But with my restrictive stock heads wouldn't I want more duration and less lift?
I'll probably gasket match them to an old torker Intake I have and leave them alone. I've never did any port work and don't want to ruin a fresh set of heads!
Your all probably wondering why I don't just sell these and buy a good set eh?
Problem is I don't think I can get the $321 back out of them they charged me to do the valve job. Seems kinda steep huh? Basic valve job, no 3 angle, bronze guides and screw in studs ($20) and they shimmed my stock springs!!?!
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Old 06-20-2006, 03:30 PM
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Just wanting to see how this thread turns out. :-)
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Old 06-20-2006, 06:04 PM
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Quote:
Originally Posted by k-star
It's called an example... It has nothing to do directly with his engine, but to show trends....

what was the 60' time with that 8.0 pass???

Yes if that engine is really a 9.2:1 350 then everything else being the same it would be quicker, (lower ET)

Keith

the 60" was 1.755
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