Hello I looked into my 350 it has the 193 heads 64cc 9.0.1 headers air gap intake.A 650 Holley dp 1.5 rolled tips summit k1107 it's to big can't pull a wet hair out of a cats *** has a 5speed 355 gears 26 tall tires in a s10 truck looking for help with cam pick for good bottom mid power
cam help
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My suggestion would be a solid roller with a duration of about 265deg 106Deg centerline. What is the vehicle you are applying this to? Most hydraulic cams are only good for about 6200 RPM if that a good solid roller with pull a fat lady of a toilet with no problem.
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The 193 heads were used on the TBI trucks. They have a swirl vane in the intake port right before the valve pocket/seat to cause good mixing of the air/fuel charge as it enters the cylinder (red arrow on image below). This helps make torque at a low rpm, but at the same time it restricts flow at higher rpm. More on these heads can be seen here.
Because of the way the heads flow, for the best results you need a cam having a relatively short duration. I wouldn't recommend a cam any bigger than Crane 272H10 for a flat tappet hydraulic cam. It's 272/272 degrees @ 0.006" lift, 218/218 degrees @ 0.050 lift, on a 110 LSA. Has a 107 ICL when installed straight up (no advance/retard added by the timing set). You will notice this is a single pattern cam. This is what I've seen recommended for the swirl port heads- BUT- I have never built an engine using these heads, so I am going by others' recommendations. Do your own research to see what you come up with, as to single or split pattern cams w/the swirl port heads.
If you do a cam change you need to change the valve springs to match it. It is always a good idea to check clearances, too. Info on that and other important areas you can read up on if you want, are:
• Points to check
• Geometry
• Adjust lifters
• Cam break in
In any event a smaller cam will suit you better if bottom end torque is your main goal. The can above is the upper limit of what I would use.
Good luck.
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If you really want to increase the performance of the 350 in your S10 truck get a pair of Vortec heads and the Sum-1104 camshaft. With your 5-speed transmission it eliminates the need for a stall converter.
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Check out the Summit Racing sum-1103.The operating range is 1600-5200 rpm Summit Racing® Camshafts SUM-1103 - SummitRacing.com. This cam willl even work with those crappy swirl port TBI heads. Like I said you need a set of Vortec heads. Swapping to Vortec heads will give you about 30hp more.
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Ithooks, there are some very good suggestions here for a cam for your "193" headed 350. I would suggest to consider one even a little smaller than those, the grind many consider an "rv" cam. Usual specs are about .420"/.443" lift, 204*/214* @ .050" duration. This grind idles smoothly and pulls hard in a heavy vehicle, and would work very well with your 193 heads. The Summit K1102, Lunati 10000LK at Summit Racing, Speed Pro CL1014R cam/lifter kit at Northern Auto Parts, Elgin C923PK cam/lifter kit at Northern Auto Parts, Melling MTC1 torque cam at Northern Auto Parts, and the Howards #CL112561-12 at Competition Products are all good examples of this grind. These cams will you give a power band of about 1000are good - 5000 rpm. A friend has an S10 with a 350 with the same heads you have, Edelbrock Performer intake, 600 cfm carb, headers, running the Speed Pro CL1014 grind. He's very happy with his.
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For the cam you have (which is a lot in terms of total duration) the heads can't flow enough to get up into a decent power band. All the add-ons in the world cannot overcome the heads you have. The headers will help a little, the air gap not at all, nor the 650 Holley in this situation. Plus, you don't have enough compression for this cam. One look at the pictures that Cobalt included tells it all. On top of that, I'm guessing this has the stock bottom end which includes GMs useless circular dish piston that kills anything like useful squish and quench, something desperately needed with this cam.
The basic problem is the heads are running out of intake flow right where this cam wants to turn on so you get zip as the former event is preventing the latter event from happening. May be it was somebody else; but haven’t we been through this a few weeks ago?
Heads:
- You can grind the vane out of the 193 head, it's a lot of work, and do a decent port clean up and valve job while you’re there to let the heads breathe up in the RPM range where the cam turns on. This will work effectively but is a lot of effort and includes more expense than meets the eye as you're more likely than not to nick a seat and end up doing a complete valve job as well. For the same kind of money and a lot less effort you can score some part number 10125377 heads. This head will fit your current intake that uses the 72 degree center bolt angle. This part number is made from either casting 14096217 or 14101083; you need to be careful here as these castings also make part number 10159552 which has the older 90 degree center bolt angle. There are a lot of these rebuilt on Ebay at reasonable prices. These are the cast iron version of the L98 Corvette/Camaro Z28 head from 1987 to 1992; except for the vane they are identical to you 193 head.
- Piston, no matter what you do to get compression up whether you mill the heads, and/or deck the block to put the compression where it needs to be with your cam, the pistons with the circular dish will prevent the necessary amount of squish and quench form occurring. This adds a good amount of torque robustness from off idle up to about 5000 RPM. A flat top piston is perfect for this but usually pushes the compression too high. A D dish or step dish piston can restore the needed squish/quench without driving the total compression ratio over the top for the fuel octane. For a double quench shaped chamber such as used on with the 193 heads you have or the L98 iron head I recommend the D dish as the better choice as the step dish pretty much nullifies the more minor quench function coming from behind the spark plug but while your in there it costs the same to get all the function instead of 2/3rds. I'll include a graph of some tests we did a few years ago on a Chevy 355 with the only difference being the piston crown shape an OEM round dish versus a Keith Black D dish.
- Cam; the stick you have is one of those low lift with lots of ramp designs; they require a lot of compression (9.5 recommended minimum) because they hold the valve off the seat for a long time at low lift. This means you have to do a lot of seat work on both the head and the valve. A 5 angle head seat with careful port and chamber blending at each end, with the valves being back cut and swirl polished. The back cut needs at least a 30 degree blend cut behind the seat's 45 and works even better with an additional 20 degree behind the 30. This gets the low lift flow up to where this small opening is useful to feed the cylinder rather than just provide a path for reversion from the effects of the rising piston. Frankly a fast stick like the Comp XE268 will have similar oh-fifty duration to the cam you have with a lot less ramp and more lift. These work great with a head that breathes well, not so good with a 193 though. The Lunati Voodoo and other fast lift cams fall in this category as well. Seating the damn valve sooner rather than later builds more lower RPM cylinder pressure by shutting off the reversion flow of the rising piston that allows it to shove mixture back into the intake till the RPM related intake velocity can develop enough mass to overcome this effect. The high compression is also used to compensate for mixture density lost to reversion on big cammed engines.
Anyway not to say the cam doesn’t' need changing, but changing to better heads and pistons will really wake this motor up.
Bogie
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140 is a little low but the late intake closing with the big cam will lower the cranking compression. The rv type cam will not make your dynamic compression ratio too high. With your Summit K1107 cam your 9:1 static CR will give you a dynamic CR of about 6.6:1, pretty low. The Summit K1102 "rv" cam will give you a dynamic CR of 7.5, a big improvement. Your torque will be much better and you should still run fine on regular pump gas. As oldbogie pointed out, your 193 heads with the swirl vane really run out of breath by 5000 rpm so this cam's power band matches up well with the heads. If you were to port out the swirl vane, or change to heads without it, this cam would still work well, but if you wanted to rev a little higher the other cams recommended with .050" durations of 214* - 218* would work well, altho give up a slight amount on the low end.
Thanks guys the motor has flat tops in it think I will go with vortex heads and summit 1102 or 1103 why would someone put $ in them 193 it has good springs and roller tips had to do some work for that 1107 cam I will look in them when I get them off the truck it will light up the tires first thru 2 but dogs from a roll
and when I start it cold can't use the choke it dies is this from the cam I have to gas tell it gets heat in it
and when I start it cold can't use the choke it dies is this from the cam I have to gas tell it gets heat in it
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Not to pick nits, but that would be Vortec, pronounced Vor-tek, a play on the word 'vortex'.
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You need to divorce the concept of ratio from pressure. Pressure has a loose relationship to ratio that moves around with temperature, atmospheric pressure, humidity, throttle opening, engine speed, etc. The concept of ratio is a mathematically based upon the volume ratios of the swept cylinder plus what's above the piston divided by the volumes above the piston. The above piston volumes include what the shape of the piston crown contributes.
The compresion ratio comes in at mimimum two flavors that the Static Compression Ratio (SCR) and the Dynamic Compression Ratio (DCR).
The SCR is simply the volume swept by the piston which is the bore diameter squared times .7854 times the stroke. The volumes above the the piston include what ever the piston crown shape affects domes remove where dishes add volume. The clearance between the piston at TDC and the block deck production Chevy is about .025 inch times the bore area plus the gasket volume (gaskets are not round so the true volume is usually a bit more than that calculated for diameter) plus the combustion chamber volume.
The DCR is the effect on the SCR that the seating of the intake valve has on stroke. The later the intake valve seats the shorted the stroke looks to the compression ratio. This is a complicated formula that is the same one used for comparing effects of different rod lengths. There are a great many DCR calculators on the web Keith Black has a good and easy to use one. Essentially what this is about is computing the SCR needed to recover the bottom end torque lost to a late closing intake. When the intake is held off its seat by the cam, at RPMs lower than where the intake manifold is building enough speed in the mixture to overcome the reverse pressure in the chamber made by the rising piston. The mixture that entered earlier in the intake cycle is pumped back into the intake. This reduces the molecular density inside the cylinder after the valve closes. This results in a loss of power on the bottom end and it pushes the torque peak as well as the horespower peak to higher RPMs and closer to each other at the RPMs where the peaks occur. The problem with rampy cams of moderate lift is that they hold the intake slightly open and leaking for a long time and the lift is such that it doesn't take advantage of the high port flow heads like the Vortec. The result is you're not getting the power you paid good money for in terms of the parts.
The minimum DCR to shoot for is not less than 8 to 1 and that would be with a cast iron head that burns regular 87 octane unleaded. This cam really doesn't get on the seat till 75 degrees after bottom center. Giving the cam credit for no reverse flow when the valve is held .006 inch off the seat that means that effective closure is 70 degrees after BDC, this drives out a wheezy DCR of 7.1 which is way low. This I calculate from a SCR 8.96 to 1 which is a guesstimate based on your data from which you claim a 9 to 1 ratio.
Unfortunatley without serious work to the engine, it is difficult to get the DCR up where it needs to be for this cam. Guess I should have run these numbers sooner, You've either got to get deep in this motor to change pistons and zero deck the block to get up around 8.2 to 1 DCR with 64 cc chambers or dial this cam way back.
Actually if you read the fine print Sumit says this cam is for a blower or laughing gas motor, and you can see that in the huge exhaust lift and timing. So this cam in addition to the late closing intake valve is more likely than not over-scavenging the exhaust as it is looking for a whole lot of exhaust resulting from a source of boost. This also is a tough problem to solve when it happens, without changing the cam to something milder.
In any case no matter what cam you use the 193 head is going to stand in the way of getting upper end power from the engine. But your current cam is rated for 3000 to 6000 RPM, the 193 heads are all out of breath by 4000-4300. So just about the time your getting up on this cam the heads are done.
Bogie
Thanks for the schooling makes good cents I get it. I did not build this motor I'm going with the vortec heads I have the intake for them and summit 1103 cam till I get my 383 done thanks for all.the info And everyone says 193 don't rev past 4500 rpm I shift this truck at that it revs 5000 plus when I take them off I will look to see if someone did a lot of work or something
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