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Old 10-18-2012, 09:44 AM
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193 heads, best cam.

i have a 1989 chevy blazer with 7" lift on 38x15x15 wheels with 700r4 with 373 rear swap. 350 std. bore and stroke with .275 dome piston with estimated 11.88:1 compression. I am budget building and wondering what the best cam to use would be. I have stock 193 heads that i will be porting. preferably a torque engine. i was looking at comp cams xtreme 4x4 cam with, 262 Intake / 270 Exhaust, Duration @ .050'' Lift:218 Intake / 226 Exhaust, valve lift with 1.5 rockers .462'' Intake / .480'' Exhaust, and 111 lobe separation. i guess what my question is. can my heads except this amount of lift and is this a good cam for my application. i am hoping for a lope noticeable idol. Its a weekend worrier not a daily driver and only sees road between mud holes. Any and all help would be beneficial.

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Old 10-18-2012, 01:00 PM
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The 193 is the dreaded swirl port TBI heads. These heads work great for low RPM power and torque, but due to the restrictive swirl vane they run out of breath at 4000 RPM. So just about any cam you pick will do no good past the point of 4000 RPM as the heads don't flow enough to support power past that point. I'd be looking into getting a set of heads before I worried with the cam.
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Old 10-18-2012, 02:54 PM
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At 11.8:1 you're going to have to run race gas or E85. I hope you planed for that. Additionally, as noted the TBI heads are crap so you need a small cam to match them. the typical 204/214 "rv cam" is about right.
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Old 10-18-2012, 04:23 PM
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Quote:
Originally Posted by ap72 View Post
At 11.8:1 you're going to have to run race gas or E85. I hope you planed for that. Additionally, as noted the TBI heads are crap so you need a small cam to match them. the typical 204/214 "rv cam" is about right.
That cam will knock like crazy and make no power. You can not use that cam in 11.8:1 engine.

I use this to figure out my Dynamic compression ration then buy a cam big enough to avoid the knock. shoot for dcr of 8.5:1 then you can run pump gas.

Wallace Racing: Dynamic Compression Ratio Calculator

A bigger cam will lower compression until the engine comes up on the cam at higher rpm where the piston is moving faster and the fuel does not have time to heat up before the plug fires.

Never used the heads. If they dont flow port em or replace em.

Hope this helps
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Old 10-18-2012, 04:46 PM
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Im allredy planing on race fuel and im not looking for high rpm. This truck is going to see very little highway if at all. It will be alot of big hills deep mud and river beds. So I want torque for the big tires plus i want the lopey idol. Not looking for crazy hp.. I bought a set of heads and they wer cracked and so im weary of huying heads or using junkyard heads.
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Old 10-18-2012, 04:55 PM
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Im allredy planing on race fuel and im not looking for high rpm. This truck is going to see very little highway if at all. It will be alot of big hills deep mud and river beds. So I want torque for the big tires plus i want the lopey idol. Not looking for crazy hp.. I bought a set of heads and they wer cracked and so im weary of huying heads or using junkyard heads.
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Old 10-18-2012, 05:02 PM
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Im allredy planing on race fuel and im not looking for high rpm. This truck is going to see very little highway if at all. It will be alot of big hills deep mud and river beds. So I want torque for the big tires plus i want the lopey idol. Not looking for crazy hp.. I bought a set of heads and they wer cracked and so im weary of huying heads or using junkyard heads.
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Old 10-18-2012, 05:08 PM
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Quote:
Originally Posted by Bogger View Post
Im allredy planing on race fuel and im not looking for high rpm. This truck is going to see very little highway if at all. It will be alot of big hills deep mud and river beds. So I want torque for the big tires plus i want the lopey idol. Not looking for crazy hp.. I bought a set of heads and they wer cracked and so im weary of huying heads or using junkyard heads.
Rock crawling needs low rpm power. Mud trucks usally have big cams and just keep it floored and low gears. 4.56 gears are nto uncommon many use even bigger.

High rpm cams make big torque just higher up in the rpm band. Low rpm cam will not lope or make enough power to rip across the top of a big mud hole. Most of the time the only way to make more torque than stock is force induction or higher rpm. Factory has taken advantage of all the torque they can get from the engine at stock compression ration and rpm.

I guess it depends on if your racing or not. If you want the tires throwing mud in the air at 40 mph your going to need some big high rpm power.

If you want to just not get stuck and do some trail riding then a smaller cam can be used. you will have to figure out the gear ratios and rpms needed for your tires to move the truck at the right speed in each gear. Granny gear first can help a ton in rock crawling with bigger cams.
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Old 10-18-2012, 05:15 PM
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Quote:
Originally Posted by hcompton View Post
That cam will knock like crazy and make no power. You can not use that cam in 11.8:1 engine.

I use this to figure out my Dynamic compression ration then buy a cam big enough to avoid the knock. shoot for dcr of 8.5:1 then you can run pump gas.

Wallace Racing: Dynamic Compression Ratio Calculator

A bigger cam will lower compression until the engine comes up on the cam at higher rpm where the piston is moving faster and the fuel does not have time to heat up before the plug fires.
since you're running race fuel ignore this.



If you want good torque you need to forget about a really radical idle, they don't go together. A 274h06 cam is about the best compromise for most people. Run it with 1.6 rockers. You can find idle videos of it on youtube to give you an idea of the sound. It also has good torque from 3,000-5,000 rpm.
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Old 10-19-2012, 07:00 AM
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Im looking at low rpm. Its not for racing. Its my play toy. I will compeat it here n there but just to prove street legal (ish) budget build can be just as good a crazy expensive built mud truck. I just have the biggest vehicle out of all my friends and I want to show them what my chevy can do. I will be changing the rears to bigger but im waiting till I am done so I can find best all around ratio. I am currently at a close stock ratio with the 3.73 rear swap. I will be going to bigger tires also after I run the tread off this set.
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Old 10-19-2012, 07:31 AM
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You may need to clearance the piston dome to fit the combustion chamber on those heads @TDC.
Its up to you to measure spring/ retainer seal/guide boss lift clearance on your heads..
The cam looks fine for the rpm you want. The 38" mudders will want a 5.38 to 5.57 gear.
I would get the GM 2100 stall "corvette" " iroc" torque converter. Used on the L-98 corvette/Iroc camaro.
It is also refered to as the "S-10 converter" used behind the high perf 4.3L V6 in the S-10.
High enough stall for the cam, has lockup . Low enough stall for rock crawling.

What is the hi low range ratio on the transfer case.? Find a source to get 110 octane unleaded gas.
You can buy it by the barrel and blend with 92 octane pump gas.

Another consideration is to use water/methanol injection for the near 12:1cr.
I would use the edelbrock performer rpm manifold For the Qjet and a Qjet carb. The early simple 4MV style.
Great fuel control and throttle response for off roading.

Last edited by F-BIRD'88; 10-19-2012 at 07:41 AM.
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Old 10-19-2012, 10:55 AM
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I live in pennsylvania. Home of the harley. I can get 114 oc 5 miles from my house and there r 2 air ports near by. The pistons are reliefed for spark plugs allredy. Where else would I have to reliefe? I have a 203tc and its 1:1 and a 1.96:1 low. I wont go higher than a 5.13 rear
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Old 10-19-2012, 12:02 PM
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Quote:
Originally Posted by Bogger View Post
I live in pennsylvania. Home of the harley. I can get 114 oc 5 miles from my house and there r 2 air ports near by. The pistons are reliefed for spark plugs allredy. Where else would I have to reliefe? I have a 203tc and its 1:1 and a 1.96:1 low. I wont go higher than a 5.13 rear
I understand.

I run 11.5:1 with larger cam and aluminum heads runs great on pump gas. With the cost of gas down here I could cover the cost of alum. heads in a small number of tank fulls of race gas. Its 8/9 bucks a gallon for CAM2 at track last time i went and that was a while ago.

Does anyone sell E85 near you that is great for high compression and cheap compared to anything labled race fuel. All the carb manufactures sell an e85 carb these days.
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Old 10-19-2012, 01:42 PM
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Its weird down here with e85. There is a place a fuew miles from me but then its almost 60 miles till next one. Plus it will be to far between filling and I dont want to absorb water in which ethenol is known for. And the bad humidity we have. Plus ill be doors deep if I go threw the rivers down here and any moisture isnt good.
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Old 10-19-2012, 02:17 PM
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Quote:
Originally Posted by Bogger View Post
i have a 1989 chevy blazer with 7" lift on 38x15x15 wheels with 700r4 with 373 rear swap. 350 std. bore and stroke with .275 dome piston with estimated 11.88:1 compression. I am budget building and wondering what the best cam to use would be. I have stock 193 heads that i will be porting. preferably a torque engine. i was looking at comp cams xtreme 4x4 cam with, 262 Intake / 270 Exhaust, Duration @ .050'' Lift:218 Intake / 226 Exhaust, valve lift with 1.5 rockers .462'' Intake / .480'' Exhaust, and 111 lobe separation. i guess what my question is. can my heads except this amount of lift and is this a good cam for my application. i am hoping for a lope noticeable idol. Its a weekend worrier not a daily driver and only sees road between mud holes. Any and all help would be beneficial.
The 193s are intended to get good gas milage at low RPMs in a heavy truck they aren't necessiarily meant nor do they create large low end torque numbers. Most any late model double quench, centered spark-plug, fairly modest port and valve size head will do that. What these heads really do is limit the upper RPM band. They gain very nicely to about 4300 then level off to about 5 then just quit. Figure that in your gearing and tire size.

If by porting you mean getting rid of the swirl vane you're on to something, they will wake up when ported but it's a lot of work. Check out castings 14096217 and 14011083 these are sold as cast iron L98 heads which is pretty much the same thing as the 193 with no swirl port vane to cut out. They are usually pretty cheap because nobody's looking for them. Heres where it gets tricky:

Part number 10159552 is the 55-86 version with 90 degree center holes, it is made from castings 14096217 or 14011083.

Part number 10125377 is the 1987 and up version with 72 degree center holes. It is made from castings 14096217 (sound familiar?) or 14101083 (watch this it's sooo close to above but it is different) these will fit your 89 TBI intake, or what ever intake you're running against the 193 heads.

All of these are 64 cc chambers with 1.96x1.5 valves and have a 170/175cc intake port. They are found on TPI and TBI passenger and cop cars including Camaro and Firebird.

A rebuilder may take your 193s as cores and save you some money.

Bogie

Last edited by oldbogie; 10-19-2012 at 02:26 PM.
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