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Old 03-31-2013, 08:51 AM
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choosing cam for mild 355?

I was looking for help choosing a cam for a mild 355 motor in a heavy c10 truck, as Its abundntly clean I can't do it haha. Motor is a 355 with a set of 195 runner, 64cc heads, rpm intake, 3.73 gears, 700r4 trans and 2600 summit racing stall. Comp lifters, pushrods and mutha thumpr cam 235/249 @50, double roller timming chain, summit racing 1.5 roller tip rockers, Edelbrock 1406 carb. Motor is a dog down low but comes to life after 2500ish rpm. As it sets now it won't even foot brake a burnout or spin the tires off the line with bald tires. I might add that I truly like the rough sounding idle. Truck primary use is street/strip. But its not oftin that it gets on public roads. Thanks for the help.

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Old 03-31-2013, 09:09 AM
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You need to recurve the distributor for that cam..
its in the wiki on distributors. That cam is best with a 3500 stall. ( the converter you have is not the right converter.
(these 2600 stall chap converters are junk. All they do is bend the fins inside. Very inefficient)
Get a real high stall lock up converter. 3200-3500stall based on a small 245MM case size.

Will be a whole different truck once the distributor advance curve is properly modified.

24-26deg at idle 34-36degt at max advance (10deg advance curve)
You cannot get the right curve by just swapping adv springs.

You may even find that (with that thumpr cam) simply locking out the mech advance system works best.
as these thumpr cams need a ton of idle timing.
Lock out the adv and set the locked fixed timing to 34-36deg BTDC.
The timing does not advance with rpm.
It will be very responsive now and idle much nicer too.
Now you can fine tune the carb
http://www.telusplanet.net/public/gi...delbrock_1.htm
edelbrock tuning.

You got the wrong torque converter

Last edited by F-BIRD'88; 03-31-2013 at 09:19 AM.
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Old 03-31-2013, 09:20 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
You need to recurve the distributor for that cam..
its in the wiki on distributors. That cam is best with a 3500 stall. ( the converter you have is not the right converter.
(these 2600 stall chap converters are junk. All they do is bend the fins inside. Very inefficient)
Get a real high stall lock up converter. 3200-3500stall based on a small 245MM case size.

Will be a whole different truck once the distributor advance curve is properly modified.

24-26deg at idle 34-36degt at max advance (10deg advance curve)
You cannot get the right curve by just swapping adv springs.
Thanks fbird. You always seem to have the answer. With age comes wisdom right? I do have a question on the stall speed. When I contacted comp about the stall they said that the cam I had I needed a 2500rpm stall and 9.0.1 compression. I might be wrong but dosent a factory 86 sbc had close to the compression? I bought the 2600rpm on there recomendation.
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Old 03-31-2013, 09:26 AM
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what times are you turning with the truck now?
Have you weighed the truck?
What fbird said is a very good starting point for your tune.One thing at a time,starting with the timing.What ignition system are you using?
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Old 03-31-2013, 09:32 AM
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Stock low perf base engines are 8.5:1 or less.

That cam and any other hyd cam that has 235 deg duration @.050" needs a 3500 stall converter.
The idiot that gave you the converter stall recommendation has obviously never used such a cam.

That cam really wants 10-10.5: cr (92 octane)

Summit does not sell the right converters for h this job. All their Summit th700r4 converters are junk tweeked stock GM converters.
You need a true 9" 10" hi stall. 3000+++stall with lock up ATI , Precision, Yank, etc.

The 600cfm carb is TOO SMALL if you were after horsepower.

Get a 750-800cfm carb. More power.

Last edited by F-BIRD'88; 03-31-2013 at 09:38 AM.
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Old 03-31-2013, 09:37 AM
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I have not run the truck yet. No local tracks within a 100 miles. Need to get to one. I haven't weighed the truck but assume itit's in the 4000 mark. The distribitor is a summit brand hei and taylor wires ac delco plugs.
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Old 03-31-2013, 09:44 AM
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Be sure the starter motor support bracket is installed.
It is easy to either lock out or limit the advance on a HEI.

HEI WIKI LINK
http://www.crankshaftcoalition.com/w...nition_advance
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Old 03-31-2013, 09:46 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
Stock low perf base engines are 8.5:1 or less.

That cam and any other hyd cam that has 235 deg duration @.050" needs a 3500 stall converter.
The idiot that gave you the converter stall recommendation has obviously never used such a cam.

That cam really wants 10-10.5: cr (92 octane)

Summit does not sell the right converters for h this job. All their Summit th700r4 converters are junk tweeked stock GM converters.
You need a true 9" 10" hi stall. 3000+++stall with lock up ATI , Precision, Yank, etc.

The 600cfm carb is TOO SMALL if you were after horsepower.

Get a 750-800cfm carb. More power.
Fbird, do you recommend changing out the cam to better suit the cr of the motor and the stall I have. Or recurving the distribitor and later changing out the stall. I say later sue to just having a child and not being able to drop 400+ on a quality stall.

I can swing a quality cam at this time.
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Old 03-31-2013, 09:51 AM
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Fix the distributor, first. it will be a whole different truck ..


if you want a milder cam get one with 218@.050" or less for that truck.
I recomend Isky Cams or Crane Cams.

EG: Isky 264/271 Mega cam #201264-27112
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Old 03-31-2013, 09:51 AM
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tune what ya got for now.even with not enough converter and carb,the truck should still launch hard.even if you change the cam,you still need to do the proper tune,get it done first.
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Old 03-31-2013, 10:32 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
Fix the distributor, first. it will be a whole different truck ..


if you want a milder cam get one with 218@.050" or less for that truck.
I recomend Isky Cams or Crane Cams.

EG: Isky 264/271 Mega cam #201264-27112
Quote:
Originally Posted by vinniekq2 View Post
tune what ya got for now.even with not enough converter and carb,the truck should still launch hard.even if you change the cam,you still need to do the proper tune,get it done first.
Is it fairly simple to recurve one? I've never done one so its sorta intimidating to me. Do yall have a recomdation on a brand recurve kit?
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Old 03-31-2013, 11:45 AM
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With that cam and the lame converter I would just lock out the distributor.
read the wiki
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Old 03-31-2013, 12:18 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
With that cam and the lame converter I would just lock out the distributor.
read the wiki
I googled for it and read the wiki. Didnt see it, I will reread it. Thank for all the help fbird. Really wish there was local individual here that new how to do a lot of stuff like this. Living in a small down starts to buf me sometimes. .
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Old 03-31-2013, 01:03 PM
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its here
choosing cam for mild 355?

You can simply and quicky lock out the adv mech just by removing the weights and springs and wrapping the bare mechanism so it cannot move, using two zip ties to tie it.
Move it to a fully advanced position and zip tie it.

Make sure the rotor is positioned correctly when re assembling it.

reset the locked timing to 34-36deg BTDC.

Not needed with mild cams
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Old 03-31-2013, 01:09 PM
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Now you will know how that thumpr cam is supposed to work.
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