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Discussion Starter · #1 ·
I'm building a 350 for my 86 chevy pickup and just have a couple questions on the cam install. I found a cam kit on Jegs (http://www.jegs.com/i/Comp-Cams/249/K12-239-3/10002/-1#) that is designed to produce high torque. this truck will be primarily a street vehicle, but would be used offroad in situations like hunting, and the occasional "hey theres a big pit of mud! lets see if we can make it through!" situation. The specs of the cam kit are as follows:
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Excellent response, good mid-range, noticeable idle.

Operating Range: 1300-5600 RPM
Duration Advertised: 262° Intake / 270° Exhaust
Duration @ .050'' Lift: 218° Intake / 226° Exhaust
Valve Lift w/1.5 Rockers: .462'' Intake / .480'' Exhaust
Lobe Separation Angle: 111°
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This kit comes with Camshaft, Lifters, Timing Chain & Gears, Valve Springs, Spring Retainers, Spring Locks. I need to know if there is anything else I would need to change in the engine to match this new cam setup? What about gears? A friend told me I would need lower gears for this cam. Any ideas?
Thanks!
 

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Discussion Starter · #3 ·
techinspector1 said:
If the motor has a static compression ratio of between 9.1:1 and 9.4:1 and a squish of between 0.035" and 0.045", this cam will work great.

A good compromise on a gear would be around 3.73:1.
Thanks! What are you referring to as squish? This is my first build, so I'm still trying to get familiar with which measurements are which and what they mean.
 

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Squish is the measurement from the top of the piston crown to the underside of the cylinder head with the piston at top dead center and includes the thickness of the head gasket. If, for instance, the piston crown is down in the bore by 0.005" with the piston at top dead center and you use a 0.040" thick head gasket, the squish will be 0.045".

Making this work requires a nice flat area on the crown of the piston to come up and mate with the underside of the cylinder head to squish the fuel/air mixture which would normally be farthest away from the spark plug, toward the spark plug to homogenize the fuel/air mixture and create turbulence so that the motor can use a higher dynamic compression ratio for the available fuel used, without incurring detonation.

Stock-type Chevy pistons with 4 valve reliefs and a dish in the middle do a poor job of squishing. There is only a very thin ring of material around the perimeter of the crown to form a squish area with the underside of the head.

Flat-top pistons with two valve reliefs work best. If you have to use a dished piston to reach your target static compression ratio, you're better off to use a D-Cup piston such as that manufactured by Keith Black. The dish in these pistons is offset to one side, allowing a large flat squish area on the other side of the piston to allow mating up with the cylinder head and creating a good squish....like this....see the large flat area on the right side of the photo....
http://kb-silvolite.com/performance.php?action=details&P_id=224

Here's a link to a site that shows an illustration of what is being discussed here....
http://www.rbracing-rsr.com/squishcalc1.html

And some more....This is by David Vizard, one of the premier Chevy engine builders in the world....You would do well for yourself to get a few of his books and educate yourself....
http://books.google.com/books?id=mm...=onepage&q=squish cylinder head Chevy&f=false

Books by Vizard....
http://www.amazon.com/s/ref=nb_ss?url=search-alias=stripbooks&field-keywords=David+Vizard&x=13&y=13

And by the way, it's way easier to determine the static compression ratio and then choose a cam to work with it than it is to choose a cam first and then try to build the static compression to the cam. There are way more cam choices than there are piston and head choices.
 

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if you are using the stock gears (2.73 to 3.08) then get a different cam.

get a compcam 252H (206/206 at 0.0500). then use the stock springs, rockers, pushrods, ect....

this cam (252H) will work well with 8.25 to 8.75:1 cr.

the edelbrock performer cam is also a good choice (204/214 at 0.050") and would work nicely if you are going to use stock exhaust manifolds (more exhaust duration).

if you use the bigger and much more aggressive compcam that you mentioned above, then makes sure to use an oil additive to prevent the cam from going flat. www.zddplus.com.

what heads are you using?

what compression ratio?

are you using headers?

what pistons?
 

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Discussion Starter · #7 ·
454C10 said:
what heads are you using?

what compression ratio?

are you using headers?

what pistons?
This is what I am in the process of determining.
Im looking at probably shooting for a compression between 9 and 10. Ive been told that a pair of 487X heads that have been properly rebuilt are a great way to go, so I'm entertaining that idea, assuming I can get a hold of a set. Ive also been contemplating the idea of vortec heads/intake. I will be using headers. The best info on the pistons i'll be using has so far come from techinspector on this thread.
 

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what gears?
what tires diameter?
what transmission?
what stall?

If you are planning to run something like a 3.08 gear, th350 trans w/stock converter, and 30 inch+ tires, then you will need to use a cam in the 204 to 210 range at 0.050". And 10:1 cr would be too high with a cam this small. 9:1 would be the most you should run for the about setup.

vortec heads would be a good idea.
 

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Discussion Starter · #9 ·
Tires will most likely be 31x10.5R15. maybe 33s if I ever lift it. I'm not sure what gear ratio I should be using. I'm still all in the "figure out what the ******* I need* stage lol! I was thinking about something like a 4.10 with the 31s, or maybe a 4.56 if I jump up to 33s. The transmission will either be a TH350 stock converter or a 5 speed that I dig up somewhere. my truck currently has a 700r-4 in it.
 

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klutchmaster427 said:
This is what I am in the process of determining.
Im looking at probably shooting for a compression between 9 and 10. Ive been told that a pair of 487X heads that have been properly rebuilt are a great way to go, so I'm entertaining that idea, assuming I can get a hold of a set. Ive also been contemplating the idea of vortec heads/intake. I will be using headers. The best info on the pistons i'll be using has so far come from techinspector on this thread.
Good luck finding good "X" heads. They are a pretty rare find nowadays. The hot rodders and bracket racers, in the day, have pretty much used them up. I know I used one up with a broken intake valve at about 7500 rpm about 20-25 years ago. LOL There are so many "better" heads out there today.

But then again, with all the reasonably priced new heads, maybe some "old schoolers" are not hoarding them any longer.
 

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Discussion Starter · #11 ·
zap60 said:
Good luck finding good "X" heads. They are a pretty rare find nowadays. The hot rodders and bracket racers, in the day, have pretty much used them up. I know I used one up with a broken intake valve at about 7500 rpm about 20-25 years ago. LOL There are so many "better" heads out there today.

But then again, with all the reasonably priced new heads, maybe some "old schoolers" are not hoarding them any longer.
Haha yeah you never know. I've kinda got my mind set on a vortec setup now unless someone gives me a good reason not to. But since brand new vortecs are only 300 bucks a pop, they fit my college kid budget and supposedly will still get me over the 300HP mark if used together with the right parts throughout the build.
 

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stay with the 700r.

use 4.11 gears with 31 to 33 inch tires.

use a 2200 to 2400 stall.

use a cam with 212 to 218 at 0.050" (compcam 260 or 268H)

use compression in the 9 to 9.5 range

vortec heads will need modification to run these cams. Furthermore, votec heads require vortec rocker arms, vortec intake, vortec valve covers. if you have all these thing for regular heads then just get a set of 180cc dart iron eagles. (same money)

get a holley 3310 750 cfm vacuum secondary carb.
 

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Discussion Starter · #14 ·
454C10 said:
stay with the 700r.

use 4.11 gears with 31 to 33 inch tires.

use a 2200 to 2400 stall.

use a cam with 212 to 218 at 0.050" (compcam 260 or 268H)

use compression in the 9 to 9.5 range

vortec heads will need modification to run these cams. Furthermore, votec heads require vortec rocker arms, vortec intake, vortec valve covers. if you have all these thing for regular heads then just get a set of 180cc dart iron eagles. (same money)

get a holley 3310 750 cfm vacuum secondary carb.

With this setup approximately how much HP will I be looking at?
 

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Discussion Starter · #16 ·
So I just finally got around to googling my casting number and it turns out that my 350 is a '68. According to some sites it may have been from a camaro. What compression ratio and stock hp did these engines have?
 
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