Cam change needed maybe ?

Ken

Ken

Member
Many Updated done 1994 GMC 4x4 Yukon Two Door and I am thinking the cam may need to be changed, I tried to go to COMP Cam's and use there chart but keep getting an error when I go to finish it ..... INFO and the cam in it now in pictures >>>
Also going to upgrade throttle body to a 58mm on a Holly Stealth Ram Jet. 383 forged & Bal. 4bolt main,1pc rear seal, roller cam & roller tipped 1.6 rockers, lift comes in at about 510/520, AEM Controller/ECM & Engine Position Module LS-1 coil on plug, JBA shorty stainless Headers, 4L80E Trans 3/4ton 8lugs 4.11 axles

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Note... On the TrickFlow G1 Twisted Wedge Heads the Intake valve is cantered to 13 deg's, 180cc intake port, 64cc chambers, 13* intake / 23* exhaust valve , ported polished and flowed and valve seats upgraded... This Cam is the same one from the original 2bll TBI Fuel injection system... gear has gone from 3.08 to 4.11 and tires went from 235/70 R16 to 225/75R16. Weight is about 4800Lbs. I have been trying to get trans shift points right learning about the AEM controller, not much luck, looking to go to a TCI EZ trans controller. But this thing won't even spin the tires unless there dusty or wet IT Just Hook's... I would think even with the CalTracs Bar's It should still spin the tires off the light, The lowering keys are backed way off and it allows the front end to come WAY UP and transfers the weight to the read end...
After this get's right on to the front steering... maybe rack and pinion :)
 
Oh When this had a 750 4bll TBI fuel system, It was pulling 2Lbs. of vacuum at WOT.... It is a real PITA to start when south of 32deg's winter time even after adding dual 1000plus CCA batteries unless you shoot some starting fluid into it, once warmed up shut it off and starts fine..... and I found the flow numbers from HOT ROD article on the G-1 Trick Flow Twisted Wedge Heads... I know mine flow better but I can't find the computer print out... I would have to guess at least 10-15 more across the board more... It's only 6miles to work and gas doesn't matter to me... would like something with more power and lumpy most likely a bit more lift but might have to check clearance's of the pistons... I know they are dished... One other thing is a retro fit from a GM IAC valve to a Ford IAC valve on the 52mm throttle body, which will be upgrades to a 58mm. When we were trying to tune/while driving this thing is still pulling hard at over 6000rpm
 
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This was the TBI System I had on this Truck before going to the Holly Stealth Ram Jet and was Pulling 2 Lbs. of Vacuum at WOT. I even had the bigger injector's, that took it to I think 400HP, never could get it to run nice always ran snotty ... I remember while tuning mechanic in pass. seat and being in 2nd gear with the 4L60E tran's and 3:08 rear end speedo and tach both off the chart figured "guessing" I was doing about 95-100 and about 6200rpm ... mind you this is a Big BOX going down the road, it get's spooky over 100 lol :) This was before lowering it also... OH and I still have the intake and this.... If someone is interested ... uses the old OBD 1 controller with a custom chip...
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changing from the 52mm to a 58 mm throttle body might seem like its going to give some significant improvement,remember the 52mm throttle body flows about 830 cfm and each individual runner feeding the cylinders requires less than 270 cfm , theres an intake stroke every 90 degrees but the throttle body flow into the common, plenum is sufficiently large enough to easily supply demand, because its intermittent, and shared from the common plenum.
but Id point out swapping to the larger throttle body is usually not nearly as effective as simply doing some manifold runner clean-up, and cylinder head port,and bowl area clean-up.
and remember youll want too keep the fuel/air ratio consistent with making maximum torque , this very often requires an upgrade in fuel injector size,
and occasionally a bigger more effective fuel pump, Ive seen lots of guys slap on killer heads and a decent intake then have that deer in the head lights look when the engine with a larger cam thats designed for max peak power, basically sucks due to the cams loss of low rpm effective compression and the lack of fuel to supply the new higher rpm air flow rates, thus both ends of the power curve suffered
the added duration on a cam that allows the engine to breath at higher rpms reduces the lower rpm torque as the valves close later so theres less trapped fuel/air being burnt per power stroke, but in theory the inertial ram effect and the higher number of power strokes per minute , and increased exhaust scavenging increasing the cylinder fill efficiency, that easily off sets that, lower rpm loss, for impressive gains in the upper rpm range, but if you can supply the fuel required the result is both ends of the power curve suffer.
a 52 mm throttle body can easily supply a 383 at 6400 rpm , its other factors that generally restrict power.
youll want to do the calculations but 30lb-36 lb injectors would seem to be in the ball park
yes a cam change could potentially aid in producing more power because the stealthram intake design, is meant to operate in the 3500rpm-6300 rpm power band so a cam like the crane 119661 is a good match, but it will only produce the expected power if the rest of the engine components ,drive train gearing and exhaust system are matched to that power band and flow rate increase, use the calculator and stick in 24 lb then 36 lb injectors too the calc's and see the difference

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http://www.smartfireinjectors.com/fuelflowchart.html
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Flow (cfm) Max. NA HP
Stock 668 300
Stock w/airfoil 710 350
52MM w/airfoil 835 400
54MM (AS&M) 900 450
58MM 1050 500
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stock un-ported runner entrances

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porting helps flow significantly, done correctly an additional 50-60 cfm of flow per runner can be gained on a stealth ram
READ THE LINKS
http://garage.grumpysperformance.co...-heads-for-small-block-chevys.3293/#post-8709

http://garage.grumpysperformance.co...8mm-throttle-body-on-your-tpi.290/#post-22467

http://garage.grumpysperformance.com/index.php?threads/selecting-an-efi-intake.1231/#post-20032

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.com/index.php?threads/calculate-fuel-injector-size.1200/

http://garage.grumpysperformance.co...ive-are-the-stock-tpi-engine-components.1509/
 
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I have a in tank Buick GN Walbro 255LPH HP fuel pump in it now and upped the fuel line Dia. with Braided Stainless Steel Fuel Line Hose... Did the brake lines at the same time,
I wrote in there somewhere on a post... It was pulling 2Lbs. of vacuum with a 750cfm TBI four bll. The stock Throttle body is old and tired, I‘m guessing it might be leaking around the blade shaft that is why I was thinking of replacing, On the upgrade in fuel injector size I will have to check not so sure what is in there now guessing stock… I am guessing but got to be close to the 500HP at least over 400, heads are ported polished and flowed, I will have to check that the throttle body is gasket matched though and there is No MAF sensor on this, Set-up on speed density and have an A/F gage to tune it to with the AEM ser.2 controller....
I also have 1.6 roller tip rockers, might upgrade to full roller sometime, with that said it would take the lift even higher on that Cam shaft, HR-230/359-2S-12.90 IG ... Intake .539 and Ex .558 do you think that will clear the piston's .... Intake lift at valve with 1.6 rocker arm will be: 0.575 inches and Ex would be will be: 0.595 inches.... ???
Right now I am going to go with these upgrades before I mess with the cam ... 58mm throttle body and floor shifter and TCI EZ trans controller.
Thank you for your time and insight on this thing been messing with it for a long time now and upgrading with that Tim the tool man Taylor thing going on like the master cylinder piston was 11/16" on the 1/2 ton went to 1 ton now is 1 1/4" piston, Radiator 1/2 ton was 1 1/4" thick 1 ton is 2 1/4" thick In the pictures of the brake drum 1/2 ton was 9 1/2" Dia. 2" wide, 1 ton is 14 1/2" Dia and 2 1/2" wide, OH it'll Stop Now, but gave up the ABS that was on the front end .... lol ... Ken :)
 
http://garage.grumpysperformance.com/index.php?threads/checking-piston-to-valve-clearances.399/
Im using that cam in my corvette, and it clears but each engine NEEDS to be carefully checked, guessing seldom works
roller TIP rockers like this are basically a total waste of time, money and effort, the tips of the valves on the rocker provide MINIMAL friction its the fulcrum the rocker pivots on at the rocker stud, that needs a roller bearing and thats where you gain most of the power gain, in reduced friction, the increase in valve lift is a small help but not nearly what the reduced friction in the valve train provides
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your FAR BETTER OFF WITH TRUE ROLLER ROCKER DESIGNS
https://www.summitracing.com/parts/sum-g6991/overview/make/chevrolet

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