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350 Vortec Truck Engine Build

11K views 29 replies 6 participants last post by  jokerZ71 
#1 · (Edited)
Hey everybody.Hope fully fixin to be able to get my block to the shop so I can get this thing back together.Motor is a 97 350 I pulled @ 250K due mainly to low oil psi.The Goodwrench crate I replaced it with is @ 283K & having the same problem.Block & crank look great & per my measurements,would not need a bore,but,i'll let the shop have final say.Pistons are currently setting .028 in the hole,so,I am havin .007 to .008 taken down for cleanup & to get a good quench.Current plans & parts as of now are Complete rebuild on heads including upgraded springs,KB 193 pistons,Sealed Power moly rings,King bearings,#14097395 Ramjet cam along with decking block & any work the shop deems necessary & a .025 composite head gasket..045 quench.I have a set of 1.52 roller tip rockers,but,not too sure about using them.A friend installed a set last week & his are really noisy.PCM will be retuned also to bring everything together.This is all goin in a 97 ECSB Z71.Daily driver @ 100 miles a day.3 to 4 smalltown local truckpulls,quite a bit of playin in the mud,& pulling my horses & trailer.My calc show me comin @ 9.7:1 SCR & about 8.2 DCR.Gears are 3:42.Hopin for about 300 to 320 HP.More interested in torque than actual HP tho. Oh almost forgot,I will be using midlength headers w/ 3" collector into 2 HushThrush mufflers then into a single 3" TP.
 
#3 ·
My concern is connecting rods. At jammin' 300 kilo miles these babies are at that design life cycle. While most of your use is as a DD playing in the mud I'm sure demands more RPM and RPMs alone plus lots of throttle opening is just killer on rods. These PMs have proven to be pretty good but they do seem to experience a higher rate of high mileage failure, that may be because older engines that still used the factor forged rod didn't tend to live as long lives for reasons other than rod failure. Like you say at 280 some thousand miles there is low to no wear on the cylinder walls which is not something you'd see 20-30 years ago, those engines would have used up the wall life by 100 or 150 thousand miles, well before the rod's design life would have been lived so those old forgings were not pressed to their life cycle limits like today's PM rods. So I'd recommend some new rods just to cover the possibility of a high cycle fatigue failure. One of my favorites for this type build can be seen at this link <<< Scat Crankshafts >>>.

I think the only way to go with valve springs is with beehives, you get the needed contol with lower spring pressures which while not the concern it is with a flat tappet cam, even a roller cam and the rollerized joints inbetween the lifter and rocker benefit from the reduced effort to keep things tracking that a lighter but more stable spring brings.

Bogie
 
#12 ·
There are usually some short bursts of high RPMs in the mudding.Mostly from slinging mud from the tires as the tread packs.The truck pulls are mostly for fun & usually shutdown due to wheelhop on the hard packed dirt befor really seein any extended hi RPMs.If I were to get into this very seriously,i'd hav to do some major suspension upgrades before adding anymore power.
 
#15 ·
I went the crate engine way before.I'm just gettin back into doin stuff like this.Being a single Dad to 3 kids kinda took most of my time & money,but,now they are grown & I have the urge to get back @ it.I built several SBC & SBF back in my younger yrs,however,most of my hi po experience has been with Harleys.I built & owned a few really quik Sportsters that would smoke alotta riceburners back @ that time period.I do realize now tho that I musta had alotta luck back then cuz now I hav a lil better understanding of things & realize I didn't know jack.LOL.
 
#5 ·
Thanks for the recommendation on the rods.I honestly hadn't figured the fatigue factor with the high milage.Very good point.The springs will be beehives & I'm gonna go ahead & have some xtra clearancing just in case I decide to go with a different cam later.If I can get another vehicle later for a DD I plan on doing some more serious mods to this truck.The engine bein rebuilt is the 250K.The 280Ish is still in the truck running.But 30K isn't gonna matter.LOL.I will plan on new rods.Original plans were for a 383,but,my youngest ran afoul of the law,so,most of my motor money went to the court & bail bondsman.Maybe I can do the 383 with the engine I'm running now after gettin this 1 finished & put in.I'll have more time & hopefully better $ by then.This 1 I'm runnin now is goin down pretty quik,so,I need to get the ball rolling.Again thanks for bringin the rods to my attention.My last engine rebuild was in 82 on a 65 327.A lot has changed since then.As you stated,that kinda milage was unheard of then & also trying to come up to speed with all computer controls & EFI.You can't just throw a buncha parts in anymore.LOL.
 
#6 ·
Oil problems on two different engines. Granted both are high mileage but I would take this time to address your oiling system to prevent any problems in the future.

Enlarge and smooth your oil galleys, port your pump (and get a high volume one if you do a lot of low rpm driving), and enlarge and smooth all of your drain back passageways. This goes a long way towards engine life.

Next, there is a big difference between cam choices, the ramjet cam may get you to 350hp, the 264hr cam you selected would go way past that, easily 40+hp more, so it depends on what you want. The Ramjet cam will get better mileage and will be a lot easier to tune. There are also MANY other cams out there that fall between those two as well- so you don't have to even pick one or the other. Roller ROckers are nice, but you may as well go for 1.6 or 1.65 ratio, the ratio helps more than the roller when it comes to power. The RamJet cam with a 1.65 ratio roller rocker would be a good combination for a mild street engine. Also, if you haven't had your heads done yet look over at headbytes.com and give that guy a call- he can rebuild and port your heads for what most guys charge to mill and do a valve job. He's not the best head guy around but he is certainly one of the best values.

For this application IMO connecting rods are connecting rods, any good stock rod that has been checked over should suffice, you're not going to make crazy power or RPM's, with the RamJet cam this thing will be done before 5500.

I'm glad you already plan on tuning though- there is a lot of power there and most people don't realize it.
 
#7 ·
I just have the urge to build this one.The engine I'm running now is a GM crate.I got the cam off EBay for $99. I wanna go ahead & get away from the dish pistons,excessive quench,etc to establish a good base in case I wanna do more serious mods later.
 
#8 ·
I've got some concerns over the heads.Blew the intake gaskets @ 120K.Engine got pretty hot,but,it ran another 130K without any issues.From what I hear,these heads will get cracks & not leak until they are retorqued.The shop says bout 8 outta 10 sets he gets in have some sorta crack.
 
#10 ·
If these turn out to be cracked,i'm definitely gonna ck into aftermarket of some kind.I know I'll catch some flak,but,my shop says that awhile back he wouldn't even suggest PC heads,but,he's used a lot of em in last couple of yrs with no issues.He buys em bare & cks em out,then does all the assembly himself.My biggest concern is with any head that says it will work with Vortec,or,nonVortec heads is intake fitment with my OEM EFI intake. There has to be a difference in
The runner hgt for it to work either way.IDK what effect,if any,that may cause.It may be perfectly OK, but,there has to be a difference in runner hgt for it to work.@ this point,i'm hopin real hard that mine r OK.I haven't seriously looked into a lot of heads,but,most I have looked @ start out @ 190cc runner size vs my current 170cc.What effect would this have.My current heads cc'd @ 62 cc.If I could go up to 67 or so,I could run flat tops instead of the D cup KB's.
 
#17 ·
Just lucked up on a set of low milage PM rods that have been inspected & had ARP studs installed.The shop doing my heads & block work had a set that a customer never returned to pick up.$180 & this includes installing my pistons onto the rods.
 
#18 ·
For not too much more money you could have Scat forged I-beam rods. 35700P - Scat 4340 Forged Stock Replacement I-Beam Rods for $212.00 with ARP WaveLoc bolts.

Or for $226.00 Scat 25700P 4340 Forged Pro Stock I-Beam Rods with ARP 8740 cap screw bolts and doweled rod caps. The Scat Pro Stock I-Beam Connecting Rods 25700 for $251.00 have the same features as the same features as the 25700P rod but has bushed (floating) small ends for the piston pins. These 2 rods are clearanced for stroker applications so they would be great in a 383! Cap screws are easily replaced on a subsequent rebuild, they don't have to be pressed in & the rods resized. The 25700 bushed rod doesn't have to have the pistons pressed on & off (but you will need to have the lock rings for the pistons). I suspect one of these may be the rods Oldbogie referred to, but when I clicked on that link it took me to the Scat home page.
 
#19 ·
Yep,them PMs do sound kinda high when you look @ it thataway.Actually tho 60 of that 180 wuz the charge for everything including installing the pistons,so,120 wouldn't really be too high.I have had problems with those clips on free floating.LOL.I've used the clips 3 times & had a wristpin back out 3 times.LOL.There must be a trick to doin it rite.Maybe now I'm more patient & settled.At the performance level I'm buildin to,it prolly isn't gonna matter either way.It would save 60 bks tho,huh?I am kinda gun shy of em tho.I may try & then get somebody to ck em to be sure I got em rite.
 
#20 ·
The stock Powdered Metal forged stock rods are excellent pieces and are stronger thyan the older "pink" bowtie rods. The design is tested to 500hp, you will run out of fuel before you come near the limits of the stock rods. You also have to remember than with the stock Blackbox PCM in these 1996-1999 GMT400 Chev and GMC trucks, you wont be able to rev over 6000rpm anyways. The stock fuel shutoff is set at 5600rpm and even if this is reset via PCM tuning to 7500rpm, the PCM's hard rev limit is 6000rpm. You can do a 0411 PCM swap and then have the ability to rev 8500rpm if you wish. The 2001-2002 Express vans used the newer 512 kb 0411 PCM with the dual 80-pin connectors and used it to control the same Vortec 305/350 engines that our trucks used. The 0411 PCM opens up tuning support for the 1996-97 trucks(as only Tunercats OBD2 and JET DST and Westers GMT support the 96 and 97 blackbox Vortec PCM's) EFILive and HPTuners support the 1998-2000 blackbox PCM's although the support is limited. Basically upgrading to the 411 PCM opens the Vortec 350 tuning right up. A guy named Lextech has taken the van and the truck pinouts and compiled a swap sheet to retrofit the 411 PCM from the blackbox PCM. Different sheets for the 96 and 97 and the 98-00 GMT 400 trucks as there are differences between these 3 model years of trucks.

The stock -13cc dish pistons stock are hypereutectic(high silicon) pistons in between forged and cast aluminum pistons.
The stock crank is an excellent nodular iron piece.

Stock cam specs are 191º/196º at 0.050" lift of 0.412"/0.428" on a 111ºLSA this cam is ised in the 1996-2003 Vortec 350 and 305, and also the 1994-96 iron headed LT1 in the 94-96 Caprice-Wagon/Impala SS, Buick Roadmaster/Wagon and Cadillac 5.7 liter engines and also used in the 94-96 200hp GEN 2 4.3l V8 L99 engine.

The RAmjet 350/HT383/MArine 350-383 roller cam you got specs at 196º/206º duration at 0.050" and 0.431"/0.451" on a 109ºLSA. On the Ramjet 350 crate engine, this same cam is ued with the 1.6:1 roller rockers which brings valve lift up to 0.461"/0.481".
If you run any of the Beehive springs such as 26915 or 26918 Comp Cams, or PAC 1218 or 2002-2004 LS6 Beehives along with the special Comp Cams 787-16 retainers that work with the Beehive springs AND the GEN 1 SBC valve diameters which is different than the 774-14 which is the beehive retainer you'd use wit the GEN 3/4 engines, you will have 0.550" clearance on stock unmodified Vortec heads.

This thread has all the parts/specs and pictures with Verniers showing the actual clearance on stock Vortec heads
GM Performance :: View topic - LT4 Hotcam in L31



I'd be a tad nervous of running a 64cc chamber with a flat top piston

With flat tops, I get 10.90:1
With the 193's and their -12cc dish I get 9.55:1. With the numbers supplied in post#1.

We have to remember that the GEN 2 LT1's are both reverse cooled, and the performance LT1's have aluminum heads.


The stock Vortec 350 is rated at 255 sae net hp@4600rpm/330 lb/ft torque@2800rpm. If you take that same engine and measure it on an engine dyno, it will dyno at 310-320 gross.

The stock CSFI or GM upgraded MPFI spiders will limit naturally aspirated power to around 390-400 crank hp.
Stock Central Sequential Fuel Injection above the GM replacement Multi Port Fuel Injection spider. For MY 2004 the vortec V6 used these upgraded spider injectors(both of these units flow exactly the same, which is 24.3 lb/hr at 63 psi fuel pressure.


I use the marine intake, pictured left stock intake right, and use 29 lb/hr injectors(at 58 psi fuel pressure)


The RAmjet intake will also work, with a bit more work than the marine intake


Ramjet intake on Vortec 350 using a CNP ignition kit.


Any intake will work, so long as you can plumb fuel injectors that can be sized to you power/fuel needs.

peace
Hog
 
#21 ·
I already hav the upgraded spider.it made an improvement over the old poppets.Some say they could tell no difference.A far as the flat tops go,I hav 2 friends.1 has a 96 Tahoe.The other has a 97 Yukon.They both built with the same parts.Aprox. 7cc flat tops.The 97 screams.The 96 is really sluggish.The only differences in the 2 engines are,1 has 062 heads.the other has 906's.That shouldn't matter.The chamber volumes on those heads can vary from 62 to 68cc.I think that may be the deal.IDK.As far as the Ramjet cam,I love the torque curve.It's either pullin,or,it ain't.Not much in between.It looks weak on paper,but,sEems to perform really good & easy on the valve train for a DD.What specs did you use for IVC on your calcs? I used 54*.GM shows duration @ lashpoint.I used 264/256.I got this as the .006 duration from a friend that used a degree wheel during an install.I've read a lot about the Marine intake over @ Pacific.Seems like a good option if you need it.
 
#23 ·
No Its the stock marine intake 58 psi (4 BAR) regulator, which has 58psi at WOT and around 52psi when at idle wit the vacuum reference hose connected.

I'm not sure what calcs you are referring to. The cam specs are from the GMPP(Now CMP) catalogues and other online sources. The duration numbers I listed were at 0.050" lift.

What kind of PCM tuning are your friends using? That made all the difference in the 97 reg cab sb. I am running the stock tune in my 97 extended cab shortbox.

7 cc's would help for sure. I was assuming 0cc's.

peace
Hog
 
#24 ·
Not sure about their tunes or who done em.The guy with sluggish 96 has since changed his knock module from an LT1 I think he said.He said it made a world of difference.The LT1 module is not as sensitive as the 1's used in the Vortec.His theory was that the flat tops were sending out different harmonics causing the PCM to pull timing.IDK if that wuz the case or not but it definitely seemed to help his problem.Go figure.I'm still not brave enuff to try the flat tops.If either of my heads turns up cracked,I may try a slightly larger chamber head.If I could go to 67cc or so,or,aluminum,I would be ok.
 
#26 ·
Your buddy probably installed the LT4 knock module. The 1996 Vette LT4 engine used roller tip and roller fulcrum rocker arms, as such, these rockers made more noise than the ball/seat conventional rocker arms. This is the reason that GHM used the LT4 knock module. This rocker noise is picked up by the knock sensor and the PCM retards timing thus dropping power.

I'm wondering if your buddies engines are running a bit to much compression? The flat tops aren't sending out different harmonics, they could be causing too much cylinder pressure for the octane/tune being used and causing detonation.
I would be using a small dish at least, or the larger chamber would work.

OEM Numbers for the Knock Module - 16214681 1996 LT4 Corvette

If you take your stock PCM and flip it over, you will see a small lid with 2 Torx screws holding it on. You just take the lid off, squeeze the 2 tabs on the knock module and pull it out, then replace it with the LT4 KM.

peace
Hog
 
#27 ·
Not sure what you mean "plus 15º".

GM lists the spec of that Ramjet 350/HT383/ Marine roller cam as having 196º/206º duration at 0.050" lift and lift with 1.5:1 rockers of 0.431"/0.451" with a LSA of 109º.
Those are the numbers that GM specs.

peace
Hog
 
#28 ·
Most comp calculators use adv duration @.004 or .006.Some use @ .050 + 15*.GM only gives duration @ lashpoint 308/288.That would not be the true adv duration.Using the @ .050 duration or lashpoint doesn't give a true IVC point to accurately figure compression.After numerous calls to GMPP & others,no one could tell me the true @.006 or .004 specs which is needed to get an accurate IVC.GM is pretty clueless as to the specs of this cam.LSA is listed on some adds as 112 while others say 109.Some say it's ground 3* advanced.Some say 4.I got my specs from a friend that degreed his cam on installation. .006 duration was 264/256. 109* LSA/109* ICL.Even SDPC or Pace could give anymore info than their ad states.
 
#30 ·
I think the KB 193's will be a good sfe compromise between FT's & Dish.Unless as I stated earlier,I end up needing heads.My heads cc'd @ 62cc.A 67cc head would put me rite where I need to be with 7cc FT's.I can get a good set of FT's @ a much better price than the KB 193's.
 
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