85irocz28driver

I have decided to get the L31-R "Vortec" Crate Motor for my IROC. It has Vortec heads, 9.4 compression ratio, and a factory roller cam. I plan on a cam swap before installing the engine. My car is a factory MAF 5.0tpi. I'd like to keep the tpi but am not completely against a carb. I intend to drive this car daily and want good power. Open to all suggestions. Oh, and I'd prefer to avoid removing/machining the heads so please keep that in mind with cam suggestions.

Fast355

iTrader: (2)

Alex Spring/Retainer set and a LT4 Hotcam or GM 846 would work nicely. I would advance the LT4 Hotcam from the drop in 109 ICL to a 105 ICL using a Cloyes 9-1157 timing set. If you go with the 846 I would probably advance it 4* as well. The GM 845 is a decent cam as well. You can count on needing a 350 Prom chip, 350 knock sensor and a set of 24 lb/hr injectors.

85irocz28driver

These cams will work? I heard the factory Vortec heads as cast required machining for anything over .480 lift at the valve

Fast355

iTrader: (2)

Not if you fully seat the valve seals and use modified retainers with matching springs.

RyanJB

I started with an L31, did the LT4 hot cam, 1.6 rockers, and had the heads decked down to 60CC chambers, topped it off with a Holley Stealth Ram, overall I've been pretty happy with it. You can use comp beehive springs to overcome the lift limit, you can have the heads cut down to accommodate the larger springs, or do what was listed above, and purchase the smaller retainers.

85irocz28driver

Cool. Hoping for 300-350hp. I know the tpi is a limitation but it looks cool and I already have it. Is it worth getting tpi upgrades or should I save for a stealth ram or other superior intake system?

85irocz28driver

By the way I appreciate all the advice. Most of my previous cars were carbureted 2nd Gens and it's been a few years since I've done a project like this.

Night rider327

iTrader: (13)

More than 1 way to skin a cat.

When it comes to the vortec heads, you are correct the stock springs are unless on anything more than about .430", maybe .440" lift and you have guide/seal to retainer clearance probs at the .470 to .480" lift..

To cure that...
Spings, you know just replace with correct spring pressure.

With the clearance probs you have a few options.
1) Have valve guides machined down.
2) Use Comp cams beehive springs and retainers
3) Use the Alex's springs and retainers
4) Use any brand 1.25" or 1.26" OD single spring with correct pressure for your cam, remove the flat inner damper spring, and do the "ghetto grind" on the stock retainers. This is where you grind 3/32" off the bottom part of the retainers. A lot of info on this over at Nastyz28.com in the vortec head sticky.. This will give you clearance for about .510" lift... If you need alittle more, use +.050" installed height valve locks and pick the correct springs/pressure for the now taller installed height.

I have done option #4 many times on vortec heads. I also use Howards valve springs as they are really good springs at a great price. $30-55... #98111, 98212, 98214 depending on what you need and what cam you use.

Fast355

iTrader: (2)

I find this mis-information on vortecs annoying at best. If you fully seat the valve stem seals they clear .480" lift all day long with plenty to spare. GMs Ramjet 350 uses the 395' marine cam and LT4 syle roller rockers on a production vortec head with no crazy mods, no trick retainers or springs. I have personally run a LT1 F-car cam with 1.6:1 rockers and .490" lift on a pair of untouched vortecs save for fully seating the seals. Still had more than .040" seal to retainer clerance at that lift.

Also almost every magazine in the late 90s/early2000s put vortecs on 350s and ran the comp XE268 with .477/.480" lift on untouched, production heads without issues. Hell GM puts a .435/.460 lift cam in the 330 hp 350.

Night rider327

iTrader: (13)

I'm glad you find it as "mis-information", but I have to disagree with you. I find your info as wrong. I have put together over 100 pairs of vortec heads and have only had 5 pairs that would clearance more than .470" lift with out the mods I listed above.

I have also tested the spring pressure on the stock springs and at best got 75#

Fast355

iTrader: (2)

I am not getting into a pissing match over this as I have also worked on 20+ sets of them. I haven't found one that wouldn't safely clear .480-.490" yet. GM Marine engines run cams with .451" on the exhaust side and that same cam ends up in the Ramjet with 1.6:1 rockers, do the math on that (.481" lift). Same production head casting, springs, seals, and retainers according to the GM service parts list for the Ramjet 350.

I put a Production LT4 cam and 1.6:1 crane self aligning rockers in a GM L31 crate engine before it found way in my Express van in 2006. .476/.479" lift on stock springs, retainers, and valve seals and ran it that way for 6 years before changing to a custom grind comp cam with .488" lift on both sides with 1.6s. Still running box stock vortecs with that setup as well, never ran into an issue. I never even had to drill the pushrod holes with the Crane rockers.

Spring pressure does fall off after some miles on these heads. If you test a new spring from GM it will be about 80# at installed height which is plenty given the mild nature of these cams, the factory intakes that falls off above 5,000 rpm, and the 5,600 rpm fuel kill. The fact these springs start losing spring pressure and high rpm performance is well known in the LT1 B-car world where guys are turning 5,600-6,000 rpm on stock cams.

86LG4Bird

iTrader: (1)

My experience with only 2 sets of Vortec heads (1 OEM 1998, the 2nd from an "Hecho in Mexico" GM crate motor) matches that of Fast355's. No problem with .470" lift. Now, if you want .050" margin, all bets are off. For myself, if I check all 16 and have clearance, why would I want .050" extra?


OP, if you are staying with the factory TPI, then reconsider those cams suggested above. The stock TPI will choke long before the LT4 Hot and GM846 get close to their intended power peak. If you're changing the intake, then they'd be great choices for the Vortec heads.
And don't even think about using the stock springs on those heads. Brand new with the stock cam, they're done by 5500 rpm. Any more cam at all, they're useless.

Fast355

iTrader: (2)

Both of those cams peak before 5,500 rpm and in my experience even a stone stock TPI setup will make good HP up to 5,800-6,000 rpm without dropping off too much. The LT4 Hotcam in a Vortec head 350 with slightly oversize ASM runners put out 375 HP and nearly 450 ft/lbs of torque when it was dyno tested, its not a bad cam in a TPI. Saw another setup with edelbrock runners and a 52mm TBI tested that put out 357 HP @ 4,900 rpm.

Just another example of oversize ASM runners on a ZZ4 with a LT4 Hotcam. Look at how that HP hangs on even well above peak!

http://www.eecis.udel.edu/~davis/z28...2/webpage.html

I don't disagree on the springs with an aftermarket cam though, just stating that for my purpose even with the production LT4 Cam and 1.6s they pulled smoothly without hiccup to 5,500 rpm. The 99 Suburban also pulled smoothly to 5,500+ rpm with the F-car LT1 roller cam and stock springs.

Both would pull easily to the fuel shut-off at 5,600-5,800 rpm.

86LG4Bird

iTrader: (1)

Well of course they'll peak before 5500 rpm under a TPI! Put them with a decent intake and they'll peak more like 6200-6400 rpm.
My point is that you will make better power under a TPI intake by picking a cam with its sweet spot near the same as the TPI's sweet spot. If looking for an off-the-shelf cam, something like Comp XE lobes with much less seat-to-seat duration will give a better power curve than either of those GM cams. A Comp "502" (218/224/112) is the largest I would go under a stock or lightly modified TPI.

Fast355

iTrader: (2)

Are we talking about the same cams??? I have had both an 846 and a LT4 Hotcam under a dual plane carb intake rated to 6,500 rpm such as the Edelbrock Performer RPM with a big 4bbl Holley and they peak well before 6,200 rpm, in fact they peak under 6,000 rpm.

In other tests a 355 with a 170cc intake runner, flowing 240 cfm, with a dual plane intake and long tube headers the 222/230/112 Crane part number of the GM846 peaked 407 HP at only 5,600 rpm. In a similar build in a 350 the LT4 Hotcam peaked at 5,600 RPM with 401 HP.

86LG4Bird

iTrader: (1)

Fast, If a GM 846 peaked at 5600 rpm, your source had either some very poor cylinder heads, a sub-par exhaust system, the cam was mis-degreed, and/or something in the intake was flubbed. I don't care what the claimed flow numbers on the heads were; there's more to good cylinder heads than static flow numbers.
The OP mentioned something about an HSR or similar intake. That just might be a bit higher rpm-oriented than the test with the 2-plane you mention.

Fast355

iTrader: (2)

The HSR runners are pretty long as well, they usually peak before 6,000 rpm as well but keep pulling strong up to 6,000.

I have the same heads and shift at 6,000 rpm with a milder 215/220 cam. I have seen the same 170cc intake runner heads make 485 HP @ 6,200 on a 234/238 roller cammed 355.

I have seen numerous GM 846 cams outside of LT1 engines peak under 6,000 rpm. Nothing wrong with the setup, just not enough cam to PEAK higher than that. I also know enough to know that the Hotcam runs best shifted about 10% over peak in a LT1 or LT4 and that is about 6,200-6,400 rpm, but peak is down around 5,600-5,800.

86LG4Bird

iTrader: (1)

Nice try, but YOU are not going to tell me where a Hotcam peaks in an LT1 or LT4 More like 6000-6200 rpm If not, you or your source is doing something very wrong


BTW, just so the readers don't think I disagree with everything you say, your recommendation above for a GM 845 cam IS a solid one.

2005Impalla

I just installed the L31 crate motor in my Camaro. It comes with the 906 castings and I don't know if there any different than the 062 castings or not. Mine had the extra hole for the timing cover so I could run a normal cover, the bypass hole was drilled already that I have seen people complain about not being drilled so I am running a normal water pump with no top bypass from intake to pump but my valve guide boss was .9" so I had to machine the heads for my springs. I wanted to use the LS6 springs but they were to small inside for my heads. The L31 motor is still worth it though even after the machine work. I am running in to a problem now were I think the vortec might have used a different timing pointer as I reused the old pointer and tried to time my car yesterday and it was reading 26* advanced with the vacuum disconnected at 750 RPM. I double checked my timing using a vacuum gage and it is pretty close to were it needs to be so just be ware you might learn a few things building this thing and will find out what is true and false about building this motor. If your looking at going all new your looking at about $4,500-5,500 so expect that. I had screw in studs installed when I machined my valve guide and used comp cams beehive springs which turned out awesome. My heads now can safely run .530 lift. The have clearance to .580 but it is recommended that you keep .050 clearance for some reason. I also had a custom cam made from comp cams for me which was less than ordering a new comp cams from jegs. It was $280 shipped to my door. If there is a cam you like but want to tweak a little don't be afraid to call the cam company and have one custom made. I wanted something a little milder than the hot cam that would peak torque a little earlier but still have a cool idle so I made mine. If you want a cheep but good cam I would consider the ZZ4 cam. You don't see a lot of people use it but it would be great in a vortec if you modify the heads which I am betting you will. A lot of people are running springs with the inner damper out on these heads but a lot of people are also running the LS6 springs too which did not fit for me. Cant fit a square peg in a round hole.

Fast355

iTrader: (2)

I like the GM 845, while the XE lobes and XFI lobes are more aggressive the older Crane lobes are easier on the valvetrain and make less noise. With the picky knock sensors less noise is sometimes a good thing.

As for you Hotcam peaking that high all I can say is there must be some good voodoo you spread over that engine before you turn the key. With properly spec'd springs and properly lashed valves I have yet to see a 170cc to 180cc intake runner head regardless of the manufacturer peak at higher than 6,000 rpm with less than mid 220* duration on a 350. I have plenty of examples to show otherwise in a carb 350 with a 165-180cc intake port.

LT4 Hotcam dyno
https://www.thirdgen.org/forums/tech...am-vortec.html

LT4 Hotcam Vortec dyno
http://www.hotrod.com/cars/project-v...ckage-install/

GM 846 with a dual plane
http://www.superchevy.com/how-to/148...tec-head-test/

In a ZZ4 crate engine it peaks at 5,500 rpm with a 165cc intake runner head
http://www.eecis.udel.edu/~davis/z28/buildup/cam/

Fast355

iTrader: (2)

This is a Dyno of the EFI Connection S10 with a L31 that had a LT4 Hotcam, Roller rockers and a Ramjet intake manifold along with coil per cylinder ignition. Its all over at 5,500 rpm.

Fast355

iTrader: (2)

Hell this is a 226/232 LE cam in a LT and even it does not peak above 6,000.

86LG4Bird

iTrader: (1)

Fast, Here's the disconnection: You're quoting stuff you read where you don't know the whole story. When it comes to LT1/LT4, I've done it and I've tweaked them to optimize them.
Just slap some stuff together and sure, the hp peak will always fall below where it will be if the parts match, and the build and tune are optimized.


But we're digressing here. For the OP's benefit, I think we agree that something like the GM845 (which is kinda tough to find nowadays) or some Comp XE lobes in the 212-218 intake duration range work well with TPI. Mucho agreement on skipping the XFI's - they are NOT worth it considering the abuse they heap upon the valvetrain. XE's aren't an issue on a conventional properly setup valvetrain - plenty gentle as high as the TPI will want to go.

2005Impalla

Don't swap cams with out matching the springs. If your going to do that I would look at having a cam ground using the comp low lift magnum lobes. There only .428" and I was told by comp cams that I could use them with the stock vortec springs up to around 5,500 otherwise swap springs. You don't want to open the valves tell your hitting your valve seals. Also if your have the heads machined have them keep the stock vortec seals they seal better than the older Chevy seals and you will burn less oil. The older seals are designed to be used with springs that have the tin on the top of the spring to keep them from being splashed with oil the vortecs don't use this tin and have better seals.

Fast355

iTrader: (2)

Not a fan of the ZZ4 cam in the least, the Hotcam properly degreed in will easily outrun the ZZ4 cam.

86LG4Bird

iTrader: (1)

That's pathetic for an LT1 with a 226 custom cam. Poor heads or a choked up exhaust

86LG4Bird

iTrader: (1)

Yup, Neither the ZZ4 nor Hotcam is a good choice for TPI.
Just like neither is good under a stock L31 intake, even though I have a ZZ4 in my L31 truck

2005Impalla

Ya I know the LT4 will out pull the ZZ4 I was going to get the ZZ4 for my current motor and install it +4* before I had my cam made because I thought it would have had better low RPM torque than the LT4. I don't know if I would go through all the trouble of keeping the motor TPI due to the cost of replacing every thing. I have the EPS intake on mine with a 670 street avenger carburetor which works good. I am still tuning my car but I like the set up so far. I might try the RPM intake later though. If your looking at doing something as large as the LT4 I would get the RPM or RPM air gap intake and maybe even a 770 street avenger. If you stay fuel injected I would replace the TPI with a stealth ram or short ram intake set up instead of just replacing the lower intake. I just like the cheep cost of carburetor's and how easy it is to swap them between other cars. If you go too large on your cam your going to need a stall converter to go with it. I designed my cam so it could be used with a stock converter and gears and it dose to well but it will be better with a stall and gears so consider that when picking a cam. If it says largest cam with stock stall its going to run better with a small stall and lower gears. Try to match your cam to your intake as best you can. Also know there might be other mods your going to want to do late after the motor is built to the drive train to improve the performance, make it stronger and drive better.

2005Impalla

O ya the stock timing chain was crap. It was loose as hell. The Clyotes high performance L31 replacement was the same dam chain as the stock one and just as loose. I used a metal cover with a Jegs double roller chain which was way better. Don't use the stock chain.

2005Impalla

I wish they sold the L31 as a short block cuz the bottom end would be a great foundation for a build with better heads on it. All in all though it is a great start for a mild street rod. I would do what I did though and machine for new springs and screw in studs so you can run what ever cam you want.

85irocz28driver

How about this?
Duration Advertised 280° Intake/290° Exhaust
Duration @ .050'' 212° Intake/222° Exhaust
Lift @ Valve .462''intake .479"exhaust
Lobe Separation Angle 112°
Intake Centerline 107°
Intake Timing @ .050" Open 1° BTDC
Close 33° ABDC
Exhaust Timing @ .050" Open 48° BBDC
Close 6° ATDC

85irocz28driver

I'm not married to the tpi but I'm looking to keep the motor fairly mild and run it for a couple years while I do the rest of the car. I'd like to keep tpi for that period. When I get the rest of the car caught up I'll pluck the motor and do a more aggressive rebuild at that time. I really enjoy reading guys. Thanks.

86LG4Bird

iTrader: (1)

Not knowing anything more about that cam than the numbers you posted, I wouldn't run that with TPI. Advertised vs. .050" duration numbers indicate some fairly lazy lobes, and quite a bit of overlap for a 212/222 cam. I think it would even be a step backward from a ZZ4 cam, which I've run but don't recommend in this application.
I don't know what you're currently thinking for a spring kit, but I'll suggest what has already been mentioned: Just get one of the economical spring/retainer kits so you're not limited to .480'ish lift, and then run one of the Comp XE cams which work much better with TPI. XE lobes are NOTHING like XFI lobes; don't be afraid of them; they're middle ground between the lazy factory style lobes and the XFI's that can beat up a valvetrain in 20k miles.

Fast355

iTrader: (2)

You are running the Alex Spring/Retainer set on both of your Vortec head setups aren't you?

With TPI I would have a hard time not running this cam, especially with the stock converter and gearing. I realize it is on a 110* LSA but its also 4* advanced and only has 41* calculated overlap @ .006. I think it would really jump off the line and beef up the already nice midrange.

http://www.summitracing.com/parts/cc...make/chevrolet

As intake limited as the TPI is this might also be a viable alternative. We all know people tease that the TPI is the best small block truck engine GM ever built that never made its way into a truck. I had one of these custom ground on a 110* LSA and 106* ICL and put it under the stock L31 intake in my Express with 1.6:1 rockers. It had alot of jump off the line and pulled better from off-idle through 3,500 rpm than the factory LT4 cam. Duration/Lift specs are very similar to the Production LT4 cam, but it has a more torque productive 110* vs 115* LSA.

http://www.compcams.com/Company/CC/c...?csid=197&sb=2

85irocz28driver

I guess I can go more aggressive than I thought. I just didn't want to over-cam an otherwise stock L31-R engine. Springs I'm fine with but I didn't want to do anything to the heads until a later rebuild at which point I'll be aiming for 450+hp. I know tpi has its rpm limitations but with a few mods should serve 5,000-5,500rpm well enough.... right?

Fast355

iTrader: (2)

If you are sticking with stock style springs and 5,000-5,500 rpm I would just use this cam. The MAF TPI is fairly forgiving with cam changes compared to speed density. For peace of mind I would probably put on an Alex Spring/Retainer set for better control with that cam grind. All said you will probably only gain 20-30 HP @ 5,000 rpm from the cam change.

http://www.compcams.com/Company/CC/c...?csid=197&sb=2

The cam that works now is not going to work for 450+ HP with a different intake.

86LG4Bird

iTrader: (1)

I'm running cheap LT4 springs and the "ghetto grind" mod on my own, but have used the Alex kit on others and recommend it.
I agree that both of these cams would be good under the TPI. My preference would be the "408" cam with 1.6 rockers.
If you go with that Xtreme 4x4 cam, I'd stick with 1.5 rockers, and don't plan on more than 5000 rpm. Those lobes are not rpm-friendly.

85irocz28driver

Cool. Im not looking for too much, just more than the stock truck cam it comes with. Like i said once i get the rest of the car where i want it i plan on building a "real" performance motor. for now i just want to replace my 305 oil burner with a "real" V8. Ill be eliminating the smog stuff, doing the exhaust, and upgrading the tpi as necessary. Part of the beauty of the L31-R crate is the fact that it gives me a good foundation at a low cost.

86LG4Bird

iTrader: (1)

I just remembered this: Unless you're pulling the heads and enlarging the pushrod holes, you may have to forego 1.6 rockers. Better than 50% chance you'll have interference with 1.6 rockers and stock heads.

Fast355

iTrader: (2)

With the Xtreme 4x4 cam and 1.6s under the L31 intake I was shifting about 5,100-5,200 rpm with all the torque really didn't have to rev it that high. With the 4L80E and 3.42s I was at 90 mph by the time the revs hit 5,200 rpm in 2nd.

85irocz28driver

I no not plan to pull the heads. I normally wouldn't swap a cam in a brand new mill but I dont plan on towing any trailers with my IROC.

Fast355

iTrader: (2)

I did not have to drill my 1996 cast 906s or my Mexico cast 2005/2006 cast 062s. The Mexico castings flowed like crap compared to the early canadian 906s though.

85irocz28driver

What fuel injected intake system would you guy recommend? I heard the "Stealth Ram" works with the factory tpi electronics. Is this true? Can any other intakes utilize my factory electronics?

85irocz28driver

I'm starting to seriously consider just slapping a carb on the stock long block for now. anyone have experience with with doing such a thing? $ is a factor.

86LG4Bird

iTrader: (1)

Rather than buying a carb + intake + all the other parts and plumbing, and then never getting it to run as well as it will with your MAF-based TPI, I'd prefer just going with a Vortec-to-TPI base. I know they're expensive new, but look on eBay and Craigslist.
Even if you have to buy it new, you will be $$ ahead in the end.

Fast355

iTrader: (2)

The stealth ram and ramjet intakes can both run on a factory setup but the Vortec TPI base would be cheaper. I have compared the one from Scoggin Dickey and Edelbrock and they appear to be the same piece except SD sells it about $80.00 cheaper. I bought my edelbrock 3817 base here on the classifieds new in the box for a substantial discount. Some people are quick to mention the 3817 base does not flow as well as the old vortec heads, while that is true it still outflows the hecho en mexico junk vortec heads that GM is turning out now.

2005Impalla

I am running a cam similar to the one you were looking at with a carb. I believe your looking at the edelbrock cam. My cam is 214*/224* @0.050 263/273 ADV .474/.474 lift with 110LSA and 106ICL it probably would not work very good with TPI but it has torque right now. I am still running 2.73 gears, stock stall converter and 28 tall rear tires. First gear is useless. I have not drove the car much only about 5 miles total cuz I am fixing other problems the car had before I bought it but it has a lot of torque. I broke the tires loose rolling in to the throttle the other day at about 20 MPH. It dose not have posi yet but both broke loose and the rear of the car squirmed from side to side. I almost got the edelbrock cam cuz it was way close to what I wanted but it was cheaper to have comp cams grind me a custom cam and make exactly what I wanted. The only thing I think I would do different next time is I ground it before I had the heads modified so I would run .500 lift on both intake and exhaust and run a 108 LSA being that I am running a carburetor and maybe cut the duration back a few degree's to increase low to mid range torque a little more. You will never find the perfect cam but being that the L31 is a roller motor it is easy to swap cams and try new things. There is usually a trade off unless your swapping the stock cam for one slightly larger.