hessm70

Alright folks to start, yes I have searched the threads for cams and advice but that has yielded more questions than answers. Let's get to it. Those of you that have built and engine similar to this, what cam would you use for a mild modded 350 with TPI? Before someone asks, yes I want to keep the TPI even though I know it is the limiting factor in performance.

Below is the potential build:

L31-R GM Crate Engine 19432779
Swap cam/springs to:
Cam ?
Springs- Alex Parts Custom Springs/retainer and locks- 100lbs seat pressure/308lbs open @ .525 lift
AS&M runners
Scoggins Dickey TPI Intake
Ported Stock Plenum
Dyno Don Headers & Y-pipe

Performance desire is: mild upgrade to the stock L98 but tunable

Cam Options- please recommend if your favorite is not on the list. Cost will not be a factor in choice- performance and tunability will be the major factors

1. Crower SKU 000482- Dur @ .050” Lift: 213°/221° RR: 1.5/1.5 Gross Lift: .505”/.525” LSA: 114° RPM: 1900 to 5900 Redline: 6400
2. TPIS ZZ09- Hydraulic Roller Camshaft $375- .483/.520- 212/226 duration LSA: 112
3. TPIS ZZ409- Hydraulic Roller Camshaft - .520 lift 226 duration LSA: 115
4. GM LT4 Hot Cam- Duration@.050: Intake 218/ Exhaust 228 Max lift with 1.5 rocker: Intake .492/ Exhaust .492 Max lift with 1.6 rocker: Intake .525/ Exhaust .525 LSA: 112
5. Lingenfelter 74211- Hydraulic Roller, Intake 211/ Exhaust 219 .Lift 530/.560, LSA: 112
6. ?

mikeceli

iTrader: (2)

BUMP , for OP.

Vader

If it is going to be a street application which rarely sees over 4,000 RPM, it won't be a limit to performance at all. That bit of extra torque is useful down in the lower RPM areas on roads and in front of a highway axle ratio - Just like the factory designed.

Besides, including the dual-channel plastic things being bolted to the top of engines recently, not much is functionally cooler than a TPI straddling the heads in shining steel and aluminum, not to mention the appearance factor.

BIRD91ZRAG

iTrader: (1)

Back in the day I had an 87 350 iroc, I put a 350 HO roller cam in it. The specs were. 480" lift and 230@.050 duration and I think it was on a 112 center.it killed the low end torque, almost needed a 2500 stall converter and it still would only rev to about 5k from the tuned port killing the top end. ​​​​​​​ stay below 225@.050 and you'll be happier. That first cam, or the ZZ09 would be my choice.

brian p

Comp cams hydraulic roller 08 -503- 8

Orr89RocZ

iTrader: (20)

Out of those 1 or 4 but id change your valvesprings. 100 seat is abit lighter than id like to see.

hessm70

Ok that was recommendation from Alex parts so I will double check that.

Kingtal0n

Too much seat pressure is unnecessarily hard on components. There are drawbacks to using higher seat pressure than needed.
IMO Do your own research.

For example I see 130lbs of spring seat 6.0L for 1000rwhp in forced induction applications 30psi of boost and 40psi of exhaust pressure with hyd. Roller cam.
The spec is different for roller cam vs flat tappet.
IMO 100lbs is more than enough for low revving TPI engines. Seat pressure in NA application = RPM capability, which you won't have much of.

Heres an example from decades ago
https://www.thirdgen.org/forums/tech...verything.html

Using the least possible seat pressure will improve valvetrain longevity.
Guides last longer.
Hydraulic lifters stay more pumped up between cycles of oil induction.
Less wear and tear using lighter springs in general.

Just be aware people frequently use too much pressure and don't even realize it. Its a kind of epidemic. There is a reason for the recommended cam and spring seat characters that seems so low or 'strange' to other people online- they all copy each other without fundamental engineering background. Always use the recommended spring and cam combination IMO

Orr89RocZ

iTrader: (20)

Heres the internet expert again lol how many hotcam lt4 cars you work with? Ive done 3 lol

100 lb seat may be ok. 308 open is meh might be enough if doing 4500 rpm shifts. We dont know anything about those springs tho. They could be super heavy 1.43” diameter springs. Then no i dont think thats good. More likely they are some 1.25” or so spring for vortec pockets. Smaller lighter spring can use less.
Hotcam its not a super aggressive lobe, we like to use more like 120 lb seat 330-350 open. Usually good enough to 5500. Beehive spring is preferred since they are small and fit vortec pockets well. A dual spring is heavier and typically needs more pressure to control same mass.

i like to factor in some extra margin because cheaper springs tend to lose some tension after a few heat cycles and run in. Better quality stuff is less likely to lose tension. 110-120/320-350 is not too much for most mild rollers. Some of those other lobes are more aggressive and will need those pressures.

more modern aggressive lobes 120 seat works well in a dual spring under 5000 with proper rate. An xfi lobe will float by 4500-4700 with that and needs more. Been there done that. You probably are shifting nearer 5000-5500 with any of those cams and ported intake mods, so its always good idea to maintain control. Esp if breaking traction and you find yourself on the limiter, which i hope you have a good rev limiter in that case.

hessm70

Thanks @Orr89RocZ I think its worth going back to Alex parts and getting additional detail and express the concerns you have brought up. These are custom so I have some options and it makes sense to get them right. The beauty of this forum is, we can have debate on this and I think it drives me to a better build which is the goal. I am not an engine expert (stayed at Holiday Inn last night-lol). I dabble and I appreciate all the expert builder input. Even at 52yrs old, I am still learning.

Orr89RocZ

iTrader: (20)

https://alexsparts.com/valve-spring-...ssure-vsk4h52/

i mean the website recommended the 120 seat springs for lt4 hotcam lol

if your springs are a beehive style they will work but i cant find them on the site. They have a 110 spring but they call it a flat tappet spring

hessm70

I sent them the Crower cam specs and they responded that they would make a custom set of beehive springs with those details.

Komet

That's cool that they're willing to make some custom springs for your application. You can also pay $10 or something for a cam recommendation from Crower and then it turns into a $10 coupon when you buy a cam. I would be curious if they spec the same cam for a TPI application, or if they might go a different route.

hessm70

Thanks @Komet Perhaps it would be well worth the money to go through that exercise.

BHR

Dont mean to derail but what is the budget here? and why are you starting with a L31?

l31 crate 5k
cam 3-500
springs 200-300
runners 500-600
vortec base 300-500
dons headers 500-900

Those are off the top of my head used to new, the vortec base has been bumped up in price and imo it doesn't flow as good as the non vortec bases. I havent used any of alex's valve train parts but have seen them mentioned on the 4th gen Fbody forums, I personally like springs from PAC and they need to be matched to the cam and the cam needs to be matched to your heads and all those need to be matched to your desire. I can tell you that those vortec heads with any mild cam and a TPI will produce way more torque than horsepower to the point that traction will become a real issue.

I dont know what you currently have but if your car came with a 350 it would be more budget friendly to use that block and just buy lighter aluminum heads and a cam for it

hessm70

@BHR To your question of budget, I wouldn't say unlimited and I wouldn't say restricted. The goal is to have a mildly modified 350 that runs, drives and is reliable. I have looked at this six ways to Sunday with regards to rebuilding the current L98 vs going with the L31 and yes if I re-built the current engine, it may be ~$2K cheaper and I really don't have a local machine shop. Now that being said, I live in Southern Indiana and I am sure there are some capable shops in Indianapolis (1.5hrs away). Whereas the L31 will be more plug and play, ready to go. Swap the springs and throw the cam in.

Not sure my decision is totally made on crate vs rebuilding existing (I have a used Accel/Lingenfelter intake). I do like the idea of all new parts. Now one could debate if GM builds a better engine than say XXX machine shop but perhaps that is for another thread.

BHR

If it was me I would swap heads on your current motor if everything else is ok with the short block. Even with the stock iron heads the mods you have listed headers, cam, intake can wake that motor up even more so if you but aftermarket aluminum heads. Keep in mind if you go with the vortec you will be limited to intake manifolds because of there taller raised intake ports you would need to re drill and weld any standard SBC intake for it to seal to those heads. What Accel intake are you taking about the Super Ram? do you have the bigger base to it aswell?

hessm70

So there in lies the issue, the engine has over 110k on it and I would not want to put new heads on it at this point so it would need at least the bottom end checked with new bearings and rings at a minimum.

This Summer I am taking it as is to the 2023 Hot Rod Power Tour with fingers crossed it makes it then next Fall I will make a decision as to whether it’s time for a new bullet or not.

And yes I realize I would need a Scoggins Dickey intake as stated for the Vortec heads. The Accel intake I have would fit the current L98 heads with whatever runners.

This thread is more about what cam
is recommended.

Komet

Tangentially off topic: by the time you buy a SDPC vortec TPI lower and AS&M runners, you could buy a FIRST TPI setup for just about the same money and it'll flow way better out of the box. I believe they offer them in any bolt pattern you want.

hessm70

@Komet yep that has also been a thought. I have looked at them several times as I have been “Christmas shopping.”

BHR

I have the lt4 hot cam and I like it, there are better cams since the hot cam was released but it all depends on what you want to do the more duration usually moves the power higher in the RPM the more lift usually gives you power everywhere, with higher lift cams more attention is needed in the rest of the valvetrain. I would use a cam with not to much duration since your using TPI as you wont be able to get into the RPM range those cams where indented to be used for, TPI even fully ported dont pull much past 5500