Sanjay

iTrader: (3)

I finished a TPI 305 5 Speed swap into a 92 RS in November. I've had very little seat time in the car cause it's winter here and it's technically in storage but i take it out once in a while. From the little driving I've done I've noticed the limitations of the TPI system already. That being said, I'm not sinking any money into that TPI 305 so I want to put something together with stuff i have lying around for a little more punch.

I have a 0.030" over Vortec 350 with a rod journal that's damaged. Came with a nice clean set of Vortec heads. It's pretty much a complete engine except for the stock L31 intake. I also got my hands on a RamJet SBC intake a few months back and I have a '89 (I think) TPI 350 in pieces that needs so much work I don't really want to think about it at the moment.

What I was thinking of doing is sticking the L89 cam in and topping it off with the RamJet intake, after obviously finding a stock replacement crank.

I was thinking of going with an LT1 Fbody cam but is that really going to make a big difference over the L98 cam I already have?

I don't want to go bigger than an LT1 cam since they can be had cheap and I don't have to upgrade the valve springs on the vortec heads.

I was considering a 383 crank since I need one but then I'd have to get machine work done to the block.

Since I really didn't want to be spending big money on this car this year I pretty much only want to spend on the following:
Used Replacement 350 Crank
Rod Bearings
Main Bearings
Gaskets
LT1 Cam (if it's worth it)
3 Position HD Timing Chain.

Everything else I should already have.

The car already has headers and the tuning will be controlled by a Megasquirt.

Any comments, suggestions, advice about what I want to do?

skirkland1980

iTrader: (2)

I'm a fan of megasquirt. Please keep me updated.

Sanjay

iTrader: (3)

Will Do!!

cuisinartvette

Make sure and mic the crank so your clearances are right. Knowing it isnt cracked or getting a quick polish helps

Make sure and degree that cam. More than 1 person has and found them to be a few degrees off even though it says its in straight up. Used to be you never had to worry about it but with stuff being made overseas you really have to.

Sanjay

iTrader: (3)

Alright, It's time I get back to this thread.

The plans for this engine have changed a bit. I now on a set of Edlebrock E-Tec 170cc Aluminum Vortec heads which solve my valvespring issue and open me up to a whole new works of cam choice.

So looking at the new engine combo and my desires for this car I need help choosing a cam.

Existing parts:
0.030" over SBC block
E-Tec 170cc Heads
Max lift is 0.575" with the valvesprings on these heads
Stock 1PC RMS crank
0.030" over replacement vortec Pistons with stock rods
Should be a pump gas friendly 9.4:1 compression, maybe a little less cause of the 0.030" overbore but I can probably make that up with a thinner head gasket.
1.6:1 Roller Rockers
RamJet Intake which will be port/gasket matched to the heads or ported if need be.
DynoDon's Headers (1 3/4" Primaries)
3" Magnaflow Catback
Y pipe to be fabbed locally with 1 or 2 high flow cats. (Not sure if I'm asking too much of 1 high cat).

The rest of the car is:
3400lbs?? (T56 with AC, no other significant weight added)
3.73 or 4.10 gears, whichever will work better. I'm thinking 3.73.

What I want out of the motor:
After looking at the dyno chart of the RamJet Crate Motor below I believe the power output/rpm range can be improved with the right cam choice.
I'm hoping to get a bit more RPM out of the motor but that's not critical.
First and foremost I want a good idle, like an almost stock idle.
I love the crate motors torque curve. I'd like to keep that and if possible do a bit better.
I'd like to get peak HP to 400 or better like 425 ish and closer to 6000 RPM
I'm thinking a 6500 RPM Redline and a 6000RPM shift point. I’m not sure if I should be pushing a stock bottom end to 6000 RPM.
Maybe I’m asking for too much RPM. I just don’t want to hit the TPI 4200RPM wall.
I want that instant torque feeling above 2000RPM (and below if possible) and to continue to pull nicely till about 6000RPM and great throttle response.
I’ve seen articles with these heads showing 460-470 peak HP & TQ numbers with quite a large cam at higher RPM numbers so that what I think I should be able to get pretty close to my goal with the right cam choice.

From what I've read I believe I want a cam with higher lift numbers than the .460/.481 @ 1.6 of the RamJet cam but will still give me good piston to valve clearance. I also believe I want similar duration and LSA numbers to the RamJet cam.
This is for a fun street car with a sleeper-ish attitude. So I want it to sound like a stock TPI with an exhaust but run a lot harder. I really don’t care about ¼ mile numbers.


I also want the car to sound smooth but aggressive like the below link. Not a hint of lope if at all possible.

I looked at the Hot Cam but I’m sure I can do better. Any off the shelf suggestions? Or should I just go with a custom grind?
I know want my cake and to eat it too but I think this is possible.

Sanjay

iTrader: (3)

Maybe I shouldn't have said "Like stock" idle.

Anything cam with an idle that can be hidden by either the right exhaust and/or raising the idle a bit will do.

Damon

You might want to look up the specs on the original RamJet 350 cam. It's got very little duration (less than your stock L98 cam), but with more lift. The magic of roller cams!

Have you considered a stock LT1 cam plus 1.6 rockers? That would give you similar lift to the RamJet cam but with a little more duration. It would DEFINITELY idle like stock.

A common upgrade, although the idle is going to be just a smidge choppier than stock, is the LT4 "HotCam" with the spec 1.6 rockers. It's got .525" lift on both sides with the recommended 1.6 rockers. Duration is 218*/228* @ .050". That makes it about 15* more duration than your stock L98 cam, which is nothing earth-shattering. EFI can still keep it idling pretty smoothly. I've used that cam with Vortec heads before (carbureted application) and it really wasn't very aggressive sounding. It could ALMOST be used against a stock converter, certainly just street driving it real easy, but it really appreciates something in the 2500-2600 RPM range if you want the strongest launch. And that's with a carburetor, please remember. I believe it would be well matched to those heads and the RamJet intake.

Sanjay

iTrader: (3)

I hadn't considered that. I'm leaning heavily towards the RamJet cam right now because assuming I get my tuning right I have pretty much the same power & torque curves as a RamJet 350. If I understood better how an F Body LT1 cam with 1.6RR's would affect the ram RamJet power curve I'd consider it further. Especially since an LT1 cam can be had for $50. Any input on this would be greatly appreciated.

I've also decided to go with 3.42 gears for now since that's what my 4th gen rear end has in it.

Damon

The production line F-body LT1 cam is nearly identical to your existing L98 cam. It should, since it was the starting point for the LT1 cam engineers many moons ago. All they did was give it about .030" more lift than the L98 using the same 1.5 rockers. Add 1.6 rockers and you're up around .480-.490" lift with NO increase in cam duration. It just makes it breathe better everywhere without changing the operating range of the cam.

From memory, the specs on the production line 94 LT1 Fbody cam are: 202/207* @ .050, .450/.460" lift (1.5 rockers) and a 115* LSA. That's pretty much dead on top of your L98 cam except yours has max lift of only about .420-ish (again, 1.5 rockers), if memory serves.

So if the LT1 cam has .450/.460" lift with stock ratio rockers the max lift would increase to .480/.491 with 1.6 rockers. It'll just breathe better as the RPMs climb with no change in bottom end torque vs. your L98 cam. The magic of roller cams.

This assumes, of course, that you have springs to handle that much lift. If not, forget having the heads machined- just get a set of Comp Cams beehives and retainers to match and you'll be good out to past .500" lift (and they do a better job controlling the valvetrain than old cylindrical valvesprings).

And, as you've noted, the price is hard to argue with on the LT1 cam. The intake you've got it would almost be a shame to go with anything smaller. It's got enough lungs to handle a cam considerably hotter even than this setup. I wouldn't even consider the RamJet cam unless you plan to tow with your Camaro.

-AO-

The L98, L31, and B-body LT1 cams are all very similar. The F-body LT1 cam is noticeably bigger. You could even put some 1.7 RR's on it. An LT4 cam with 1.5 rockers would be similar to an LT1 cam with 1.7's.