I think I've settled on a cam for my L03. Specs are:

209/214 duration at .050" - 265/274 adv. duration - .471/.490 lift - 112 lobe separation

This will be going in with ported and polished 601 heads with a three-angle valve job, appropriate springs and pinned studs.

There'll also be a new intake manifold along Edelbrock Performer lines. The TBI will be ported and 90 lb/hr injectors installed, along with an adjustable fuel pressure regulator and high-capacity fuel pump. Headers (1.5" primaries to match exhaust valve size) on the exhaust side with a 3" pipe with no cat to a high-flow muffler.

The rear-end will be a 3.42 posi and the tranny will get the TransGo reprogramming treatment.

I'll be doing all the PROM tuning myself.

This will all start going on over the next few weeks so I'm looking for opinions here as to what problems people can foresee with this setup. Better to have an idea before I start unbolting things Adequate manifold vacuum, etc?

 

If your going to put on a new pump and an afpr I don't think 90lb injectors will be necessary, stick with the stock injectors or at the most go with some 65lb injectors, you can always play with the fuel pressure to get it right. I would also step up to 1 5/8in primary headers as well. If you want to keep the stock hood go with the RPM intake not the RPM Airgap. Everything else looks like a good plan to me. I'm sure you'll here more from the others on here real soon.

Steve

 

i've been doing a lot of research on this. i think you're being too conservative with the cam, especially with the lift. comp cams' xr258hr, the cam they recommend for stock 305 tbis, has .480/.488 lift and .206/.212 duration @ .050 with a 112 lsa. the tech i spoke to called it an "economy cam" designed to run with stock heads, exhaust, etc. you've gone to the trouble to port and polish your heads to make them flow more air; that efforrt is wasted if you don't run enough cam to exploit that airflow.

i'd think you need the lift to be somewhere in the .500 range and the duration at least in the .210 range. keep in mind that the more duration, the harder it will be to tune.

here's comp cam's cam selection page. scroll down to page 144.

http://www.compcams.com/Technical/Cu...ML/128-169.asp

 

Steve, I didn't see the sense in going with header primaries bigger than the exhaust valves themselves. In any case, the head is not going to flow out more exhaust than the cross-sectional area of the exhaust valve allows. So what good would the bigger diameter primaries be? I was concerned about losing low-end torque with the bigger primaries too.

I was looking at the Comp Cams xr258hr. Some things about it made me a bit curious. For one, that might be a conservative cam for a 350, but for a 305? And also, they recommend that cam for a stock motor, but I don't think stock heads will safely handle that lift ...either because of retainer to valve seal clearance or because the pressed in rocker studs will be pushed to the limit. The stock springs will certainly be on the light side for that type of lift, at least if you want to rev either bit high. So, right away, that cam would be pushing the limits (maybe even exceeding them) of what stock heads can handle.

Plus that cam has to lose a few inches of vacuum over the stock L03 cam, so I would think that PROM tuning would almost be a necessity. Perhaps the oxygen sensor could make the necessary VE corrections, but I'm sure the computer would be in a constant state of making fairly large corrections every single sampling of the sensor data.

Now, I'm certainly not putting down that Comp cam in any way - to be honest, that cam looks to me to be one of the best for a TBI motor if you don't want excessive tuning difficulties - but I have to question how sane it is to put that cam in with stock heads, springs and chip.

Look at it this way, if that cam is an "ecomony cam", then what are the LT1 and LT4 Corvette cams? Neither one of those are as aggressive as that cam is? Come to think of it, has GM ever put a cam as aggressive as that in a computer controlled vehicle - even the highest output 'vettes? (I'm no expert on recent 'vettes by the way, so I could be wrong.)

For some reason, I get very cautious when considering cams over 210 @ 0.05" duration. For one, I have to question how much low-end torque a 305 would be losing by going over that duration. But also ...my car now, at idle, is around 31-32 kPa manifold pressure. Knock the vacuum down a bit and she'll idle in the 40 kPa range. That only leaves 50, 60, 70, 80, 90 and 100 kPa for table entries in the VE look-up table. That wipes out an entire column, and makes the tuning that much more difficult without those extra VE entires - you don't have as good a resolution over the MAP/RPM range as you erase columns from the useful tuning range.

Now, I'm not speaking from experience here - I haven't tried to tune any cams over 210 @0.05 duration - but something about that figure just scares me away.

Come to think of it, GM's VE look-up table method is an absolutely HORRIBLE way to try to run a high-performance cam - at least it is with entries for only every 10 kPa. It would be much better if there was some way to insert entries at every 5 kPa or so. 10 kPa jumps just don't allow you to fine tune very well. Even stock, at idle, the car selects it's VE value from the table that's not right for the idle pressure. My car, stock, idles at 31-32 kPa, so it selects the VE value from the next closest entry in the table - which is NOT for 31-32 kPa. So, right there, the VE value at idle is "wrong". So the oxygen sensor is constantly causing the mixture to be "tuned" as the car is just idling. That's from the factory! As you drive the car then, it's practically always running at pressures in between the values in the VE table (rarely ever dead-on 40, 50, 60, etc, kPa), so it's always selecting incorrect values and having to use the O2 sensor to adjust "on the fly".

If there was some way to alter how that VE vs. MAP and RPM function worked it would be much better.

Anyway, sorry for the rant

Do think I would be able to effectively tune anything longer than 210 @0.05" duration? How do you think the low-end torque would be?

 

As for the VE lookup, wait for RBob and the really smart guys to get the romless daughter board, and 60 code out.

As for cam choice, FWIW, i'm going with a 210/218 .510 .510 112 with ported 416's and a single plane. you should be able to tune a cam that is larger, but what you are going to run into, is you won't want to spin the RPMs needed to take advantage of it. that 210 cam should be good to close to 7k.

 

I wouldnt go over 210* in a 305 unless you are going to run a stall converter. I tuned a ZZ4 cam (208* intake) in a 305 and it was borderline needing a loser converter. On the subject of headers 1 5/8 works fine on a 305. Remember that the exhaust gas is still expanding as it leaves the engine, sorta shoots the theory about the cross sectional area.

 

JokerRS,

Ideally, what stall speed TC would you recommend for that cam? I'm possibly considering something mild, like in the 2000-2600 RPM range.

 

With my 305 and ZZ4 cam, power came on strong at 2500. I think if you were trying to avoid masive wheel spin you might go with something about 2200-2300.

 

My 2400 which actually stalls at 2200 is pretty nice with the 205/207 duration. Power comes on strong about 2800-3000 rpm, but the stall makes driving around town feasible. Ive wanted a cam thats nearly exactly the same size as Dewey is getting, but I cant justify spending any more money on a 305 tbi. I always though .515 .515 208/215 112* would be the custom cam if I got one ground to go with the vortecs and the performer RPM.