Slowridr

iTrader: (1)

So I have the original 305(LB9) and putting it back in my car. It came from the factory with the peanut cam (1987), I'm not putting that back in there. Whats the largest cam I can use without changing from stock springs, etc.

I understand that .470 lift is as far as you want to push it on the stock head.

I found a nice listing of cams from different makers on this site here
https://www.thirdgen.org/mods3

Now who has the biggest reasonably priced cam that I can put in this LB9 and not have to change anything else including the tune? The Crane 2032 seems to be the one to get but its very expensive. Here is a link to it at Summit.

http://www.summitracing.com/parts/crn-104224

Orr89Rocz recommended this one in another thread and it seems about as big as you can go without getting into new springs etc.

http://www.summitracing.com/parts/CCA-08-409-8/

Fast355 recommended this one for another application on the site but I noticed the lift and decided to consider it as well.

http://www.competitionproducts.com/E.../products/389/

Here are its stats

Elgin, Hydraulic Roller Cam, Chev 305-350, 288/284, 210/215
Chev 305-350 ('87-'94 w/OE Roller Lifters)
Adv. Duration: 288/284
Duration @ .050": 210/215
Lift: .462/.470
Lobe Center: 110
1500-5200. Mild street, improved power.

With this last cam being right at .470 lift should I expect any kind of issues. I have seen many folks say .470 is as far as you should go with stock heads but I'm wondering if I'm risking any problems doing that. If no problems will arise I think this is the one to get for my situation. Any other options out there?

Is using a cam that is at the max lift for the LB9 stock heads a bad idea?

I will likely add headers and maybe put the N10 exhaust on the car but that will be about it.

Slowridr

iTrader: (1)

As I read more stuff I get more questions. I read this from the article on this site.

So the Elgin cam is at 110 degrees. So it will have a mild lope I would assume. Not outrageous but mild. I like that. I also assume that the LB9 will lose some torque. This leads to my next question after some searching and reading on the Lunati website about how cams work. Here's the link.

http://www.lunatipower.com/Tech/Cams/CamSpecTerms.aspx

At the end of their write up they talk about Advance/Retard when installing the cam.

Advance improves low-end power and response. For a general summary of the affects of camshaft timing, refer to the following tables:


Advance
1)begins intake event sooner
2)opens intake valve sooner
3)builds more low-end torque
4)decreases piston-to-intake-valve clearance
5)increases piston-to-exhaust-valve clearance


Retard
1)delays intake event
2)opens intake valve later
3)builds more high-end power
4)increases piston-to-intake-valve clearance
5)decreases piston-to-exhaust-valve clearance

So now some more questions:

- So if I lose low end torque with this cam (which I don't like) I can get it back by advancing the degree of the cam lobe when installing the cam?

- If I get the torque back do I lose the lope that the lower duration gives when advancing the cam during installation? I would guess not because lobe separation does not change but I don't know.

- Another question is how far can you advance the cam before exhaust clearance concerns come into play?

- What exactly are the concerns that develop from to much or too little exhaust clearance?

I could be completely wrong about my assumptions but I am hoping someone will chime in on this.

Nelz

http://www.hotrod.com/how-to/engine/...mshaft-basics/

110 should be perfect for a 305.

Slowridr

iTrader: (1)

Thanks for that link! I've found some very helpful formulas too as I've tried to become literate in this cam choosing stuff. From that article you linked too I found this quote very enlightening.

"If the compression ratio with the longer cam is raised so that the same cranking pressure as the shorter cam is seen, we find that much of the low-speed torque loss is recovered. In addition to this, the longer cam will deliver a much better top end when an appropriate compression increase is made. This is an important factor, so don't overlook it. If you don't feel inclined to run a compression to match a longer cam's requirement, then stick with a shorter one, as it will produce better results."

Orr89RocZ

iTrader: (20)

Lsa is just a byproduct of the valve events. 110 on a small duration lobe like 206/210 cam wont be near as bad as a 112 on a 224/230 cam in same motor. Overlap is what can hurt low speed power and trq.

Depends on what you want out of the motor but long runner tpi stuff has plenty of low rpm power. Typically run lower duration and can get away with tighter lsa if you can tune it. There is somechance of alittle overlap at low idle rpm will play with the o2 sensor readings and cause some misfueling calcs. You can tune around this but its the general reason why efi cams were always said to need wider lsa. Not entirely true anymore with modern systems. Tuneability has come along way

Nelz

http://members.uia.net/pkelley2/Overlap.html

That's roughly how to calculate overlap

Nelz

Try this Cam. Its a cam from David Vizard's how to make max Chevy horsepower.

DV258-10HRH (for 305's). 206@0.50 lift with 1.5 rockers is .470.

Call Lunati and let them know its a post 87 block so that you get the roller cam with the right snout for the factory thrust plate.

Otherwise if you want a flat tappet cam (non roller)

Ask for this cam.

DV262-10HFH. (For 305.)

219@0.05 and lift is at .470 with 1.5 rockers.

Go to 1.6 rockers and you have too much for the stock springs. I'd still check for retainer to guide clearance as David Vizard's cams have short duration and a lot of lift.

92GTA

iTrader: (11)

Heads up but with smog testing, a 112 could be a fail unless your tune is flawless. Because of this we usually always error on the safe side and do custom cams that give us everything we want but on a 114. Not sure where you live so I wanted to mention it.