Hello, I am looking for advice selecting a cam for a build that I have just started. Here are some of the parts that i will be using and I am at the point of ordering a cam and there are so many options, and with me being new to the turbo scene, and using a small unorthodox turbo I could really use the advice regarding what lift and duration and LSA to choose with this setup. Any advice would be greatly appreciated. Thank you

• 1967 firebird
• 1977 Pontiac 400 block .30 over 406ci
• flat top piston with large reliefs cut in
• Pontiac 6x-8 heads
• Intake valves 2.11
• Exhaust valve 1.66
• Chamber volume 101cc
• FiTech blow through efi throttle body
• Holset H1C "baby" turbo

 

Just curious why the turbo choice? The small turbo will really limit hp, and most likely rpm. You'll want a cam with no or even a reverse duration split, low duration numbers, and a wide lsa to help with the high drive to boost pressure ratio.

 

The turbo choice is because it was free. My dad had a brand new one laying around and with this particular build I don't want to spend a ton so I decided it would be something different to try to work with what we had. I'm not looking for crazy boost or high hp numbers, or to wreck parts. just looking for a way to have a little fun and learn a little bit in the process. The cam I was considering was Comp cams xtreme energy Cam, Hydraulic Flat Tappet, Advertised Duration 274/286, Lift .488/.491, But going off what your saying the duration probably isn't the best on that particular cam

 

Anything you do to make more na hp/tq will only be counter productive with a turbo that's already small. Run the stock cam, and do a cam swap if you upgrade the turbo later on.

 

If I ran two turbos would that be more productive? I do have a second one lying around

 

2 would be much better. It may be a little too much turbo depending on your goals, but better to over turbo than under. A good running 400 should work quite well with 2.

 

So say I do go with 2, I do not own any cam at all for the engine at the moment but want to order soon. Would the above mentioned cam be a good fit? Just looking for some general baseline numbers to follow for lift and duration when matching a cam for a turbo application, and thank you very much for the useful information you have provided so far.

 

You didn't give a lot of info on the cam, but with twins a more off the shelf na style cam would work quite well. You still want to keep duration low to keep overlap down, but something mid 220's @ .050 or smaller, and a lsa 110-112* (112 is a good all around number). As far as lift, you only need as much as your cyl head needs.... many stock heads are all done by .500", and going extreme on lift only wears parts out quicker ( a much bigger problem with todays oils, and flat tappet cams).

 

Thanks again for the great info. I've decided to go with two turbos. I called Howard's Cams today and spoke with one of their guys and ended up ordering a custom grind 485 lift, 223 intake, 323 exhaust, 112 lsa, +4 degrees advanced. Per their suggestion

 

Look at the casting code on your engine block, if it ends in 557 you need to google 557 carnage. Many of the blocks produced from mid 75 on were a thin casting not good for a boost build. Some 77-78 trans ams were produced with an xx code block which was a copy of an early casting which is a very strong block. Pontiac knew they had a problem.

Not trying to be a dick. I just dont want to see someone build a bomb.

 

Yeah it's a 1977 557 block and I have seen that it's probably not the best block for this particular build but it's what I have so I'm going to use it and if it blows it blows, it's not going to be a crazy high dollar build and I only plan on running 7-10 pounds of boost. I do plan on going with a lifter valley brace I think it's called made by butler performance or another company I think is SA performance or SD performance or something like that. Im hoping with the low boost and the block strengthening it holds together. Thanks for the info, any info is much appreciated.

 

As long as you know what you have its cool.

I have a 70 firebird with a s475 on a 462 Im using a summit 2802 with 1.65 rockers this cam has worked well for me for over 10 years boosted 10-12 psi.

If I were you I would look at the summit 2801 it should work good in a 406 and its cheap. Your compression is probably 8-1 or lower this should work in your favor with that 557 block. Ideal turbo I would run a s475 but if the budget wont allow get one of the china gt45 with the biggest exhaust housing you can get your hands on.

 

I know this is an old thread, but how did that 557 block fare under some boost?