cam question

[lt1sy]

What are the downsides of running the comp 09-430-8 cam? To me it looks great for turbo as its not a split duration only thing is lsa is 110 but ive run cams with choppier lsa on turbo setups without any loss in performance.

Anyone running the 430 with the lift numbers a well setup rocker combo should spin a 4.3 up to 5500-6k real quick with no problems. I would like to see what your opinions are on this.

 

[Don W.]

Re: cam question

Well... First I'm no cam guru so this is mere token observation. That being said I'm running a "custom" Comp cam in my motor and I'd have to say I'm very pleased. Last race of the season I ran 11.95 @ 116 with a 1.797 60'. All on just under 20# of boost. Remember I have nothing to compare these numbers with, IE other trucks, similar build etc but I think these numbers are pretty good.

You'll need to be sure to check that your springs don't bind at these lift numbers. Overlap might be on the high side for a turbo motor and IMHO here's the big problem. You have 60* of overlap. That's way to much. As I understand cams for turbo motors have anywhere from 0 to single digit overlap numbers. Maybe even a negative number. My cam has +5*.

I'd definitely research this further.

If you want the info on my cam LMK I'm sure Comp can make it for you. I have all the part numbers ect. If necessary I can even put you in touch with the cam designer/guru at Comp that recommended this cam. His recommendations might be different for your exact build. He did say that he had a cam he would rather use (for my build) but it required 1.6 rockers and I already had 1.5's.

EDIT: Regardless of your decision don't just slap the thing in the motor. Degree the cam, either by you assuming you know how or pay someone. Well worth the $$ in my opinion.

HTH

 

[ajt86]

Re: cam question

Custom grind is the way to go... call a reputable shop that knows these engines... tell them your mods and they will do the cam thats right for you. Its only a few hundred $$ more

 

[lt1sy]

Re: cam question

im unsure why the 430 cam wouldn't be a good choice except for the LSA duration nor lift is split which is good for turbo cams, ive made good power with tight LSA on forced induction since im not spinning this thing to 6500-7000 rpms the tighter LSA should bring the power in from down low to the mddle the turbo will take care of the top end pull.

 

[Don W.]

Re: cam question

The issue here is the overlap. A turbo motor runs against relatively high back pressure. Rule of thumb I've heard is a pound of back pressure for a pound of boost. Don't hold me to it. Regardless, any overlap contributes to reversion. (I think that's the correct word.) Meaning the exhaust flows backwards at the end of the exhaust stroke diluting the intake charge. Little or no overlap helps to mitigate this.

HTH

 

[dgoodhue]

Re: cam question

A turbo motor runs against relatively high back pressure. Rule of thumb I've heard is a pound of back pressure for a pound of boost. Don't hold me to

I have read that all out race turbo set ups are 1:1 ratio range, a ratio like that will have poor spool up in normal driving situations. A stock turbo's are usually in the 2.5:1 back pressure to boost ratio. 1.5 to 2:1 ratio is typical for after market turbo setups. (I think I read this on turbo Buick).

 

[Don W.]

Re: cam question

I have read that all out race turbo set ups are 1:1 ratio range, a ratio like that will have poor spool up in normal driving situations. A stock turbo's are usually in the 2.5:1 back pressure to boost ratio. 1.5 to 2:1 ratio is typical for after market turbo setups. (I think I read this on turbo Buick).

Good info Dave. I was only going by what I had heard, Take it for what it's worth. I've considered taping into the manifold just ahead of the turbo and actually measuring the back pressure. A real measurement on a real SyTy motor. That would be interesting. Obviously if I do this I'll post the info.

 

[randy merritt]

Re: cam question

Very interesting discussion about back pressure and cams. I am running a comp 415, and I picked up 40 AWD hp (about 54 crank hp, assuming a 35% loss) just by opening my exhaust dump. I wonder if the reduced back pressure from the open exhaust "helps" a smaller cam run better? I am no expert on this stuff. Good information and subject, and Merry Christmas.

Randy

 

[qbnkiller]

Re: cam question

Opening the exhaust dump is post turbo. That will only help if the cork in the system is in the exhaust system (muffler). Measuring backpressure like Don mentioned will help identify if you have a cork in either the turbine wheel or turbine housing.

As dgoodhue mentioned, some backpressure is wanted for good spooling and drive ability on a street truck.

There is so much that can be done with a custom camshaft. I have seen it with my own eyes, on my own engines, and the myriad of other boosted engines we build daily.

 

[Sean Krupa]

Re: cam question

The 09-430-8 was the cam I originally was goin to get this winter for my Vortec heads/cam swap. It was suggested by Harry Anderson and told me to advance it as much as I could for more low end power.

But after doin more research I've decided to contact Alex qbnkiller for a custom cam for my build. Will be ordering soon.

 

[randy merritt]

Re: cam question

The 09-430-8 was the cam I originally was goin to get this winter for my Vortec heads/cam swap. It was suggested by Harry Anderson and told me to advance it as much as I could for more low end power.

But after doin more research I've decided to contact Alex qbnkiller for a custom cam for my build. Will be ordering soon.

Yea, Alex is an OK guy in my book.