Roush 427R engine or carburator problem

[ha_pe_1968]

Hi!

Please help me i need an advice:

I have a SPF Diamond edition and a Roush 427R. The carburator is
the 870 Holley Street Avenger. (car has 5700 miles)

We were testing the emissions today and seems that i have a problem:

When the engine is hot i had this result:

idle : 900 rpm, CO 4%, HC 4000ppm
at 2000rpm, CO 7%, HC 500ppm

normally the CO at 2000 rpm should be below the result at idle.

When the engine is colder the HC is better (around 2700ppm)

What would be your advice to do? For me it sounds like a carburator problem but i am not sure.
If it is the carburator could it be the powervalve or where can i start to search?

Thanks a lot for help

Peter

[blykins]

Are you familiar with carburetors enough to do some tinkering? It just needs some tuning. Carburetors out of the box can't be in a perfect state for every single engine that they can be bolted onto. I'm sure Roush didn't take the time to dial it in either and the Street Avenger carbs are mediocre at best.

I routinely replace these carbs for Roush customers with night/day performance differences.

[ha_pe_1968]

Originally Posted by blykins

Are you familiar with carburetors enough to do some tinkering? It just needs some tuning. Carburetors out of the box can't be in a perfect state for every single engine that they can be bolted onto. I'm sure Roush didn't take the time to dial it in either and the Street Avenger carbs are mediocre at best.

I routinely replace these carbs for Roush customers with night/day performance differences.

Hi Brent!

I was buying the car with the carburator. It was dyno tuned by Dennis Olthoff. Last year the results were ok but not this time. My friend is working as a professional mechanic and working a lot on older cars. But he was not sure what it is, (he thought it could be the powervalve) so he told me to ask people which are more familar with this carbs and engines.
It would be great to get this thing working again - but in winter i will buy one from you cause i have reading a lot things about you and your shop. And have reading too that this Street Advenger is only a ok solution.

Peter

PS: nobody was screwing around this carburator since the good resulst from last year and timing and ignition is ok too

[blykins]

How does it drive?

[ha_pe_1968]

Originally Posted by blykins

How does it drive?

I would say normal. A lil bit rough below 1.500 rpm but this is since beginning and think the result of the 427R cam. Over 1.500 everything feels fine and strong.
Peter

[jhv48]

If it drives fine, don't mess with it! That engine will never come close to passing a smog test.

When you are ready for more power and better throttle response, replace it with a double pumper from one of the forum vendors.

[ha_pe_1968]

Originally Posted by jhv48

If it drives fine, don't mess with it! That engine will never come close to passing a smog test.

When you are ready for more power and better throttle response, replace it with a double pumper from one of the forum vendors.

Jim, you are right, but i can not understand that the results are a lot worse in comparison to the last year. And its not normal that the CO is raising at higher rpm's. So of course i am interested what was going on and if it is defenitely the carburator. Would be not a good thing to replace the carburator and have the same problem.

Peter