Reply With QuoteI think the 108 will kill you on a turbo, too much over-lap. I would do a 112 or maybe even a 114 to keep more boost in. Just my .02
Mike
http://www.***boat.com/image_center/...engine-med.JPG
I am running 470 CID (.070 over JE flat tops) Twin turbo drawing threw A holly 850 with open chamber square ports the compression ratio is 8 to 1, clay smith Hydraulic H9080.o.b which is 236@.050 and 0.290 lift(493 lift w/ 1.7 rockers) on 110 lobe centers the cam is advanced 4 degrees. This is in a 20.5 Bahner. It has an American turbine pump w/ Berkley stainless A/B impeller done by MPD in Costa Mesa.
I recently removed the 049 oval port heads and a holly 750 carb,
Installed Chevy square ports witch I spent 2 days match porting & cleaning up ports. Went to a holly 850. On 10lbs of boost and 100 octane auto gas it used to turn 5600 rpms with old heads, when i went to square ports and a 850 carb it gained nothing, in fact I think it laid down, it doesnÂ’t seem to accelerate as hard. But still only turning 5600
I am thinking The cam is too small, I know square ports like rpm think I am going to go with a roller cam next.
I have A solid roller out of my old aspirated engine witch is 264 @.050 and 0.385 advertised (0.650 W/1.75 rocker and .024 valve lash) on a 108 LC. Is this cam way too big for a turbo setup? If so what duration should I start with on a solid roller cam?
Any ideas?
Thanks Ken Buys (flycsna@lvcm.com)
I think the 108 will kill you on a turbo, too much over-lap. I would do a 112 or maybe even a 114 to keep more boost in. Just my .02
Mike
That cam is not designed for supercharged or turbocharged applications, way too much overlap, you will lose the boost, blower cams use 114 lc. Duration depends on what kind of rpm's you are looking for?...My .02...
I agree with the above cam recommendations but I'll go just a bit further. Check your exhaust pressure, if it exceeds your boost pressure then you need bigger turbo exhaust housings. [Larger A/R ratio] As for cam recommendation try a cam in the area of 248 intake dur. and 236 ex. dur on 114 L/C. This is a turbo specific cam done for me by Comp Cams. It in a 18' v-drive and pulls to about 7200 rpm. with the same basic setup you are running now.
The Spectra at the left came with a twin turbo system on it with square port heads and a 850 holley. Set up and running when i bought it, it would turn a stainless "A" impeller to 6200 at 10 psi boost. The cam that was in it was a Engle TCS-7 .529 in .502 ex lift and advertised duration at 286 in 269 ex at 114 centers. You need that short duratin exhaust to build "pressure" in the exhaust to keep the velocity up to spool the turbo up to speed. I sold this complete turbo system to a guy in California by the name Tyson Lloyd I have seen him on this board he might be able to give some help also. Good luck with it!
(By the way, this is a hyd flat tappet cam)
Twin turbo picture......
Posting Permissions