hello everybody. i'm looking to see if i can get some help with my car's performance. well my dad just purchased a C5 vette and all it has done is a CAI and bassani cat-back exhaust. i own a 1995 z28. the heads have been ported to reach within 90% of 300 cfm (as i was told by the local porter dont have numbers on hand), i'm running the XFI 468 cam with 918 beehives, 1.6 pro mag rockers, impala head gasket, throttle body bypass, no smog, 160 thermostat, full exhaust, long tube hooker headers, 3 inch hooker y pipe, 3 inch exhaust to a flowmaster and exits with duals, CAI, built 4L60E with a 3600 stall, LT4 knock module, throttle body air foil, MSD 6A, MSD blaster coil, taylor 7.5mm wires, bosch platinum 4 spark plugs, B&M shift improver plus, and computer tuning by one of the best guys in my area. my question is, is my car missing something or could something be not right in my combo? My dad and i raced earlier this evening and he jumped me a lil in first gear but once he hit second he pulled hard away from me!! Can some one help me out to figure whats going on because with everything done to my car i don't think he should of beat me like that!!! so please help me figure this out. I appreciate any help
Nando

 

You have nothing to base your car off besides your dad's vette. The only way WE would know your car sucks is if your 1/4 mile time is junk. So head to the track.

 

the nearest track is about an hour from where i live. i am planning on getting out there sometime but i dunno how soon. if it helps any, before i did the top end in my car and was just bolt ons 2800 stall stock tranny i raced an ls1 camaro with under drive pullies a computer programmer and maybe a cat back and we were pretty even most the way with me pulling on him lil by lil. then my dad had a 90 5.0 convertible which he recently traded for the vette. this 5.0 had an edelbrock performer intake, ford racing X303 cam, edelbrock performer heads, 3:73 gears, 5 spd, bbk CAI, bbk 75 mm thottle body, underdrive pullies, dual friction centerforce clutch, and it was dyno tuned and turned out 303 RWHP and 300 and some RWTQ. when we'd run it'd depend who got the jump wether it be from a roll or dead stop. then after i did everything that is currently done to the camaro we did a highway run and stayed pretty even till bout 120 and i pulled away from him hard.so i dunno if that is any help.

 

Never seen head numbers expressed anything like what you are saying, 90% of 300 is 270 which is not a bad peak number but flowbenches are not rhe measure of a head.

The XFI stuff pretty well SUCKS.
The Bosch multi electrode plugs are a joke nothing but a sales gimmick, real plugs might help you.
The B&M shift improver is a joke, $2 worth of resistors and wire that could have been BETTER done in the programming or better yet a Transgo.

What brand is the stall??

 

which plugs would you recommend? i purchased the car with the shift improver so. . . i should put in a trans go shift kit instead and just remove the improver? the torque converter is from a guy with a high-performance shop.

 

is there any way to get it runnning good with the XFI 468?

 

Running good? With mild port work, my 94 made 320/320 on the dyno from about 2500 to 5500 with that cam, on very similar other mods. On hooker SHORTY headers. I ran 12.7 at 108ish. On the other hand, I expect closer to 400 rwhp on the GM 847 cam with long tubes.

It sounds like your porter may have killed ALL the bottom end and most of the area under the curve to achieve higher flow numbers at high lift... common mistake of amateurs. "Hog it out big" does not do too well with modern heads.

Lose the plugs, go with TR55 (yes, TR55, no other model or brand), lose the B&M, your tuner should have had you throw it away already. My trans corrections are all in the tune.

And if you have no dyno numbers, just exactly HOW did the tuner know what the results of his efforts were? You got time to run Dad at 120 on public roads, risking your license and safety, you got no excuse not to take your *** to the track. Go, get real numbers, or better yet, get tuned on the dyno and THEN go to the track.

Also... spend 50 bucks on a cutout. Cutout beats ANY catback out there.

 

320 in a heads and cam car should be reason for embarasment, proof the XFI grind does not work.
That is 242 / 248, .584 / .579 113 LSA right?
That is too big for most strokers.
The Crane 227(210/224) cam will make that much power cam only, heck one guy got 315rwhp through stock exhaust manifolds with a Creech tune.

The 847 is again too big, my car makes around 400rwhp by all accounts based on track performance, my cam is closer to the Comp 503, just mid 220s on the intake side, peaks somewhere around 6100rpms.

The converter from means nothing, could be a $70 Dacco piece of junk, a $800 Level 10 pices of Junk, a $500 Edge good converter or a $700 good Vigilante or yank good converter. A lot of shops have wrong ideas about the 9.5" performance units like Edge Yank and Vigilante but they are THE ticket for a quick street car, and quality can vary signifigantly.

I breifly had a Level 10 billet 2600 stall 9.5" and it drove sloppy and ran hot, after the tranny went I went with a 2800 Edge drove better and cooler, heck the current 3400 Edge drives better and cooler than the 2600 Level 10.

You have made a lot of poor choices sofar or bought the car poorly modded, I suggest you start looking for RESULTS before buying parts.

Not talking recommendations you want to look for RESULTS. A lot of guys out there have weak cars they do not realize are weak so they recommend the same mistakes they have made themselves. Others are not man enough to admit mistake and tell others to do the same because if everyone does it, they think it makes it right.

I have heard from someone I trust the XFI stuff can work if you use springs above Comp's recommendation but still 242 on the intake is too big for a 350ci motor held below 7200rpms.

I do not know where the above poster is getting the idea that your porter killed lowend, my heads were done by who I feel is the best shop for LT1 heads period, they are not hogged out, they achieve 274cfm at .550", 275cfm at .600" yet still match stock peak flow by just .300". Just 20cc of material was removed from the port, some of the most popular ported LT1 heads have 35cc+ removed and that is just what is claimed, actual measurement by third part has the real number higher yet on some sets, they still work, not as well as a set done by a better shop but are much better than stock.

Then again your porter could have made a mess, we have no way of knowing that though.