Z-RATED94

I too would say you need more cam and a real tune. The 306 shouldn't be to bad for driveabilty, seeing that you have a manual trans. But I have a few questions. Why the manual if your worried about track times? That's a little harder to do than a stalled auto for most people. Also, did you have new valve seats put in for the size valves your running?

red94chicken

i had the 280 xfi in my lt4 and only mph'd 111.9. they suck *****

MeanGreen97Z

They have a low duration with steep ramps. If you don't have the proper springs for them they will create some float.

nhill_05

I'm not so much worried about track times; that's the only thing i have to compare my car with. I put a 6 speed in because i shelled 3 4L60Es and was tired of having them rebuilt. Plus its more fun to drive... I was just expecting to be in the 12s with my setup. I know gears would've gotten me there but they'll have to wait. A good tune is a little more important to me.

As far as the valve seats go; yes, i replaced them. It was a lot of work, but i think it was worth it.

I'm pretty set on the 306... unless anyone has a better cam in mind.

I really wanna blame the cam on this one... I have heard the xfi cams suck, but it was already too late. Money down the drain i guess...


Thanks agian

Kevin Blown 95 TA

The cam doesn't suck, it's just not right for your engine since it is shy on duration. And you are making it worse with stock ratio rocker arms. Change the cam, change the rocker arms, make damn sure you got your springs set up right, spend some time on tuning it, and you should be ready to try it again.

slowZ

that sucks man. i have the xfi 280 in my low compression 383. i haven't had it to the dyno yet but it has way more power than my supercharged 355 lt4 hot cam setup that ran mid twelves at around 117. look around see if you have a vacuum leak or something dumb like a burnt wire, its easier than changing a cam

nhill_05

First of all, lift doesn't net much gain. Duration is where its at. Even with the right ratio rockers it wouldn't make much more power. The XFI cams were designed for fuel injection which is why they have high lift with moderate duration. I just overestimated the cam. Nuff Said!

As for changing the cam goes.... it's not that big of a deal to me to drop the engine again. I've got the means necessary and the time to do so... I could care less about how difficult it is.

I am fairly certain with a good dyno tune and a bigger cam, I would make the numbers i am used to seeing.

I never calculated the compression ratio, but i was told by my machinist that i would need a 20cc dished piston to retain the stock compression ratio of 10.4:1. The pistons i bought had an 18cc dish.

95TA04GOAT

We have somewhat similar set ups. I gained 30+ RWHP and .5 seconds off a dyno tune compared to a mail order tune. I don't know where your located but check out Carolina Auto Masters if your in the area.

nhill_05

Thanks. That's what i'm hoping for. I am gonna probably do a 306 swap and get a dyno tune. I'm thinking that should get me somewhere close to what i'm used to seeing.

bubba4

I'm running a CC306 in my 383 and although many people are not a fan of this cam, its easy on valvetrain parts and I'm driving mine daily. It should perform great for you. I just ran a 11.92 @ 113 with a 1.72 60 ft(spinning). Its not the best time in the world ,but, my point is its a good performer with a great sound.
Lloyd
95 Z28- LT1-383,AFR190's,CC306,Pacesetter LT's,58mm TB,30lbs inj,tci street fighter,A4(built),3.42's,Nitto 555R 275-40-17's, and much more,Oh yeh I also have a mail order tune (PCMforless).

nhill_05

That sounds like exactly where i want to be. What is disliked most about the CC306? Is there a better choice? 11.90s are nothing to be ashamed of. It would be sick to have an 11 second street car.

96capricemgr

Lots of problems, the cam is on the small side but even with that cam a well done 383 should run much better.
Cam would be one of the last things you should change.

I think you need to begin considering the possibility that you got in way over your head and made one gigantic mistake with the whole build, then you can begin figuring out ow to fix it.

Z-RATED94

Granted it should run better, but over your head and made one gigantic mistake with the whole build? I don't think it's that bad. Many projects don't work out from the get go. It took me a few trys (springs, teaking the tune, and shift points) to go from a disappointing low 13 to a very low 12. Then I caught some good air and managed a high 11.
To the OP, give it time and keep after it, it will pay off in the end.

96capricemgr

"bigger is better" mentality on the valves suiggests the heads are probably blindly enlargered.
Accel opti shows a complete lack of research blindly buying on brand.
Adjustable regulator shows a lack of understanding as to what such things are for.

Low compression with a cam that is a bad choice even if he had choosen appropriate duration, "latest and greatest" marketting campaign means it must be the best right?
Race gas on an engine that is the same compression as the stock LT4 from GM, again complete lack or research or understading.

1.5 rockers on a cam specifically designed for 1.6s, but yeah needed those big valves that was a better choice than using the lift he should have had.

"shelled 3 4L60Es", the 4L60e will survive in a 9 second 4000+lbs car but he couldn't get them to work in a 13 second car????? Something very wrong there, a bone stock tranny should have been fine. The M6 will "shell" axles instead, solved a lot there.


I do think there are pretty good gains to be had in tinkering at this point, but the build is still a trainwreck.

30AnniversaryZ28

I have/had a hotcam in my 383 and it ran low 8s in the 1/8 compared to high 8s stock. It made 333/390 with a couple fuel leaks, realllllyl lean a/f, and a miss up top.