hey guys having problems with the new 383 and we did a compression test, with 11.1 static compression and a cc305 my psi cam out to 225. were we advanced a tooth on the timing chain install?

 

Sounds about right for a new 383. Should make 520/530TQ@5500 and 560/570FWHP@6500(depending on head flow) when ya get it all tweaked out if everything is right.

 

so you think thats right? ive been told the limit of pump gas is like 185psi or so. those hp and tq numbers seem way too high for anything using the parts in my sig. i obviously wasnt shooting for anything that high. the engine is surging and bucking at low rpms, and the idle surges bad until it dies, seems down on power, and it pings bad under hard load. my static was only about 8.67 with my setup and i used a psi calculator to get about 175psi. why am i off from that? some people say my compression is up so far because i have my the cam advanced a tooth with my timing chain. trying to get as many opinions before i have to pull the cover off again. thanks for the help

 

Ya noticed I said depending on head flow and it would have to be 300+CFM to do that.

Don't let people tell ya things they only heard and don't know.

"Welcome to the real world" The calculators aren't always right and neither is the info put into them. Ya got to have the experience to know weather the answer is close to right.

Ya got a tune yet?

 

If you have a 305H your dynamic compression ratio is about 7.75:1 with an 10.95-11.00 static compression ratio. 225 psi is way too high for your intake closing point of 79 deg abdc. Recheck your cam timing, piston to valve clearance may be getting close too if it is off. Its always better to recheck something that you are unsure of than to assume and be sorry later. If your lifters haven't pumped up yet by prelubing with a good tool they may be collapsing enough to really skew your readings until the engine has fired so you may be okay after all. Cam timing could also be checked with the engine assembled. You will need to measure tappet lift at the pushrod when degreeing the cam. Intake opening @ .050" should tell you what you need to know.

 

Wrong
A 305 has an IVC of 68*@.006.

 

yeah i have a tune, and it pings like crazy and runs like total crap, we have checked and recheck every sensor and plug wire on the thing. everything seems okay. okay so assuming a cam was advance by a timing chain being off could this cause higher compression? i was under the impression that with a static of 8.67 in a 383, my psi would be significantly lower than that, maybe in the range of 170min-190max. im just outta ideas as to why this thing is running so crappy.

 

Yeah.... that sounds about right for a 225psi cranking compression.

 

what sounds about right, the hp #'s or the pingin. are my symptoms consistent with a timing chain advanced a tooth? thats really what i want to know. sstroker what would you consider the limit of psi for running 91 octane? and if its below 225 which i would think it would be, why is my 8.67 dynamic compression engine coming up with such high pressure?
-sensors check out
-spark pattern primary and secondary looks great
-checked internal and external for vaccum leaks, none
-checked injector duty, its high but not enough to cause problems at idle i wouldnt think
-ran it with a scanner that can datalog and everything looks good except for the 10*retard due to the pining under hard load

 

You really kill me.

http://www.compcams.com/Technical/Se...umber=12-214-4

Notice that is for a 110 deg int c/l. The cam is installed on 106. So I believe that is 79 deg abdc unless I've got it all wrong.

 

Think maybe ya need more of the right info or this isn't the cam he is running.

Camshaft Specification Table
Part Number 07-305-8
Engine 1993-1996 Chevrolet
350ci,
LT1 & LT4,
8cyl.
Grind Number LT1 276HR-14
Description
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.51 0.51
Duration At 0.006 Tappet Lift 276 290
Valve Timing At 0.006
Open Close
Intake 28 68
Exhaust 83 27
These Specs Are For The Cam Installed At 110 Intake CL
Intake Exhaust
Duration At 0.05 220 230
Lobe Lift 0.34 0.34
Lobe Separation 114
Recommended Valve Springs 986-16

This is the info I have!!!!!!!!
Notice it is ground on a 114 and installed on a 110. Do you not know how to read the spects????

 

Clearly I don't. Are we now calling cams with 276 deg adv 305's? Did I miss a post listing the cam grind or part number?


Luckily he has your help........

 

No ya didn't miss a post,it's the part number.

Just like this one a CC306


Camshaft Specification Table
Part Number 07-306-8
Engine 1993-1996 Chevrolet
350ci,
LT1 & LT4,
8cyl.
Grind Number LT1 290HR-12
Description
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.51 0.54
Duration At 0.006 Tappet Lift 290 307
Valve Timing At 0.006
Open Close
Intake 37 73
Exhaust 90 37
These Specs Are For The Cam Installed At 108 Intake CL
Intake Exhaust
Duration At 0.05 230 244
Lobe Lift 0.34 0.36
Lobe Separation 112
Recommended Valve Springs

This is an LT1 board not a SBC board.

 

Ummm...Wrong cam quote dude. That one is not even an roller..

Here's the LT1 specific CC305
-->Linky<--

Unfortunately no online specs at Comp's site... I suppose I could scan in my old cam card though.

Dave C.

 

Thanks for the link, but where does Comp refer to that cam as a CC305? I've been through my Comp book and they also make no mention of a "305" cam for an LTx.
The fact that he is running a roller would make no difference on advertised cam specs and intake closing. Only installed centerline would be a variable.

I really would like to know where the slang grind numbers came from so I may understand how to help someone in the future. Factoring DCR and cranking compression takes time, not to mention dodging some of the locals.

Last I checked this is a Camaro board, not an LTx specific one and this is Advanced Tech so maybe I need a new cam spec decoder ring.

edit: after Googling the CC305 cam I came across numerous posts from LTxers across the country who are using this cam. Oh well. I wonder where the number came from. I may never know.

Good luck T/A Racer. A late 4.6 Ford has about 215-220 cranking and runs pretty good on BP Ultimate and 8 psi of intercooled boost. You should be able to get your n/a combo dialed in and running well. Hope you dodged the tornado.