My1986IROC-Z

I have my 305 (You can stop laughing now) in the shop for a rebuild and having the Comp Cams XE 256H cam and lifters installed:

Operating Range: 1000-5200 RPM
Duration Advertised: 256° Intake / 268° Exhaust
Duration @ .050'' Lift: 212° Intake / 218° Exhaust
Valve Lift w/1.5 Rockers: .447'' Intake / .454'' Exhaust
Lobe Separation Angle: 110°

I have headers, 3" exhaust all the way back and it is a TPI with 3.23 gears. What is your opinion on how it will fare in regard for driveability and HP for a little 305? I chose this cam from a good board members recommendation that I would not have to burn a custom chip to make it work. Honest Opinions on this set-up are appreciated and I don't need the why didn't you build a 350 comments. Thanks
Tony

My1986IROC-Z

Bump

Sonix

iTrader: (1)

That should work just fine, give you a bit of a power boost down low, and will keep the car running normal.

The 110* LSA and TPI is something you considered? that would red flag me....

My1986IROC-Z

Why would this red flag you? I am kind of ignorant when it comes to the cam specs.

Sonix

iTrader: (1)

oh ok, i'll elaborate:
TPI is a finicky injection system, upset the balance, and it'll go crazy.
You got advice from a fellow member to go with a mild cam not to upset the TPI correct? That cam was suggested due to it's low duration. Good. However, TPI also likes high LSA angles, ie 114.
I'm not an FI guru by any stretch of the phrase, so take this with a grain of salt. I'm not sure if the 110* LSA would work, or if it'd cause trouble without a custom chip. Look at comp cams catalogue, you had the XE series (good choice), now scroll down to "computer controlled friendly cams", or whatever they call them. Virtually the same specs, but with a 114* LSA. I think the cam would be a XE256H-114 or something like that.
But I'm guessing you already bought this, and so the advice is moot here...

86Z

iTrader: (4)

that cam is going to be fine with a 110 LSA because of the duration that TPI likes.

Tibo

iTrader: (15)

The closer the LSA is, the less power it is capable at making down low, at the expense of some power up high. A wider LSA is more ideal for a TPI engine. Higher gears will help out tremendously if you go with that cam though.

Sonix

iTrader: (1)

?
no offense tibo, but I think you're 100% wrong on what you said....
perhaps double check it, I think you may have mixed some of that up.

Air_Adam

I have to agree with Sonix... 110* LSA is probably a bit too close for TPI. TPI doesn't like a close LSA (lobe separation angle), basically because it makes the engine run 'rougher' at low RPMs than the same cam with a wider LSA, like 114*. Thats because a narrower LSA creates more overlap between intake and exhaust, which can "confuse" TPI at low RPM.

Tibo

iTrader: (15)

Non taken, corrected.

Sonix

iTrader: (1)

ah ok, that sounds right

I would think if the cam makes more power down low, you could get away with lower (numerically) gears as the power is found lower...
I'm just think of the opposite of: big lumpy cam, needs high ratio gears, ergo, smaller cam, can have low # gears...

I thought that TPI needs 114* LSA, as that's what comp cams calls a "computer friendly cam", whereas a 110* LSA is normal...
Like I said, i'm no expert, but maybe a phone call to comp would solve the problem My1986IROC-Z ?

My1986IROC-Z

Excellent idea Sonix. I found there computer friendly 256H last night and it is 112 LSA. I am going by the engine shop this morning to see which one they used. When I dropped it off I explained to them that I was using a TPI set-up so they may have selected the 256-12 cam for me, I'll go by and find out this morning. I appreciate all the input so far and I have learned a little about cams in the process. Thanks to all that have chimed in and I will post later today what the engine hs recommended and what comp cams thinks also.
Tony

My1986IROC-Z

Here is whats up. Went by the motor shop this morning and they ordered the standard 256H (LSA 110) cam. I talked with them and and we got it changed and they will have a 256H-4 which is a Ex 256 cam with LSA 112 for computer controlled TPI engines. This should set everything straight for this build - woo hoo. Thanks for all the advise from everyone and I will comment on this thread when she runs in about a week.
Tony

Tobias05

good luck! Go 305, haha

65panhed

I run the 256 112 in my carbed car because comp rep recommended it. I sometimes wish I would have gone with the 262, but the car runs great..........Merry Christmas and Happy New Year........