Cam opinion please
#1
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Joined: Jan 2005
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From: Eastern Georgia
Car: 1986 Iroc-Z
Engine: 305 TPI (used to be Carb)
Transmission: 700R4
Comp Cams Extreme 256H - please read
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
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
Last edited by My1986IROC-Z; 11-29-2005 at 12:56 PM.
#3
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
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....
The 110* LSA and TPI is something you considered? that would red flag me....
#5
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
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...
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...
#6
Joined: Jul 1999
Posts: 1,991
Likes: 10
From: CT
Car: 1986 Camaro SC
Engine: 305 TPI Procharged D1SC
Transmission: Tremec TKO-600
Axle/Gears: Moser 12 Bolt 3.73 posi
that cam is going to be fine with a 110 LSA because of the duration that TPI likes.
#7
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From: Desert
Car: 1991 Z28 Vert
Engine: 383 single plane efi
Transmission: T-56
Axle/Gears: 8.8 with 3.73s
Originally posted by 86Z
that cam is going to be fine with a 110 LSA because of the duration that TPI likes.
that cam is going to be fine with a 110 LSA because of the duration that TPI likes.
Last edited by Tibo; 11-30-2005 at 08:02 PM.
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#8
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
?
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.
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.
#9
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Joined: Oct 2002
Posts: 9,067
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From: Saskatoon, SK, Canada
Car: '83 Z28, '07 Charger SRT8
Engine: 454ci, 6.1 Hemi
Transmission: TH350, A5
Axle/Gears: 2.73 posi, 3.06 posi
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.
#10
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From: Desert
Car: 1991 Z28 Vert
Engine: 383 single plane efi
Transmission: T-56
Axle/Gears: 8.8 with 3.73s
Originally posted by Sonix
?
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.
?
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.
#11
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Joined: Jul 2004
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
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 ?
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 ?
#12
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Joined: Jan 2005
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From: Eastern Georgia
Car: 1986 Iroc-Z
Engine: 305 TPI (used to be Carb)
Transmission: 700R4
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
Tony
#13
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Joined: Jan 2005
Posts: 220
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From: Eastern Georgia
Car: 1986 Iroc-Z
Engine: 305 TPI (used to be Carb)
Transmission: 700R4
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
Tony
#15
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Joined: Sep 2003
Posts: 224
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From: OKC Oklahoma
Car: 1984 Z28
Engine: L69 305 HO
Transmission: 5 speed manual
Axle/Gears: Auburn pro yukon 3.73 gears and axl
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........
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