GM847 camshaft: Pros and Cons?
05-26-2010, 07:09 PM
#1
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GM847 camshaft: Pros and Cons? I am planning to build a 383 in the next 1-2 years and was wondering what everyone thought/expirerenced about the GM847 in a 350/355 or a 383. From what I hear it sounds like that cam runs good in the middle and top. Does anyone out there have one that they run daily in a 350/355 or 383? I'll be using ported stockers and 52mm tb, headers, etc. I will also be using an auto trans unless I find something to trade for or buy an M6.
Also, does anyone have the specs for the 847 with 1.6s? Thanks
Also, does anyone have the specs for the 847 with 1.6s? Thanks
Last edited by 1SWT95Z; 05-26-2010 at 07:10 PM. Reason: added more info
05-26-2010, 07:16 PM
#2
Here.
Originally Posted by StealthFormula says this
GM847: (234/242 .575/.595 112lsa) w/ 1.6RR's
The largest cam of the bunch. Over the years it has proven itself as a cam that puts out good numbers and good track times. Very strong mid-range and top-end with some low-end loss. Will put out slightly better numbers than the cc306 while exhibiting similar drivability. Not recommended for cars that are daily drivers or that have stock bottom ends/heads due to its large size in duration. Stock heads don’t allow this cam to be used to its full potential so one with a built bottom end and head work would benefit greatly from this cam. Automatics require high-stall converters and gears and 6-speeds require steep gearing to run this cam successfully. Degree of cam surge will be determined by how good the tune is, stall size/gearing etc.
Pass Emissions?: No
Shift Point for Maximum Performance: 6400+rpm
Idle Characteristics: Very Choppy Idle
M6; Require Gears?: Yes
A4; Require Stall?: 2800+ Stall Speed
The largest cam of the bunch. Over the years it has proven itself as a cam that puts out good numbers and good track times. Very strong mid-range and top-end with some low-end loss. Will put out slightly better numbers than the cc306 while exhibiting similar drivability. Not recommended for cars that are daily drivers or that have stock bottom ends/heads due to its large size in duration. Stock heads don’t allow this cam to be used to its full potential so one with a built bottom end and head work would benefit greatly from this cam. Automatics require high-stall converters and gears and 6-speeds require steep gearing to run this cam successfully. Degree of cam surge will be determined by how good the tune is, stall size/gearing etc.
Pass Emissions?: No
Shift Point for Maximum Performance: 6400+rpm
Idle Characteristics: Very Choppy Idle
M6; Require Gears?: Yes
A4; Require Stall?: 2800+ Stall Speed
05-26-2010, 07:42 PM
#6
Other things to consider in a cam grind are vehicle weight, car usage, exhaust components, intake manifold, carb/fuel injection, power adders, and compression ratio.
05-26-2010, 07:44 PM
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i run the 847 in my car and i am very happy with it. i have a 355 running about 11.5:1 with the 847, 1.6 comp pro mags, heads milled .010 unported (i know could benefit a lot from porting) stock TB ford 30lb injectors, pacesetter ceramic long tubes with true duals, no cats, and sweet thunder mufflers, and a t56 and the 847 runs great in my car, i drive it as much as 600 miles a week to work and back and with the 6 speed and 3.73 gears i average 19-20mpg doing about 30%/70% highway/city. with a good tune it has good manners but has amazing power. like the other guys said you can get more out of an LE or AI setup with a custom cam and ported heads that compliment eachother, but the 847 is still a good cam too in my opinion
05-26-2010, 08:40 PM
#11
i run the 847 in my car and i am very happy with it. i have a 355 running about 11.5:1 with the 847, 1.6 comp pro mags, heads milled .010 unported (i know could benefit a lot from porting) stock TB ford 30lb injectors, pacesetter ceramic long tubes with true duals, no cats, and sweet thunder mufflers, and a t56 and the 847 runs great in my car, i drive it as much as 600 miles a week to work and back and with the 6 speed and 3.73 gears i average 19-20mpg doing about 30%/70% highway/city. with a good tune it has good manners but has amazing power. like the other guys said you can get more out of an LE or AI setup with a custom cam and ported heads that compliment eachother, but the 847 is still a good cam too in my opinion
05-26-2010, 08:44 PM
#12
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mine runs fine*. untuned** it only barely outruns (1/2 car or more) a similarly equipped camaro sporting a tuned cc503. same weight, tranny, gears, engine components (except for me having a GM847 & 1.5rr as opposed to his cc503 and 1.6rr) and tire height (i am on a narrower tire).
*fine is relative to my opinion of street manners and performance and could be considered subpar given my personal level of skill which could be equal or significantly less than yours.
**was originally tuned for stock ported heads on a high mileage motor and nothing has been altered since
*fine is relative to my opinion of street manners and performance and could be considered subpar given my personal level of skill which could be equal or significantly less than yours.
**was originally tuned for stock ported heads on a high mileage motor and nothing has been altered since
05-26-2010, 08:56 PM
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I ran a gm847 on a stock LT1 with 1.52 rockers. I had a mail order tune with the idle set at about 850 but the car ran perfectly I wish I had the idle down around 650. Don't believe all the info you get from people who don't have experience with this cam. Even if its overkill for your setup it will still be very driveable and will make more power than small cams, but the car might reach its full potential with a good midrange cam.
05-26-2010, 09:06 PM
#14
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Does the 847 seem like it wont run down low or on the street at lower rpms? I guess a smaller duration/lift cam would make more power from lets say 1500-5800 and the 847 would make more from 5800-6400 or is the 847 better everywhere in the curve?
05-26-2010, 09:14 PM
#15
I ran a gm847 on a stock LT1 with 1.52 rockers. I had a mail order tune with the idle set at about 850 but the car ran perfectly I wish I had the idle down around 650. Don't believe all the info you get from people who don't have experience with this cam. Even if its overkill for your setup it will still be very driveable and will make more power than small cams, but the car might reach its full potential with a good midrange cam.
Which begs the question...why go with the 847 on stock heads in the first place?
Last edited by RamAir95TA; 05-26-2010 at 09:20 PM.
05-26-2010, 09:30 PM
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Right now I have ported stockers. 180cc intakes and 65cc exhaust. I think they flowed 272 on the intake and 194 on the exhaust. Does anyone know the ideal ported head size/flow that works really well with the 847?
05-26-2010, 09:50 PM
#19
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my stock heads were ported to 200cc intake, the exhaust port was untouched valves were 2.02I 1.60E the combustion chamber was reduced to just a hair under 54cc and i was running impala ss head gaskets further increasing comression. i was told then that it was not enough head. i now have 180cc darts and was talked out of getting the 200s because i was told it bould be too much head for the cam. the porter and the guy at the speed shop both had a difference of opinion. both head combinations i feel run the same given the cam. no times to back it up yet because i have a bad 2nd gear synchro.
05-26-2010, 11:13 PM
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yea i am aware i could gain a lot from head porting or aftermarket heads... and i plan to do one or the other somewhere down the road. the way mine is tuned now its a mail order tune and it isnt perfect but good one the less. my car idles at about 900 wich is a little higher then i would like but still has a very nice lope. i rev my engine to a 6800 redline no problem and this cam deffinately pulls hard in the mid and top, but dont let anyone tell you it has no bottom end, i can break the tires loose at will just about whenever i want and sometimes when i dont want with a hit of throttle. a friend of mine has a 99 mustang gt with a vortech at 10psi and bolt ons with gears and 5 speed and my car will rape that thing out of the hole and walk it the whole way from there.