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Thread: Comp 270H Cam with TBI on 401??

  1. #1
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    Default Comp 270H Cam with TBI on 401??

    I am wondering if this cam will work well with TBI on my AMC 401. It will have Eldo performer intake, Headers, and 9.8 -1 forged pistons. I am hoping to get just a little more cam than stock and thought this looked like a good one.

    Comp Cams have the 260, 270, 280, 292. The lift and duration go up as the model number does. Here is the specs on the 270H I am looking at

    Specs are as follows:

    270/270 advertised duration
    224/224 duration @.050"
    .480/.480 lift with 1.6 rocker ratio
    110 degree lobe separation
    RPM power range 1800-5800
    Hydraulic cam
    From the Comp Cam catalog:

    270H Magnum is a great cam for high performance driving in street machines. The 270H has a rough idle in small blocks and a noticeable idle in big blocks. This is the largest cam you can use with a stock torque converter. The 270H will not affect power accessories, but should be used with headers and a 4 BBL. carburetor. This is the perfect cam for cruising
    1979 JEEP CJ7 "NIGHTMARE". Sold it.
    1985 Jeep CJ7. Done!
    1983 CJ7 Renegade. 4.6L stroker, NSG 370 6 speed, Dana 300, 2 1/2 lift, ARBs.
    1983 CJ8 Scrambler. Full restoration underway.

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    I am in the process of rebuilding my 360, decided to try the Comp Cams 268H with TBI. Will probably have it back in the CJ in a month, will let ya know what it is like.

    There are a lot of theories on cam selection, I am thinking the 270 may not be big enough. However I am far from an expert!

    I did a lot of reading here
    Bulltear
    . Some great info on cam selection and engine rebuilding there.
    4.0L, aw4, 231 Mega sgort shaft, SOA, D60 front locked, D70 rear Locked, 38" Michelin XML's, Red Nek hood scoop.


    You can't please everyone, but it IS possible to make' em all mad at the same time.

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    Registered BruceW63's Avatar
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    You might want to check out this forum---> http://www.amcforums.com/cgi/yabb2/YaBB.pl?board=eng

    or this one---> http://www.amcforum.net/

    and see what other guys with 401's have to say.

    Personally, I'd go with Summit's 8601 cam

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    I've got a 360 with the Comp Cams Magnum 280H .490 lift and I'm running 1.7:1 Roller Rockers that gives me a total of .520" lift int. and Exh. She's pretty lopey... If anything with a TBI I'd go with a smaller lift for the intake and a larger exhaust lift.... example: .490+ int and .510+ exh.. Either way, the 270h will serve you good especially once you fine tune it.
    There's a guy running around the Norfolk area with a Pacer who has 1.6:1 Roller rockers on his intake valves and 1.7:1 roller rockers on his exhaust valves...
    1982 Wagoneer Frame slowly being caged, AMC 360, Ford NP435/NP205, 35" swampers, D44 Front, AMC 20 Rear Will be upgrading to 1 tons and 42" tires once I find a Ford NP203.

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    Lift = why the Summit is my choice, with 0.496 intake and 0.52 exhaust. Breathability.

    A Pacer???? I assume with a 304, or did this guy go bigger?

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    Bigger... maybe a 360 could be bigger... It's MEAN!!! He had to cut the inner fenderwells for everything to fit.. Headers etc.
    1982 Wagoneer Frame slowly being caged, AMC 360, Ford NP435/NP205, 35" swampers, D44 Front, AMC 20 Rear Will be upgrading to 1 tons and 42" tires once I find a Ford NP203.

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    Quote Originally Posted by fifesjeep View Post
    I've got a 360 with the Comp Cams Magnum 280H .490 lift and I'm running 1.7:1 Roller Rockers that gives me a total of .520" lift int. and Exh. She's pretty lopey... If anything with a TBI I'd go with a smaller lift for the intake and a larger exhaust lift.... example: .490+ int and .510+ exh.. Either way, the 270h will serve you good especially once you fine tune it.
    There's a guy running around the Norfolk area with a Pacer who has 1.6:1 Roller rockers on his intake valves and 1.7:1 roller rockers on his exhaust valves...
    Question...Why would you go with the different lift on the exhaust and intake with TBI??? The 270H has alot smaller lift than the Summit 8601.
    1979 JEEP CJ7 "NIGHTMARE". Sold it.
    1985 Jeep CJ7. Done!
    1983 CJ7 Renegade. 4.6L stroker, NSG 370 6 speed, Dana 300, 2 1/2 lift, ARBs.
    1983 CJ8 Scrambler. Full restoration underway.

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    Mike, one important thing you have to watch, even more critical than duration and lift, is where the valve events (opening and closing) are occurring. We used a Clevite 284 hydraulic cam with these specs:
    218/218 @ .050
    .488/.488 lift
    and unfortunately I don't have the rest of the spec numbers in front of me, but you can find them over on that Bulltear thread I sent you.

    The problem with our cam was the intake was closing too early, and creating more compression. This is good for power, but wasn't working with pump gas, even 94 octane. If the intake stays open a little later, it lets some compression bleed off. If you listen to what others have tried, make sure you are on the same sheet of music with what fuel they are running and what you want to run. I'm assuming you want to run pump gas.

    By the way, we were running the same pistons you have as you know. We were running a carb, not TBI.

    Read up on that Bulltear post and learn about the difference in static and dynamic compression ratios, and how to calculate them. You want to keep dynamic compression ratio below 8 to 1 to be able to run pump gas without pinging.

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    I would think the 270 will work good for you
    a bigger cube inch motor can take more cam then a smaler ci motor

    dont go any more then a 110 center line
    duration stay around the 224 go higher the power band moves up also
    the valve over lap bleeds off the cranking press

    my cam card crower solid 292


    1978 cj-7 golden eagle had since 1979
    304 -360-401
    401 .030 over- full floating flat top pistons
    crower solid cam 292/298 - .500/.510 lift
    .246/.250 duration.050
    th-400 / 4500 stall
    Dana 44 5:13 gears
    aj glass body
    http://smg.photobucket.com/albums/v1...401/?start=all
    http://smg.photobucket.com/albums/v3...cj7/?start=all
    11.669 @ 112.33 mph 33x10.50 slicks and 4" lift in the 1/4 mile all motor no spray / 7.358 @ 93.03 mph in the 1/8 mile

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    Fuzz.... What Compression Ratio are you pushing?... 10.5:1? give or take a "little". What did that cam run you if you don't mind me asking.
    1982 Wagoneer Frame slowly being caged, AMC 360, Ford NP435/NP205, 35" swampers, D44 Front, AMC 20 Rear Will be upgrading to 1 tons and 42" tires once I find a Ford NP203.

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    Quote Originally Posted by Letchcore View Post
    Question...Why would you go with the different lift on the exhaust and intake with TBI??? The 270H has alot smaller lift than the Summit 8601.
    It's all based upon set-up... For different applications & performance..... flow... velocities...etc
    1982 Wagoneer Frame slowly being caged, AMC 360, Ford NP435/NP205, 35" swampers, D44 Front, AMC 20 Rear Will be upgrading to 1 tons and 42" tires once I find a Ford NP203.

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    Quote Originally Posted by rwsr50 View Post
    Mike, one important thing you have to watch, even more critical than duration and lift, is where the valve events (opening and closing) are occurring. We used a Clevite 284 hydraulic cam with these specs:
    218/218 @ .050
    .488/.488 lift
    and unfortunately I don't have the rest of the spec numbers in front of me, but you can find them over on that Bulltear thread I sent you.

    The problem with our cam was the intake was closing too early, and creating more compression. This is good for power, but wasn't working with pump gas, even 94 octane. If the intake stays open a little later, it lets some compression bleed off. If you listen to what others have tried, make sure you are on the same sheet of music with what fuel they are running and what you want to run. I'm assuming you want to run pump gas.

    By the way, we were running the same pistons you have as you know. We were running a carb, not TBI.

    Read up on that Bulltear post and learn about the difference in static and dynamic compression ratios, and how to calculate them. You want to keep dynamic compression ratio below 8 to 1 to be able to run pump gas without pinging.

    This is good info. Check thisthread for some good information to keep in mind about choosing a cam. Lotta good info about the timing events, static/dynamic compression nad how a cam effects this (around page 11). It is definately a good read and some valuable info in there.

    Couple this to remember:
    Generally speaking,
    Longer duration = Less tourque
    More lift = more tourque.

    LOL, I like to keep a pen and pad nearby when I read threads like that one. Always good to jot some stuff down.
    4.0L, aw4, 231 Mega sgort shaft, SOA, D60 front locked, D70 rear Locked, 38" Michelin XML's, Red Nek hood scoop.


    You can't please everyone, but it IS possible to make' em all mad at the same time.

  13. #13
    Registered fuzz401's Avatar
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    12:1 to 12:5 some were in there
    cost dont remember any more

    1978 cj-7 golden eagle had since 1979
    304 -360-401
    401 .030 over- full floating flat top pistons
    crower solid cam 292/298 - .500/.510 lift
    .246/.250 duration.050
    th-400 / 4500 stall
    Dana 44 5:13 gears
    aj glass body
    http://smg.photobucket.com/albums/v1...401/?start=all
    http://smg.photobucket.com/albums/v3...cj7/?start=all
    11.669 @ 112.33 mph 33x10.50 slicks and 4" lift in the 1/4 mile all motor no spray / 7.358 @ 93.03 mph in the 1/8 mile

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    Registered BruceW63's Avatar
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    you know, really we all have our individual ideas, experiences, etc. and we base what we say on them.

    but we aren't experts.

    the folks at the various factories are, and as far as I know, they all have guys who are probably more than happy to help with a selection. they can ask questions in real time, and they deal with cams all day long. they're the ones who can ask all the right questions and give you their ideas based on what you tell them. so that's what I'd do = call the factory.

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    Quote Originally Posted by mycj7 View Post
    This is good info. Check thisthread for some good information to keep in mind about choosing a cam. Lotta good info about the timing events, static/dynamic compression nad how a cam effects this (around page 11). It is definately a good read and some valuable info in there.

    Couple this to remember:
    Generally speaking,
    Longer duration = Less tourque
    More lift = more tourque.

    LOL, I like to keep a pen and pad nearby when I read threads like that one. Always good to jot some stuff down.
    Yep, unfortunately "1980_Cj7" in that thread over on Bulltear is really me. I just used my Son's handle and didn't bother to register myownself. Read and research Mike. It's tedious, this cam and compression ratio stuff, but don't make the same mistake we did. I'd seriously recommend sending those pistons back and getting some lower compression ones while you still can. The forged ones are a pain anyhow. We're going hypereutectic next time.

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    Quote Originally Posted by fuzz401 View Post
    12:1 to 12:5 some were in there
    Interesting, I just realized your compression ratio and price per gallon of racing fuel required to run it are the same, ha, ha.


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    Mike, there are a lot of good links over on that Bulltear thread to Keith Black Silvolite's site where they have lots of good articles, compression ratio calculators, etc.

    The other problem we found with the Ross pistons you have is they end up .017" down the hole rather than being flush with the deck like they are supposed to be in the 401. This is bad for quench which also contributes to pinging.

    Here's also a link to a thread about a 401 someone else built that worked out really well. He has actual dyno results posted too. You could check what parts he used. http://www.bulltear.com/forums/viewt...r=asc&start=12

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    my ross pistons were 0 height - I cant complane about them

    1978 cj-7 golden eagle had since 1979
    304 -360-401
    401 .030 over- full floating flat top pistons
    crower solid cam 292/298 - .500/.510 lift
    .246/.250 duration.050
    th-400 / 4500 stall
    Dana 44 5:13 gears
    aj glass body
    http://smg.photobucket.com/albums/v1...401/?start=all
    http://smg.photobucket.com/albums/v3...cj7/?start=all
    11.669 @ 112.33 mph 33x10.50 slicks and 4" lift in the 1/4 mile all motor no spray / 7.358 @ 93.03 mph in the 1/8 mile

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    Quote Originally Posted by rwsr50 View Post
    Yep, unfortunately "1980_Cj7" in that thread over on Bulltear is really me. I just used my Son's handle and didn't bother to register myownself. Read and research Mike. It's tedious, this cam and compression ratio stuff, but don't make the same mistake we did. I'd seriously recommend sending those pistons back and getting some lower compression ones while you still can. The forged ones are a pain anyhow. We're going hypereutectic next time.
    Ouch, that's rough. Rebuilding my first 360 atm myself. Hope it all goes well!

    Any new information on the 401 problems?
    4.0L, aw4, 231 Mega sgort shaft, SOA, D60 front locked, D70 rear Locked, 38" Michelin XML's, Red Nek hood scoop.


    You can't please everyone, but it IS possible to make' em all mad at the same time.

  20. #20
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    very nice Fuzz! With that compression ratio what other "needs" came into building up the block etc? And Why didn't you move up in cam? I take it that for that compression ratio and cam choice you have a decent idling motor? (Smooth choppy Sound).. Reason I'm asking: I have a 280H and 1.7 roller rockers 10:1 FF Ross pistons and it's bored .030 and she's a bit choppy... I know Hyraulic and Solid are two completely different animals and you'll get more potential energy out of the solid... I never ran the solids.. If you had to choose between Solid, hydraulic, or rollers... which one would you choose for the money spent to power gained ratio?
    1982 Wagoneer Frame slowly being caged, AMC 360, Ford NP435/NP205, 35" swampers, D44 Front, AMC 20 Rear Will be upgrading to 1 tons and 42" tires once I find a Ford NP203.

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