Hi!I'm new to the forum, but I have read a lot of posts in the past.Could you help me chose a proper camshaft for my 66 GTO?Some information about the engine:- 428cui (at 435cui now)- 72cc Edelbrock D-Port heads (SCR 10.6-10.7:1 with 93-95octane)- forged H-beam rods, forged pistons, rebuild stock crank- tri power stock (other jet sizes available if needed)- 2,5" exhaust with h-pipe and headers- msd ignition- good cooling system (3" radiator, big electic fan with thermostat, alum. waterpump...)- 4 speed manual transmission, rear gear ratio not known but rather shortSome informationa about my goals:- fair idle quality is okay, no daily driver- most times it will be used for street driving (not racing)- don't want to need more than 5500-6000rpm- really low end torque can suffer a little, mid range should be good - don't want to have detonation problems with the SCR, so I may need a bigger cam with probably more than 110° lsa as I also need some vacuum for my power brakesCam ideas: (I want to use a CompCams)- 275DE with 219/228 @0.05", 110 lsa- 268XE with 222/230 @ 0.05", 110° lsa- 280H with 230/230 @ 0.05", 110° lsa- 274XE with 230/236 @ 0.05", 110° lsa- 041H with 231/240 @ 0.05", 114 lsaI'm most interested in the last one, the 041.. what do you think? I need to keep dynamic compression low I was told. Will the 114° lsa make me lose much power if I compare it to the other cams? What cam would you recommend? Thank you!Chris
hello chrisare you an active member? your status says cancel, why is that. dont know if you'll get many posts if you aren't active on the site.Need to know if your heads are off and bottom end is apart. are you in austria?your writing style, comments and format suggest you are informed and technical. dont mean to nosy but i guess i am. what is your job and background if you don't mind?
Hi!I had to register new.. my name is now "Chris_Austria" instead of "Chris-Austria".At this time the engine is removed and all parts are waiting to be put together. I had first wanted to use the 265DE but that was with the low compression (9.4:1) which I think is too less with aluminium heads and so I changed the heads to 72cc Edelbrocks that will put me up to about 10.62:1.Yes, I am in Austria. My background is I'm very interested in technical things related to cars. My job actually has nothing to do with my hobby. (it's law related, not very technical at all).Maybe someone can help me with the camshaft issue? I already thought a lot about it and caluclated what happens with different camshafts.. but thats theory.. if someone can tell me how a 041H worked out in his 400-435cui it would be very helpful as well as basic information about how 230° intake combined with 114° lsa works together.Cam choise is much more complicated than I thought
hello again ok now i know you are real. i just had a frustrating exchange with someone else that wanted cam info. wasted my time. enough said. if you want technical info then read the post by jim hand, dseth and tuffnuff [on dawns dream build. there is a lot of info there however i kind of think you might have read them already because you supplied a lot of good useful info. if you have not read them then check them out, i just posted a lot of computer generated cam info on the "wise info wanted" post by dseth. no need to retype it. it's late so i may give you innacurate info. the jim hand post is xlnt for your 114 lobe center vs compression question. basically the closing time of the intake valve has more affect on compression than lobe separation. unfortunately comp conveniently does not post some valve timing info unless you buy the cam then it comes in the box but it's obviously too late then. they may tell you if you call them though. here's the deal. you are one lucky guy because your motor is still apart. You can download comps computer program for free. go to comp cams and scroll down left side to camquestonline. fuel if i remember right your octane is high what is it?reduce compression simply take heads to performance shop and have them increase combustion chamber size. i have done it on several heads. you can also use a thicker head gasket however it wont lower comp enough if your octane is 91 or less. the aluminum heads absorb about 1 point of compression so to speak. they run cooler so you van effectively run 1 point higher in compression without increasing detonation risk. you can therefore run higher comp with aluminum heads. 9.5:1 aluminum should not detonate especially with 100 octane. you may even be able to run 10:1. you need to decide. power brakesunfortunately you will sacrafice some performance using the comp cams you are looking at. i suggest an auxillary vacuum can if you're worried about it and don't mind looking at it under your hood.lobe centergenerally speaking [not always], wide lobe center means a wider softer power band compared to a tight lobe center which produces a more narrow hard hitting power band.cam selectionwhy dont you run a roller? i have built and driven several motors with the three xe cams you mentioned so i can tell you what my ecperience has been with them. the 268h has a soft idle in a big motor with mild unimpressive performance. the 274xe is moderate performance, it will feel sort of fast with 350 or higher gears and will spin the tires a little with minor effort. 288xe is pretty nasty for the non racer, it's as big as you probably want, definitely feels fast definite rough idle definitely bad for power brakes without cannister and will spin tires pretty easy. 280h decent cam wouldn't use though the xe series hits harder than the h series and comes on sooner. most factory passenger cars i have experience with have a 114 lobe center. in general they provide a smoother idle than a narrower lobe center.had a my cam suggestionmy guess for the comps tou are interested in are first get a hydraulic roller xr276hr with high rev lifters [preferrably crane not comp] the cam is very similar to the 274h but generates more hp with less friction so it has quicker revs and less heat generated. comps lifters suck, cams are good. second choice cam is the 274xe. 041 camnever used one specs are decent275denever tried itvalve spring 125-135 closed around 380 opoen. high closed pressure can kill a flat tappet cam on break in. and 135 is enough anyway. break in oil use joe gibbs or valvoline vr1.did this earlier today with the 274h and 276 roller hope it helps. low rise dual plane intake.208 in valve 166 ex valvelarge headers w open ex.800 carb9.5:1ported headshydraulic non roller comp cam 230/236, advertised 274, lift .488 .491, lobe separation 110. they do not list the valve timing events. this is very close to your lunati.comp xe274h 230/236, valve 488 491, 274 advertised, lift .502 .510 lobe sep 110 108 449.7 hp at 5500 485.6 torque at 4000with comp roller xr276hr, 224/230 278 .502 .510 lobe sep 110 108, huge gain.482.2 hp at 5500 512 torque at 4000roller cam with hi flow dual plane. it has stupid gains over low rise one above, plus it brings the hp and torque 500 rpm closer together. i'd like to drive this set up.557 hp 5500, 566 at 4500 torgueintake valve events found on comp cams site. These numbers can be decieving. The roller cams have much more hp than their hydraulic counterpart. cam btdc abdc rpm range degrees open041h 1 49 1800-5700 230 275deh 31 63 1500-5800 274 280h 34 66 2000-6000 280 xe268h 28 60 1500-6800 268 xe274h 31 63 1800-5800 274 xe284h 36 68 2300-6500 284 roller camsxr276hr 6 38 1800-5600 224 xr288hr 12 44 2200-6000 236
double post sorry
Chris I reinstated your old account so you can get your private messages.
Engine builder,self taught auto body guy.Horsepower sells engines and torque wins races
Chris,Welcome to the forum!The "041" cam is COmps repro of the Pontiac RA-IV cam. Nice idle quality and lots of low end torque and good HP numbers. Barnett mentioned the Comp tool.. Use it and compare.. Becareful of the "dynamic" compression ratio term.. It could be misconstrued to believe it will help with some things and it won't. The attached link and the forum post " Jim Hand" by Tuff might help you with this.http://www.davemiranda.com/dmhotrods.htm
Any idea why you want to go with a Comp cams?You have good heads, use them. Put more lift in it. I'd go easy on the duration until you get your rear gear established but something in the low 230 range at .050 would do well, you have ample compression.And keep it on a smaller lobe sep, your combo will support that and if you have a taller gear that'll help in low end grunt. A smaller lobe sep will make more power sooner, all else being equal.Pm'd you as well at Chris-Austria.Thanks and best of luck in your build!!
MarkEngine builder, located in Central Florida
Hi again,Sorry that I now have a new name again, but I cannot login with either of the old ones. If I want to get a new passwort for example it tells me my mail account doesn't exist and if I use the correct login name and password from the first email the message I get is "incorrect login information" Please if someone could make my first account work "Chris-Austria" is my desired user name. I only can make a new account every time, write one post and next time I try to log-in I can't.Back to the camshaft topic. Thank you very much for the provided information. A smaller lobe separation would also generate a lot more crank pressure (if I test it with engine analyzer). I read that best crank pressure is about 170-190psi. With the 041H it's 182psi or 192psi (4° advanced). But I'm not sure how accurate these number and finally how important they really are.I don't care too much if I loose maybe 15ft/lbs torque at the same rpm because of the higher lobe separation, but I want to make sure that a 230° intake duration isn't way too much and makes my engine very lazy at low rpms. I found lots of information about such durations with 400cui and 455cui but nothing with my combination of parts.For example dynamic compression and crank pressure are a lot higher with the 274XE than with the 041H, but they both have the same intake duration @ 0.05". The advertised duration is differnt if I got that right, because of the lobe separation and therefore the differnt ABDC and overlap?I read really a lot about all technical aspects, I never really had the intention to "study" camshafts.The most important thing is I wanted to get first hand information from other people who run about the same durations cam in his/her 428/435.The reason to chose a CompCams is because the shop where my engine will be put together gives the guarantee for the rebuild only if I use a CompCams. I could choose another one, but if I do so and something is wrong I have to pay for the repair. Also I almost never read something bad about them and they seem to work pretty good in the engines of some people I know, but none of them has a 428.. they all have 400's and they use durations between 214 and 230. (but with lsa 110° as most of the CompCams have this lsa) So my final question... a 230 intake duration even at 114° lsa (4° advance) would provide good low end and strong mid-high end torque?My calculations say that the 280H and the 041H are the ones with the lowest dynamic compression and crank pressure.. the 280H has a 110° lsa and also 230° intake duration. So maybe this will be the better choise? If I compare numbers they both make about the same power at same rpms (the 280H a very little bit earlier and the 041H makes power a little bit longer, but the 041H has lower dynamic compression).So hard to decide.. if I shouldn't care that much about dynamic compression, I guess the 280H's power range is a little bit better for a street setup.What do you think?edit: almost forgot.. the reason I don't want to use a roller camshaft at this moment is the price.. sure I could make even more power, but I don't feel like I need it and already have the assembled heads with springs for hft cams. (max valve lift 0.55" and the 041H has 0.47" with 1.5 rockers or 0.516" with 1.65 rockers if my information is correct)
Chris, all your accounts are active and should work.
When The Flag Drops.,. The Bull ***t Stops.,. P. Engineer, Engine Builder
Thank you! I'll log out from the account now and try! If I don't post any message in the next 15 minutes I can't edit:I cannot log-in to the other account, but this one seems to work... I'll use this one and you can cancel the other if you like!Don't know why the others don't work, but the message is always "your login information is incorrect".
chris i have run the 041 in a 406 and 462 but not a 428. 462 with #48 heads 041 cam eddy per rpm. i was trying to lose some torq to help the car hook on the street no luck. 406 #62 heads same intake same cam with crane variable duration lifters. it pulled hard from 3000 to 6000. your 428 will make the cam seem smaller. pontiac iron runs a 428. you might check out some tight lash solids. i have a 270 in a 462/6x heads. very quiet, pulls good up to 5000 stock 72 intake. make shur you round off all of the sharp edges on the pistons and heads(chamber). close to 0 piston to deck height will also help with detnatation.(jim hand)
76 455/4spd TRANS AM69 GRAND PRIX 455/5SPD
Left you another pm.Also, how is your fuel rated RON or RON+Motor/2? Big difference, I learned that the hard way.
MarkEngine builder, located in Central Florida
Please send pm's to "chrisaustria" I cannot access the other accounts.The fuel is measured in "ROZ" (=Ron)91 US octane = 95 ROZ93 US octane = 98 ROZ95 US octane = 100 ROZ (the highest available at most gas stations in Austria)There is also 102 ROZ if I want to use it, but I would have to pay much more and don't think this is necessary. (the BMW M3 I drove has 11.5:1 and only needed our 98 ROZ!)Maybe I should add that I first had about the same SCR with 670 iron heads and it didn't detonate with 100 ROZ and 10.5:1 SCR. So probably it won't detonate with the modern chamber aluminium heads I guess.. but I now want to try it with 95 ROZ (91 US octane) first and only use the much more expensive fuel's if necessary.@rowsleySo the 462 with the 041 had too much torque at low rpm's? That sounds nice to me the 435 is just exactly between your 462 and 406.. so maybe it may provide good power up from 2000-5500 rpm? (or 2200-5500rpm without the variable duration lifters)What can you tell me about idle quality and vacuum for power brakes with the 406 and 041cam? Did it feel very lazy at low rpm's and needed the 3000rpm to make good power or has it made good power even at low rpm's and really pushed harder if you reached the 3000 mark?
Hello ChrisI see you still have questions regarding the cam. I also see that you are Austrian so you’ll probably relate to this. I am part german and part norwegian [sorry guys it’s not my fault]. So on one hand, half of me want's to understand something new to me like this is for you. Therefore, half of me want's to research all the technical info, analyze all the charts and cross all the t’s and dot all the I’s before I do something new, and the other half of me simply wants to just ravage and pillage my motor apart and just jam the biggest mutha camshaft I can buy into it and hit the gas.There is a saying your fellow countryman “Arnie”, [Arnold Schwarzenegger] as we like to call him over here [as well as some other things at times] has, which is, “JUST DO IT”. However be careful, I am referring to the camshaft not the maid.Here’s something that no one has mentioned yet but they probably would, however if you’ve done this then it doesn’t matter. All the piston mfg’s and some compression calculations base their calculated compression ratios on the assumption that your block has been “0” decked. If it has not then you have a few options 1. Assume that your pistons are approximately anywhere from .005-.020 in the hole [not a good plan]. 2. Have the builder assemble your motor and measure each hole because the block surface could taper from one end to the other. 3. Have them 0 deck the block if necessary. 4. Go get drunk.You mentioned you didn’t want to spend the extra money for a roller cam so you obviously need to decide if you want to spend the money for this. Everyone’s tight on cash these days but some steps should be taken to insure good problem free performance.Thanks for the fuel info I asked about mark had an xlnt question for you regarding the ron/roz rating’s. PS- I will send you a private message later.