I'm preparing to install a Pontiac 468 with Aluminum E heads (ported and polished, Long tube headers,2.5" exhaust, forged internals and roller valve train. The roller cam is a custom grind 294/302. The transmission will be TKO 600 with .64 OD. I'm trying to determine the rear gear to run, I'm considering 3.73 maybe 3.55. I'm worried about traction... Also what RPM do you think this motor could be safely reved to? Thanks for your input.MichaelEDIT: I had added some detail ( not enough I know) in a reply below. Sorry to be so newbie EDIT 2: Here's my cam card if anyone can make sense of it..also 1.6 roller rockersEDIT 3: Added new info post, I've made a mess of this haven't I? In the future should all updates go in the original post??? PM me to make me less dumb...thanks
I guess it depends on what you are going to do with it: quarter mile, eighth mile, road course, or going to Hamburger Dan's on Saturday. On the street I would not go any taller than 3.23. eighth mile maybe 3.73 possibly 3.90. You will need to be more specific about the car setup and its intended use for more than a guess. For example, what car is it going in.
hello crankorRight off the bat you are not making sense. you are worried about traction but you are buikding a 468 with a massive vam. the obvious answer is build a smaller motor and/or use a smaller cam. that being said her's all i got for now.as mr milt pointed out more info is needed otherwise most of it is pure speculation. Plus it is absolutely impossible to speculate what it could be "safely" revved to without knowing exactly what brand name and part numbers of the parts are you are using including exact cam type and specs. Even though some here can give you a reasonable estimate of safe rpm's once they know the details, you are still best served by asking your professional builder.1.using the comp cams desk dyno your motor will have at least 580 hp at 5500 and 580 torque at 4500. this is with a smaller xr288hr comp cam. your results should be higher. rpm 2500-5500.2. with $12k or more in quality parts you could safely spin it to around 7k but why would one want to.let us know what you got and what your doing with it. doesn't need to be a mystery.
Thanks for taking the time to reply, sorry for the vagueness. I just didn't put enough thought into my post I guess. I just bought the engine a month or so ago, I'm going to put it and the tremec tko in when my driveshaft and clutch pedals come in. It's going into a '67 firebird, that currently has a peg leg 2.56 BOP rear. The 468 has eagle forged and balanced crank, forged h beam rods and forged pistons. Torker intake and edelbrock 750 carb. Cam grind: Intake run clearance .026 lift .555 duration 294; Exh run clearance .026 lift .555 duration 302. Intake opens 38, closes 76 exh closes 34, opens 88. 72 deg overlap. I was asking about the rev limit, because the cam is kind of big so the power will likely peak pretty high. With the beefed up internals and the roller cam/lifters/rockers. I was wondering how many more rev's you guys think it should be safe to take it to. I'd figure that it should be good for 6000-6500 from what I understand the torque should be pretty steady (hopefully) But thought I should get opinions from people more knowledgeable than I. The car will be mainly street driven with a rare drag race thrown in, so will not see that kind of RPM often if ever. Again, thanks for your knowledge. Not trying to be mysterious really just ignorant, curious and excited to get this sucker rolling.
hello crankor your definitely not ignorant. you're smart enough to know what you don't know and ask for help. i don't know how to do a heart transplant but that doesn't make me a moron [i may be one but at least that doesn't make me one].MAKE SURE THE RETAINERS, AND ROCKER ARMS ARE NOT CHINESE. IF THE ROCKERS SAY NOTHING THEY ARE LIKELY CHINESEMAX RPM - Refer to my post above for my "guestimate". Other opinions will vary.1. is it an assembled crate motor with a guarantee from a reputable builder? if not you are taking a huge risk running it as is without disassembling and checking everything first. 2. are they eagle rod's?3. it's bad to spin high rpm's on a daily driver. will you drive it on the freeway everyday etc. 4. to reduce tire spin run taller gears like mr milt's 323 recommendation or higher like 300 but then you loose the purpose of having so much power.4. a. 373 would make first very low and almost [but not quite] render it useless basically turning you car into a 4 speed plus you would spin tires very easily. 5. with little freeway driving i would use 343 - 350 with that high rpm cam 5. those trannys suck because the ratios are too wide. first is too low and will just roast the tires. mcleod makes one [m800] with closer ratios if you haven't bought the tko yet. 6. has it been balanced?7. it will have about 20-30 more hp with an 850 carb per rough dyno spec. 8. is it a solid or hydraulic cam?9. do you have the cam specs at .006 and .050?10. you will need high perf motor mounts or "chain" the motor to the firewall or it will turn your stock mounts into scrap metal.thanks
How tall is your rear tires.I have approx the same OD in my Monte Carlo. That has a 26" tall tire. At 70MPH the engine is spinning approx 2700RPM with a 3:73 rear gear.Even with all the good pieces 6800RPM to 7000RPM max RPM.Bob
Crankor,I'm presuming that the motor internals were balanced? If so, the shop should have given you an index card with small end weight, large end weight and piston/pin weight. There's a mathematical formula for calculating RPM, and you'll need to plug in a safety factor.It involves Rod strength, Mass of reciprocating parts (hence the weights needed), length of stroke (longer lowers RPM limits), Inertial loading factor, and factor of safety (usually a 2).For example take a 455 SD;factory small end weight is 355 gramsPiston, pins and rings 830 gramsTotal reciprocating weight is 1185 grams2.8" stroke-RPM limit is 96243.25"- rpm limit is 88343.375- RPM limit is 87043.56"- RPM limit 73573.750" RPM limit is 71034"-RPM limit is 67894.21"- limit is 6549One quick down and dirty way to calculate this is to take the factory weights/specs and your new weights/specs and do some old fashioned division.factory weights/new weights and then take that result X factory limits. (safety factor of 2 is built in)But there's a lot more to this than calculating RPM. If the internals are not balanced at tight tolerences the motor might shake itself apart. Other parts of the motor may limit your RPM range. It does no good to build a motor bottom end capable of 8000RPM when the top end is only good for 6500 RPM.. And then, when you have all of that considered and balanced to perform, you'll have to start calculating vehicle speed. Does no good to have a drive train capable of 150 MPH when the car suspension, tires and steering gear are not set up to handle that.Disclaimer/Qualification:The RPM limits calculation information was taken from "Pontiac High Performance Engine Design and Blueprint Assemply" By Craig Hendrickson and Kern Osterstock of HO racing Specialties.
You guys might want to reread his post. It states "balanced" and also has valve lash specs. That means it's balanced and it's a solid roller.A 294/302 advertised duration solid roller is way too big for your combo. That's 294/302 at .020 so it's even larger at the most used .006 for a hydraulic. I would come back on the duration but increase the lift with ported heads, not sure why they wouldn't have done that. That grind doesn't make sense with your build. And it may not drive that well at lower rpm's, any idea of the final compression ratio?Thanks, hope this helps.
MarkEngine builder, located in Central Florida
Mark,Not trying to hash out a point here, but in Crankor's post he stated "The 468 has eagle forged and balanced crank, forged h beam rods and forged pistons."As we both know, balancing involves everything from the clutch diaphragm to the harmonic balancer along w/pistons, rings, rods and pins.. I made the presumption when he said balanced, he was talking everything and not just balancing a crankshaft from a manufacturer.I am in agreement that cam duration is way radical for the type of driving he said he wanted to do, but it's his motor, his pocket book and his choice.
hello crankor and fastoneefii sent you both a private message.
My71:Mark,Not trying to hash out a point here, but in Crankor's post he stated "The 468 has eagle forged and balanced crank, forged h beam rods and forged pistons."As we both know, balancing involves everything from the clutch diaphragm to the harmonic balancer along w/pistons, rings, rods and pins.. I made the presumption when he said balanced, he was talking everything and not just balancing a crankshaft from a manufacturer.I am in agreement that cam duration is way radical for the type of driving he said he wanted to do, but it's his motor, his pocket book and his choice.I don't quite understand your statement beginning with "I made the presumption" but that's neither here nor there.And I agree, too much cam, but it's his money, his choice and he has to drive it. Better him than me.Thank you.
MarkEngine builder, located in Central Florida
hello crankorwhere did you go? please answer the questions i and others have asked if you need further suggestions. my71 posted an xlnt quide for you. i think your stroke is at least 4.25. check to be sure. his chart says 6500 rpm max, pepsi1 and i say 7 max with good parts. i suggested you were nuts with the motor [meaning cam] and my71 and fastoneefi agreed. they didn't need my help to come to that concensus though. they also know very well what they are talking about. do you have an idea as to how it will idle and run? i applaud you for wanting something "crazy" "lol" to drive around. i was 16 once too and wanted the same thing, make the guys envious and impress the chicks however i'm not 16 anymore and have all the horsepower [viagra] i need. please keep us posted i for one just gotta know!PSjust shove it in there with some 355's and see what happens, if you need xtra traction just throw grandma in the trunk
I'm not sure why but I'm sensing a lot of hostility in this thread. I'd like to say first that I value all of your opinions. That being said, I dunno why everybody is getting worked up over this. The cam was in the engine when I bought it, I'll give it a try. If it totally sucks, I'll swap it out at some point. Didn't mean to start any *** here. I was just trying to get an idea of what to expect while I wait for the rest of my parts. Best of luck on your projects guys. I'm out.
hello crankor no hostility from me meant at all just tryin to be funny and i don't think the others mean anything either. keep in mind we know how it will run and i personally think it would be funny as heck to drive up to the local weekly car show with something like that. i just wouldn't recomend it to anyone as a daily driver. how bout 7 miles to a gallon too?PSYou won't need a seat belt, you'll need a neck brace and a bible!thanks again
Yes crankor, your observation is correct. Some of our newer members have not learned common respect. Don't let it spoil your experience with the HPP forum.If you can ignore this and focus on the replies from those who have been with us for a longer time, I'm sure you will find solid answers. We all tend to back away from threads that are taken over in an aggressive and unfriendly manner.Perhaps if you post your question on a new thread, and give us a clear picture of the whole setup, I'm sure there are many of us willing to lend assistance.Peace!