Thread: Torque

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Still working with my 454, stuck on a cam decision. I want this engine to have a lot of low end grunt, looking for good torque off idle and i don't believe it will see much more than 5000rpms if that. I have been looking at summit's cam lineup...the cams between $50-$100 but not sure what specs i should be looking for to make good torque down low, any knowledge to share with me to help with my decision, or reccomended cams?

A cam must be based off of your static compression ratio and then use the cam specs to adjust your dynamic compression ratio to run on pump gas and make the most torque.


Read this article and you will understand alot more to make a better decision on what cam matches your engine combo and to achieve your desired results the first time.

http://www.popularhotrodding.com/tec...ics/index.html


You need to understand the basics first ,otherwise you will not understand the answers given.

Then once you understand the basics ,we can help you more.

You need to determine static compression first.

Here is a calculator for that ,ask any questions you need to determin what you have.


http://www.rbracing-rsr.com/compstaticcalc.html

Do this and report the results ,then we can help you choose a cam.

Some other important information is transmission type/rear gear ratio and car/truck weight. Intended use of the car/truck.

Hope this helps .......ask any questions you are unshure of ....lots of people to help you here.

Wow great article thanks, I have been reading up on cams for about a half a year now and that helped alot. I'm not sure of my compression ratio, the motor is still in pieces, any simple way i could figure it without buying a bunch of expensive equipment?

Try to answer some of the questions you asked now others will have to wait.

TH-400 tranny, 411gears, I think the weight is around 4000lbs...its a 1967 C-20...the 454 was bored .060 to make it 468now

The heads are 427 heads oval port closed chamber tall deck...casting # on them is 10101140, i am gasket matching them along with taking down the short side radius, again not expecting big time ponys with these heads, there just what i have to work with, should make decent torque though

I did have a question about tall deck bbc's, any advantages or disadvantages to tall decks?

I am a first time bbc builder so the advice really helps, thanks guys!

Originally Posted by co68956

Wow great article thanks, I have been reading up on cams for about a half a year now and that helped alot. I'm not sure of my compression ratio, the motor is still in pieces, any simple way i could figure it without buying a bunch of expensive equipment?

Try to answer some of the questions you asked now others will have to wait.

TH-400 tranny, 411gears, I think the weight is around 4000lbs...its a 1967 C-20...the 454 was bored .060 to make it 468now

The heads are 427 heads oval port closed chamber tall deck...casting # on them is 10101140, i am gasket matching them along with taking down the short side radius, again not expecting big time ponys with these heads, there just what i have to work with, should make decent torque though

I did have a question about tall deck bbc's, any advantages or disadvantages to tall decks?

I am a first time bbc builder so the advice really helps, thanks guys!

i done short decks 9.800.the tall decks 10.200+ they work better with big stroke cranks 4.500+ you can get more rod in them .as for max tq with a flat top pistons and cheap cam look at 500/500 @050.215/225 lc 115 or 502/525@050.215/225 lc 112 i do not play with hyd flat lifter cam s in bbc any more. i been playing with them for 30 years.i build a hand full of them every year so i built many over the years . i use hyd rollers or solid roller cams if low buck look at GM #12551622 roller cam 483 224 @050 lc115 $40 for cam thru competition products. if you do not need a fuel pump lobe, is cam will not have one .. i have used this cam as well it is a cheap way out to a roller .you need a cam plate out of a gen 6 block use a gen 6 chain set and retro lifters it bolt on deal

Do you have the pistons already ...?



You need the cc of the pistons .
The cc size of the chamber on the heads.
Your not building a max effort drag engine ,so advertized cc ratings for both of those will be close enuff for your application ,no need to get exactly precise.

Once you find those numbers ,you can make a close guess as to what the static compression of the engine will be.
I looked around online and did not see the cc of the chamber for the heads listed.You might want to do some searching for those numbers ,maybe even call GM if all else fails.


Pat knows alot about these engines ,he does this stuff everyday ,listen close to what he talks about!!!!


One other thing to take into account for static compression and that is the deck height of the block,usually a undecked block will have the pistond down in the bore some ,instead of whats called a 0 deck height ,this will chang the static compression numbers some.
Pat may be able to tell you the standard numbers of what these pistons are below the deck if your block has not been decked.

If the block was just decked to straighten it ,you may need to wait untill the pistons are installed to get this number.If the block has been 0 decked then use that figure to determine static compression.

If you look at the static compression calculator it will list all the specs you need to determine what you have,make a list of these and write them down,they come in handy during the build and for future reference.

you do not want to take down the sort side radius less you want a junk set of heads theres not much there on a stock head as well has a gasket match is a wast of time less you know were the intake is going to set on the engine when done .it is way better to have the heads abit big . bigger then intake and dump in from the intake .you are far better to work in the bowls a 4 angle valve job. and work in front of the valve and in back like a 30 on the back side of the ex valve

[QUOTE=shawnlee28;35824


Pat knows alot about these engines ,he does this stuff everyday ,listen close to what he talks about!!!!


One other thing to take into account for static compression and that is the deck height of the block,usually a undecked block will have the pistond down in the bore some ,instead of whats called a 0 deck height ,this will chang the static compression numbers some.
Pat may be able to tell you the standard numbers of what these pistons are below the deck if your block has not been decked.

If the block was just decked to straighten it ,you may need to wait untill the pistons are installed to get this number.If the block has been 0 decked then use that figure to determine static compression.

If you look at the static compression calculator it will list all the specs you need to determine what you have,make a list of these and write them down,they come in handy during the build and for future reference.[/QUOTE] it can be as much as 020+ on the piston in the hole from O deck

Thanks again guys, this site is alot more helpful then others i have tried...

I do have the pistons, they came with the block, but they are new speed-pro pistons. I have also been searching for the cc of the chamber of those heads with no luck, i might need to give GM a call or find an email address for them. I'm also not sure of the deck height, i purchased the engine with all machine work completed, the guy was going to piece it together and sell it but couldnt find time to complete it.

I will be using a mechanical fuel pump, I found one of the 2 specs you listed for flat tappet on a marine cam, the other i have had no such luck. Will watch that short side with these heads.

I have found a set of re-built heads for fairly cheap. I found a bit more info on them also. 2diff years a '71&'72 valves at 2.06Int./1.72Exh. oval port, open chamber, 113cc chambers... casting #s are 3993820 & 3999241...as i was typing this it occured to me that i read somewhere the older heads would not work with my Gen.V block due to different size water passages...can you confirm this?

Again thanks alot guys, this is alot better than fighting with someone telling me according to his equasion a q-jet will not work, I need 750cfm so i have to get a holley... entertaining, but not at all informing

For some reason or other, I feel like dropping a penny's worth here. Based on my experience with rat motors in the late sixties and early seventies, I would not use a flat tappet cam in one today; in fact, I doubt I use a flat tappet cam in any engine nowadays, if I could get a roller for it. Times and technology change, and in the case of cams and such, mostly for the better, these days.

You need to determin which speed pro pistons those are and find the cc spec..........you can probably tell from sight by looking at the pictures online.

I dont see anything wrong with the heads you have ..that number lists them at 91 up closed chamber oval ports for a 427 t motor....pat will know about if those heads will work.....if they will work ,no reason to spend more money if you are on a budget.


Look at the deck on the block ,can you see any machine marks ...you should be able to tell if it was decked any by looking for gaskett marks.

Are the pistons domed ,flat top or dished?


I would also spend the extra money on a roller cam,instead of different heads.Pat listed roller lifters that will work for cheap,just need to figure out your static compression to know what cams that will work the best.


It may seem like a big hassel now ,but the time getting all of your specs now will pay off later.

Originally Posted by co68956

Thanks again guys, this site is alot more helpful then others i have tried...

I do have the pistons, they came with the block, but they are new speed-pro pistons. I have also been searching for the cc of the chamber of those heads with no luck, i might need to give GM a call or find an email address for them. I'm also not sure of the deck height, i purchased the engine with all machine work completed, the guy was going to piece it together and sell it but couldnt find time to complete it.

I will be using a mechanical fuel pump, I found one of the 2 specs you listed for flat tappet on a marine cam, the other i have had no such luck. Will watch that short side with these heads.

I have found a set of re-built heads for fairly cheap. I found a bit more info on them also. 2diff years a '71&'72 valves at 2.06Int./1.72Exh. oval port, open chamber, 113cc chambers... casting #s are 3993820 & 3999241...as i was typing this it occured to me that i read somewhere the older heads would not work with my Gen.V block due to different size water passages...can you confirm this?

Again thanks alot guys, this is alot better than fighting with someone telling me according to his equasion a q-jet will not work, I need 750cfm so i have to get a holley... entertaining, but not at all informing

them heads will not work on the mark 5 or 6 they get very thin by the lifter valley side of the deck and the head gasket will not hold you would have to check this but 99% of the time it is no way .them cams are Howards i use ERSON now but there many cams out there but stay close to them numbers and yes run a roller even the one i listed and use a electric fuel pump. if them are 427 heads i will see i think them are small port heads with both intake and exhaust rotators on the valve springs

Part # from the speed-pro box reads, H727CP digging through summit i found this, Dish with 2 valve reliefs, and compression distance shows 1.625

I work out of town all the time so i will not be able to check the deck untill this weekend, im pretty sure there were no gasket marks

I will take your advice and step up to a roller cam, have been wanting to and i suppose the budget cut from the $1300 alumanum heads to a set i already have can warrant the extra expense involved on the switch.

Will be getting this block on the engine stand this weekend so with any luck i can get some specs posted...i would rather go through the hassle now and know my engine then try to figure out later where i screwed up when the engine doesnt meet my needs, thats why i ask questions first, rather than throw a huge cam in it and expect it to run good

it will be very low CR with that piston less you head has a very small chamber cc wise if the CH is 1.625 then you will have to cut 040 off the deck to be O or 010 in the hole gets you 030 off the deck so check that CH but that seam to be about rigth for a speed pro replacement piston .i would dump them..you would be better off with just a flat top if your heads have big chambers. they should be more like 1.648 CH like the SRP .that would help not to cut so much off the deck and have some CR

Ok, drop dish, pick up flat tops, speed pro # ZH625CP with 2valve reliefs flat top, compression distance: 1.640in. piston head volume: +2.00... do those sound a bit better?

Maybe I should have consulted the advice from this forum a little earlier...

Another question, planning to ditch the old stamped steel rockers anyways, but have been planning on sticking with the 1.7:1 ratio...would i benifit from upping them to 1.8:1

might as well throw out the rest of the mix to hear the responses, not decided on manufacturer of the dual plane intake...probably summit to cut costs, and have a friend who rebuilds q-jets for the fun of it, so i could get one for dirt cheap there, the small primaries will help with my miserable mpg's and the secondaries should be enough to give it a good kick in the butt when the time is right...sound ok? 750cfm or try to find the 800s?

stay with 1.7 we use them up to 800 lift. if you want hi lift then get it ground that way is the way i see it. you can buy a cheap intake like a professional products but the ports are so so and the over all casting end to end are abit short .save your money and buy a weiand stealt 60 bucks more and worth it. steel stamps are fine for street use if you not going to buy a good roller rocker arms stay with the stamp one Gm made over 400hp with them and i bet you i did to YES flat tops H625CP if your using speed pros