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Old 05-04-2013, 06:43 AM
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383 stroker chevy camshaft

Hi all, my name is lorenzo and I'm an Italian enthusiast.
As here is so difficult to have info about chevy V8 engines I need to disturb you for some suggestions.
I'm building a 383 stroker for a '99 chevy tahoe with vortec heads and electronic injection.
I'm starting from an ATK short block with dished 12cc pistons, EQ vortec heads with 170cc intake runner, 64cc combustion chamber, 3/8 stud, 1.6 rocker arms, 0.600 valve max lift.
My big and first problem is to find the perfect camshaft to have real strong torque at low end.
As I drive usually from idle to 3500 rpm on mountain roads I need too much torque around 1000 to 3000 rpm.
I've see too many website in US, as Compcams, Edelbrock, Crane but actually I haven't found a camshaft with needed dyno results.
Did you ave suggestions??
I'm sorry for my english, I hope that have you understand.
Thanks a lot
lorenzo

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Old 05-04-2013, 07:16 AM
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Hopefully the member Techinspector 1 will chime in and with some addition questions be able to run your set up on a dyno-sym with takes into account your parts for a computer estimate outcome.

Your English is fine. Welcome to the site,good to have you.Hope you enjoy your stay.
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Old 05-04-2013, 07:52 AM
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I don't know what octane level of fuel you have over there, I'm assuming Italy, but over here we have about a max of 93 octane pump gas. That will only support about 9.5:1 compression ratio for an iron headed, low rpm, high torque engine. Good EFI system will help raise the compression some.
The specifics you posted come to around 10.8:1 comp ratio with the calculator I use(link at the bottom of the article)
.Dynamic CR
Unless you can get fuel with a much higher octane for daily use you'll need to change heads to have around 76cc chamber volume for 12cc pistons, or pistons with around a 24cc dish with 64cc heads to get around 9.5:1CR.
I hope you haven't already purchased the parts unless you have higher octane fuel than we do. I could be wrong. It wouldn't be the first time.
FWIW,
ssmonty
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Old 05-04-2013, 08:10 AM
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Using lower CR is probably your best bet so you can close that intake valve as soon as possible.Not sure you will need 1.6 ratio rockers.Do you have any flow numbers for your heads?
and what Gary said,welcome and hopefully Techinspector will jump in soon.
Im thinking around 210@ 050 and .500 lift,lobe center and displacement angle to be determined
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Old 05-04-2013, 10:14 AM
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Thank you Guys,
I've wrote to ATK last month and they says that with 64cc heads I will have 1:9.8 compression.
My truck use gasoline and LPG. LPG is not a problem, it have more octane than gasoline. usually gasoline is 98 octane.
I'm waiting for the heads from Rogers Performance CH350C head that is a 64cc chamber with 170 cc runner, 1.6 rocker ratio intake and 1.5 in exhaus.

Talking with compcams they suggest me two different camshaft XR276 and XR264.
I have look at dyno result and I had prefered 276 but the dyno chart start from 2000 rpm and I don't know what happen under 2000 rpm.
Then I have look at X4258HR, that is specific for 4x4 with too much torque at low end but compacams says That was not so good because I may want to keep some rpm band.
Thanx foe your help!!
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Old 05-04-2013, 10:20 AM
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P.S. we use LPG because is not expensive as gasoline. I don't know the gas price in US but here we spend 9,2$ per gallon!!
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Old 05-04-2013, 03:06 PM
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I must appologize for making a stupid mistake on entering data into my calculator program. I had the gasket bore and thickness entries swapped. I come up with approximately 9.8:1 CR as well after pulling my head out of my butt. Again I appologize.
You didn't say if its a roller cam you want, what rear gear you have, what tire size you have, or whether its a 4x4, or 2WD. I'm guessing that everything is a stock 2WD w/roller cam. Pretty heavy ride.
Looking at my Camquest program I see a X4260HR(210/214dur@.050",474"/474" lift w/1.5:1 rockers, 111 degree LSA) that has an rpm range of 1200-5200rpm, and described as "Good midrange power, good performance increase. Largest to use with stock convertor".
Adding the parameters for a 383 at 10:1CR, 1.94"/1.60" valves, dual plane intake w/750 cfm carb I get 489ftlbs@3500rpm, and 409HP@5000. It shows over 350ftlbs from 1000-5000rpm. I would think it would make for an excellent throttle response, and plenty of torque for those mountain roads. The software I have doesn't have parameters for EFI specifics.
If you don't care for that I would go for the XR264 if you have high enough octane fuel to withstand the high cylinder pressures at low rpm.
Their descriptions are usually based on a 350cid engine. A 383 would lower the rpm range a bit which I believe would better suit your needs with such a heavy vehicle IMO.
I'm sorry as I don't have a clue what to expect with LPG for fuel.
FWIW,
ssmonty
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Old 05-04-2013, 03:13 PM
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Quote:
Originally Posted by lollo View Post
Thank you Guys,
I've wrote to ATK last month and they says that with 64cc heads I will have 1:9.8 compression.
Depending on the piston deck height and gasket thickness, I suppose you could get the motor down to 9.8:1, but why would you want to? You're looking to build a workhorse, not a racehorse. If you build the motor right up against the wall with no margin for error, then take on a bad load of fuel, what will you do? Not only that, but don't expect the quality of fuel worldwide to improve any in octane rating. Matter of fact, don't expect it to remain the same. We in the U.S. got Shanghai'd in the 1973 Arab Oil Embargo and the only fuel we had was unleaded 87 octane swill. This could happen again tomorrow and all the fellows out there who are right up against the wall (like using 9.8:1 static compression ratio with iron heads) will find themselves wishing they had designed a more conservative build. Those fellows running carburetors will have to twist the distributor, pulling all the ignition timing out of the motor and limping it along. Those of you with electronic management systems will have to deal with the system pulling all the ignition timing out of the motor to prevent detonation and suffer the performance and mileage that will result.
[/QUOTE]

Quote:
Originally Posted by lollo View Post
My truck use gasoline and LPG. LPG is not a problem, it have more octane than gasoline. usually gasoline is 98 octane.
I'm waiting for the heads from Rogers Performance CH350C head that is a 64cc chamber with 170 cc runner, 1.6 rocker ratio intake and 1.5 in exhaus.
Wrong heads, wrong rockers. If you like the Rogers heads, use their 76cc heads, part number CC167ES2 along with your 12cc pistons so you can bring the static compression ratio down to a realistic 9.0:1. The reason you don't want the small chambers and the higher static compression ratio has not so much to do with fuel quality, but the relationship of the intake valve closing point of the camshaft, married to the static compression ratio. 9.8:1 with a cam short enough to put power where you want it will make excessive cylinder pressure, again, putting you right up against the wall. There is a direct relationship between the static compression ratio and the intake closing point that cannot be ignored. 1.6 rockers will add only a few hp and will load the valvetrain to do more work, resulting in more wear and more things to go wrong. Use the 1.5 rockers and give the motor a break. Workhorse, not racehorse.

Quote:
Originally Posted by lollo View Post
Talking with compcams they suggest me two different camshaft XR276 and XR264.
I have look at dyno result and I had prefered 276 but the dyno chart start from 2000 rpm and I don't know what happen under 2000 rpm.
Then I have look at X4258HR, that is specific for 4x4 with too much torque at low end but compacams says That was not so good because I may want to keep some rpm band.
Look at the first cam on this list. Use it, or a similar grind from another manufacturer, along with building the motor 9.0:1 with the larger 76cc heads and you will have the low end performance you are seeking. The CompCams X4258HR would be an excellent choice to use with a 9.0:1 static compression ratio.
http://www.cranecams.com/90-93.pdf
Build the short block with 12cc, minimum 1.425" compression height pistons having a generous flat area on the crown to mate up with the underside of the cylinder head to generate good squish. Cut the block decks parallel with the main bearing axis to zero deck, matching the stack of parts you will be using. Zero deck with a 0.039" to 0.041" thickness gasket will give you the tight squish you need for a workhorse motor.

That's my best shot.

Last edited by techinspector1; 05-04-2013 at 03:27 PM.
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Old 05-04-2013, 04:57 PM
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Thank you very much.
I've talk online with many technician but you are the only one that give me exhaustive answers.
So, I was wrong, I have to change direction!!!
I would be very grateful if you could tell me if the CC167ES2 heads are a good choice or there are better heads than this one.
I can not afford to make mistakes as I was doing!! I can not make experiments, I need to do a well done job.
My costs, with shipping and taxes, are twice!!
May you suggest me the perfect 383 combo for low end torque engine?
I have no problem with the assembly but I need to put together the right pieces.
Unfortunately, as I said, the information and knowledge of engines chevy here is very poor.
I have 4l60e, 3.42 gear ratio, 33" tires, 4x4.
This is the block:
http://www.summitracing.com/parts/hpe-sp15

Last edited by lollo; 05-04-2013 at 05:16 PM.
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Old 05-04-2013, 08:56 PM
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The engine specs sheet report the compression ratio with 58, 64, 70cc chamber.
with 58 is 10.4:1
with 64 is 9.8:1
with 70 is 9.2:1
so, with 76 it will be 8.6:1
It isn't too low?
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Old 05-04-2013, 09:19 PM
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The Engine Quest heads will do as well as any other for your purposes. The flow is very close to the L31 Vortec heads and they are not crack-prone like the L31's. I found this flow on the Stan Weiss site, flowed by Weingartner on a straight-out-of-the-box, unmodified CC167ES2 head, 2.02" intake valve, 1.60" exhaust valve, 167cc intake runner on a 4.125" barrel and no exhaust pipe....

0.100"....70....64
0.200"...124...109
0.300"...173...158
0.400"...207...164
0.500"...230...167
0.600"...238...166
0.700"...241...166

Ideally, flow would be tested on a barrel that is the same size as the cylinder on which it would be run, 4.030" in your case, but the larger barrel flows better by unshrouding the valves, so that's why most manufacturers will fudge and use a larger barrel, because it sells more heads. In the whole scope of things, it's probably not a big deal and doesn't amount to but a few cfm. On the flip side of the coin, these heads bolted onto a +0.030" 400 block with a bore size of 4.155" should flow better than the flow bench figures that used a 4.125" barrel.

I've run a Sim on both the cams, the Crane I suggested and the Comp that you suggested and although they're very, very close, I would give the tip of the hat to the Comp X4258HR cam, installed 4 degrees retarded on these 0.050" numbers....
Intake opens (-8)
Intake closes (34)
Exhaust opens (36)
Exhaust closes (-6)
If you don't understand how to degree a camshaft, learn how here....
ISKY Racing Cams - Do It Right. Race with the Legend. Camshafts, Connecting Rods, Valve Springs, Lifters

This Sim was run with a 500 CFM Tuned Port Injection setup and 1 5/8" long tube headers through mufflers. Suggest installation of "X" or "H" pipe before the mufflers to smooth exhaust note and increase fuel mileage slightly.

Here's how the hp and tq worked out.....

RPM....HP....TQ
1000....80....421
1500...134...468
2000...184...483
2500...223...469
3000...261...458
3500...287...431
4000...300...394
4500...298...348
5000...276...290

Peak volumetric efficiency 82.1% @3000 rpm's
Peak BMEP 190.3 lbs @2000 rpm's
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Old 05-05-2013, 05:03 AM
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Hi everyone, I've been following this great forum for a few years although I never registered until today.
Me too I'm a chevy truck owner (mine is a TBI though) and being a friend of lollo I'm helping him in his quest for torque

I'm impressed by the figures of the motor !
480lb/ft@2000rpm WOW !! A 4wheeler dream !
I hope his tranny is in good shape !

Now a few question, is it worth to spend a considerable amount of money on the heads or would we be fine using the stock vortec heads that he has on his motor now, given the mild build ? And in that case how should the heads be reworked ?
Also I read somewhere that TBI heads are better than Vortecs in order to produce low end torque. What's your mind on the subject ?

How about running full dual exhaust instead of joining the exhaust before the muffler, and regarding mufflers would glass packs be ok or better use different style with more backpressure ?

Lots of questions, I know.....

@ Techinspector. THANK YOU so much for the time you spend in running the syms. I am aware the time it takes to run all the possible combinations. When I will have the money to get me a new motor I will ask for your advice, or I will builld one just like lollo's since we have exact same requirements ! THANK YOU !
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Old 05-05-2013, 10:06 AM
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Did you think those heads will be good as CC167ES2??

CC167CS2 167cc 67cc Straight 2.02 1.6 11/32 .530"/.531"
I'm thinking about compression ratio!
With 67cc I can have 9.5:1
Did yuo think that is too much??
8.6:1 with 76cc is not low? or it's fine?
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Old 05-05-2013, 11:16 AM
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Quote:
Originally Posted by lollo View Post
Did you think those heads will be good as CC167ES2??

CC167CS2 167cc 67cc Straight 2.02 1.6 11/32 .530"/.531"
I'm thinking about compression ratio!
With 67cc I can have 9.5:1
Did yuo think that is too much??
8.6:1 with 76cc is not low? or it's fine?
It seems that you have your mind wrapped around more static compression ratio than I do. You may not understand the relationship between static compression ratio and horsepower. For each full point of SCR, horsepower increases 4%. So, if you have a motor that makes 200 hp @8.00:1 SCR, then raising the SCR to 9.00:1 will yield 208 hp, all other things being equal. Raising the SCR to 10.00:1 will yield 216 hp, all other things being equal. Raising the SCR to 11.00:1 will yield 224 hp, all other things being equal. So, it's not like you will make this huge quantum leap in power as you raise the SCR. As you raise SCR, you must alter the point at which the intake valve closes, closing it later and later as SCR increases so as not to make unmanagable cylinder pressure. Actually, the only thing being accomplished by raising the SCR on a street motor is changing the range of operation.

The cam that I used to do the Sim on your motor makes power from 1000 to 5000 rpms and will do what you said you wanted the motor to do initially. If you increase the SCR, you will have to change cam timing to close the intake valve later which will change the range of operation to higher, taking power away from the bottom and placing it on top of the range. Any cam that you choose has an effective operating range of about 3500 rpm's and you can place that range anywhere you want to by altering the intake and closing points of the camshaft. You can make power from 1000 to 5000 or you can make power from 2000 to 6000 or you can make power from 3000 to 7000 or you can make power from 4000 to 8000. I'm using 4000 rpm units here instead of the more realistic 3500 rpm blocks because the cam companies want you to thing that power comes in 4000 rpm blocks. Realistically, it would be 1000 to 4500, 2000 to 5500, 3000 to 6500, 4000 to 7500 and so on.

If you are to build a motor that makes power from 1000 to 4500, like the motor I DynoSimmed for you, then you must use certain intake opening and closing points and certain exhaust opening and closing points to coordinate with a certain static compression ratio to get there and make everything work together. The virtual motor that I built for you features a 9.00:1 SCR with an operating range of 1000 to 4500 because that's what you said you wanted. Again, if you want to raise the SCR, then you will have to use a different cam than what I used, raising the operating range to a higher level and give up making power from idle.

The 76cc heads used with 12cc pistons makes ~9.00:1 SCR, depending on the piston deck height and head gaskets that you use. Matching the Comp X4258HR cam to this combination makes power from 1000 to 4500 as shown in the DynoSim. Tell me how you want to do this differently and I'll change the values around and run a different DynoSim for you when I get time.
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Old 05-05-2013, 12:37 PM
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Thank you very much, I will build the engine as you have tell me, with 76cc and compacms X4258HR.
So, you have say that I don't need to use 1.6 rocker ratio but 1.5 is enough.
The combo will be:
1) ATK stroker 383 short block 12cc dished pistons
2) EQ vortec heads, 76cc, 167cc intake runner, 2.02 in. valve, 1.60 ex. valve
3) compcams camshaft X4258HR
4) 1.5 roller rockers arms (compcams magnum)
5) edelbrock performer intake manifold
I need to choice headers (tri-y or shorty), fuel pump, injection (I can use OEM efi system or upgrade if needed), and everything is necessary to have a complete crate to swap!

Last edited by lollo; 05-05-2013 at 12:50 PM.
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