Does this DCR sound right to you?

[Guest iskone]

I got a DCR calc from one of Grumpy's links and here is what I got.

I am using a 383 with 64cc chambers and a XE274H (pn: 12-246-3) for my numbers.

 

3.75 stroke

4.03 bore

5.7 rods

 

64cc chambers

.04 compressed head gasket thickness

0.0 deck clearnce (I don't have a block yet so this may change)

6cc valve reliefs

 

274 Adv. Int. dur.

286 Adv. ext. dur.

110 LSA

106 Int. center line

 

The calc says my DCR is 8.903 and 10.957 SCR with this combo.

From what I read you don't want to venture out past 8.25 or 8.5 max DCR.

 

What doesn't sound right to me is this a pretty basic build and the 274H is mild. So why is my DCR so high?

If it was really that high wouldn't guys be blowing engines all the time with this setup?

 

For some more info about my build I'm intend to use Speed Pro coated pistons that they say is a 10.8 SCR

 

Any help would be great

 

Thanks

[pparaska]

Your DCR is that high BECAUSE the 274 duration is somewhat mild. To lower it, either lower the static compression ratio, or use MORE intake Duration. Actually, you really just need to play with the Intake Valve Closing point. Move it to later ABDC, and the DCR will fall.

 

BTW, I used 15cc dished pistons on my 406, for just that reason - to lower the static compression ratio to 10.5:1

[Guest iskone]

thanks. As far as the DCR is concerned is the 8.5 max with iron heads or all heads.

I was thinking about using Dart Pro 1's

[grumpyvette]

while your figures are close for a .0.0 deck combo the blocks more likely to come with between a .023-.024 deck and require a .021 head gasket which will put you closer to a 8.5 dcr with a crower cam below

that 110 lsa comp cam is part of the problem

swap to a CROWER cam # 00232 with similar specs but a 114 LSA and 110 Int. center line

your engine will run and breath better at higher rpms with extremely little loss in low rpm torque, I try to AVOID comp cams in most cases simply because their tech support has constantly given BAD advice and the extemely fast ramps they use tend to make for a noisy valve train with no major improvement in how the engine runs in my opinion compared to similar CROWER,or CRANE designs

 

http://www.crower.com

 

its also a good idea to polish the combustion chambers surface, and round off the sharp edges slightly, while the combustion chamber volume gained will be small it helps reduce true cpr,the resistance to detonation will improve slightly so its a win/win deal

 

then have extra valve clearance notch distance cut to give you both a 11 cc negative piston dome volume and much safer valve to piston clearance,(that won,t require much on most pistons, add about .080 depth on both valve notchs) or swap to pistons with aproximately a total of 10cc-12cc reverse domes (dished)

that should place you at about 8.0-7.9 dcr for pump gas

[Guest iskone]

Thanks. I can't get the specs for that cam to come up on the Crower site so I looked at 00242 instead. I'm gonna keep checking back with Crower to see if they fix the problem.

 

I don't think I will have the cash to polish the chambers. Maybe I could do it myself, I have almost every David Vizard book and he goes over all that.

 

Would it be nesscery to with the valve reliefs notched? If so is it going to be better to use the notched flat tops or the dished ones?

 

I am trying to get a DCR of about 8.25 and use 92 octane.

Would Alum. heads help any?

[grumpyvette]

Thanks. I can't get the specs for that cam to come up on the Crower site so I looked at 00242 instead. I'm gonna keep checking back with Crower to see if they fix the problem.

 

the comp xe274 has 230/236 dur and .490 lift

the crower 00232 has 230/238 dur .488/.501 lift the differance is in lobe centers/LSA and the close ramp speeds

 

 

I don't think I will have the cash to polish the chambers. Maybe I could do it myself, yes you can! its time intensive but really easy to do! I have almost every David Vizard book and he goes over all that.

 

Would it be nesscery to with the valve reliefs notched? NO ! but it HELPS gain chamber volume AND prevent valve to piston contact If so is it going to be better to use the notched flat tops or the dished ones?

generally a slight dish in the 10cc-12cc area will be better in an application like yours

 

I am trying to get a DCR of about 8.25 and use 92 octane.

Would Alum. heads help any? aluminum will help a great deal! its less prone to detonation as it transfers heat faster

[Guest iskone]

You are the man Grummpy!

I should have been more clear about my aluminum head question.

Is it safe to run a 8.5 DCR on the street with Aluminums?

[grumpyvette]

personally Id be trying to get even aluminum head dcr down to about 8.0:1 for street use and IRON heads no more than about 7.8:1 simply because CRAP GAS labled as high test is comon, and it only takes one hard run with detonation to break a piston, theres not much sence in running right on the ragged edge for just a few hp on the street

a (Z) with a properly built 383 will easily beat 90% of the cars on the road any where why push your chances of blowing the engine

if you really must run a kick butt combo add a 150 hp nitrous plate system on that 383 with FORGED pistons and a switch that retards the ignition timing and jet it richer then ideal. when its in use! getting to or exceeding 500 plus hp is then a joke

yet you don,t need to put up with the bad habits a 500 hp plus engine potentially has when its not in use!

[Guest iskone]

I used the figures you gave me to do the new DCR calcs and I still get 9.236 wtih the .021 head gasket and 12cc dished.

 

If I use a .04 head gasket 14cc dished I still am high with 8.69

 

I don't want to use 72cc chambers so I'll keep looking for the right cam and piston setup.

 

500hp is quite alot I think I'll take your advice and shoot for 8.0 DCR.

I only want to make 400-450 hp and about the same torque.

[grumpyvette]

iskone?

are you useing ADVERTIZED 278/286 duration, or 230/238 DURATION and valve timing figures at .050 lift figures, what other specs and which cam ? If I use a .04 head gasket 14cc dished piston and 64cc heads,

because I get 10:1 scr and 7.8:1 dcr with the crower cam, 0.0 deck and a .040 head gasket

the crower cams LSA is 114 and installed at 110

[Guest iskone]

Well with the last cam I used the figure you gave me.

Did I need to do some more math before I punch in those numbers.

What am I doing wrong?

[grumpyvette]

first pull up the center tab and input the

278/286 duration and 114 110 angles then calculate the result

you should get an int close at 69 degrees abdc

then input your other data on the other tabs

your dynamic stroke should be about 2.82"

then input the 64cc heads and -14cc piston dome and .040 quench

 

heres where you get the dcr software for those guys reading this that don,t understand what we are talking about!

 

http://cochise.uia.net/pkelley2/DynamicCR.html

[Guest iskone]

No wonder, Iwas using the installed at center line numbers

 

This time I used a .021 head gasket 10cc dished and a .023 deck and got 8.09 this looks good to me.

 

Now to just get everything else in order and I should be good to go!

 

By the way I hope to use a close ratio T56 from D&D Performance with my stock 3.55 R200 what do you think about that.

I read a few threads and it seems like a good match for my engine.

 

Thanks for all of your help!

[Guest iskone]

Here is the table I got using that cam

 

Engine Power Torque Int Man Vol IMEP FMEP BMEP

RPM (Fly) (Fly) Pressure Eft % Pressure Pressure Pressure

2000 148 389 14.67 79.4 201.2 17.8 155.4

2500 193 404 14.64 81.9 200.4 19.3 161.6

3000 235 411 14.61 83.8 200.7 21.0 164.1

3500 283 424 14.57 88.1 204.2 22.8 169.5 .

4000 329 432 14.51 91.6 207.7 24.7 172.7

4500 369 431 14.44 93.4 209.3 26.7 172.2

5000 396 415 14.37 93.6 204.9 28.9 166.0

5500 405 386 14.30 92.1 194.8 31.2 154.4

6000 390 341 14.23 87.7 178.2 33.6 136.4

6500 363 293 14.20 83.1 160.5 36.2 117.3

7000 326 245 14.18 78.2 142.5 38.8 97.8

7500 289 202 14.17 73.4 127.2 41.6 80.7

 

It got a little smooshed.

Any one know how to get the dyno graphs to save as pictures so I could post them? I lokked in the manual but didn't see it.

 

The 274H makes more torque down low and climbs faster makeing more HP as well. But not by much at all.

I think I'll end up going with the 00232.

[grumpyvette]

the differance between the cams is that the crower will run smoother and pull better on the mid to higher rpm side, and have less strain on the valve train, as the ramps tend to be less harsh, youll tend to rpm the motor higher before valve float, youll never notice the differance in low rpm performance because either cam in a 383 will smoke the tires easily but youll sure notice the differance in idle and width of the peak torque curve, ( thats worth giving up a couple peak hp if any in my opinion) but the CROWER will easily out run the COMP GRIND useing NITROUS due to its LOWER PUMPING LOSSES and more efficient EXHAUST due to the longer duration and wider LSA

[Guest iskone]

I'll go with the 00232 for sure.

I plan on using roller rockers, total seal gapless rings, coated skirt pistons, an air gap intake, an electric water pump and when I can afford it a oil pan with some baffles.

 

I'm thinking that with these mods I can get some more power out of the 383 then the DD2000 says.

I also think that less friction on the rotating ass. will help my engine live longer as well.

 

If these manufacturers would give power gains in percentages rather than horse power it would help me figure out what mods may and may not be worth the money.

 

Update*

I ran the combo wit ha single plane in take and the bottom end loses about 30 pounds of torque from 2000 to 3500 but at 4000 and above the single plane takes the lead with a peak at 452 at 4500.

 

I think I"ll go with the single plane 360ftlbs of torque is plenty at 2000 rpm. 400lbs. at 3000

[Kevin Shasteen]

10.0:1 with Cast Iron Heads will be flirting with Detonation on a high temp-high humid day. Any reason why you have chosen this over aluminum heads?

 

Before you decide on an intake manifold you need to keep in mind that DD "ASSUMES" your internal port pressures are optimum.

 

In the real world your port pressures are interacting with the atmospheric pressurs and too what degree your engine is throttled: so optimum port pressure on an engine sim such as DD may not translate into the real world. An 8.25:1 DCR will get you excellant torque if your Volumetric Efficiencies are moderately optimum.

 

I think the cam Grumpy has suggested is a good one too-as far as which Intake Manifold you need: I would simply say that we as tuners spend thousands of dollars on our engines and then we decide to approach the cam or intake manifold as if there is only one possible choice: as in the "Perfect Cam" or the "Perfect Intake Manifold".

 

When in reality our choice is nothing more than a choice. What I'm trying to say is to not lock yourself into just one intake manifold when manifolds sell for $100 to $300 as this amount of cash is miniscule when compared to how much we have already spent in components as well as time.

 

Experiment with multiple manifolds till your butt O'meter likes one manifold over the other.

 

Other than that I think you, the others are looking at a real torquer. a 383 touting 10.0:1 SCR with a 7.8:1 DCR will kick but. (Still not sure about the 10.0:1 SCR with Iron Heads)....is this going to be your daily driver?

 

Good luck and let us know how it turns out.

[Kevin Shasteen]

(sorry for the double post-I hate it when I accidently do this)

 

Anywah, one other issue I have with the Dart Pro 1 heads on this engine going into a Z is the port size is only 180cc. This size port will cause your airflow velocity to max out early in the rpm range. In a heavy car such as a 1970 Impalla this is not a concern; yet, in a light weight Z too much torque too soon will make your car severely traction limited.

 

Perhaps you may want to think about cylinder heads with larger ports in the 195-220cc range. This will delay the peak airflow velocity inside your ports which also delays maximum torque coming on the cam too soon....hopefully long enough that your wheel spin is minimum.

 

Kevin,

(Yea,Still an Inliner)

[Guest iskone]

Thanks for the advice.

 

First I 'm not using iron heads at all I've never even thought about using iron heads. I am planing to use Dart Pro 1's. I just wanted to klnow if I could run a higher DCR when I asked about iron heads since I would be using Aluminums.

 

Right now it looks like I've got all the componets figured out.

I'll end up with a 10.48 SCR and 8.19 DCR

Dart Pro 1's 230cc with 64cc

Light weaight dished pistons w/ 5.7cc

5.7 I beam rods

Crower 00232

1.6 aluminum rockers

 

As far as an intake is concerned I plan to try a few till I get thew one I want. I got a David Vizard book that goes into intakes quite a bit so I'll re-read that as well.

 

DD2000 says I'll get 455/455 I think I'll be happy with this and my 3.55 R200 and the close ratio T56.

[Guest iskone]

I almost forgot! 99% street!