[Z Code 400]

Thanks...

Keep in mind this is a factory flat-top piston without valve reliefs, .025" down in the hole, with a .039" gasket (Victor 350) and 72cc chambers. Refer to post #9 for the corrected valve events @ .006" lifter rise...Robert

[Murf'sDad]

Originally Posted by Z Code 400

Thanks...

Keep in mind this is a factory flat-top piston without valve reliefs, .025" down in the hole, with a .039" gasket (Victor 350) and 72cc chambers. Refer to post #9 for the corrected valve events @ .006" lifter rise...Robert

Revised #'s are 9.46:1 scr and 7.55:1 dcr.

Stewart

[screamingchief]

All those DCR calculators will spit out the same numbers,IF the input data is plugged in correctly with each DCR calculator variant.

The .050" based DCR calculators will match the "seat" timing DCR calculators if you just ignore all the +15° non-sense,and instead input the known/actual seat events instead of the .050" events +15°.

It's a case of they're all trying to get to the same place,but they're all trying to get there using somewhat different methods.

Though when one realizes what's going on,than that fella can get them all to put out the same numbers regardless of which calculator is being used.

This has been discussed here in the past a few times.

I know I can get all those DCR calcs to spit out the same numbers,and I'll add this,if I could'nt get them to do such,well then I would'nt trust DCR theory as far as I could throw it,and honestly I still dont put too much faith in DCR as a whole,but I'll admit it's an interesting tool to play around with just for kicks.

Do a keyword search on "DCR",that info should come up.

HTH

Bret P.

[Murf'sDad]

Originally Posted by screamingchief

All those DCR calculators will spit out the same numbers,IF the input data is plugged in correctly with each DCR calculator variant.

The .050" based DCR calculators will match the "seat" timing DCR calculators if you just ignore all the +15° non-sense,and instead input the known/actual seat events instead of the .050" events +15°.

It's a case of they're all trying to get to the same place,but they're all trying to get there using somewhat different methods.

Though when one realizes what's going on,than that fella can get them all to put out the same numbers regardless of which calculator is being used.

This has been discussed here in the past a few times.

I know I can get all those DCR calcs to spit out the same numbers,and I'll add this,if I could'nt get them to do such,well then I would'nt trust DCR theory as far as I could throw it,and honestly I still dont put too much faith in DCR as a whole,but I'll admit it's an interesting tool to play around with just for kicks.

Do a keyword search on "DCR",that info should come up.

HTH

Bret P.

Agreed. I find this calculator takes the guess work out of it. It specifically states what to enter, you don't have to finagle the numbers or guess how it was developed.

Stewart

[screamingchief]

It's not really "messing" with the numbers,or "guessing" how each calc was developed.

It's more a matter of all the input data matching on whatever calc is being used.

That's on the users end,not on the calcs.

The input data is'nt "fudged" or anything like that to get the calcs to agree,the input data is all 100% legit,not changed or anything like that at all,it's just making sure the user input is the right set of data to get them to all agree.

All those DCR calcs must be based on the same basic mathematical formula,if they were'nt,then you likely one would never be able to get them to agree with each other,at least not when legit input data was used.

It's the way they each calc chooses to lay out the data input format on those different calcs that confuse the user @ times,the calcs have no idea what data they're looking for to get the "correct" end result,that's why I say it's the users that have trouble figuring out what input info is needed.

In the past I explained how that likely happened.

Cam companies often dont give seat event data on their cam cards,typically they only provide events @ .050",so what were the bulk of folks using those DCR calcs to do?

Either they had to figure out the math involved to find the seat events themselves,or the folks providing the calcs had to figure out a way to compute DCR based on the more common .050" event data,so the "fix" chosen was that .050" +15° deal.

The only cam co.s that consistently gave both seat & .050" event info were Crane & Isky cams,everyone else provides just one or the other sets of event info,Comp for instance cant make up it's mind on that at all,they will typically give one or the other,but never give both.

Now I myself know how to get whichever set of events are missing on any given cam card (within a degree or two),so I pretty much knew how to get the numbers I needed to get good info outta any of those the DCR calcs.

But for some,it's not gonna be as easy or make as much sense I guess.

All I was getting at is they all will get you to same numbers if you know what data each calc is looking for in a given input.

GIGO applies here bigtime.



Bret P.

[Z Code 400]

Hey Murf,

Here is another DCR calculation for you, if you don't mind. This is regarding the 'big' motor I have on the stand:

4.181" bore X 3.750" stroke - 6.625" rod (Pontiac 412 CID)

86cc heads, .039 gasket, 4.250" gasket bore

Zero Deck, 6.7cc valve reliefs

Intake closing event @ .006" is 67.5°

Thanks...Robert

[Murf'sDad]

Originally Posted by Z Code 400

Hey Murf,

Here is another DCR calculation for you, if you don't mind. This is regarding the 'big' motor I have on the stand:

4.181" bore X 3.750" stroke - 6.625" rod (Pontiac 412 CID)

86cc heads, .039 gasket, 4.250" gasket bore

Zero Deck, 6.7cc valve reliefs

Intake closing event @ .006" is 67.5°

Thanks...Robert

No problem to do it, but I need the advertised cam specs; duration, LSA and ICL.

Stewart

[Cliff R]

Robert, are you "building" this engine or just installing the parts while it's still in the vehicle?

FWIW, I'd consider zero decking the block to establish a quench distance closer to .035", instead of the current .065" clearance.

My experience has taught me that the engine will make more power with less spark lead, run cooler, and manage lower octane fuel with closer to .035" quench, than .060" or more.

This also throws a small monkey wrench into your calculations, as the lack of combustion efficiency with the additional quench will not show the same results when the engine is placed in service, when compared directly to an engine that is squared/decked for closer to .035" quench.

The cam is also a bigger player than anything else in the ability to effectively manage low octane fuel(s) at relatively high compression ratios. I've been able to run, without issues anyplace, high compression ratios with low octane fuel, 87-90 octane on our engines with careful camshaft selection, where we place the camshaft, minimum quench distance, and full control of timing and fuel curves across the entire engine speed/load range.

We have done this with both iron and aluminum heads.

I will also say this. Without exception, every single running hot/overheating/detonating/not running worth a crap Pontiac engine "build", that we've had in here to custom tune, had one common denominator.........the pistons were WAY below the deck at TDC!!!.......Cliff

[Z Code 400]

Happy Thanksgiving, Cliff!!!!

Yes, I am aware that zero-deck is better for many reasons. That's why I took the time to zero-deck (+.0025" actually) my 413. The 350 engine is out of the car and on the stand, but I'm not tearing it down past the basic 65,000 mile shortblock to swap the cam and heads. The idea is to get the engine back in the car as quickly as possible (after detailing the engine compartment) and start driving and enjoying it again. The 413 can then be completed in my leisure.

If I were to strip this 350 down and zero-deck the block, with the 72cc '092' heads and flat-top, no valve relief pistons, I would have near 10.00:1 SCR and would have to take that a step further and switch to a camshaft with more SAE duration, wider LSA, etc. That would defeat the entire purpose of throwing the motor back together and getting the car back on the road ASAP.

Recently, I've swapped early heads onto stock Pontiac 350's and they ran great, despite having less than the ideal quench distance, one as high as 9.65:1 SCR. That's why the factory setting of .025" below the deck (on my Pontiac 350) doesn't concern me that much. I believe that the quench distance thing isn't as much of an issue in the smaller bore/shorter stroke applications.

Keep in mind we ran 440 Chryslers on the street for years with 9.50:1 and 10.00:1 SCR and they have 'zero-quench' with the open chamber, 906 heads; there is no quench area whatsoever on them and we never had a detonaton problem there either.

I also agree with you that with higher SCR applications, camshafts with more duration @ .006" and wider LSA's are beneficial as they do not build cylinder pressure (DCR) like the tighter LSA camshafts and 'fast-ramp' lobe profiles do. The way you have your engine setup is a great example of this. I didn't want to run that much squeeze, as I feel out varying fuwl quality out here would cause me troubles.

Now, on my 'WS' code 1970 Pontiac 400 engine...It had the crappy 411NP 8-Valve Relief Pistons, a whopping .047" down in the hole with Fel-Pro Blue Gaskets, #13 heads and a very mild 'RV' style camshaft. This car/engine originally belonged to a neighbor who lived across the street from my parents. When it was rebuilt in 1986, they dropped the compression with the 411NP pistons. I drove and rode in this car for years and it pinged like hell until they put the 'wrong' pistons in it with the 'wrong' quench distance.

After the swap, even though everything was technically 'wrong,' the car ran great on 87 octane with 38° total timing. I tuned this car up numerous times over the years, before buying the engine out of it in 2002.

Not an ideal combination, but considering that no Pontiacs ever came from the factory with zero-deck, I think I can squeak by on this one...Robert

[Z Code 400]

Originally Posted by Murf'sDad

No problem to do it, but I need the advertised cam specs; duration, LSA and ICL. Stewart

The events for the 231°/235° - 110° LSA camshaft (106° ICL) are as follows:

IVO: 35.5°
IVC: 67.5°
EVO: 77.5°
EVC: 29.5°


Thanks....Robert

[Murf'sDad]

Originally Posted by Z Code 400

The events for the 231°/235° - 110° LSA camshaft (106° ICL) are as follows:

IVO: 35.5°
IVC: 67.5°
EVO: 77.5°
EVC: 29.5°


Thanks....Robert

9.29 scr and 7.24 dcr. 9.33 scr and 7.27 dcr if your pistons are .0025" out of the hole.

Stewart

[Z Code 400]

Wow....that's a little lower on DCR than I was hoping for....Robert

[goquick]

Hi Robert, It looks like the calc. are predicting what we discussed. I think you will like either cam in the engine. I do thionk the smaller one might accellerate a tad quicker, but the other one will pull more higher up in the power band. the issues is then why? The limited airflow in the heads.
Now for when we talked about it and you asked me what i thought on power, that was my experience with the 354's. Kind of nice to see the prediction calc.'s say it's in the same ballpark powerwise. Either way, I think you will enjoy the little 350.
Now as for my little solid lifter 354, and better heads, I need to find a car to put it in!

[Z Code 400]

Thanks GoQuick, and yes, the calculations are very close to what we discussed!!!!!

I am beginning to think the smaller cam will be better overall, even if it makes slightly less peak HP than the larger camshaft. I think the smaller cam's .466"/.467" net valve lift is probably a better match for the '092' head flow values.

Thanks for the reply!!!!!!!

[screamingchief]

Originally Posted by Z Code 400

Wow....that's a little lower on DCR than I was hoping for....Robert

It's all relative really,when you get used to seeing the numbers you get using the seat valve events instead of the .050" events,they start to make just as much sense as any other set of DCR numbers do.

It's just a slightly different frame of reference.

I like to look at both sets of numbers and compare them,that's where things can get really interesting.

I always like to look @ the big picture,see everything that's possible to see.



Bret P.

[Z Code 400]

Won't be long now until it is ready to go back in the car. I decided to use the smaller (220°/226° - 111.5° LSA - 0° overlap @ .050") camshaft, retain the E-Performer and tune it as best I can. Might even go roller in the 412 now that I have 'bought some time' with the 350 project....Robert

[Murf'sDad]

Robert:

The Performer should work very well on the 350. Just not much good in a 400 or bigger.

Enjoy the build and the drive.

Stewart

[Z Code 400]

That's exactly what I was thinking, Stewart. I have on laying around, so why not put it to good use. Just like the 092 heads....Robert

[Z Code 400]

For a 1.52 rocker, what's better??? Stamped steel or the Comp Roller Tips I have on the shelf???

[Murf'sDad]

Originally Posted by Z Code 400

For a 1.52 rocker, what's better??? Stamped steel or the Comp Roller Tips I have on the shelf???

I'll get crapped on for this, but run the Comps. Lots of people say they are no good, but ... you've got them. I ran a set on a med-hot SBC I built and had not problems at all. Save the money for the 412.

JMO, Stewart