skinny z

I had another thread requesting compression test info but it was iron head specific.
I'll open this up to aluminum as well and draw my own conclusions.

Besides the actual test results, it would be handy to include the elevation at which the test was performed. Compression results in Denver are quite different from those in Florida.
The usual other engine specs would also be useful. Engine type and displacement, cam timing, calculated compression ratio, etc.
Thanks.

1gary

PM sent.

skinny z

PM replied.

skinny z

The following would really help.
Engine type with bore/stroke.
Connecting rod length.
Cylinder head material.
Calculated compression ratio.
Camshaft specs w/ adv duration, LSA and ICL.
Compression test results (warm or cold).
Test elevation and temperature.
I use a variety of calculators to try and correlate cranking pressure and dynamic compression.
Thanks again.

EDIT:
If you don't have compression test results that's fine although it would help verify the data points. I can work out the theoretical compression pressure if the rest of the info is provided.

LB9GTA

iTrader: (1)

Engine type with bore/stroke. 400sbc - 4.125 x 3.75
Connecting rod length. 5.56
Cylinder head material. aluminum
Calculated compression ratio. 9.1
Camshaft specs w/ adv duration, LSA and ICL. 280, 113, 109
Compression test results (warm or cold). cold
Test elevation and temperature 712 ft, not sure about temp but guessing 15c

skinny z

Thanks.
I have a spread sheet with a few different engines and their specs listed. I have to figure out how to post a chart here (Excel).

Orr89RocZ

iTrader: (20)

Forgot all about this. Will get some data

jokerZ71

If you don't mind me asking,what are your goals for this?I mean,what are you trying to accomplish?If your goal is to have a go to list that says if I have xx:1 SCR,then my cranking compression will be xxx,your results are gonna be really misleading & inaccurate.There are too many variables.An engine with 9.5:1 could have 145 psi while another engine with 9.5:1 with different cam timing events could have 180 psi.Your spreadsheet would be about 14 miles long if you try to cross the CR to cranking psi for every combo & cam specs.I may not understand exactly what you're trying to do.

skinny z

This why I've asked for cam specs too. Compression tests don't lie.
Ultimately, I'm trying to determine max DCR for a pump gas street engine.
The compression test values take out the BS factor when someone says they're running 12:1 with "x" cam specs,
It's just a data base. Something to check out and compare should you want to.
It may be helpful too. Say you do have a legit 10:1 engine with a 274 adv intake cam installed straight up and you have 140 psi cranking pressure. Right away you'll know somethings not right. You can run this in reverse as well. If you have an engine with known cam timing and you're seeing only 150 psi, then based on the cam, you can dial in the correct SCR.
Just another building guide. Self serving in a way because of the mistake I made trying to run 10.5:1 SCR/8.5:1 DCR w/ iron heads and 205 psi crankng pressure.

Orr89RocZ

iTrader: (20)

Mines gonna skew test results i think. I bet it cranks very low but 24 psi boost on pump gas and north of 1000 whp has to have some cyl pressure, yet it was fine lol

I do know my old 401 with 195 heads at 9:1 comp and jones 233 cam cranked 140 psi. I only took it to 17 psi tho but it was fine on 93

jokerZ71

Again,this data could be very misleading due to all the variables inviolved.Especially to a novice builder using it as a guideline.Take for example it's fairly accepted that 8.5:1 DCR on an iron headed street engine is OK on pump gas.9:1 for an aluminum head.That's assuming a properly built engine with proper quench/squish engineered in,spot on tune,efficient cooling,etc.You can have 2 engines with same SCR/DCR & cranking compression with all of the above specs built into the engine with say Vortec heads,flat top,or D cup pistons .039 quench/squish.Then take the same engine with excessive quench/squish,full dish pistons & say a 64cc camel hump head.Same chamber/piston volumes,etc to create the same SCR/DCR & cranking compression.The properly engineered Vortec engine may run it's butt off while the other will detonate itself to death.There are just to many variables.

skinny z

No arguments here. As I stated, this is just a data base with info relating to various engines. If someone were to use ONLY this information to design an engine then they might get what they deserve without additional research. The expanded spread sheet has provisions for listing engine type in addition to the other spec (which I'll post once I figure out how to add an Excel file to the thread).

skinny z

Yeah, you power adder guys really through a wrench in the works!

skinny z

I reread your post when I got home and you mention something that stands out and it happens to be exactly the reason I'm building the data base.
I built an aftermarket Vortec headed 355 (RHS Pro Torker) with a relatively short cam (274/282, 224/230, .574"/.569") and through a series of events (posted elsewhere on this site) I ended up with 10.4 SCR and 8.5:1 DCR. Quench at .040", flat top pistons, excellent cooling system, etc and it would not stay out of detonation. Even with the timing pulled back to a measly 30 degrees (with a slow advance curve and little initial timing) and 100 octane fuel, it would knock at the hit. Standing or rolling start didn't matter. I received tons of tuning advice on that one but eventually gave up, had the chambers worked over to gain a few cc's and went with a thicker head gasket in order to pull my SCR down to 10:1. I've run 10:1 with Vortec heads all day and never had a hint of trouble provided I followed what you described earlier regarding cooling, tune and all that.
The purpose of the data base is collect information and see who's done what with what. You want to know something? Not one person has come up with anything that runs those numbers with iron heads. That's why I'm asking for all the engine specs to be included along with a compression test. No test, no validity to the claim.
Anyway, I'm just throwing this out there. It makes for interesting conversation if nothing else.

skinny z

Not sure if I messed up my calculations but I have you at 9.78 SCR and 8.14 DCR (using Pat Kelly's Dynamic Stroke Length, Cam Timing and Compression Ratio Calculator.
Your engine spec's were very interesting which is why I asked for the data.
If I've miscalculated, please let me know where.
The ignition timing curve you have would certainly help control detonation regardless of the compression ratio. There's the thing though, an engine responds much more to timing than it does to compression.
You may be able to squeak out a few more horsepower percentage-wise by raising the compression ratio and this is the approach I took when I assembled the latest iteration of my iron headed 355. I tried to maximize that value however through a series of events, (swapping out a different short block under the heads and cam) raised it too much.
Pulling out timing was the only way to make the engine workable and even then I still had trouble.
What I learned was that reducing the timing to one that's less than optimum KILLS and engine's performance moreso than any move on the compression ratio might.
Here's an interesting paper in that regard.

http://www.contactmagazine.com/Issue...ineBasics.html

Based on that information and lacking any real world examples of 10.4+:1 SCR and 8.5 DCR with iron heads (unless my numbers regarding yours are wrong), I've backtracked on my latest build, had the chambers worked over for a couple of cc's and fattened up the head gasket. I've dropped my SCR to less than 10:1 and the DCR is in around 8:1.
We'll see where that gets me.

Fast355

iTrader: (2)

Something is wrong....it was a 383, not a 350 or 355. 4.030 bore x 3.75" stroke.

6cc dish on a .040"quench, 64cc chamber 355 is about 10.4:1 scr.

skinny z

I went off of the info from this post.
I thought that was you.
All of the above works out to 9.78 SCR and 8.14 DCR.
As for the 355 with a 6cc dish and a .040" piston height below deck, yes, that's 10.4:1. That's where I'm at and it's not workable without killing the timing and performance. 100 octane fuel too.

Fast355

iTrader: (2)

Don't know why we are getting differing results, but I just put the numbers in Pat Kelley DCR calculator and got 10.54:1 SCR and 8.85:1 DCR. 210 psi cranking compression also tells the tale.

jokerZ71

I came up with the exact same #'s as you based on the supplied info.3.75 stroke,12cc piston,68cc chamber,.043" quench.I rounded up to 9.8:1 SCR & 8.2:1 DCR w/ 164 psi in the cylinder.There's no way this engine is laying down 380rwhp.It would be hard pressed to put out 380fwhp.The parts are just not there unless you are shooting a 120 shot into it.Assuming a 20% drivetrain loss,which,would be low with that rearend & driveshaft setup,you have to be putting out 475 HP @ the crank to achieve 380rwhp.Then to be able to support that kinda torque & weight w/ a stock 700R4??????I can't see it.A Vortec headed 383 w/ LT4 Hot cam is a 425,MAYBE 450 fwhp.The hot cam has over 10 to 15 degrees more duration & .020" more lift than the cam stated in this build.

Orr89RocZ

iTrader: (20)

My thoughts as well. I dont see 380 whp there

Fast355

iTrader: (2)

I can't read my own writing, it was 62cc, but thats only 10.41. That being said it was 380 RWHP and 210 psi cranking. Total seal rings were nearly 20 PSI cranking compression over file fit rings in this 383.

Stock 700r4 did not like it at all. Flared badly on every 1-2 shift even with a Transgo shift kit set on kill, 093 servo, and wide 2-4 band. I went through 6 different 700r4/4L60E transmissions. Most notable failure was I broke an input drum as well as sheared the case lugs of the rear of the case that hold the low-reverse clutches. That happened suddenly catching traction on the street after a burnout.

Pushed a 5,300 lbs brick to a 101 mph trap speed in the 1/4.

My 9:1 350 was 360 RWHP with the same heads and cam and trapped 99 mph, just FYI. It wasn't the quickest thing off the line with the stock 1,600 rpm converter and 3.08s, but still ran low 14s at 99-101 mph.

You don't have to have alot of cam duration or compression to make good power with a ~180cc intake port flowing 260 cfm @ .500" through 2.05" valves and 205 cfm @ .500" exhaust flow.

My 9.6:1 Hemi with similar head flow numbers put down 385 RWHP with a 212/212 @ .050, .540/.540, 114* LSA, 110* ICL cam.

My 97 Express recently put down 330 RWHP through a 4L80E, GM 9.5" corporate 14-bolt and it has stock heads, stock 9.4:1 SCR and a 206/210 @ .050 cam, marine intake manifold, and LT1 cast iron exhaust manifolds.

jokerZ71

There's no way that combo of parts is putting down that much HP or torque.That's a baby cam.360 HP @ the crank.MAYBE.The 906's would be totally maxxed out @ those levels.What parts in this engine are capable of supporting that kinda power??? What is it in this build that is making 100 more HP than any other typical build w/ similar parts? You are claiming more HP & torque than a ZZ383 I an engine w/ considerably milder parts.
I know builders & tuners can tweak out a little to give them an edge over another engine w/ similar parts,but,to claim over 100 HP over what your parts can produce & support is really hard to believe.It wouldn't be a far stretch to say that it's impossible.

Orr89RocZ

iTrader: (20)

If those track times and vehicle weighs are legit then it does make power. My 6.2 ls3 truck is 5300-5500 somewhere in there and made 330 whp tuned. Supposively it could trap 94-96 but never ran it. Granted thats thru a 6 spd auto and 31" tires...but still. I dont see the parts making that power but the times are showing somewhat reasonable

Fast355

iTrader: (2)

Funny you say this, I saw a bone stock marine 350 Vortec with 292 net HP rating with a 196/206 cam make 360 FWHP with 1 5/8" primary long tubes and a little tuning on the MEFI 4 computer.

You act as if the Fastburn heads are good, in reality they are junk flowing for the huge ports.

Stock L31 put down 198 RWHP, with bolt-ons and tune put down 240 RWHP through stock manifolds. LT4 cam + LT1 manifolds made 280 RWHP. 206/210 cam made 298 RWHP. Marine intake + 3.5" CAI & 85mm maf + 4L80E swap from 4L60E put down 330 RWHP.

Fast355

iTrader: (2)

I have proven time and time again, you don't need a huge cam to make good power numbers.

jokerZ71

No you don't,but,you need more than what you have to put down 380 rear wheel HP.That engine w/ the parts you list very well could be 380 @ the crank.MAX.Tell me what makes your engine 100 HP more powerful than any other combo w/ similar parts.For 380 rwhp,you would need a minmum 475 @ the crank.The parts you have WON'T do that.Period.You originally stated 68cc chambers,which would be understandable due to unshrouding for the 205/160 valves.Then when your calcs are questioned,you state 62cc,which means the heads would have to have been milled approx .030".You state they were only cleaned up.As far as proving anything,what proof have you provided for these power levels?Dyno sheets,time slips??? Anybody can calculate HP @ any given speed, trap time & weight & say they have this or that,but,your own parts list does not in anyway support the power you are claiming unless you are confusing rwhp w/ fwhp. & it's not just the cam that raises doubt.It's the entire combo.Nothing you have in this build will support those kinda #'s.

jokerZ71

Sry,i just saw your reply.I agree with you.DCR is not the do all be all of how an engine will run or perform.It is simply 1 tool that is used in combination with everything else.I wasn't busting your chops over the test.I was just curious as to the goals & what you were shooting for.I hope it comes together to help us out.

Fast355

iTrader: (2)

I have posted plenty of dynosheets for these setups over the years I have been here. SEARCH is your friend.

For example, this is my production LT4 cammed bolt-on L31



This was a 9:1 350 with production Vortec heads and a GM production LT4 cam, Edelbrock 2116 Vortec performer intake and 2" Marine TBI.



Same engine with a 2912 single plane, the reed cam above and the ported vortecs. This engine was every bit of 440 HP at the flywheel with the tiny little cam in it. It was running 61# injectors at 50 psi (125 lb/hr x 2) @ 80% DC. The throttle body on this engine was off a 405 HP TBI 502 marine engine and I had to bump the fuel pressure from 30 psi up to 50 psi to keep it from running over 85% DC. It would break 295/50R17 tires loose at a 30 mph roll in a heavy 1983 G20 Van with 3.08 gears.



This one is probably the one that will get the most hate....This engine was a 8.75:1 TBI 350 with a stock set of 810 swirl ports and a production GM LT4 cam.

jokerZ71

So I can only assume that your building tuning skills allow you to use the same parts as someone else & squeeze 100 more HP from it?Those charts would be rite in line with what those engines would produce @ the crank.Not @ the wheels.As to the engine we are discussing that you claim 380rwhp/475rwhp,exactly what is the "magic part" that makes this happen?By the way,a cpouple of those graphs look amazingly like print outs from dynosim software & they in no way show that those #'s come from the engines you list.What you are claiming is impossible.Your engine built as you stae DOES NOT make the 475 HP it would take to have 380 rwhp.

Fast355

iTrader: (2)

You must think that a small block responds like crap to performance parts. A STOCK LT1 with bolt-ons and a Hotcam is a 425 HP engine. Ported stock heads can make 475 HP all day long and its only 10.4:1. It was probably more like 440-450 HP as that is more than enough to make 380 RWHP through a 700r4. I tuned a 95 Camaro LT1/A4 with LT4 heads, intake, and hot cam that ran a 12.5 @ 108 on a 2.1s 60' through the stock manifolds in 3,000+ DA on street tires and put down 360 RWHP/350 RWTQ. Stock 3.08 gears and a S10 converter. A STOCK LT1 is a 13 second car in good weather, so tell me again about how much HP a small block can not make.

Hell my little 317 HP 5.6 in my daily driver pickup truck makes more HP/TQ to the wheels than it was rated at the crankshaft with only an intake/muffler/cat delete/tune.

So once again, I don't know where you are getting your numbers from, but they are out of tune with what people are achieving in real life.

jokerZ71

I never claimed an SBC can't make good power or those #'s.I simply stated that yours doesn't.Not with the parts you have listed.An HT383 only produces 340 fwhp w/ a cam with 10* less duration.But you claim more than a 100 HP gain.As far as my #'s,they come from realality.Even if you assume a 15% drivetrain loss thru that rear & driveshaft,450 HP is an extreme exaggeration @ best. Better yet,show a time slip or dyno chart that actually backs up your claim that shows rwhp & relates to the actual engine/vehicle you claim these #'s for & I'll STFU.Otherwise I call BS.Show any dyno chart w/ comparable parts that put this out.Not some printout from a dynosim program.

Orr89RocZ

iTrader: (20)

Just find it hard to believe with that 206 cam. I've seen and played with enough combinations to know 380 whp thru an auto takes alot more cam than you claim. Now worked vortecs with 2.05 valves i know can flow enough for that hp but that baby cam just cant use the heads potential. Your sbc 23 deg head motor is as efficient as a bolt on Ls3 which will do 380-400 in autos, 410-420's whp in a manual. Thats modern tech 15 deg 2.165 valve heads

Fast355

iTrader: (2)

Quit making assumptions you have no proof of.

Those are DYNOJET and MUSTANG dyno numbers aka RWHP from engines I have built and run and can provide complete specs for all of them.

As for your HT383 comparison, STOP. It is nothing more than a Marine 350 Vortec with a 3.8" stoke crank and matching pistons. NOTHING SPECIAL just some 062 heads that flow less than 230 cfm intake and has a tiny 196/206 tight LSA cam that sits in the engine advanced. With port fuel injection and headers it makes 360+ HP at the flywheel.

That being said a HT383 with headers, an airgap manifold, a 750 speed demon and 1.6:1 rockers made 379 HP @ 4,600 and 474 TQ @ 3,700. Swapping in a 230/236 duration, .510/.510" lift cam made 455 HP on unported stock vortec heads.

Fast355

iTrader: (2)

More like 212 with the 1.6:1 rocker

The 206/210 cam in my stock head vortec 350 is 330 RWHP through a 4L80E and 14 bolt.

I have seen a Ramjet crate engine make 365 HP with the stock 196/206 cam and later 062s on it that flow less than 230 cfm and the air/fuel ratio was in the 11s on the dyno.

jokerZ71

Going from a 1.5 to 1.6 rocker only changes dur by 2* @ .050 lift.

jokerZ71

To the O/P. I apologize for my off topic post & detracting from your thread.I forgot where I was.LOL.

Fast355

iTrader: (2)

We are getting way off topic, but its more like 3-4* @ .050 for a 1.6 rocker over the factory crappy stamped rockers that vary from 1.4-1.50 depending on where they are in their rotation. Regardless it can be a ~20 HP gain on a small cam.

jokerZ71

The HT383 is a 383 cu in engine using a cam that has about 10* less dur than what you have.It's 340 HP rating is based on 1 3/4 headers w/ a 750 carb.Your engine specs are very similar yet you claim over 450 HP.Those charts prove absolutely nuthin.Especially since none are for the engine we're discussing.You can't even find a Car Craft article w/ their inflated dyno #'s to even claim what you're claiming.That's pretty bad rite there.I can swallow a lil BS,but,when it stinks so bad that I can't get it to my mouth,Ima throw it back @ ya. & that's exactly what your claims are.....BS !!!!!!!!!!!

Fast355

iTrader: (2)

Quit going off the ratings and shut up and learn. You keep quoting the HT383 and it has a TINY camshaft. It is a very lazy grind, not to mention STOCK HEADS.
HT383
http://www.hotrod.com/techarticles/e...p/viewall.html

Ramjet 350
http://www.hotrod.com/techarticles/e..._crate_engine/

LT1 350
http://www.gmhightechperformance.com..._motor_part_2/

Keep in mind I have bigger valves, ALOT more intake/exhaust flow, and a bigger cam than any of these started with.

One of those charts is from the sameheads, same cam in a 350 that was turned into the 383 in question. If a 9:1 TBI 350 can make 360 RWHP with those heads and the same cam, it just proves a ~10+:1 383 easily made 380 RHWP.

jokerZ71

Those ratings are a lot more accurate than any info provided by you.@ least they do have some valdity to them.When I get ready to learn something,you can bet your @$$ it won't be from you.If I needed to learn how to BS & exagerate,I coulda kept my ex wife.She did @ least provide somethin to look @ while I was listening to her BS.

Fast355

iTrader: (2)

Go back under your rock and be slow in your TBI truck.

Marine 6.2 is NET rated at 320 HP at the propellor shaft with restrictive marine exhaust, flame arrestor, and accessories installed. With headers, a touch of tuning, and GROSS dyno it is 370+ ALL DAY LONG.

Here is another dyno that came from my 97 Express. 206/210 cam, stock heads, marine intake, LT1 manifolds. I am guessing driveline loss is over 20% with a 4L80E and 14-bolt.

jokerZ71

I don't got a TBI truck.It's 97.TBI went out in 95.Whenever you wanna learn somethin just holla.Bet mine is faster !!!

Fast355

iTrader: (2)

Quicker than my Express maybe, but its not hard when you have 6,200 lbs to move with only a 3.73 gear and a 2.48 first gear. I can run 55 mph in 1st and over 90 mph in 2nd and have had it over 120 on a smooth flat area. But get it out on the road and it recently outran a 2014 5.3 truck on the highway.

You won't touch my import V8 truck without alot of nitrous!

And my bad on the truck, I saw the pic and instantly thought TBI, in fact your truck in Mexico would have TBI.

jokerZ71

Yeah I know.You can also **** cucumbers & work great miracles also.Thank you for the entertainment.This has really made my day pass by quickly & provided me w/ much entertainment.Thanks. I'm all done now tho.By the way,maybe that is part of the problem.You only look @ the pics instead of reading the info.

skinny z

Wow. My intention wasn't to start a war here.

I did find Fast's build numbers to be impressive if nothing else. I'm not too sure how to take chassis dyno numbers as they can be very different from brand to brand and from machine to machine. Different brands (Mustang, DynoJet,etc.) load the engines in different ways. Similar machines are also calibrated to different values so numbers can be skewed all over the place (how's that for diplomacy?).

For what it's worth my 10:1 stock Vortec headed 353 (cranking pressure 190 psi) laid down a whopping 282 rwhp through 1 5/8" medium length headers into a single 3" stock location muffler and a 700R4 w/ 10" converter . WOT AFRs were a little lean at 13:1. It still managed 12.7 @ 106 mph at 3700 lbs. You do the math. It did have what looked to be a reasonably flat torque curve which I'm sure contributed to the vehicle's performance. With the muffler bypassed with a single cut-out, a similar combo picked up 2 mph in the 1/8th so there's power lost with a crappy exhaust that's certain.



All that said and despite all the conjecture and name calling, I can't for the life of me get an 8.4:1 DCR iron headed engine out of detonation even by castrating it with less than 30� total timing and a very lazy timing curve. Before anyone says anything, all the prerequisites for running high compression were addressed. Efficient cooling system, good AFRs, sensible timing curve, etc.

So, what I'll do here is post my data base when I can. I can't upload an Excel spreadsheet (according to JT) so the best I can do is print it, scan it, save it as a j-peg and post that. I just need new ink for my printer.

It'll be interesting to see how a few different builds stack up with relevant data listed and whatever results the various contributors have provided.

If anyone else wishes to contribute I'm looking for the following information:

Engine type and size with bore/stroke.
Connecting rod length.
Cylinder head material.
Calculated compression ratio.
Camshaft specs w/ adv duration, LSA and ICL.
Compression test results (warm or cold).
Test elevation and temperature.

jokerZ71

It's a funny thing.There are 2 brothers local here who have a small shop.1 of them has a 96 Tahoe w/ 5.7 Vortec.The other has a 97 Yukon w/ 5.7.They rebuilt both engines w/ the same parts,cam,& both PCM's tuned @ the same place.I forget what the actual SCR/DCR worked out to,but,they both had the Summit flat tops w/ a .030" over bore.Seems like it was just over 10:1.The 97 ran like a striped ape.The 96 was a slug.He finally swapped knock modules to the LT4 module which is less sensitive.He was getting false knocks so timing was being pulled.It helped,but,it never ran as it should.They did a compression ck on both engines.They were within 5 psi of ea other.Like I said DCR is only 1 tool to be used in combination with everything else.An important tool when calculated correctly with good valid info.So many things can throw you off.Slight differences in piston or chamber volume.Timing marks not dead on.Just a small amount of oil entering the cylinder @ those CR can detonate badly.Vacum leaks can cause lean spots.There's so much that can effect how an engine will perform & react.Again,I apologize for the off topic post.Been a long boring day @ work & I think I had just read those IMO,inflated engine specs 1 too many times & @ the wrong time.Even tho I just recently joined here,i've been around for awhile,mostly researching tuning tips,etc.Lots of good info here. for that stuff.I wish ya luck on your test here & hope ya figgure somethin out from it.

86LG4Bird

iTrader: (1)

Wow! That is spectacular! You get an L31 manifold to peak at 5600 rpm! with a little cam like that! Just awesome! and even with manifolds!! How do you do it?

redneckjoe

i dont trust any of those chassis dyno numbers. seems like all the machines are different? you can look at 2 similar builds by 2 different people, and the numbers will be WAY different.

IDK how healthy it is for a motor either? because your not simulating g-forces pushing the oil back to the pick up.

Fast355

iTrader: (2)

Shouldn't be so suprised. It peaks at 5,800+ in a LT4 with manifolds. Not to mention my L31 intake was ported and had a 78mm bored throttle body.

We put a 92-95 "W" cam in my brothers 97 S10, ported the lower intake, put shorties on it and it makes peak power at 5,500.

TxTtopZ

Your still messing with those vans? Man, at this point I think its safe to assume your running a business thats supplying kidnappers and bank robbers with get-a-way cars.