My 470 RB build

-
Mopar-Man

Mopar-Man

Big Block Better Burnout
Joined
Oct 10, 2009
Messages
1,450
Reaction score
1,041
Location
Orlando, Florida
Well my motor is coming right along after some machine shop delays due to too much work (poor guy) and he got it all mocked up. The block bored .055 and looks perfect. The deck after a 4 corner mock-up is square due to the last time it was milled and the line bore is dead-on as well. So I saved some $$$ there. Only problem was the pistons are .012 above the deck so I have to run a Cometic MLS .051 head gasket to get an .039 quench with 84cc 906 heads. I am running flat tops with .005 side clearance so there shouldn't be a piston rock issue. I COULD have milled the piston tops but due to this being a nitrous motor we decided a thick crown was better than a thin gasket.


440 .055 over
7.10 BB Chevy H-beam rods
Mains offset ground to BBS Chevy size and to a 3.90 stroke
KB Icon pistons PN IC824 with .990 wrist pins
1/16" 1/16" 3/16" Mahle ring packs

I show 10.5 compression using the Diamond Pistons calculator on their website (it is extensive!)

Any thoughts before I put this thing together?
 
i hope you clay the pistons and hope those pistons have correct valve reliefs...
 
Sounds nice except the chebby rods,( just kidding ) i wish i was that far along. i am still cutting out frigging rust.
 
I could not duplicate that 10.5:1 Compression Ratio on any of the Calcs I tried(including Diamond) ? lowest I got was 10.8 being "generous" ?
however,
I do not know your exact Gasket Volume, etc., etc.,
No Matter,
I'm sure you are already intending on using "Good Fuel", NOT attempting 92-94 Octane Pump Gas at the 10.5 CR on the IRON Heads ?

E85 ?

906 Heads are an Open Chamber ?
Where are you getting .039 "Quench" ?
No significant part of the 906 "Open Chamber" will be anywhere near ".039" ? further compounding the GOOD Fuel at all times requirement ?

Good Luck with the build,
remember to File the Ring gaps and Pinfit for NO2.
 
Headgasket volume is 4.410. I believe the valve reliefs are 7cc. When I inputted all of the data (which I do not have in front of me at the moment) it was 10.57:1. I am going to moderately overcam this engine so it will kill some cylinder pressure and let it run on 93 octane. All I care about is how it runs on the bottle. The 4000 stall converter will prevent any low RPM load. The rings are file fit. What do you mean by "pinfit" for N2O? I have full floating pins. I will be running a wider than N/A ring gaps on the compression rings. I think quench was the wrong word to use. I should have said piston to head clearance. Is this too tight?
 
805moparkid said:
i hope you clay the pistons and hope those pistons have correct valve reliefs...
Click to expand...

EVERYTHING will be measured. I know the valve reliefs are good up to a 2.30 Intake valve but I don't know if they will be deep enough until we put the cam in and turn the motor over by hand.
 
Its what I call a smart stroker build. Using the parts you have used will bring the rotating and recirocating weights down, essential for making good h.p. I like it!
 
needsaresto said:
Its what I call a smart stroker build. Using the parts you have used will bring the rotating and recirocating weights down, essential for making good h.p. I like it!
Click to expand...

That's exactly what I am doing! See, me and my buddy are building TWO engines at the same time. We grouped our parts and figured out what would make GOOD power but still be AFFORDABLE for both. I took a ton of weight out of reciprocating assembly. The old pistons were down in the hole and the new are .012 out WITHOUT HAVING TO DECK THE BLOCK AGAIN! This thing is going to rev like a light switch. I lowered bearing frictionals losses by going to smaller journal sizes. I went from .030 to .055 over and 3.75 stroke to 3.90 stroke. I have the cam already which is definately big for these fully ported 906's BUT I will be switching to aluminum later. The bottle will fix any torque i may lose currently.
 
ICON Publish 4.5 cc for that Piston
If you use the Big Bore Felpro's @ .051, #1105 or 1039, they publish 13.7cc Compressed Volume.
So you are right, that comes in around 10.6:1

Pinfit is the Clearance, or "Fit" of the Pins in both the Rod small ends AND the Pistons.
With Nitrous loads @ RPM the Pin will actually "deflect" slightly, which ovals the Pin Ends.
Fit the Pins at .001" in BOTH the Rods and the Pistons to prevent galling.

IMO,
10.5 is too High for the Open Chamber Iron Heads on 92 Octane AND the 7.100 Rods(dwell time) with ANY Cam, no matter lack of low rpm load or not.
Once it hits the Cams Volumetric Efficiency sweetspot, with that BIG open Chamber,
It will be detonating.
Just because you aren't hearing it, don't mean it ain't there.
You will know, by the constantly climbing Temperature Gauge, even when driving easy.

No Matter,
The 7.100's are nice for extracting more outa the burn, but with the Open Irons @ 10.5,
you had better plan on supplementing the Nitrous side of the System with at the VERY LEAST C14 Fuel or better,
because you will DEFINTELY be waaay past the Detonation Range when on the juice !
No amount of timing retard for the Nitrous will matter because the 92 Octane will self ignite BEFORE any retarded sparks arrives.

just a suggestion, no wars wanted,
A 2 Gallon "Pony" Fuel Cell Filled with C14 or C16 Fuel mounted up behind the Grill, with a seperate pump, DEDICATED strictly for the Nitrous side would help immensely, so that at least the Timing Retard when you hit the juice can work ?
 
Challenger340 said:
ICON Publish 4.5 cc for that Piston
If you use the Big Bore Felpro's @ .051, #1105 or 1039, they publish 13.7cc Compressed Volume.
So you are right, that comes in around 10.6:1

Pinfit is the Clearance, or "Fit" of the Pins in both the Rod small ends AND the Pistons.
With Nitrous loads @ RPM the Pin will actually "deflect" slightly, which ovals the Pin Ends.
Fit the Pins at .001" in BOTH the Rods and the Pistons to prevent galling.

IMO,
10.5 is too High for the Open Chamber Iron Heads on 92 Octane AND the 7.100 Rods(dwell time) with ANY Cam, no matter lack of low rpm load or not.
Once it hits the Cams Volumetric Efficiency sweetspot, with that BIG open Chamber,
It will be detonating.
Just because you aren't hearing it, don't mean it ain't there.
You will know, by the constantly climbing Temperature Gauge, even when driving easy.

No Matter,
The 7.100's are nice for extracting more outa the burn, but with the Open Irons @ 10.5,
you had better plan on supplementing the Nitrous side of the System with at the VERY LEAST C14 Fuel or better,
because you will DEFINTELY be waaay past the Detonation Range when on the juice !
No amount of timing retard for the Nitrous will matter because the 92 Octane will self ignite BEFORE any retarded sparks arrives.

just a suggestion, no wars wanted,
A 2 Gallon "Pony" Fuel Cell Filled with C14 or C16 Fuel mounted up behind the Grill, with a seperate pump, DEDICATED strictly for the Nitrous side would help immensely, so that at least the Timing Retard when you hit the juice can work ?
Click to expand...

You don't think i can run pump gas on the street and race gas at the track? I will be using a programmable Mallory 685 box so i can pull timing via a toggle switch if need be. The plan is RACE GAS AT THE TRACK. Eventually I will get some Edelbrock Victor heads which will be well matched to the cam I am running. I believe there is a Dart on here that runs a 440 and a tunnel ram with 11.0 C.R. on 93 octane and aluminum heads. He is running a similar cam profile but with less duration as his is a roller and mine is a solid flat tappet.

Here ->>>>

0.030 over 440 with wisco protrue flat top pistons 11.1.1 compression
steel crank
comp cams solid roller 264 @ 0.050 and 634 lift with crane 1.6 roller rockers
bowl ported indy EZ heads flown 310-315 at 0.600 lift
M1 tunnelram with two box stock carter comp 750 carbs
tti 2x3-1/2 headers
727 with cope racing valve body and race rebuild kit
dynamtic 9.5 inch converter 4500 stall
back braced 8-3/4 with a 30 spline moser spool
4.10 gears which i broke on the 5 pass. now will have 4.30 gears
mopar 002/003 super stock springs
mopar 50/50 drag shocks
stock frontend with comp 3 way shocks set at 90/10
15x8 weld drag stars and M/T 275/60/15 drag radiels
 
Just my opinion, it's your Engine, you do what you want.
Please believe me,
I have NO REASON to wish to rain on your parade, and I sincerely hope everything works GREAT for you.
No Mileage for me typing here ?

That said,
I just personally believe you are gonna have problems, trying to run the 10.6 with 7.100 Rods on 92 octane with the Iron Heads.
I've been there, done that, many times over the past 30 years Drag Racing.
Look for it to manifest itself as continually climbing Temp Gauge during normal driving.
You will think it's Water Pumps, Radiators, Thermostats, etc., etc., all to no avail.

I do not understand what you are saying about ANY type of Timing retard system, when the Air/Fuel charge will be "detonating" all by itself BEFORE the Spark arrives on the Street, using Pump Gas ?
Like I said earlier, just because you aren't hearing it, won't mean it isn't there on the Street.
The burn will be "Fast & Erractic" to control on 92 Octane, which exposes the Cylinder Walls to peak Pressures and temps at the wrong time.

The Race Fuel at the Track will be FINE !

The GOOD NEWS is the Aluminum Heads WILL run just fine on the Pump Gas, even up to the 11.0:1 mark, once you switch over ?
The greater Heat Dissapation Characteristics of the Aluminum over the Cast Iron allows about 1 full point compression increase on Pump Fuel ?
Aluminum Heads can run MORE CR than Iron without detonating.

Generally, max safe CR for 92 octane is;
9.5:1 with Cast Iron Heads with .5 to .7 MAX play for any Cam Duration(cylinder pressure)
and
10.3:1 with Aluminum Heads with about .5 to .7 Play for Duration.
BOTH of the above,
assume somewhat close to "Stochiometric" A/F Mixtures. Trying to go further by "drowning" the 92 Octane "detonating" flamefront with more fuel is both Tricky, and usually fruitless to performance/driveability.

IMO,
I think the "Engine Challenges" in the Comic Books are somewhat responsible for these CR Misconceptions about what is "safe" for Pump gas ?
You'll see builders doing Engines for those Challenges with ABSURD CR's for the Pump Gas being used, even on Aluminum Heads, for the simple reason that they DON'T CARE 1 iota how long it lasts, they just wanna make power for the DYNO and WIN the Challenge !
In the "Real World", alot of those Engines wouldn't last 2 weeks under normal Street driving conditions, if at all, and would Detonate themselves to death using 92 Octane.
Remember,
A "Little Bit" of Controlled Detonation, on the "Edge"of the detonation Range for the Fuel used makes VERY GOOD Power, BEST found on the Dyno,
but,
it's a very sharp CLIFF edge going past that point, where power drops dramatically and engine wear begins occuring at an accelerated rate.

At 10.6 on the Iron Heads using 92 Octane, the "wick" is already lit, you are burning up Ring Lands/Rings/Main Caps/Flaking Brgs at an accelerated rate UNTIL you can get the Aluminum Heads on there and save whats left ?

Just a "suggestion"
Why not Bite the Bullet for the Aluminum Heads right away and make it SAFE for 92 octane on the 10.6 CR right now ?
I know it's expensive, but compared to what you have already spent building the Engine, it's good insurance to protect your Investment ?

Good luck with it,
I'm out.
 
Heck with todays crap gas I can here detonation in EVERYTHING I DRIVE!!! Doesnt matter be it a chev ,ford whatever. Try driving slowly uphill in a narrow crowded street with walls on either side,lots of those around here.You can here the pinging mighty feirce.
 
needsaresto said:
Heck with todays crap gas I can here detonation in EVERYTHING I DRIVE!!! Doesnt matter be it a chev ,ford whatever. Try driving slowly uphill in a narrow crowded street with walls on either side,lots of those around here.You can here the pinging mighty feirce.
Click to expand...

huh... my slant with 10:1 iron head and 30 degrees timing locked dosent ping even when its 110 out side and the engine is almost 210*...

running pump 91 in AZ
 
I gotta tell ya, Challenger340 that make make some good points here. But I have ran this build by Crower Cams and they assure me that if I run a 112 lobe center cam that has about 10-15 degrees more duration that optimal I can in fact run 93 octane Florida pump premium. I know how to read a sparkplug and will keep an eye on them for aluminum particles. If I/We are incorrect, then off with the heads! :) No need to spend $2000 if I don't have to. I only have $500 in these ported 906's! They were traded to me and that includes ALL machine work, stainless valves, new guides, new seals, new double springs and titanium retainers! Now you see why I am trying to make this work. I have such little $$$ in this motor I don't think you could build a small block Chevy for this price!
 
OK I get using what you have,but in this case it's penny wise/pound foolish. All you need do is change the con rods to a stock length and all will be good.


But hey it's your motor and $$..
 
needsaresto said:
OK I get using what you have,but in this case it's penny wise/pound foolish. All you need do is change the con rods to a stock length and all will be good.


But hey it's your motor and $$..
Click to expand...

Oh really? So that the piston can be half an inch down in the bore? :banghead:
 
Dynamic compression and component choices are what is crutial for a pump gas engine. Did you happen to post the cam specs? I'm looking for the intake valve closing point at .050".
I typically run pistons above deck. The issue I see right off the bat is the top ring placement and the above deck deal. If your block has a big bore chamfer and the piston is "up" that top ring will not have much iron above it which means a lot of heat will be focussed on it. Chamfer is many times done by hand and is very subjective.. your builder may want a larger one, others don't. You will want the smallest one you can get the rings into. If you're running the top loose, make sure it's loose enough and I'd call the ring manufacturer tech line and get the 2nd ring spec. It's not a compresion ring nor subject to the big heat so normally I'd run it run larger than the top ring. It will be tighter than your top ring because of the NO2 gap there, but too tight can push the top ring of the ring land and you'll lose ring seal.
In terms of open chamber Mopar heads... You are hobbling yourself using them but you know that. IMO the best bet is to design and build as if you were using closed chambers with the expectation that when you change the heads, all will be good and you'll need to change more than the heads. Then simply accept the low static ratio and cam to make the best of it now. If you're concerned with piston to head clearance with 906s, dont be. That piston could stick up .080 and not hit anything with them and the steel shims.
 
Mopar-Man said:
You don't think i can run pump gas on the street and race gas at the track? I will be using a programmable Mallory 685 box so i can pull timing via a toggle switch if need be. The plan is RACE GAS AT THE TRACK. Eventually I will get some Edelbrock Victor heads which will be well matched to the cam I am running. I believe there is a Dart on here that runs a 440 and a tunnel ram with 11.0 C.R. on 93 octane and aluminum heads. He is running a similar cam profile but with less duration as his is a roller and mine is a solid flat tappet.

Here ->>>>

0.030 over 440 with wisco protrue flat top pistons 11.1.1 compression
steel crank
comp cams solid roller 264 @ 0.050 and 634 lift with crane 1.6 roller rockers
bowl ported indy EZ heads flown 310-315 at 0.600 lift
M1 tunnelram with two box stock carter comp 750 carbs
tti 2x3-1/2 headers
727 with cope racing valve body and race rebuild kit
dynamtic 9.5 inch converter 4500 stall
back braced 8-3/4 with a 30 spline moser spool
4.10 gears which i broke on the 5 pass. now will have 4.30 gears
mopar 002/003 super stock springs
mopar 50/50 drag shocks
stock frontend with comp 3 way shocks set at 90/10
15x8 weld drag stars and M/T 275/60/15 drag radiels
Click to expand...

With that cam and aluminum heads you'll be fine on pump gas, just tune it.:thumblef:

As for open chambered , maybe..tune, maybe detune...or run it with the plugs loose.'joke'
Ive seen 11.2 done with closed chambered iron and 87 octane, so maybe so
 
IMO,
The problem when "cheating" CR for pump fuels ?
Is a problem based on with working with Dynamic Compression, and closing points on a Camshaft as the determination of Compression(bleed off), and suitability for Fuel Octane ?
is the efficiency of the Cylinder Head during scavenging at overlap, in conjunction with the final VE achieved when actually running at the Cam's sweetspot ?

Many dyno simulations can get close depending upon the imput data,
nonetheless, IMO,
a true wave factor simulation must be run according to actual head data, not a staright FILL & DUMP program ?
Even then, variances from stocchiometric A/F can also change a Wave Factor simulations accuracy ?

Again, IMO
NO @ IRON HEADS are the same, even with similar Flow sheets
I you are going to attempt cheating a Pump Gas Octane on higher CR's with Cam Duration bleed off,
Get on an Engine Dyno.

No Wars wanted.
 
You must log in or register to reply here.
-

Back
Top