I've got a customer who has a BDS 8.71 blower with two four barrels on one of his street pump gas 440 motor cars, it had a valve train failure and I'm getting to fix it for him I didn't build this motor originally
I've built blown pump gas hemi, BB Chevy and SB Chevy but no Mopar wedges.
My question to you that have built and driven them is what static compression ratio do you have and how much boost on pump gas?
This motor did not have a boost gauge so the customer has no idea what boost it was making, I'll fix that for him He has a 30 tooth and a 32 tooth pulley on the motor which according to my calculations is right at 6.2 % ratio under drive or over drive, am I right on this math
The old combination was stock stroke with 906 heads with right at 8.8 to 1 compression ratio, he wasn't happy with it and wants it to have a little more power and better tire spinning power for burn outs after the local cars shows are over
I'm planning on better new aluminum heads with 440 intake port size to be able to reuse is his current blower intake manifold and increase the cubic inch to 505 C.I.(4.350x4.250)and probably increase the compression ratio to between 9.2 to 9.5 to 1 ratio, what say you about these thoughts
Thanks in advance for your help and comments

8-71 means no intercooler. I'm guessing he wants to keep the same drive if possible.
What does he have for ignition control? Is boost retard possible?
Is the radiator big enough?
How do you feel about water/methanol injection?

Unless you know different, I suspect the manifold's discharge area is an open box. You could reduce intake charge temps and clean up mixture distribution some by masking the manifold down to a triangle located under the front of the rotors.

The triangle actually looks suspiciously like a NACA (submerged) duct, with the sides parallel to the rotor angle, and the base located directly under the rotor noses. Yes, the area is much smaller than OEM but flows more air.

Soften the chamber on the iron heads and polish it,Port the heads[mine had 280 cfm] try to keep the swirl in the cylinder.How does the piston look with carbon to indecate fuel flow,quench?These are some of the things I did with my iron heads but I was on race gas.My Isky sft cam .570ish lift 110 had a lot of tq but also a lot of overlap[70 deg]
ps:as you can guess this cam suffered from the overlap and was a tight lash.

I wouldn't get too carried away with increasing the CR.

While it can help with off idle bottom end torque which with 505 cubes should be a non issue anyway, it can limit how much power you can potentially make. An 8:1 combo has more volume to supercharge fuel and air into than a 9.5:1 combo does.

More fuel and air equals bigger bang.

Kevin

I used to drive this thing all over NorCal but with a meager 6-71. It had iron heads and drove around on 9lbs of boost all day long on Cali pump swill. It did see as much as 20 a few times at the track on Sonoco 100. I can tell you the head gaskets were not long for the world like that. But this was the late 90's and if I were to do it again I think it could be made to love a bit longer now.

I'm going to use a set of aluminum heads with either 75 CC or 84 CC chambers which means having a reverse dome piston with either a 32.0 or smaller reverse dome piston to get the compression down instead of going to a lower deck height and loose quench.
Speaking of softening the chambers Edlebrock does make a head with the softening done to allow a quench dome piston Thanks for bringing that up
I'll do the math on that head next

Back in the 70's, Sunoco 260 pump gas, 7.5 static, 7-8 lbs of boost.

I’m putting a similar motor together. 500 with 84cc edelbrock 9.3-1 and 5 lbs of boost.

I bought a pair of 950s, linkage, scoop, fuel lines and some other stuff from a guy who built a blown 440 and Big Al sold him a cam and guided him though the build. Afterwards he switched to fuel injection. We discussed his setup and he sent me a pic of the cam card. I ordered the same cam from comp.

What intake?I have Edl 85cc std port heads with a BDS intake,Wiseco dish 22cc but I suspect you will use a Ross piston.My can is like posted above.

Same BDS. I’m doing another one, Megablock 517 with trickflow 270s and a maxwedge port modman with blower plate.

Cab these should work for you with 84cc eddies

Just re read this, Sorry, didn’t mean to hijack if I did
Yes looks like 6.25 % under or over with a 30 and 32 pulley.

Final compression ratios in excess of 12.4:1 are not recommended for use with "pump gas." The higher the final compression ratio, the higher the octane rating of the fuel must be in order to help prevent detonation and serious engine damage.
The formula for calculating your exact final compression ratio is as follows:
Final Compression Ratio (FCR) = [ (Boost÷14.7) + 1 ] x CR

Boost = Maximum blower boost
14.7 = psi at sea level
CR = engine compression ratio

Altitude plays an important role in determining compression ratios. If the altitude in the area where you normally drive is significantly higher than sea level, then your compression ratios will also vary. To determine the effects of the altitude on a calculated compression ratio, use the following formula:
Corrected Compression Ratio = FCR - [ (altitude÷1000) x 0.2 ]

= Pump Gas = Good Gas

We, him and I, live in central Oregon which is above 2500 Ft to the furthest north he will take this car and around 4500 Ft above sea level to the south down near Klamath Falls, OR.
My house is right at 4300 ft. and his is a little higher, I think. He may have moved since I was over to his house to the south and east of me 10 yrs. ago
The car and engine where built by someone else a long time ago, stock 906 heads, forged +.030 Seal Power flat top pistons down on the hole around - .090 with stock LY rods with ARP bolts
I'm still working on making up the parts to order list but it will get a new set of aluminum 440 heads with stock size 440 intake ports so we can reuse his BDS blower manifold, a 4.250 forged 4340 steel stroker crank along with a bigger and better solid roller cam, better 7.100 long rods and a better ignition and fuel system to make sure he doesn't hurt it due to lack of fuel supply at WOT
More to come later

What fuel system is in use? 8mm pullies??

Would you mind if I posted pics of my heads,BDS intake being that is what you are using?I used HS offset rockers also.

Please do post those pictures
I ended up ordering some Eddy E street heads so I can reuse his BDS blower intake and Comp Cams SS rocker arms, I'm having Bullett make me a new cam that is quite a bit bigger in lift and duration, old lift was right at .512 and the new cam should have around .620 net lift. Their grinding it on a 112 LSA and I'll probably install it between straight up and no more than 3 degrees advance on the intake lobes to start with.
I'm still debating on what compression ratio to start, probably around 9. to 1 depending on the current block deck height

Expect your boost numbers to drop with those heads and cam.

You likely need to remind the guy that boost is resistance to flow. The new setup will use more air so less of it will stack up in the intake. You're always on the right track when you make more power with less boost.

He has to get out of the mindset of talking boost numbers. Someone else will be packing more boost and make him think he's missing out.

Do I have to explain this all over again?

Since the cylinder volume and the combustion chamber volume are both pressurized to the same extent, the original compression ratio remains unchanged by boost pressure, and the compression ratio is not increased. However, cylinder pressure and knock sensitivity are increased due to greater charge density.

I have the std port Victors so IDK how much info you can use now but here goes.My BDS intake sat just a ;ittle low for the bottom of the port to be smooth so I used 2x.040 gaskets around a .090 aluminum spacer I made and the intake sits 1" up from the engine just clearing the valley pan.This is the ft wiseco piston I started with but now have a dish like you want and will find a pic.