Max pump gas psi - iron vs alum

[Garys1969RR]

Having to rely on octane boosters or mixing race gas with pump gas S U C K S.
It is much better to build an engine to run on common pump gasoline. These cars are supposed to be fun to drive. They shouldn't be a pain in the ***.

Yes thats true, but I need the C/R to get into the 12s with this motor. Luckily I have a gas station near my house that sells all 3 types of fuel. And I don't need fuel very often with the miles I drive. When I install the Eddy RPM heads in April, then will see how much difference the improved air flow makes.

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Once I got it all down, its real easy to put in the right fuel with no issues. This car is alot of fun to drive and has great throttle response, with lots of low end torque.

 

[HT413]

Lots of great info here guys, thanks a bunch. Honestly, my plan is to mimick one of the stock stroke builds in the 11 sec or the 12 sec threads over on the racing forum. Not that I'm going for an ET, but I think the low 12's in a 3800lb B body is the level of performance I can afford and still more than streetable enough to provide years of reliability.

Meep, your build is definitely one that I'm taking seriously, though I plan on running my RPM intake (you can keep that 6 pack lol).

Ronnie, I've put a lot of thought into your comment about getting the quench dome just right for the head and that makes a lot of sense. It also makes me think it might not be for me, because I do plan on putting on some alum heads at some point which I'm guessing would likely have different requirements. So maybe I do go with a flat top and just build good quench into it now and if I do go with aluminum later, stick with a same or slightly smaller cc later. Chances are if I love the combo, it'll stay this way for several years.

So perhaps I run with this idea - stock stroke, one of the popular flat tops, maintain about 0.045 quench and 915's. Try for right around 10:1 and run a cam that will keep the cranking pressure to about 160 or so. Think that will be pretty worry free at sea level if I tune it with a wide band O2 gauge?

 

[IQ52]

What I think is, we have taken the time to post dyno results for engines running 120 PSI cranking compression that have resulted in 450-650 HP on pump gas. Why ever try taking it to the edge of detonation if you don't need to? Gregoryfrankenredburger knows the heartache as do many others.

 

[HT413]

What I think is, we have taken the time to post dyno results for engines running 120 PSI cranking compression that have resulted in 450-650 HP on pump gas. Why ever try taking it to the edge of detonation if you don't need to? Gregoryfrankenredburger knows the heartache as do many others.

IQ, that's exactly what I'm sayin - tell me where the safe zone is. That way, when I decide on the cam, I can be sure it keeps me where I need to be. The build is wide open; I have a std bore 440 block, the oem forged crank and happen to have 906's and 915's to play with.

I've seen you recommend staying below 175psi, and I see Greg and others have has success in the 160's with aluminum heads, but how does that compute with iron heads with or without quench?

Btw, I do thank you for sharing all your hard work, I've been following it here and on FABO. I'm hoping to learn from your work and Greg's odyssey and stay in the comfort zone.

 

[Meep-Meep]

I think you have to treat every engine build as a complete assembly because making radical changes will get you into trouble. There are some non variable items such as chamber shape, bore size, stroke, rod ratio and all want to have a certain amount of octane and A/F ratio to keep happy. You will be bound to some fixed rules. My experience has been planning street engine builds and careful assembly and working with factory parts. I built my 440 to make a point that you don't need a ton of aftermarket parts to have a good running street engine that will last a long time. A good vacuum signal is not just for power brakes. It makes your carb work better too.

 

[mopar12372]

pump gas super in cali is 91

 

[HT413]

Funny, meep, with all the talk about AL adding 1 pt of compression, etc., I really thought someone would say, "hey, with good quench, iron heads can take *** psi all day long." Ah well, shows what I know lol. When I have the block machined and ready I'll be back with enough specifics to run up the flag pole and give you guys more of a stationary target.

 

[Garys1969RR]

So many things to consider here. C Ratio, quench, cranking PSI, Intake closing point, head airflow, fuel choice. In the end, good cyl head airflow will get you the best results. Go easy on the C/R, I'm sure it will run great!

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And good quench isn't a cure all. It just helps the compressed mixture to burn more evenly and LESSENS the tendency to ping.

 

[Meep-Meep]

Quench is important to promote swirl in the chamber and it's effectiveness might be measured on how efficient the chamber becomes. A fast burn efficient chamber will require less total advance, so one can say if the quench is doing it's job then you can get by with less timing. My .035" quench 440 still seems to like 36 degrees but I can (and should) try less to see if I get an improvement in power. The other variables are the octane vs. compression ratio vs. cylinder pressure. At some point you feel like you are chasing your tail.

 

[IQ52]

IQ, that's exactly what I'm sayin - tell me where the safe zone is. That way, when I decide on the cam, I can be sure it keeps me where I need to be. The build is wide open; I have a std bore 440 block, the oem forged crank and happen to have 906's and 915's to play with.

I've seen you recommend staying below 175psi, and I see Greg and others have has success in the 160's with aluminum heads, but how does that compute with iron heads with or without quench?

Btw, I do thank you for sharing all your hard work, I've been following it here and on FABO. I'm hoping to learn from your work and Greg's odyssey and stay in the comfort zone.

Each individual engine is an experiment of one. If you don't have the time or money to experiment you go with something that somebody else has already proven safe. Or take your chances.