440 Compression Ratio Advice

Posted By: bobs66440

440 Compression Ratio Advice - 01/05/12 02:15 AM

I am building a stockish 440. The .030 over flat top pistons are .085 in the hole. The cam I'm using calls for minimum 9.5:1 compression. I'm on a budget and having a difficult time finding affordable heads to get me there. I was going to order the reman Aerohead 915s with 78cc chambers which would get me around 9.6:1 with .020 steel shim gaskets. Perfect, but since I figured my budget, the price has gone up on them and with shipping, they will be almost $900 for the set. Too much in my opinion for stock cast iron heads.

My next thought was the 440 Source Stealths for about $180 more. A no-brainer right? Except the chambers on those are 80cc(+-) and I have to use the .040 composite head gaskets. That will get me 9.24:1 compression. Not far off, but under the minimum. And I really don't want to go through the added expense of tearing them apart and having them cut.

Now for the question...will this be a significant/noticeable difference?

Opinions?

Thanks!!

Posted By: 05dakota

Re: 440 Compression Ratio Advice - 01/05/12 02:36 AM

different pistons?

Posted By: lewtot184

Re: 440 Compression Ratio Advice - 01/05/12 02:41 AM

most economical solutions are mill the heads or change the cam.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 02:45 AM

Well, the bottom end is all new and all together already. Ans, as mentioned, unfortunately I'm on a budget so new pistons really aren't an option.

Posted By: torkrules

Re: 440 Compression Ratio Advice - 01/05/12 02:46 AM

Quote:

different pistons?

If you can, I would go for zero deck height and use a .040" gasket. This will give you good fuel mixing. With an aluminum head (something like a small chamber Edelbrock) and zero deck height you can run around 10.0 comp and not run into detonation problems on pump gas.

Posted By: gch

Re: 440 Compression Ratio Advice - 01/05/12 02:54 AM

Unless you can find a deal on some ported(or stock) iron heads(several for sale here)that allows you extra money to mill them for the desired compression,I would go with the stealths.I would recommend any assembled head be checked(new or used).It would'nt be that much more to mill them and correct the intake side if need be.

With aluminum you could run up to 10.5-1 for more power and be okay depending on cam size.

You have a nice shortblock that would really wake up with some good(better than stock) heads.Take a little longer and go the extra mile.Your butt-o-meter will thank you.

Posted By: BSB67

Re: 440 Compression Ratio Advice - 01/05/12 04:04 AM

This is the classic delimma of the low-buck short block. It appears that you have correctly figured it out, you have no good low cost choice. It will probably cost $2000 to make it right. Everything else will be a compromise. If you have the money for the Stealths, that is probably your most practical compromise. Some people run a shim gasket with them successfully.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 05:16 AM

Quote:

This is the classic delimma of the low-buck short block. It appears that you have correctly figured it out, you have no good low cost choice. It will probably cost $2000 to make it right. Everything else will be a compromise. If you have the money for the Stealths, that is probably your most practical compromise. Some people run a shim gasket with them successfully.

How do you think it will run with the 9.24:1 with that cam? I asked at 440 Source and he said definitely not to use the steel shim gaskets. Also that the difference in compression wouldn't be noticeable and would be ok to run as is...but I would think they advertise a minimum for a reason??

Cam Specs:
Summit SUM-6401 cam.
Which states min. 9.5:1 compression.
int .465
exh .488
adv dur. .282 int/.292exh
int. dur @ .050 .224
exh. dur @ .050 .234

Posted By: DaytonaTurbo

Re: 440 Compression Ratio Advice - 01/05/12 06:02 AM

Many on here have run aluminum heads with the steel shim gasket. They spray the gasket on both sides with permatex copper coat and you're good to go.

FWIW, the summit cam you have listed there is not that aggressive of a cam. You can easily run that cam with 9.2 compression. I ran more cam in a smogger 440 with an actual calculated 8:1 compression and it did okay. Also, the .4 of compression difference between the two sets of heads you are thinking about, will not be noticeable on your combo. My brother has a 66 charger with a 440, stock heads, same 6401 cam and probably about the same compression as you're shooting for and it runs well.

Another option is to see if someone is selling a used set of closed chambered iron heads in the for sale section here on moparts. Sometimes there are good deals to be had, however the stealth heads will flow better OOTB than those stockers.

Posted By: GTX MATT

Re: 440 Compression Ratio Advice - 01/05/12 07:10 AM

Don't worry about it, just put the cam in and run it. You won't notice the difference.

Posted By: RUNCHARGER

Re: 440 Compression Ratio Advice - 01/05/12 07:12 AM

I wouldn't get anything in a knot over a .2 or .4 point in compression.

Sheldon

Posted By: BSB67

Re: 440 Compression Ratio Advice - 01/05/12 12:09 PM

It will be okay. A cam with a little less seat timing will make it a little more responsive down low. I matters less with a 4 speed.

Posted By: torkrules

Re: 440 Compression Ratio Advice - 01/05/12 12:27 PM

Quote:

Many on here have run aluminum heads with the steel shim gasket. They spray the gasket on both sides with permatex copper coat and you're good to go.

FWIW, the summit cam you have listed there is not that aggressive of a cam. You can easily run that cam with 9.2 compression. I ran more cam in a smogger 440 with an actual calculated 8:1 compression and it did okay. Also, the .4 of compression difference between the two sets of heads you are thinking about, will not be noticeable on your combo. My brother has a 66 charger with a 440, stock heads, same 6401 cam and probably about the same compression as you're shooting for and it runs well.

Another option is to see if someone is selling a used set of closed chambered iron heads in the for sale section here on moparts. Sometimes there are good deals to be had, however the stealth heads will flow better OOTB than those stockers.

You can always use Cometics. They make a .027 thick gasket if needed.

Posted By: Mr.Yuck

Re: 440 Compression Ratio Advice - 01/05/12 01:08 PM

Quote:

Quote:

This is the classic delimma of the low-buck short block. It appears that you have correctly figured it out, you have no good low cost choice. It will probably cost $2000 to make it right. Everything else will be a compromise. If you have the money for the Stealths, that is probably your most practical compromise. Some people run a shim gasket with them successfully.

How do you think it will run with the 9.24:1 with that cam? I asked at 440 Source and he said definitely not to use the steel shim gaskets. Also that the difference in compression wouldn't be noticeable and would be ok to run as is...but I would think they advertise a minimum for a reason??

Cam Specs:
Summit SUM-6401 cam.
Which states min. 9.5:1 compression.
int .465
exh .488
adv dur. .282 int/.292exh
int. dur @ .050 .224
exh. dur @ .050 .234

I ran 12.90's @ 104 with the same cam in a MAYBE 9:1(stock speed pro replacements) 440, RPM intake Holley 750DP, non-ported 906 heads, 1 3/4 headers, same 175k convert, and 3.91 all packed into a nice light (3850) 67 coronet. I wouldn't worry too much about it. If you go w/ the stealths you always have room to grow.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 01:21 PM

Ok guys, Thanks for the replies! Sounds like the Stealths are the way to go. I appreciate it!

Quote:

Quote:

Many on here have run aluminum heads with the steel shim gasket. They spray the gasket on both sides with permatex copper coat and you're good to go.

FWIW, the summit cam you have listed there is not that aggressive of a cam. You can easily run that cam with 9.2 compression. I ran more cam in a smogger 440 with an actual calculated 8:1 compression and it did okay. Also, the .4 of compression difference between the two sets of heads you are thinking about, will not be noticeable on your combo. My brother has a 66 charger with a 440, stock heads, same 6401 cam and probably about the same compression as you're shooting for and it runs well.

Another option is to see if someone is selling a used set of closed chambered iron heads in the for sale section here on moparts. Sometimes there are good deals to be had, however the stealth heads will flow better OOTB than those stockers.

You can always use Cometics. They make a .027 thick gasket if needed.

I was on their site and all I see is .040 gaskets. Are the .027 ones custom?

Posted By: JohnRR

Re: 440 Compression Ratio Advice - 01/05/12 03:44 PM

Quote:

Ok guys, Thanks for the replies! Sounds like the Stealths are the way to go. I appreciate it!

Quote:

Quote:

Many on here have run aluminum heads with the steel shim gasket. They spray the gasket on both sides with permatex copper coat and you're good to go.

FWIW, the summit cam you have listed there is not that aggressive of a cam. You can easily run that cam with 9.2 compression. I ran more cam in a smogger 440 with an actual calculated 8:1 compression and it did okay. Also, the .4 of compression difference between the two sets of heads you are thinking about, will not be noticeable on your combo. My brother has a 66 charger with a 440, stock heads, same 6401 cam and probably about the same compression as you're shooting for and it runs well.

Another option is to see if someone is selling a used set of closed chambered iron heads in the for sale section here on moparts. Sometimes there are good deals to be had, however the stealth heads will flow better OOTB than those stockers.

You can always use Cometics. They make a .027 thick gasket if needed.

I was on their site and all I see is .040 gaskets. Are the .027 ones custom?

The cometics are very expensive, run the .040 gasket that the source recommends.

Also plan on having the heads disassembled and the valve job checked and also check the retainers and locks. Have the chambers CC'sd also, they may be a little bigger than advertised.

I ran that cam ain an advertised 9.2 compression 383that had 130k miles on it , probably more like 8.0 , and it ran well.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 05:05 PM

Are there quality issues with the 440 Source heads?

Posted By: JohnRR

Re: 440 Compression Ratio Advice - 01/05/12 05:16 PM

Quote:

Are there quality issues with the 440 Source heads?

Can't say either way but EVERY thing you buy needs to be checked , NOTHING is ready to run out of the box.

Posted By: Mr.Yuck

Re: 440 Compression Ratio Advice - 01/05/12 05:24 PM

Hey Bob do you have a set of decent iron heads now? Have you checked Moparts for a set? I'm guessing you can get a good set of iron heads for around $350-500 and they would be fine for what you have.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 06:38 PM

I have been watching the ads and there's really not too much...that's affordable anyway.
I have a set of 906 heads that need to be completely gone through but they are, what, like 85-90cc or so? That will put my compression way down in the basement. Then I would have to go with another cam or pistons. The Aeroheads were really the perfect solution because they are 78cc, but the price with shipping ended up in the same price range as aluminum heads.

I priced out rebuilding my heads locally and it's a little cheaper, but I still have the compression issue.

The engine in the car now is a stock (I believe) '66 440 from a Imperial or similar. I'm not sure what heads are on that but they are in worse condition than my 906s...I suppose I could pull the valve cover and at least see what they are....and keep looking in the ads.

BTW Mr. Yuck, I saw your car in Car Craft (I think it was anyway). Very cool!

Posted By: lewtot184

Re: 440 Compression Ratio Advice - 01/05/12 07:36 PM

after reviewing your cam selection i don't think you have a real compression ratio problem. that cam is basically the old crane power-max 278. it has 5 degrees of advance ground into it and closes the intake valve within a degree or two of a stock magnum cam. your compression ratio with those pistons, 88cc head and .020 shim gasket will be around 9:1. mill .030 off the heads and you have 9.5:1. this should get the cranking cylinder pressure to around 160-170psi. i have a 440 that uses more cam than what you have at 9.3:1 compression ratio (using quench dome pistons) and 160psi cranking pressure and what it does to the rear tires with a 3.23 gear should be considered an "act of violence". the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

Posted By: JohnRR

Re: 440 Compression Ratio Advice - 01/05/12 08:07 PM

Quote:

the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.

Posted By: JohnRR

Re: 440 Compression Ratio Advice - 01/05/12 08:16 PM

Bob , a rebuilt set of 915 were just posted in the bb for sale forum , they are in rochester NY ... are you there yet ??

Posted By: lewtot184

Re: 440 Compression Ratio Advice - 01/05/12 08:43 PM

Quote:

Quote:

the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.

john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.

Posted By: Mr.Yuck

Re: 440 Compression Ratio Advice - 01/05/12 08:48 PM

Quote:

Quote:

Quote:

the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.

john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.

I would not even worry about "quench" on an engine like this

Posted By: JohnRR

Re: 440 Compression Ratio Advice - 01/05/12 10:03 PM

Quote:

Quote:

Quote:

the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.

john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.

I'm not saying anything other than an 8.93 compression engine with no quench should be able to be tuned to run on 93 , if he is set on getting it up to 9.5 then that is a different story all together.

My experience with the big summit cam and open chamber 906's with no quench was ok with super as long as I had the vac advance disconnected , I never got the chance to do much as the motor expired before early after the spring driving season started .

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/05/12 11:26 PM

Quote:

Quote:

Quote:

Quote:

the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.

With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.

john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.

I'm not saying anything other than an 8.93 compression engine with no quench should be able to be tuned to run on 93 , if he is set on getting it up to 9.5 then that is a different story all together.

My experience with the big summit cam and open chamber 906's with no quench was ok with super as long as I had the vac advance disconnected , I never got the chance to do much as the motor expired before early after the spring driving season started .

I don't mean to seem ignorant, though I'm a little confused. So, what you are saying is my set up with the stealth heads, at around 9.5:1 compression, will not be able to run on pump gas?? Or are you talking about the 906 heads?? Sorry about the dumb questions, but I'm on a steep learning curve.

Posted By: BSB67

Re: 440 Compression Ratio Advice - 01/06/12 01:18 AM

Quote:

Or are you talking about the 906 heads??

Yes, they are

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/06/12 02:31 AM

Ok thanks. So, I should be ok with the Stealths at 9.2:1?

Posted By: gch

Re: 440 Compression Ratio Advice - 01/06/12 02:42 AM

Probably get away with 89 except for the hot summer months.Don't worry about it.

Posted By: DaytonaTurbo

Re: 440 Compression Ratio Advice - 01/06/12 03:08 AM

Quote:

Ok thanks. So, I should be ok with the Stealths at 9.2:1?

Yup.

Posted By: bobs66440

Re: 440 Compression Ratio Advice - 01/06/12 02:27 PM

Thanks everyone for your help. It is appreciated!