Compression ratio for 440 rebuild, advice wanted

[C500]

The engine builder is putting the engine together, and I'm after some advice from the experts on compression ratio to make sure he's going in the right direction.

440, +30 thou block (4.35 bore, 3.75 stroke) deck surfaced
CAM: Crower Hydraulic (271HDP) Flat tappet, Advertised Duration 271/284, Lift .486/.496 Part 32242
HEADS: Stock factory cast iron 906 open chamber heads, measured at 82cc
PISTONS: JE / SRP Flat top, Forged aluminium, 2.062" compression distance (piston head volume 6cc)
Cast iron HP exhaust manifold
Edelbrock CH4B dual plan intake.
Crank grind -10 thou

Gasket thickness here will depend on the compression ration, but looking like 10.1:1. Engine builder says this is too much for this setup, and should be using a thicker gasket to bring the CR down to around 9.3:1

Any thoughts on these ratios and suggested gasket thickness?

[BSB67]

I like your build.

I agree with your engine builder, unless you are at 5000 ft

[C500]

I like your build.

I agree with your engine builder, unless you are at 5000 ft

Thanks, appreciate it. 

[BSB67]

How exactly did the 906 heads get down to 82 cc?

It is always easy to spend someone else's money, but you are just a set of aluminum heads away from a very nice set up.

[b5blue]

Correct, consider a set of Sidewinder Aluminum heads at this point. My build with 346 heads and similar compression using HP manifolds and CH4B intake had me chasing ping. Sidewinders resolved the ping and removed 50LB dead weight. Added better flow overall for increased performance/efficiency so I'm very happy with outcome. Offset costs of rehab heads/whatnot and gain per buck over long term pretty reasonable. Good Luck!  

[C500]

How exactly did the 906 heads get down to 82 cc?

It is always easy to spend someone else's money, but you are just a set of aluminum heads away from a very nice set up.

That's a good question, the engine builder asked me the same thing. A previous owner would know the answer. What heads would you recommend with this setup, and I guess ally heads would need better exhaust manifolds too?

[C500]

Correct, consider a set of Sidewinder Aluminum heads at this point. My build with 346 heads and similar compression using HP manifolds and CH4B intake had me chasing ping. Sidewinders resolved the ping and removed 50LB dead weight. Added better flow overall for increased performance/efficiency so I'm very happy with outcome. Offset costs of rehab heads/whatnot and gain per buck over long term pretty reasonable. Good Luck!  

 

[BSB67]

So the heads were likely cut a bunch.  That means that intake surface of the head needed to be cut to get it to fit.  If you stay with the 906 heads, you should at least do a trial fit.    

People on this forum and Moparts say good things about Sidewinder heads from Todd Marsh.  His heads sound like a good value.

[BSB67]

................and I guess ally heads would need better exhaust manifolds too?

No

[C500]

So the heads were likely cut a bunch.  That means that intake surface of the head needed to be cut to get it to fit.  If you stay with the 906 heads, you should at least do a trial fit.    

People on this forum and Moparts say good things about Sidewinder heads from Todd Marsh.  His heads sound like a good value.

Thanks again 

[b5blue]

  I'm running a set of 69 HP exhaust manifolds with my Sidewinders with close to stock exhaust. Yea if the 906's were shaved down bunches and you've any valve recession from repeated valve jobs you have lost ground from ideal already.  Being el'cheapo my heads were assembled but box stock. I cleaned up a few minor burrs from machining and a bit of flash inside 2 of the coolant passages and they were good to go. (File and Dremel tool, about 1/2 hr. of farting around.)
  Mine is a daily driver, just added A/C and not raced ever. Plenty of power and no issues.   

[firefighter3931]

I like your build.

I agree with your engine builder, unless you are at 5000 ft

Thanks, appreciate it. 

Good advice.....I agree with your engine builder and Russ (BSB67) 

That's a very nice street cam but it does build some cylinder pressure. We installed that cam in Denis's (66Chargertoy) 440 that was very similarly built to what you are proposing. It had some detonation issues which became worse once he installed HP manifolds and removed the headers. The HP manifolds are a big heat sink and will aggravate the detonation problem. Header tubes are better at wicking heat away from the cylinder heads. Denis had a set of open Chamber 346's on the engine and the timing was dialed in perfectly but retarded to 32* total. We tuned the A/F ratio with my Wideband setup as well and it was spot on. Even at that it would sometimes ping on 94 pump premium. 

After some discussion he decided to install a set of closed Chamber aluminum Stealth heads. Huge difference ! He has even driven the car using 87 octane "regular" gas with NO detonation. We reset the timing to 35* total with 16* base timing. Throttle response is fantastic and he's seen 15mpg on a hwy cruise. The engine runs cooler as well. Overall it was a big improvement vs the old factory iron heads !


I would strongly consider a set of aluminum heads for this build....in the end you'll be much happier 



Ron 

[Challenger340]

Pretty much what has already been stated,
* 906 heads are typically 88 to 90 CC's, unless they have been milled a bunch to get down at 82 CC's, best check/verify everything first if Iron Heads are the plan. Cast Iron Heads with that Cam should be limited down 9.5 C.R Maximum, or you will be tuning around some detonation.

* IMO, BEST option are the Stealth Heads, which when painted are IDENTICAL outwardly to the production heads if you are seeking that "factory" look, with the added benefit of being Aluminum which can easily run 10 + Compression with no detonation issues.
This is no slag on the Sidewinder heads(good heads), but they are square cut/flat on the ends and stick out like a sore thumb as non-factory pieces.

[b5blue]

Yea the Sidewinders stick out enough that I had to grind down a long bolt to the power steering for clearance.

[C500]

 I'm running a set of 69 HP exhaust manifolds with my Sidewinders with close to stock exhaust. Yea if the 906's were shaved down bunches and you've any valve recession from repeated valve jobs you have lost ground from ideal already.   Being el'cheapo my heads were assembled but box stock. I cleaned up a few minor burrs from machining and a bit of flash inside 2 of the coolant passages and they were good to go. (File and Dremel tool, about 1/2 hr. of farting around.)
 Mine is a daily driver, just added A/C and not raced ever. Plenty of power and no issues.    

Just had a good look at the Sidewinders... pretty impressive. I'm trying to keep everything looking as original as possible under the hood which is why I was planning on keeping the 906 heads in place, so the sidewinders unfortunately won't cut it.

I like your build.

I agree with your engine builder, unless you are at 5000 ft

Thanks, appreciate it.  

Good advice.....I agree with your engine builder and Russ (BSB67)  

That's a very nice street cam but it does build some cylinder pressure. We installed that cam in Denis's (66Chargertoy) 440 that was very similarly built to what you are proposing. It had some detonation issues which became worse once he installed HP manifolds and removed the headers. The HP manifolds are a big heat sink and will aggravate the detonation problem. Header tubes are better at wicking heat away from the cylinder heads. Denis had a set of open Chamber 346's on the engine and the timing was dialed in perfectly but retarded to 32* total. We tuned the A/F ratio with my Wideband setup as well and it was spot on. Even at that it would sometimes ping on 94 pump premium.  

After some discussion he decided to install a set of closed Chamber aluminum Stealth heads. Huge difference ! He has even driven the car using 87 octane "regular" gas with NO detonation. We reset the timing to 35* total with 16* base timing. Throttle response is fantastic and he's seen 15mpg on a hwy cruise. The engine runs cooler as well. Overall it was a big improvement vs the old factory iron heads !


I would strongly consider a set of aluminum heads for this build....in the end you'll be much happier  



Ron  

Thanks Ron, the stealth heads sound like the ideal thing for this build. I have a bunch of things to do and $$ to spend (including paint) before she's back on the road. I'll get it together with the 906 heads, and consider upgrading to a set of stealths once the dust settles and I've tried the 906's out.........ok, just been checking out the stealth heads.... these are the ones http://store.440source.com/Stealth-Aluminum-Cylinder-Head-COMPLETE-SINGLE-HEAD/productinfo/200-1055/ ? Now I'm thinking to get these in now. Looks a pretty easy bolt-on, they come pretty complete. Assuming the Cam would be set different to how it would be with the 906's? Would I need to make any other changes (settings or parts) to accommodate the stealths over the 906's?

Pretty much what has already been stated,
* 906 heads are typically 88 to 90 CC's, unless they have been milled a bunch to get down at 82 CC's, best check/verify everything first if Iron Heads are the plan. Cast Iron Heads with that Cam should be limited down 9.5 C.R Maximum, or you will be tuning around some detonation.

* IMO, BEST option are the Stealth Heads, which when painted are IDENTICAL outwardly to the production heads if you are seeking that "factory" look, with the added benefit of being Aluminum which can easily run 10 + Compression with no detonation issues.
This is no slag on the Sidewinder heads(good heads), but they are square cut/flat on the ends and stick out like a sore thumb as non-factory pieces.

Yeah, someone has milled them quite a bit, you guys got me keen on the stealths now   , really appreciate everyones posts  

[Brass]

I would ditch the iron heads, get the stealths or sidewinders, and dial up the compression for aluminum heads.  

[firefighter3931]

Good advice.....I agree with your engine builder and Russ (BSB67) 

That's a very nice street cam but it does build some cylinder pressure. We installed that cam in Denis's (66Chargertoy) 440 that was very similarly built to what you are proposing. It had some detonation issues which became worse once he installed HP manifolds and removed the headers. The HP manifolds are a big heat sink and will aggravate the detonation problem. Header tubes are better at wicking heat away from the cylinder heads. Denis had a set of open Chamber 346's on the engine and the timing was dialed in perfectly but retarded to 32* total. We tuned the A/F ratio with my Wideband setup as well and it was spot on. Even at that it would sometimes ping on 94 pump premium. 

After some discussion he decided to install a set of closed Chamber aluminum Stealth heads. Huge difference ! He has even driven the car using 87 octane "regular" gas with NO detonation. We reset the timing to 35* total with 16* base timing. Throttle response is fantastic and he's seen 15mpg on a hwy cruise. The engine runs cooler as well. Overall it was a big improvement vs the old factory iron heads !


I would strongly consider a set of aluminum heads for this build....in the end you'll be much happier 



Ron 

Thanks Ron, the stealth heads sound like the ideal thing for this build. I have a bunch of things to do and $$ to spend (including paint) before she's back on the road. I'll get it together with the 906 heads, and consider upgrading to a set of stealths once the dust settles and I've tried the 906's out.........ok, just been checking out the stealth heads.... these are the ones http://store.440source.com/Stealth-Aluminum-Cylinder-Head-COMPLETE-SINGLE-HEAD/productinfo/200-1055/ ? Now I'm thinking to get these in now. Looks a pretty easy bolt-on, they come pretty complete. Assuming the Cam would be set different to how it would be with the 906's? Would I need to make any other changes (settings or parts) to accommodate the stealths over the 906's?

The Stealth's look exactly like the stock heads.....even the spark plugs are straight like the factory castings. 

Denis has the same cam as you and all he did was upgrade the retainers/locks to the Comp stuff. He also had a performance 3 angle valve job done. The std stealth valvesprings are fine with HDP271 cam.

Overall the upgrade was excellent ; noticeably more power, better throttle response, less weight on the nose of the car and a cooler engine bay. Definitely a win/win with no downsides. 



Ron

[C500]

Looking at getting a set of stealths, and a valve job done. Anyone keen to hazard a guess what sort of horsepower this build would make?

Specs again:
440, +30 thou block
CAM: Crower Hydraulic (271HDP) Flat tappet, Advertised Duration 271/284, Lift .486/.496
HEADS: Stealths, 3 angle valve job
PISTONS: JE / SRP Flat top, Forged aluminium, 2.062" ch
Cast iron HP exhaust manifold
Edelbrock CH4B dual plan intake.
Carb: Proform 750 Mechanical secondary
Crank grind -10 thou
Johnson Hylift Lifters
Balanced rotating assemble, block stripped, tanked, crack tested and sonic tested, deck surfaced.

[c00nhunterjoe]

The intake and exhaust manifolds will hurt max power with that cam choice. If you are dead set on using exhaust manifolds, then consider a custom grind cam. Either way it will make good torque down low and i will throw out 470hp 495tq

[C500]

The intake and exhaust manifolds will hurt max power with that cam choice. If you are dead set on using exhaust manifolds, then consider a custom grind cam. Either way it will make good torque down low and i will throw out 470hp 495tq

Thanks coon hunter! I may upgrade the cam later on, but for now will be good for some cruising and lighting up the tires. The HDP cam I have is designed to compensate for the poor flowing factory exhaust port by hanging the exhaust valve open longer to allow the cylinder to clean out the spent gases. The wide 112* LSA reduces overlap which is extremely important with restrictive manifold exhaust (thanks Ron  )
The pistons have large valve pockets too..... thinking of potential future changes 
The intake is an aluminium dual plane. 

[C500]

Gents, first of all... thanks for the advice from everyone on this build    

secondly, I have just ordered a set of stealth heads  Should arrive in a few days, and then off for a valve job 

The old 906 heads were almost ready to go  Can't wait to get er done with the stealths, the excitement levels are nearing fever pitch....

Dunk

[68CoronetRT]

If you do the Stealths, please please please replace the springs/locks/retainers before running them. I did the locks/retainers before install and then broke a spring less than 2,000 miles later.

[C500]

If you do the Stealths, please please please replace the springs/locks/retainers before running them. I did the locks/retainers before install and then broke a spring less than 2,000 miles later.

I have 10° comp cams retainers and locks, didn't know the springs should be replaced too   I bought a set of comp cams 911 springs that I was going to use on the 906 heads... assuming these springs will also be a good choice with the stealth heads   https://www.summitracing.com/int/parts/cca-911-16
Thanks 68coronetRT

[68CoronetRT]

I believe those were the comp springs I was looking at. I ended up with the Crower springs that were a little closer to my seat pressure I needed for my cam. My cam is a little larger than yours, but not much.

I was very disappointed when I talked to 440source about my situation. But a quick in car valve spring job(2 days) and all was good.

Oh and be ready to drill the intake push rod holes quite a bit  . A good carbite bit will do the trick.

[firefighter3931]

If you do the Stealths, please please please replace the springs/locks/retainers before running them. I did the locks/retainers before install and then broke a spring less than 2,000 miles later.

I have 10° comp cams retainers and locks, didn't know the springs should be replaced too   I bought a set of comp cams 911 springs that I was going to use on the 906 heads... assuming these springs will also be a good choice with the stealth heads   https://www.summitracing.com/int/parts/cca-911-16
Thanks 68coronetRT

Sure, the Comp 911's will work fine on the Stealth heads with the 10* retainers/locks. The Comp springs are superior to the stock "Stealth" valvesprings so if you have them you might as well install them 

Those 911's are fine with the Crower 271 cam....no worries there 



Ron

[C500]

If you do the Stealths, please please please replace the springs/locks/retainers before running them. I did the locks/retainers before install and then broke a spring less than 2,000 miles later.

I have 10° comp cams retainers and locks, didn't know the springs should be replaced too   I bought a set of comp cams 911 springs that I was going to use on the 906 heads... assuming these springs will also be a good choice with the stealth heads   https://www.summitracing.com/int/parts/cca-911-16
Thanks 68coronetRT

Sure, the Comp 911's will work fine on the Stealth heads with the 10* retainers/locks. The Comp springs are superior to the stock "Stealth" valvesprings so if you have them you might as well install them 

Those 911's are fine with the Crower 271 cam....no worries there 



Ron