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Thicker head gaskets/ less compression...

Kern Dog

Life is full of turns. Build your car to handle.
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Hello, first time in the racers forum. Hope that someone can offer a few suggestions.

I've posted numerous times in the other forums here about the detonation issues I've had with the 440/493 in my Charger. I think I've found a fix, but I still have a few questions.

The engine is a .030 over 440 with a 4.15 crank. Pistons are flat tops, .017 in the hole, currently have a .039 head gasket. 84 cc Edelbrock performer RPM heads UNported. The compression ratio specs out at 10.73 to one. MP '509 cam installed straight up, between 185-193 cranking compression.
The quench distance is at .056 and many here have agreed that as it is, I don't have much quench happening at that range. I want to switch to a bigger cam and think I have found one that should help, as its intake closing is later that my '509 by at least 4 degrees. The Comp Cam XE294H will have 250/256 degrees of duration @ .050 with .553/.558 lift using my 1.6 rocker arms . 110 LSA.
The question here is the head gaskets. Several sources for a .051 exist. I'd run a .060 Cometic but at nearly $300 a pair, that is pretty steep. The .051 gaskets have different bore sizes. The smallest I've seen is a 4.410 like the common Fel Pro ones I have now. I've seen other .051 gaskets with a 4.590 bore size. I punched the two bore sizes into a compression calculator and found this:
With .039 gasket: 10.73 compression
With .051 gasket, 4.410 bore, 10.45 compression
With .051 gasket, 4.590 bore, 10.36 compression.
Using a standard 440 block and the Edelbrock heads, is it a problem to use the gasket with the larger bore size?
Thanks, Greg
 
going past .060 for quench distance is the breaking point. .056 is not bad. with some carbon build-up you'd be in the .040's. a .040 quench distance just runs cleaner. going to a thicker head gasket will probably make things worse. i did the thicker head gasket thing many years ago trying to cure detonation, things didn't get any better.
 
In 2006 I ran .060 Cometics with a Comp XE285 cam. Car ran great with 91 octane in spring weather of 75-90 degrees. It wiped a lobe befre the hot weather set in.
I'd just get another pair of Cometics but they are over $300 a set!
 
IMHFO the camshaft change with more overlap C/L or LSA like 112*- even 114* would be the best thing to do 1st {depends on what 509 MP purple shaft cam you have 108* C/L or with 114* revised C/L}, to bleed off some compression & make better flow too boot, especially on a mostly street/occasional strip combo, before you try the thicker head gaskets & lose the proper 0.040" quench area, that creates a better burn... Personally I wouldn't run a gasket 4.590", with that big of a bore on a 4.350" bore engine, the 4.410" or closer to 4.350" would be better, with the larger bore gasket it could make some weird spark/combustion in the wrong areas, causing even more detonation possibly or lifting the head & blowing head gaskets possibly... I always try to use a bore in the head gasket pretty close to the bore in the block, so you don't get ignition/combustion or hot spots or sharp edges, that can & will cause detonation, under the head, that's not in the combustion chamber area... if that makes any sense... what kind of ignition ?? & total timing does the combo have ??, where does the mechanical advance come in ??, can you make it come in latter ??, have you modified the distributor at all ??, & if so what have you done in that area ??, are you still running a vacuum advance, if so if it's an adjustable unit turn the adjuster all the way in, or disconnect it all together & run between 32*-36* total {depending on your combo} at like 3000-3500rpm... our 91 octane here in Calif. is crap too... lean conditions can cause allot of detonation problems too... what carburetor are you using & is the carburetor tuned properly ??... that's my $0.02 cents... where's Jim LaRoy/IQ52 when we need him ??, he's the best guy to ask, that I know on here anyway...

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Mopar Performance sells a 0.040"-0.042" w/4.380" bore composite gasket too... P4349559 or P4876070 I'm not sure if they are sold in complete sets or not, or if you can get the head gasket only or not... I don't remember, sorry
 
I am the guy that has been posting here along with several other sites. I promise that once I get this running right, I'll quit posting about my problems everywhere.
Maybe I am just slow to catch on. Since I have had so little practical experience with an engine of this caliber, I don't know who to trust. I've built several engines in the past, but this one has the highest compression, the most cubic inches, the biggerst carb, headers and pretty much everything. I've been told everything from use a thicker head gasket to Use a THINNER head gasket. I've read that a bigger cam would help. One guy at a reputable shop tried to push me into a thicker head gasket and a SMALLER cam! A friend in my car club is a firm believer of the MSD ignition as opposed to the Mopar Perfomance setup I have now. He thinks that the timing curve in the MP distributors is too fast and aggressive and that the MSD stuff is easier to tune.
Dwayne Porter suggested I pull the engine, deck the block to achieve a zero deck piston, have the valve sides of the pistons milled .040 and screw it back together. I really don't want to pull the engine anytime soon.
To recap:
440 block, .030 over
Ross Flat top pistons, 6 cc valve reliefs, .017 in the hole.
Fel Pro head gasket, .039 thick.
4.15 stroke, 6.76 rods. 185-192 cranking compression.
MP 292/509 cam 108 CL, installed straight up with 1.6 ratio adjustable rocker arms, 3/8" pushrods.
The calculated compression is 10.73. I am limited to less than 31 degrees of spark lead on 91 octane due to detonation. I have an Edelbrock Performer RPM intake, an 850 VS carb with 85/92 jets and a 3.5 PV, 2" TTI headers with 2 1/2 exhaust.
 
I thought the 1.6 rockers helped quell the problem or is it still pinging some?
 
It has 110 and 91 gas in it now, I'd have to run it down near empty and add 91 exclusively to know for sure if it rattles.
The rocker arm change made very little difference in power. It is because of this I figured the detonation may return with pump gas. I would happily forego a gasket change if a better cam makes the difference. RustyRatRod offered to help me choose a cam. He is against using another hydraulic. I am against a roller due to the cost. I may consider a flat tappet solid with the EDM type lifters. If changing the cam helps, I'd leave the heads on with the .039 gaskets!
 
The thicker gasket might work but it's a crap shot at best IMHFO anyway... On my street engine I have a 383 @ 0.040" over/4.290" bore/479ci, 6bbl MP Manifold mildly worked, with Quickfuel & Promaxx components jetted/tuned properly for my combo, 1350+cfm & a 4.15" stroker with older 11:1 compression pistons {Zero Deck}, 0.039" FelPro composite gaskets for aluminum heads w/4.410" bore {I wish was smaller}, a pretty mild camshaft now, an older custom grind 0.520"int/0.542"exh lift {good for the street}, Crane Hydraulic Roller, with 1.6: Crane roller rockers, same Eddy 84 cc heads but mildly ported, w/proper springs etc., it has a profile 107* atdc on the intake {276*/214* @ 0.050" duration} @ max lift & 117* btdc on the exhaust {284*/222* @ 0.050" duration} @ max lift 1400-6200rpm, can go a little higher in RPM but doesn't make any better power above that level... Chrome CEI box & MP CEI Distributor, heaviest springs & lightest mechanical weights, I could find/get, to slow down the advance some {don't remember where I got them, had them sitting around, for years, MR. Gasket I think}, full advance including with the adjustable vacuum adv. turned all the way in & still working, 18* initial timing {cam installed straight up 0*'s} 34* total advance @ 3300rpm, a Blaster 2 coil, ultra-low ohm @ 40-50 ohm per ft. Taylor wires... Stepped 1-3/4 to 1-7/8 into Flowmaster scavenger 4-2-1 collectors, thru a 3" mandrel bent, full Flowmaster Delta 50 Series mufflers & exhaust with a H-Pipe & out the rear... this same type combo with more cam, smaller combustion chambers & more porting, lighter car, same intake & carbs, 4pt roll bar, sub-frame connectors, with old M/T Drag radials & CalTracs went 9.77 @ 135 in my last 68 RR 3520#'s {without me in it, add 250#}, it isn't the most powerful combo ever NOW, mostly because of the pretty mild camshaft, allot less port work... but is trouble free, never detonates, never gets hot {cross my fingers}, runs great on our lousy 91 octane pump gas we have out here... IMHFO runs like a raped ape for a street car, especially with 3.23:1 gears right now, will be 3.73:1 or 3.90:1 soon after I finally paint the car & finish everything else, that I still need to install, that's sitting on my shelves... Sorry I don't have the original cam card, just some old notes...

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A hotter ignition, especially with a longer dwell/spark like an MSD & properly tuned ignition & properly jetted carb {I'm not a big fan of the Eddy Carbs}, all that could possibly help... maybe even a $350-$400 Methanol/Water Injection system would help also...

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It has 110 and 91 gas in it now, I'd have to run it down near empty and add 91 exclusively to know for sure if it rattles.
The rocker arm change made very little difference in power. It is because of this I figured the detonation may return with pump gas. I would happily forego a gasket change if a better cam makes the difference. RustyRatRod offered to help me choose a cam. He is against using another hydraulic. I am against a roller due to the cost. I may consider a flat tappet solid with the EDM type lifters. If changing the cam helps, I'd leave the heads on with the .039 gaskets!

No offence to Rusty at all... Cost !!, how much trouble & money have we spent already ??... I'm personally a big proponent of Roller anything, solid or even Hydraulic...LOL... It's a small amount of $$$ compared to the rest of the build & they are by far "the best type camshaft you can use"... opinions will vary vastly I'm sure... they ain't cheap either... but I would still call some camshaft mfgr.s/experts, get some other opinions... a good solid lifter cam/combo isn't a bad idea either, just a cheap alternative to the Roller, just keep on top of the adjustments don't use a 106*-108* for the street & maybe a split profile cam, intake & different longer exhaust duration, will help some too, if you need to bleed off some compression...

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I'm not a camshaft expert !!, I just know what works for my specific combo...
 
Thank you Budnicks. You must be paid by the word around here!
 
By the word, yep thats my Bud(dy)nicks. I'm around Budnicks, it just seems I've been drowned out by all the "white noise". Oh crap, I'll probably be accused of being racist now.
 
RustyRatRod suggested a solid flat tappet cam from Lunati. It sounds interesting:
PN # 30210912.
316/326
261/271 @ .050
540/563 lift w/1.5, 576/600 w/ my 1.6 rockers minus .022 lash for a net of 554/578.
The guy at Lunati thought it would be too much. I told him this isn't a 383 or 440 but a 493. It didn't seem to make a difference to him. He suggested the next step down to a 293/303 PN 30210917.
Specs:
254/264 @ .050 552/570 ( 568/588 with 1.6 after deducting .022 lash)
The milder cam doesn't seem a whole lot more than what I currently have. Rusty's choice seems like it could really wake up this car!
 
By the word, yep thats my Bud(dy)nicks. I'm around Budnicks, it just seems I've been drowned out by all the "white noise". Oh crap, I'll probably be accused of being racist now.

Good to see & hear from you again... Jim/IQ52 what would you suggest to do/use & why ??... just curious, there's not very many other people, I would actually ask or trust, in their suggestions &/or selections, let alone their trusted opinion anymore...LOL...

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Thank you Budnicks. You must be paid by the word around here!

Sheesh damn I wish I was.... he he ha ha, I just have a hard time getting my point/opinions & thoughts across, with out writing a damn novel...LOL... I always seem to have to add something, before I finish, that I think is relevant... trying to pass on knowledge, I've experienced or good information, not the typical internet dribble...
 
Budnicks, your words are always appreciated from my point of view.
 
Budnicks, your words are always appreciated from my point of view.

Thanks, That's very kind... I try to help when I can, kind of long winded sometimes too...LOL...
 
I'll preface this with I don't know ****, but I know who does.

Gregory you've had RustyRatRod, Budnicks, IQ52, and I'm pretty certain Meep-Meep weighed in .. I don't know who all else, oh yeah I think Supershafts and maybe Cranky too. You've got good council so I'd focus on what these guys are telling you, pick one if they are willing to answer all questions and run with what one of them tells you. There is more than one way to skin a rabbit .. they're all experts and may have slightly different suggestions on parts, but overall they're pretty consistently telling you the same thing. Pick one and do what they say and don't try and mix and match the advice. They will suggest a package approach based on what you have and what you need that will work together, like I said more than one way to do things.

I can't speak to what every other tom-dick-and-and-harry are telling you around the interwebs but I'd quit posting new threads and pick one expert willing to guide you and go.

These guys have been there and done it. They do know their ****.
 
Tallhair:
Your screen name could have been my nickname several years ago. I used to style my hair tall.
I did and do appreciate all the advice that has been offered. The detonation has kept me from fully enjoying the car, which is the main reason that I've been so diligent with all of these posts. The trouble I have had online is that while many members have suggested a cam replacement, only ONE guy had a specific cam to suggest. RustyRatRod came up with a suggestion that met the criteria. You see, I read multiple posts here, talked to 2 guys at Comp Cams, 2 guys at Mancini Racing, a guy at Hensley Performance and Dwayne Porter. I couldn't pin any one of them down on a specific cam to choose. Maybe they were all afraid of being blamed if I wasn't happy with the cam?? The guys here and on Fabo did suggest to choose a cam with a later intake closing, some said a cam with 260 degrees or more @ .050, etc. I'm sure that they all meant well. I figured that my engine build wasn't some custom job-there are several hundred if not thousand of them out there. I wanted to know what EXACT
cam they had or what they had tried.
The cam and lifters are in transit. They may get here tomorrow or Friday. I just made a valvespring installer/removal tool today and plan to use it once all the parts arrive.
Thanks, Greg
 
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