383 Aluminum Head Dilemma

[Banzaiii67]

I believe you need to use a multi layer head gsk such as Cometic with an alum head. The Stealth heads are usable OOTB if you don't go over .510 lift. More lift I would change the locks and keepers. Also some pocket clean up and blending will help the flow somewhat.

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Well after reading that link above on head gaskets, it looks as if a lot of guys are using steel shim head gaskets with copper coat, or hi temp alum paint, on alum heads and getting away with it. Makes them look more attractive to me, as I like the .020 steel shim gasket. Never had any problem with them on an iron head. They are about $25 a pair. We used the 1135 Mr Gsk steel shim gasket on a 383, and no probs. C/R of 13 to 1.

From the small bit of research I've seen on the web, it appears you definitely can use a .027 Cometic MLS Gasket. A guy on moparts has one on his Charger. A bit pricey at $165. Of course they are custom built to your bore and you can reuse them. I don't know if I have enough confidence in running a prepped steel shim gasket on a aluminum head for .007

 

[Meep-Meep]

The most important thing I have found is matching the cam to the compression ratio and not go big on the overlap - at least for the street. Lower overlap cams have better vacuum and all out of the box carbs seem to work better when there is a strong vacuum signal. The single most important item that will affect the engine is the cam so look into changing that first.

 

[19polara64]

From what I've read on Cometics, the head and deck surfaces have to be prepped just right or they won't seal. No first hand experience, just what I've read when trying to sort out may compression problems.

 

[Garys1969RR]

head gaskets

From what I've read on Cometics, the head and deck surfaces have to be prepped just right or they won't seal. No first hand experience, just what I've read when trying to sort out may compression problems.

I have heard that too, about the deck surface must be real smooth to use a cometic. I feel that the steel shim is still the best way to go. More reliable, $100 less cost, tighter quench, I have never had one fail. So if they can be used with an aluminum head as many have done, by using copper coat as a sealer, why not use them? I think I will try using them with alum heads if I ever get some.

 

[Meep-Meep]

Yes, the MLS gasket requires a mirror finish or it will eventually fail. 15 RA is about right.

 

[natas33]

A 1'point increase will do. 2 is not needed. You Chevy is a bit different. In than it needs 2'points. Squeeze is squeeze. A few mag. Have all ready proven this BS

you probably right at least 1 is enough, but if you can run 2 more when going aluminum without detonating then I guess 2 more would remove all doubt cr loss isn't causing lack of power

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I have heard that too, about the deck surface must be real smooth to use a cometic. I feel that the steel shim is still the best way to go. More reliable, $100 less cost, tighter quench, I have never had one fail. So if they can be used with an aluminum head as many have done, by using copper coat as a sealer, why not use them? I think I will try using them with alum heads if I ever get some.

im thinking to try this when my heads get here. you think the steel shim raised surface wouldn't imprint a little in the aluminum possibly? then when if you remove/replace heads the new gasket went on a bit different and possibly will end up heads needs surfacing every time. maybe safer to just run an felpro as they can only imprint the aluminum around the bores not all over the head surface

ive never tried steel shims on aluminum heads so I don't know

 

[Garys1969RR]

That would be a question for IQ 52. He has a lot of experience with cyl heads. If you not concerned about C/R or quench distance, then use the Fel Pro. I like a tight squish area, so I run the thinnest head gasket I can get, as my pistons are .017" below deck. So with a .020 gasket I have .037" squish and my motor runs great! 12.58@109. A mile high elevation. 3600 lbs.

 

[Banzaiii67]

The most important thing I have found is matching the cam to the compression ratio and not go big on the overlap - at least for the street. Lower overlap cams have better vacuum and all out of the box carbs seem to work better when there is a strong vacuum signal. The single most important item that will affect the engine is the cam so look into changing that first.

While I sorta thing this might be too much cam for the compression at the moment.. One way or another I want to have over 9:1 after I take off the heads.

Seems like the budget way is too take .030 off the stock heads, put new valves in (stock size), do some pocket porting and assemble back together with a steel shim head gasket.

BTW, Mopar Muscle built a 383 with 9.2:1 compression and stuck Comp XE285HL cam in it, but it was never on the road per sehttp://www.moparmusclemagazine.com/...pgrading_the_383_magnum_avs_carb/viewall.html

 

[Meep-Meep]

While I sorta thing this might be too much cam for the compression at the moment.. One way or another I want to have over 9:1 after I take off the heads.

Seems like the budget way is too take .030 off the stock heads, put new valves in (stock size), do some pocket porting and assemble back together with a steel shim head gasket.
BTW, Mopar Muscle built a 383 with 9.2:1 compression and stuck Comp XE285HL cam in it, but it was never on the road per sehttp://www.moparmusclemagazine.com/...pgrading_the_383_magnum_avs_carb/viewall.html

Don't forget to cut the intake face of the head to compensate for the heavy cut on the surface. Otherwise the intake won't fit.

 

[Banzaiii67]

Don't forget to cut the intake face of the head to compensate for the heavy cut on the surface. Otherwise the intake won't fit.

I can't remember the rule, do you cut the intake face of the head the same amount? I seem to remember .030 was the max you could mill BB Heads without having custom pushrods

 

[IQ52]

You would mill .0123" off the intake surface for every .010" you remove from the combustion chamber side.

If your engine is making 400 HP and you take off a gasket that is .039" and replace it with a steel shim head gasket that is .020" thick you will gain approximately 6 HP. Not worth messing with trying to seal the .020" steel shim head gasket to the aluminum head.

What? You thought .4 of a point of compression gain was worth 25 HP? Nope!

 

[Mebsuta]

To me it doesn't seem that you will get much gain for the expense of aluminum heads. I'm running very well with iron heads and a small cam. The comp 274 might not be a good match for your low compression so I'd look into that first.

That's what I was thinking. 130 psi cranking compression is probably around 8:1. I have regular old 383 HP. It has about 150 psi cranking compression, and is probably 8.8:1.

 

[mopardave64]

OK, lots of excellent discussion about CR, but does Bonsaiii67 want a race car or something that's streetable? I have a built 440 (comp cams magnum 288R with .550 lift, solid roller valve train, slightly ported 906 heads, .060 over block, decked and squared) and I can't get it to run on pump gas without pre-detonation unless I retard the timing so much I end up with diminished responsiveness along with starting and idling issues. 110 octane and 37 degrees advance and this thing is an absolute beast over 3000 rpm. Doing some rough calculations, I figure the motor is probably around 10.5:1 and definitely less than 11:1 but I'm not sure how much was removed during machining. So, because I want to drive the car not race it, I'm also considering yanking the cam and going with new aluminum heads, but I'll probably just keep the 906 heads (and the stock look) and focus more on a valve train for driveability instead of horsepower. Just my 2 cents.

 

[67 B-body]

Don't forget that an aluminum head needs up to 2:1 increase in compression ratio to run the same effective CR as a cast iron head. If you had 8.8:1 before, an aluminum head at 10.8:1 wont gain you any power from a CR increase.. only gain will be from the better flow/design of the heads. You could end up slower using aluminum heads if they don't raise you up to at least 10.5:1 compression and they don't flow anything significant over your old cast heads. If i were edelbrock id be making their budget priced heads in a smaller chamber offering to suit 383/400 owners.

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I once had a late cast crank low compression 440 that came with a car I bought.. it was already bored over 0.030 and recently by the looks as the short motor looked perfect, so i milled .100 from the heads, probably over .050 from the block (cant remember but I took a lot of meat off!), and put mopar steel shim gaskets on it.. to raise the CR. I hand ported the 452's and put in a 509 hydraulic, 2" headers, torker intake, 850dp, 7AL-2, mopar race distributor, and full manual vb 727 with a 10" converter.. it hauled for a budget engine. With a good cooling system it never had any problems. Big 5 row radiator, 160 milodon water pump and high flow stat with a Moroso electric drive motor on it.

Don't be afraid to mill the factory heads .100 ..With 5 bolts per cylinder and if you don't overheat it you wont have any issues.. I think. I can only go off what I did and it worked for me at the time.

Aluminum heads if they don't get your 383 up to 10:8:1 cr, don't expect gains from the compression alone. Aluminum sucks so much heat from the chamber versus a cast iron head that they have much less efficient combustion running the same CR as a cast iron head.

Mopar themselves has the 2:1 rule.. 9:1 in a cast iron head.. run 11:1 in aluminum. People can argue this all day.... but my LS1 running near 11.3:1 CR on pump gas and over 500hp proves to me that aluminum runs WAY colder combustion than cast iron. I think Mopar was right.. and it's written right here infront of me in my 1998 Mopar parts catalogue that has somehow survived and stayed with me since 98.

I think the topic is actually the "ability" to run two more points in compression without having the pre-ignition issues found with the cast iron head. Not the necessity of running two more points of compression to be "equal" in performance.
If the point / fact were " needing two more points in comp" were being implied, that would suggest everyone who has performed a cast iron to aluminum head swap has already lost performance as a result of heat loss through the cyl head.
It is true that aluminum is very inefficient insulator against heat, but the end user can find for him/herself weather or not the lack of cyl head temp is causing an issue in combustion..... Just read your plugs!
IQ52 has done some pretty extensive testing between head manufactures including factory cast iron types..... I'm sure the proof is in the recordable pudding..

My .02 cents...

 

[IQ52]

In as far as the tests were taken, there was no decernable difference in detonation resistance between iron and aluminum heads of the SAME COMBUSTION CHAMBER SHAPE. Appearently Mopar people encounter less detonation switching to an aluminum head because of the more efficient combustion chamber you get and not the heads composition, i.e. iron vs aluminum.

 

[natas33]

In as far as the tests were taken, there was no decernable difference in detonation resistance between iron and aluminum heads of the SAME COMBUSTION CHAMBER SHAPE. Appearently Mopar people encounter less detonation switching to an aluminum head because of the more efficient combustion chamber you get and not the heads composition, i.e. iron vs aluminum.

Chamber shape plays a role.. but that an iron head with the exact chamber shape as an aluminum head has any chance of having the same detonation resistance at the same CR, I would like to try that in my car with 11:1 CR.

I'll run 11:1 CR on good pump gas in any typical closed chamber aluminum head.. for more than enough reasons than just mopar telling me. And i'll run 11:1 on an iron head with the exact same chamber in the same engine with the exact same pump gas when i want to melt stuff in my engine.

 

[IQ52]

Chamber shape plays a role.. but that an iron head with the exact chamber shape as an aluminum head has any chance of having the same detonation resistance at the same CR, I would like to try that in my car with 11:1 CR.

I'll run 11:1 CR on good pump gas in any typical closed chamber aluminum head.. for more than enough reasons than just mopar telling me. And i'll run 11:1 on an iron head with the exact same chamber in the same engine with the exact same pump gas when i want to melt stuff in my engine.

Good for you! Do you have any empirical data to back this up? Or are you just going by your gut feeling?

I say this because I have seen the cylinder head tests and have run my own 730 HP iron headed (906 heads) big block at 11.9:1 compression with 93 octane and can point you to the national magazine where it was recorded.

 

[HT413]

Regarding the 75 cc Eddie RPM heads, i just called eldelbrock and they are being manufactured, no longer on back order. The rep said summit and Jegs have em.

They also have the Estreets in 75cc now. Both Jegs and summit have them too.

75cc Estreets $1473.99 for the pair
75cc RPM's $919.99 each

http://www.edelbrock.com/automotive_new/mc/cylheads/chrysler/bb_estreet.shtml

http://www.edelbrock.com/automotive_new/mc/cylheads/chrysler/bb_perf_rpm.shtml


http://www.summitracing.com/parts/edl-60829
http://www.jegs.com/i/Edelbrock/350/60829/10002/-1

 

[johns]

Yep. Hydrocarbons burning your eyes. Running rich.

Or not enough initial timing

 

[Banzaiii67]

Btw, E-Street are $1249 from summit.

http://www.ebay.com/itm/Edelbrock-E...Parts_Accessories&hash=item5af5bca9ea&vxp=mtr


And i'm pretty sure they have angled plugs, as some have wondered.

"Spark plugs have been re-oriented to a 15-degree angle to improve combustion efficiency."

Sales Brochure Link

http://www.catalograck.com/ImgVD/EDE/50905093-E-StreetCylinderHeadsforB-RBBBMV.pdf