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valve to cyl wall clearance with alum heads

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Glenwood

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Has anyone installed aluminum heads on a stock bore 383 or 426W (4.25") without clearance issues?

I've been contemplating going to aluminum heads but I can't determine if I will have clearance issues with the cylinder walls.


Trick Flow 240 for example has a minimum bore size requirement of 4.32”. They have a large intake valve of 2.190 and an exhaust valve slightly bigger than stock at 1.76, whereas most of the other brand aluminum heads I've found have a 2.14 intake and a 1.81 ex.
I know that the max wedge blocks were notched for the large 1.88 exhaust valves. I don’t know how the cam lift values play into this tolerance, but my cam has lifts of .494I/.513E.


I’m interested in the promaxx 9440 which uses the same 2.14/1.81 valves but I’d hate to shell out a couple of grand (CAD) for heads & gaskets to find out they won’t work.
 
Glenwood said:
Has anyone installed aluminum heads on a stock bore 383 or 426W (4.25") without clearance issues?

I've been contemplating going to aluminum heads but I can't determine if I will have clearance issues with the cylinder walls.


Trick Flow 240 for example has a minimum bore size requirement of 4.32”. They have a large intake valve of 2.190 and an exhaust valve slightly bigger than stock at 1.76, whereas most of the other brand aluminum heads I've found have a 2.14 intake and a 1.81 ex.
I know that the max wedge blocks were notched for the large 1.88 exhaust valves. I don’t know how the cam lift values play into this tolerance, but my cam has lifts of .494I/.513E.


I’m interested in the promaxx 9440 which uses the same 2.14/1.81 valves but I’d hate to shell out a couple of grand (CAD) for heads & gaskets to find out they won’t work.
Click to expand...
a quality machine shop could notch the tops of the cylinders for valve clearance.
 
Valve pockets will have to be opened for the larger valves cam lifts always have to be considered
 
If you do decide to do the heads have a machine shop fly cut the pockets if your not running a gigantic cam clay the pockets roll the motor over by hand to check if they hit
 
Glenwood said:
Has anyone installed aluminum heads on a stock bore 383 or 426W (4.25") without clearance issues?

I've been contemplating going to aluminum heads but I can't determine if I will have clearance issues with the cylinder walls.


Trick Flow 240 for example has a minimum bore size requirement of 4.32”. They have a large intake valve of 2.190 and an exhaust valve slightly bigger than stock at 1.76, whereas most of the other brand aluminum heads I've found have a 2.14 intake and a 1.81 ex.
I know that the max wedge blocks were notched for the large 1.88 exhaust valves. I don’t know how the cam lift values play into this tolerance, but my cam has lifts of .494I/.513E.


I’m interested in the promaxx 9440 which uses the same 2.14/1.81 valves but I’d hate to shell out a couple of grand (CAD) for heads & gaskets to find out they won’t work.
Click to expand...

Porbly no help here, but I`ve got 2.19 intake and 1.81 exhaust valves on 4.350 BORE.
 
I'd rather not have this fresh block disassembled to be notched. If I can't swap my 906 heads to closed chamber alum heads with the larger valves, then I may look into some closed iron heads 915 or even 516s and have the larger stock sized valves installed.
Just looking for opinions and experiences. I've spent hours researching this subject but cannot find a definitive answer as to if anyone has installed aluminum heads on a stock bore of 4.25 without notching
 
Glenwood said:
I'd rather not have this fresh block disassembled to be notched. If I can't swap my 906 heads to closed chamber alum heads with the larger valves, then I may look into some closed iron heads 915 or even 516s and have the larger stock sized valves installed.
Just looking for opinions and experiences. I've spent hours researching this subject but cannot find a definitive answer as to if anyone has installed aluminum heads on a stock bore of 4.25 without notching
Click to expand...
There’s been tons of people that have the real problem is cam lift monster cams things need clearance
 
Did you call the manufacturer call them tell them all your specs and they will confirm everything for you sometimes best to go to the source then search the web
 
I sent a note to trick flow and got a reply confirming the minimum bore size, but they did not specify. I can only assume that the large intake valve is the problem since the exhaust valve is close to stock size.

I also sent a note to Promaxx, but no reply yet. I have a hard time believing that with all of the eddy/stealth heads being sold that they are only being installed on 440/400s and not on 383s (or less popular 413/426s) without additional machining being needed. At least I haven't found any threads on this matter yet.
 
Glenwood said:
I sent a note to trick flow and got a reply confirming the minimum bore size, but they did not specify. I can only assume that the large intake valve is the problem since the exhaust valve is close to stock size.

I also sent a note to Promaxx, but no reply yet. I have a hard time believing that with all of the eddy/stealth heads being sold that they are only being installed on 440/400s and not on 383s (or less popular 413/426s) without additional machining being needed. At least I haven't found any threads on this matter yet.
Click to expand...
I'm not a giant fan of Promaxx due to past issues. Give Tom Marsh at Marsh Performance a call about his Sidewinder heads. Things have a great review and are personally checked and finished machined by Tom and they cost about the same as a pair of 440source heads.
 
interesting comment on another board...

"I emailed Jason at Promaxx and he sent me some pictures and flow graphs on the Mopar SB heads. Then when I found out that the Sidewinders are the actual Promaxx castings that are built up to the customers needs, I started emailing a Sidewinder vendor. The vendor told me that the Sidewinders have the same flow as the Promaxx castings unless additional porting is required.
I attached the Promaxx 171cc flow graph for reference."
 
Glenwood said:
interesting comment on another board...

"I emailed Jason at Promaxx and he sent me some pictures and flow graphs on the Mopar SB heads. Then when I found out that the Sidewinders are the actual Promaxx castings that are built up to the customers needs, I started emailing a Sidewinder vendor. The vendor told me that the Sidewinders have the same flow as the Promaxx castings unless additional porting is required.
I attached the Promaxx 171cc flow graph for reference."
Click to expand...
hmm interesting to know.
 
IMO, the large valves MAY clear the 4.25 bore, I'm not sure, appears they do. BUT why put the high flow big valve heads onto the stock bore without clearance to allow flow into and out of the cylinder. I always matched the top of the bore to the head chamber size & shape and also opened the chamber around the valve on iron heads to maximize flow capability at lower lifts. Check every dimension including valve pocket diameter & depth.
 
dukeboy_318 said:
I'm not a giant fan of Promaxx due to past issues. Give Tom Marsh at Marsh Performance a call about his Sidewinder heads. Things have a great review and are personally checked and finished machined by Tom and they cost about the same as a pair of 440source heads.
Click to expand...
That would be Todd at Marsh.I have spent alot of money there!!:drinks::lol:
 
66Satellite47 said:
IMO, the large valves MAY clear the 4.25 bore, I'm not sure, appears they do. BUT why put the high flow big valve heads onto the stock bore without clearance to allow flow into and out of the cylinder. I always matched the top of the bore to the head chamber size & shape and also opened the chamber around the valve on iron heads to maximize flow capability at lower lifts. Check every dimension including valve pocket diameter & depth.
Click to expand...

I have no direct experience on this, but I think 66 makes a good point. The big valve probably "fit" in the bore, but you might be blocking some of their flow potential with the cylinder wall blocking some air flow.....no good info from me, I'm just thinking out loud. I've often wondered if the max wedge motors' blocks were notched for this reason.
 
Get a steel shim gasket for a 413 Truck motor
lay it on the head
lay it on the block
pretty easy to tell where the valves are in respect to the steel shim- it is a smaller bore gasket than the oversize one size fits all available today
I use them when I open up the chambers to unshroud
notching the exhaust does not help flow - actually a scallop the plunge notches are ugly you have to know how far your top ring comes up
you say your motor is together already?
If I remember some stock heads overhang the bore already
the truck/ marine/ industrial shims are stainless if anyone is interested I can dig them out and get numbers tonight
I forget who has them- not in passenger car light truck gasket catalogs-
 
Last edited:
Kind of hard to check without the heads.

I sent Marsh an email so maybe they will have some insight into the fit.
 
I installed Edelbrock performer rpm heads on a stock 69 engine with comp cams .510 lift cam without issue. 2.14 intake valves. This engine came from a wrecked 69 super bee. Had only 125 miles on it.
 
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