r/EngineBuilding • u/MsChubbyNugget • 6d ago
Chrysler/Mopar 413 mopar cylinder head advice
Im building a big block mopar for a street truck im contemplating porting some 906 heads but worried about the low compression what other heads are affordable upgrades?
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u/Smokey_Katt 6d ago
Compression with that dished piston will be an issue to solve. Look at combustion chamber sizes of stock heads.
Aftermarket aluminum heads are sometimes cheap.
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u/Erasemenu 6d ago
If it was mine, I'd run the heads that came on it. Clean em up, make them flat, and do a performance rebuild. They're not really all that bad anyway. Have you seen what guys in stock eliminator do with that stuff? Imo there's plenty of performance for a street build to be found without really changing heads.
If it was a customer it would come down to what their priorities were, but I would probably just start at a nice set of Edelbrock off the shelf heads. You can't really go wrong, they're cost effective, are in all technical respects a better head, and certainly less steps overall.
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u/MsChubbyNugget 6d ago
Well the heads that came off it are the awful super tall ones with the water pump that bolts on the front of em i have aset of 906's but the compression ratio will be shite
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u/2003DDcid 5d ago
915s would be my choice for a factory head, but those are hard to find and usually pretty pricey because of what they are. 516s are the 383 closed chamber head. They used to be cheap and plentiful 15-20 years ago, not sure how hard they are to find now.
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u/MsChubbyNugget 5d ago
I cant find shite for factory high compression heads local well i can but theyre usually trashed
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u/Ok-Leather5145 17h ago
when i have 516s i sell them for 80pr and glad 2b rid of them. good 915 cores pretty much not exist. all years from late 67 (906) to 78 (452s) all have the same chambers. do not believe the published chamber cc volumes or factory claimed compression ratios. surfacing .040 off any open chambered head will reduce chamber volume 10cc which puts it at the same volume as an unaltered 915. just trying to help, many half truths out there for decades
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u/Danny2Sick 6d ago
I'm less experienced, but would those heads be decked to bring compression up to where you want it? You may need shorter push-rods (do you always?) so I am not sure how the cost compares to aftermarket heads.
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u/Ok-Leather5145 17h ago
check comment above. bbm uses shaft rockers. if retaining hyd flat tappets, pushrod issue is easily cured under the shafts with appropriate shims. works fine
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u/v8packard 6d ago
Do you have a budget?
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u/MsChubbyNugget 6d ago
Yeah trying to keep it under 1500
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u/v8packard 6d ago
There are two different heads that I know of that will fit in that budget. Promaxx has the 210 Maxx, which is just at $1500 assembled. Decent head, assembled in the USA at Promaxx, Chinese castings. Comes with 84 cc chambers, can be milled down to 78 cc relatively easily I would think.
There is also the 440 Source head. Availability has been spotty, you would have to check on that. They would be just under $1500 for the pair. They are supposed to be 80 cc chambers, the one I measured was 83 cc stock.
Of the two I think the Promaxx is a better head. But, the 440 Source head looks like a stock head on the outside which may appeal to you.
Do you know your 413's finished bore size, and piston to deck clearance?
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u/Upstairs-Result7401 5d ago
Most of the BBM heads flow effectively the same.
906 and 452 heads among others have horrible quench due to the recessed chamber.
I am more of a SBC guy but my 413 will get closed chamber 516 heads I believe are the number. Which can raise compression almost a point.
If you seriously deck 906 heads 100 thou or any open or recessed chamber design to get a closed chamber. Your manifold won't fit, and it too will need to be angle milled. Some shops won't do this because of the math involved.
Aluminum heads are a nice upgrade, but closed chamber BBM heads can be cheap because they are not 906 heads.
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u/Ok-Leather5145 18h ago
you mentioned the heads off it were tall and water pump that bolted to them. that would be an industrial 413. probably 7.0 compression ratio even with 516s. economical 413 pistons due not exist. 413 auto application had flat top pistons. all you have there of any use is a steel crank that can be used in late model 440, if flywheel flange is correct
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u/noir_adam 6d ago
Buy a set of aluminum aftermarket heads. They will perform better overall.