I recently acquired a pair of gen V 502 mags that are currently dead stock, and likely ready to be gone through. And I cannot seem to just leave things alone, so I am looking at options to build these up a bit. I plan to freshen up the bottom ends with rings/bearings/gaskets. I was looking at increasing the valve sizes in the stock rectangle ports, and it just does not seem to be cost effective in todays world. Not to mention it seems like all of the machine shops in my area keep disappearing or are months if not years out on lead times. I have a pair of 500EFI cams sitting on the shelf that I intend to use, I have dry to transom exhaust and all supporting mods as far as oil cooling and what not from my current engines/parts stash. Carbed 800 Holleys and Edelbrock air gap intakes

So I have been looking at some of the offshore cast heads, and strongly considering the AFR 325 enforcer head. I initially thought that ordering bare heads was the way to go and adding all top end parts. But after reviewing the parts list that comes on these heads from AFR which are the same parts as their higher end heads, I am now debating on ordering complete heads for a roller cam. The PAC 1940 springs seen to fit the build and the valves from all of the research I have done will live well in the N/A world. The thing that I think will need to be addressed is the valve stem clearances need to be checked and likely increased. But at 922 a piece, I am having a hard time justifying the cost of upgrading the stock heads.

Am I missing anything here, or does this sound like a good option? I appreciate and positive feedback and info!

https://www.airflowresearch.com/335cc-bbc-enforcer-cylinder-head/p548?srsltid=AfmBOoq8N80zje20w2Rc0FOx-zmjMEHdjWQrky6n9rqMUIhlhoub4_9R

https://www.summitracing.com/parts/afr-3001?seid=srese1&gclid=EAIaIQobChMI78Ts1YGlkQMV9wa tBh0iYAN0EAQYASABEgJgyPD_BwE

I'd be more inclined to use these heads.

https://www.airflowresearch.com/300c...nder-head/p599

agree with sut 30....325, 335 are a little big for 502......I ran AFR 305's on a pair of 540's na made 630 hp

I appreciate the responses, I had the same thoughts on the runner sizes, but have also read great results with them on 502s. This is more of a bang for buck build rather than a no expenses spared to get every last hp out of them. Going to the higher end AFRs are not an option based on budget, 2 pairs of heads are going to be close to 10k by the time I buy everything to bolt them on and pay tax/shipping, that is just not an option here. I am open to other options such as the maxx flows 290s and building them myself, which was originally what looking to do. The enforcers benefit is what appears to be great parts included on assembled heads that saves a few bucks compared to piecing them together and the AFR lifetime warranty on the castings. The plan if I buy these is to tear them apart and make sure clearances are all correct for marine. It is going to be either stock heads redone with bigger valves or use a set of these cheaper aluminum option heads that seem to have lots of great feedback. In my mind, the parts on the heads are far more important than the casting themselves, theses heads, bedsides possibly the exhaust valves are all parts I believe will live. I was thinking that inconel valves were going to be swapped in even though most say the nail head valves included are good for N/A, I have had past issues with valves and do not want to cut corners there or with springs.

I went through all that and decided to have my stock cast heads machined correctly. Bored blocks because of water damage to 509's. 630 HP with no reversion on Gil manifolds. I can send you info on shop if interested at Lake Ozark.

630 is impressive with stock heads! What are the specs on the build? Any idea how much cash you put into the heads? My other option is to watch for a couple of pairs of blue engine heads to pop up that already have the correct stuff done to them from merc. I did that on my 454s that I could use, I just do not want to break those motors down to steal parts, since they are 100% complete.

Just made 509cid, flotek 290cc ovals 670hp j1349 corrected Power. The cheap afr Will work But IS too Big For 502cid, check promax and flotek 290cc ovals, might Be The same Price than The China made afr enforcer.

Those heads are on the list, they will cost a hair more because I will be building them from scratch, but I can still keep them within the budget. I also know that I will have all top end parts in them going that route. What pistons & cam where you running to get to 670? 670 is further than I thought I could get with a 502/509! The promax 290 will also help me out with compression, 110cc chambers vs 122. Thank you for the info!

Basically started with 500HP's, bored new pistons, new cam's (custom grinds), head work, and good block machining. Good friend bought my old 502's, did the same to the 502's stock bore, same cams, same head work, same block work, different intakes and carbs. Made right at 600.

JE/Srp Pistons, domes milled to 8cc, 10 to 1 compression. Ronn sporl hyd Roller 240/245, 0.650/0.650" , 114lsa. 108icl. Flotek and promax 290cc IS The same casting, But flotek has bigger 2.3" intake valve. Promax intake IS 2.25" wich i think IS better suited For The Port. Ron sporl has milder lobes also, next size down IS a 230/235 114lsa, that might Be My pick For slightly lower 9-9.5 compression.