mike tkach

iTrader: (3)

yes,pleasantly suprised

Full Force

iTrader: (5)

ya... Dean told me easy 510-520 hp if we do it right.. just with heads and cam change..

MILD THUNDER

iTrader: (3)

Yup.

I'll have to look thru my old magazines. Engine masters modified a 454 crate engine. They had installed a pair of dart 310 Pro 1 alum heads, a different roller cam (it was a stock roller cam 454HO rated at 425HP). The cam specs if I recall right, were around 236/242 114 or 112lsa, and around 600 lift. By bolting the Dart heads on, the compression was around 8.2:1. With a single plane intake, holley 950 carb, It gained about 100HP over the stock crate 454HO. Had they milled the heads, or changed the pistons, the power would have went up quite a bit more. 8.2:1 alum headed engine will run on 87 oct all day. If they had went to 9.5-10:1, I think they would have made 550-575HP easily. These were stock heads, no porting, and a off the shelf cam.

On some of this stuff, there really isnt a need to re-invent the wheel. the 454 bbc, is about as common as it gets. There lots of good proven combo's out there.

Theres alot to heads, and flow numbers in my opinion can be decieving. Low-mid lift numbers can be just as important as flow numbers in the upper spectrum. Another area that affects flow, is bore size. Bolting on a pair of heads with oversize valves that flow big numbers with a 4.500, or 4.600 bore, onto a 4.250 bore, can change things substantially. The smaller bore can really shroud up the intake valve. Bore notching can help that out a bit, but its still not as good as the big bore engines. Normally, taking a 454 to a 468ci, can be worth some power. Not so much because the displacement is larger, but the valve unshrouding that takes place.

If I was buying new heads, I'd take a look into the AFR 290 oval ports. The 265's mentioned would work very well for a 427/468, but if you ended up say deciding down the road a few years, to build on some 502/509ci blocks, the 290's would still work well for you. Heres some flow #s from a 290 afr on a 4.310 bore (468)

4.310 bore fixture

Intake

.200....170 CFM
.300....241
.400....294
.500....332
.600....361
.650....370
.700....374 (have seen a few production pieces in the 376-378 range @ .700)

Exhaust (with 2" diameter curved pipe)

.200....157
.300....190
.400....232
.500....260
.600....278
.700....292

Full Force

iTrader: (5)

Dean was talking a set of smaller Brodix, he said they are working well on mild 454's.. I gotta keep it simple since I am very cheap...lol and again... its just a 86 Baja...not ever gonna be a rocket...ha

endeavour32

iTrader: (4)

For the 454 go with the AFR, its a better head than the Brodix and less money. The AFR will out flow it in mid lift numbers up to around .65. If I remember right the Brodix will outflow the AFR after that. Thing to remember is that you will never be running a cam that big in a marine 454. As Mild Thunder suggested the 290 AFR is even better. I thought about using that head on my last engine but was told that I wouldn't see enough gain over the 265 to justify the cost. Now as suggested if you think you may build a higher RPM 502 then it may be worth it, but it is an extra $800 for that head over the 265. Now if you can get a good deal on the Brodix go for it, its still a really good head. But at normal retail the AFR is the better value.

Full Force

iTrader: (5)

I take in everyones advice and will not make decisions until winter, I also know Dean Gellner knows his chit as a known marine engine builder, I don't plan to build bigger engines for this boat as far as shortblocks, the cost vs speed gain just is not worth it to me, I can get the Brodix Dean was talking about with Inconel valves for just under 2000 an engine, ready to go on...I am also not gonna go nuts changing things around as I am on serious budget, I still have the idea of returning these to bone stock 420's and just running em if money is tight, we will see how things look after a summer of 4.50 fuel... LOL

endeavour32

iTrader: (4)

Thats a good price! I think the AFR's cost me around $2200, they are very close performance wise. For $200 less I would also go with the Brodix. As far as going bone stock, be very careful. I just had a set of heads rebuilt. When it was all said and done For a bit more I could have had nice aftermarket heads. If I could get a do over, I would have sold the stock heads and bought aftermarket heads.

Full Force

iTrader: (5)

I have tons of friends with parts, I would redo stock heads myself as long as they don't need too much, anymore then 500 a set total, I would wjust buy new...

MILD THUNDER

iTrader: (3)

As I stated before, I personally would not bother removing the merlins, to put the GM rect port heads on. If the engines are running fine, I'd just run it. I dont believe you will gain anything, and more than likely, even lose a little. I know you're trying to get the boat where its "supposed to run", but engine power isn't always the case, especially on a hull like you have. Over the years, hook in the hull or transom, stringers, foam, etc that has become "wet" or waterlogged, can easily knock a few MPH off. I have a buddy with some 420hp 454's in a 34 scarab iii. On a good day, he sees about 60mph.

I'd save up for some brodix heads that dean suggested, and roller cam/lifter setups. Go over the bottom of the hull very well, maybe a little prop work.

Full Force

iTrader: (5)

I understand, but also was told by Dean and others that the heads are killking my torque that makes me able to run the right props... so I gotta get that torque back... doing all the work myself makes it very easy to swap parts around... no big deal to me... as most pay to have these things done, saves me lots of money..a weekend wrenching to possibly pick up 2-4 mph is worth it to me and not lug the engines down...