Big Block Suggestions Needed
 

Ok, I have scraped the small blocks for my Formula. I have a line on a couple of 454 blocks but they are two bolt mains. They are interested in swapping me the blocks for my 400 small block and vortec heads. My plans are to build mild motors for cruising with an occasional WOT run. Would the two bolt blocks hold up under marine conditions or should I hold out for 4 bolt mains. I dont want the extra expense of adding splayed mains. Also what would you recomend for the building these motors? Cam, head intake suggestions are greatly appreciated. I plan on using Bravo 1 outdrives.

Thanks

Re: Big Block Suggestions Needed
 

Watch the centerline measurement of the small blocks...BBs may not fit without major mods :(

Re: Big Block Suggestions Needed
 

The two-bolt mains are fine for your intended use. Be sure to have the blocks checked for cracks before sealing the deal.

Re: Big Block Suggestions Needed
 

The blocks have been mag'd. The boat transom, stringers, and floor are being replaced. I will be needing suggestions for centerline of the engines along with the X dimension of the drives. I will be completely rebuilding the boat. All this work for a bet. I will win my steak dinner...LOL

Re: Big Block Suggestions Needed
 

I also want to stay with Iron heads, aluminum are just out of my projected range at the moment, unless an absolutely insane deal falls my way.

Re: Big Block Suggestions Needed
 

Center line of 34-36 IN. 36 inches will work best for exhaust issues. For bravo drives you might contact Competition Marine Center in MO. Eagle makes a good stroker rotating assy to get 496 CU IN from your 454 blocks. Get the optional high strength ARP rod bolt option. For heads look at DART.

Re: Big Block Suggestions Needed
 

Mine are at 33" with Gils. I have to pull an engine to check plugs. The 2 bolt mains are good for 600hp if all the proper blueprinting is done and arp studs are used.

Re: Big Block Suggestions Needed
 

You can throw all the money you want at the stroker kits and high-dollar parts, but the simple truth is that GM stuff will make 500 horsepower and hold up very well. Good used parts such as cranks, rods and heads are available from engine shops here on the board.
By the way, there are a lot of people on OSO running two-bolt blocks, cast cranks, and rods with 3/8 bolts, and with dyno results in the 500-550 horsepower range. Quality machine work and a clean assembly process is where you can't cut corners.

Re: Big Block Suggestions Needed
 

Ok, I think 500-550HP NA is the goal. 454 two bolt mains. I need compresion recomendation , and which Chevrolet head should I look for? Also cam and intake suggestions. This is my first large boat project and I need all the advice I can get.

I do computer work for a local machine shop, Brand Racing Engines who will do all my machine work and my neighbor, Lynn Morris ports heads from his home. He does a lot of big block apps for national dragsters and local drag teams. So my machine work is taken care of. I just need to be on the lookout for the parts.

My buddies at the machine shop can give me good direction, I just want some more specialized advice since its a boat instead of a drag car.

Thanks for the input guys...
Steven

Re: Big Block Suggestions Needed
 

I understand that Dart Iron Eagles are a very good iron head right out of the box. Or let your neighbor go to work on some GM 088 or 990 castings.

Re: Big Block Suggestions Needed
 

I've got a set of BBC oval port vortec heads that just came off my motor that I will let go CHEAP! They came out of a fresh water only boat and only have ~140 hours on them. They are in great shape. Drop me an email if interested. [email protected]

Re: Big Block Suggestions Needed
 

I've got 4bolt mains w/ rectangular port heads and rebuilding now.
Decided to go to 500HP. Builder says no problem. Very reliable. Will just be a bit more lopey at idle. Gotta go w/ a good exhaust system though!

Re: Big Block Suggestions Needed
 

People have been having good luck with the Merlin oval-port heads as well as the stock GM rectangle-port heads. 9.5:1 compression is what I shoot for in the 454's we've done here. The SpeedPro piston L2465F is what I've used in the past but I wasn't impressed with the last set I put in a motor. I'd buy SRP or JE for the next ones.

Re: Big Block Suggestions Needed
 

Thanks for the help so far guys. I am scavanging for parts right now. Looks like plans are to keep the motor around 5500RPM max. I can use oval ports at that rpm range. Anybody have pros or cons with the oval ports other than they run out of air over 6000 rpm without lots of porting? How are the Vortec heads that 2quick is offering? What intake and cam would work well with that design to get the goal HP. I will not go over 9.5 to 1 on the pistons to keep the fuel requirements down.

Steven

Re: Big Block Suggestions Needed
 

The Merlin heads that we've been using in the 330 buildups have ended up with a chamber volume if 117cc, making the compression ratio a little higher than the 9.5 advertised in the SpeedPro book. The guys have all been running them on 89 octane fuel with timing set at 32 degrees total advance.
It's been said on this board that the GM 049 oval-port heads work very well below 5500 but I don't have any experience with those heads. I think Formula31 has the 049 heads.

Re: Big Block Suggestions Needed
 

Correct. Ive been spining my 049 and 781 ovals to 5400 easily. This year I zero decked the blocks so they will be up a little and I might have to have my props treaked. We'll see. I use the L2399F pistons which are a little lower in compression as I am at the mercy of marina fuel.

Re: Big Block Suggestions Needed
 

Prater,
I have 2 sets of 088 rect port gm heads and 2 hp 500 roller cams if you are interested. These parts are from fresh water with 275 hrs on them and are in excellent condition. The heads have manley extreme duty vavles (inconnel exhaust), 2.250 intake and 1.880 exhaust and have rocker arm studs, guide plates, springs, retainers and locks. These parts supported 530 hp at 5400 rpm with 502 cid. Jeff

Re: Big Block Suggestions Needed
 

Wags382, do you have lifters with the cams? Price?

Re: Big Block Suggestions Needed
 

I ran 781's to 5800 rpm. I had a machine shop mill a set of 2349 pistons to about 9.5-1 compression. If you use the 2399 they will make 8.9-1 or so. with 119cc heads.
I used a 2 bolt with arp studs, formula 31 is right.
It ran strong for 2 seasons until I fried it (bad seawater pump) I would use a forged crank if you are going to rev in the 5000rpm neighborhood ! Arp 3/8 bolts in the rods are ok.
7/16 rods are better though. Above all else get it all balanced at a good shop. I've used the 049 heads too. A pocket porting job and gasket matching along with the 2.19 + 1.88 valves, and smoothing out the short side radius onder the valve seats really will wake up a motor. One of the biggest things holding these engines back is exhaust. If you can , get the best manifolds or headers you can afford. They will really help make power. BBB :cool:

Re: Big Block Suggestions Needed
 

Aren't some of the heads not interchangable do to the water jackets: Mk4 vs. Gen 5? Just so you don't pick up some heads and have them worked over only to find out they don't match up to your blocks.

Re: Big Block Suggestions Needed
 

Felpro makes gaskets to bolt mark4 heads on a gen5 block. I think 17046 is the number maybe 17048 too BBB

Re: Big Block Suggestions Needed
 

Also these motors are mentioned as two bolt blocks, gen5 and newer only come in 4 bolt . They have to be mark4. Use felpro 17040 head gaskets. Am I post hoggin' ? :eek:

Re: Big Block Suggestions Needed
 

Yeah bbb,quit hoggin the board!!! :D :D :D get over to the brezze :evilb: :evilb: :evilb: your buddy tripps

Re: Big Block Suggestions Needed
 

Big Block Billy,

Thanks for the info. I dont think your hoggin, I really need the help...

So everyone agrees that the Vortec heads will work on the older block with the special Fel-Pro gasket?

Re: Big Block Suggestions Needed
 

The Merlin heads will also work on MKIV and GENV engines.
The FelPro 17048 head gasket is for a bore size of 4.500, I believe the 17040 is for a bore of up top 4.350, 4.310 for sure.

Re: Big Block Suggestions Needed
 

Check into this carefully. I was told that my GM Mark 4 heads would not work properly on a Gen 5 or 6 block no matter what gasket. Im not sure about the other way around. Aftermarket heads on the other hand will fit any of them. I think.

Re: Big Block Suggestions Needed
 

I picked up a complete 454 today from the salvage. they did not gaurantee the lower end but did gaurantee the heads rebuildable. supposedly had a rod knock. the heads were 049 castings. $100 we just had to dig it out of their motor pile inside an old barn. Just drpped it at the machine shop to be checked out...