I am going to start to restore a 27 Magnum sport hull I acquired recently. I am considering 2 options . First option twin small block and Alpha's . Second option twin big block and TRS. I can get a deal on either drive option and have both a big block and small block to start already. Am I crazy to consider putting a pair of big blocks with trannys and TRS in this hull. The big blocks would not be big HP .
Thanks RG.

Review previous posts 5th one listed on same subject...Small Blocks was the over all recommendation. Also remember you have a low freeboard ... get your exhaust AS HIGH AS YOU CAN. Bud

Rick,

Glad your about ready to start on the 27. You got a good head start with Parnell's old boat.....keep us posted!

Seeing as how I have a whole bunch of big block parts I have decided to go with a twin big block install, call me crazy. Currently the TRS drive appear to be mounted 32 inches apart I am wondering if that will work or will it be too tight for comfort, I will be running CMI Etop exhaust. Any input would be helpful. Rick G.

Rick ,call me it will not work...many potential problems if you put a pair in. You will need to move the drives,raise the exhaust so you can avoid back wash,build a higher hatch,and you still have a good change of sinking the boat. 312-607-3115.Also send me the length of what your step pad would be. Bud

+2 on Buds comment. My c on c is 33 1/2 and I dont think you could go any closer. I have stainless marine exaust and about 1 1/2" between. Also, as said, the height and width of the exaust is problematic on a sport depending on the hatch design. I've seen pics of one with log style manifolds but with those and exaust tips at /below water at rest, seems very risky to me.On a side note, I have all the trs stuff I took off my starfire (except drives) if you're interested.

- Marshall

Thanks Bud I will call. But I'm still a bit confused , as I have to build a hatch anyway height is not an issue. Is it just a weight issue. That creates the problem or am I missing something else here?
RG.

Rick,

Big blocks and TRS equals alot of weight . . WAY TOO MUCH for a Magnum 27!

I read everyone elses threads on this topic when I started my restoration .. and chose two SBC 29 1/2" center to center . . each engine will have 475-500 hp

Read the posts and old threads from Mange who built the Swedish Arrow 27, a Magnum 27 clone with a single BBK . .90 + mph . .

These boats are rough water hulls and weight in the stern will point your bow to the sky if it doesn't sink at the dock!

Mario L.

Guys I am not doubting anything you guys are saying. But a big block with aluminum heads weights no more than a cast iron head small block. There is where my confusion lies. Why would a twin small block sport not sink at the dock , but a twin big block will . Even a cast iron big block only weights 85 lbs more than a small block. I am not trying to be difficult I just need to know the determining factors . Are you all saying a twin big block alum head set up will not work but a twin cast iron small blockbset up of the same weight will ? Please clarify for me as I certainly don't want to spend all this time and effort and sink my boat at the do k.
Thanks RG.

My father had a 1974 27' Sport with twin BBC TRS drives. He raised the drive height, and ordered a set of CMI exhaust (I know the headers were not CMI Sport Tubes and this was at least 12 to 15+ years ago). The drives were on 32" centers (still are), and the headers after all the pre-manufacturing discussions and drawings about fitting did not fit, CMI gave gave my father a full refubnd but what he wanted was headers that would fit. It was close but they could not fit, now I do not know if the CMI E-tops will fit on 32" centers, but the set of CMI's my father ordered did not, so he went back to the log exhaust manifold with jacketed S shaped tail pipes, he was extremely disappointed the headers did not fit. So with all that if your motors are on stands put the exhaust on (less tail pipe) put them together and take a measurement.

He had factory engine boxes to accommodate for the height, and shaved more material to make room for the flame arrestors once he raised the drives.

As far as twin BBC being too heavy for a 27 Sport, I was the driver and passenger in a twin 454 cu.in, Magnum Sport, it rode well and ran great from 82-85mph in a variety of water conditions, we cruised from 42-46 mph and the boat was a pleasure. That is my first hand experience. I do think the boat would have been awesome with a set 427 cu.in. SBC from Bill Mitchell and a good set of exhaust, but like you, my father had two (semi-tense) LS-6 BBC in his garage (10.5:1 pistons) in his garage when he bought his Magnum without power. These BBC's had Chevrolet cast iron cylinder heads. So I tend to call bullsh*t when people say the twin BBC set up is too heavy, for some maybe they the twin BBC set-up did not like it, but for many it works and has worked for many years (Jolly Roger, Rated X, and the boat pictured below).


My father's old boat. That was my favorite boat of the all the boats he had, not the fastest he ever owned, but was just plain fun, and when racing other boats, it never put the fear of God in me. Good luck with repower, there may not be one perfect answer, but my father, at that time, had a limited budget; that may drive your decision as it did my father's when he started to repower his Magnum. So hence the BBC, and no regrets.

We raced so many boats in the Ocean, Delaware River, and Northern Chesapeake Bay over all kinds of waves, and that boat flew straight, here it is at 81 mph on radar in 1991 or 1992 Barnegat Bay NJ (that was one tough radar gun that humbled many hot-rodders that day). We did launch it on occassion in the Ocean at 80+mph but sh*t happens when it is trimmed out racing 41' Apaches at 85 mph, but it flew straight. There may have been the one huge wave or two when when we were racing on a day, maybe, we should not have been racing, but that was the rare exception.