THRILLSEEKER

I have twin stock small blocks in my 28cig and was wanting to upgrade. The inside manifolds are roughly 6 inches apart. I was wondering what are the biggest block size engines that I can squeeze in there and be able to work on without pulling the motors or staggering? Has anyone ever done this or should I just build up my existing small blocks?

Sean

Those boats were built with big blocks and TRS drives in addition to the small blocks you currently have. I believe 6 inches is plenty of space as the width of a big block is only about 3 inches wider than a small block.

What drives and how much space do you have in front of the motors?

My eng compartment wasn't tight in fronot of the motors, but I don't know how much room you'll have if you're running TRS drives with tansmissions...

turbo2256

IN my opinion stroke the SBC to 383 some good port work a cam blowers if you must but I have been in a twin 502 28 and a juced SBC and liked the handling of the small blocks better eisier maintince economy.

THRILLSEEKER

Sean I have Trs drives and Velvet trannys. There is probably a foot of space between the front of the engines and the engine comp.

Sean

I have to agree with turbo...although I have never been in a big block 28, my 28 with 300hp small blocks handled real well and was quite nimble. My only caveat would be if you are running TRS drives and the cons are that they will rob precious horsepower from both.

If you run big blocks with all the additional weight of the trans and drives it's gonna sit REAL low in the water and you will have to run the exhaust through the deck. You should be okay with clearance on the front of the motors.

Personally, I would build some nasty small blocks maybe throw on a procharger(to keep the hatch stock) and run bravo drives...it's be a rocket.

THRILLSEEKER

So if I beef the hell out of my sb's will the trs/velvet combo handle the high rpms?

Sean

rpms...that's a good question...maybe Marc from BAM can answer, but my experience tells me that torque is the big drive killer, not RPMs, so I think you're safe there within reason...now the shop who built my motors just built a pair of 383s for a 28 Formula and they're only gonna be running about 5200rpm...are you thinking of building a set of NASCAR motors?

THRILLSEEKER

Not Quite nascar but if I do change my existing engines its not going to be a little change You mentioned 5200 rpms on a 383
My 300 tempests will run 5200 wide open. Does bore size have any effect on rpms?

AC

My brother in-law has a 1981 28 Cigarette with big blocks built from the factory. The boat has twin 454's. The boat runs around 80 mph. It's tight when it comes time to work on the engines.
We cut out two good size doors behind the back seat for access to the front of the engines - a must to get to the front of the engines.
Make sure the exhaust are above the rub rail.


AC

birdog

NO WAY would I change !! I love snall block Chevs !!! Cheap parts , light weight, Bullet proof !