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Offshoreonly.com (https://www.offshoreonly.com/forums/)
-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   Large inch NA build (https://www.offshoreonly.com/forums/general-q/378655-large-inch-na-build.html)

hogie roll 03-20-2023 09:02 PM
Originally Posted by BBYSTWY (Post 4862478)
I like where this thread has gone! Keep it coming fellas....I'm not currently building engines trying to meet these goals just mainly opened it up for discussion...

Should we clear up some of the acronyms for us stupid people? CH CD etc?

Is the general consensus that you can't get tq and hp up areound 700 with a GM 502 mag block then? In a 540 or 548 configuration? I read through everything and it seems like the hp is "easy" but tq will suffer...did I read that right?

Thanks for all the replies! Turning into a very informative and fun thread I think!
If you’re limiting displacement and compression ratio, there aren’t any other places get more torque.

Smitty275 03-20-2023 09:22 PM
Originally Posted by Brad Christy (Post 4862521)
Dan,

We’re not actually building an engine. Just dreaming. And collecting info for the engine I WANNA build someday.

The tread started as NA, and I know *I* can’t use a blower on a 565 in my current boat. The 565 is probably all the hull would really want. I can’t speak for anyone else, but I’m asking about NA.

I have no idea about CR. I’m the student here.

Thanks. Brad.
(937)545-8991
CR/ Compression Ratio is efficiency. Higher the CR the better the efficiency which equals more torque. So you want to run as much CR as the fuel you plan to run will tolerate based on cam timing, and iron or aluminum heads, etc.

BBYSTWY 03-21-2023 05:28 AM
Originally Posted by hogie roll (Post 4862532)
If you’re limiting displacement and compression ratio, there aren’t any other places get more torque.
Only limit I was initially thinking was using a gm 502 short deck block...if you ran a good iron head on 93 premium what kind of compression ratio could you run? If you punched out to the 540/548 area could you run 10:1? 11:1? and will that remedy some of the torque issues? Just spitballing to get some good updated info out on the boards. I searched the subject before posting this thread and couldn't find much recent info pertaining to the subject other than a few engine build threads.

getrdunn 03-21-2023 05:37 AM
I wouldn’t run no more than 9.5:1 with iron heads on 91/93. Ck out my 565 builds if you haven’t. For NA I absolutely love them.

KWright 03-21-2023 07:23 AM
I have dart short deck blocks, so we went to 565 cu in. 9.3 cr. When we rebuilt the engines for the poker run we updated to RFD's new heads. The only other changes were dry sump oil systems and going from 1 7/8 exhaust to 2 1/8 in.
so by the old rule we should of lost some of our low end torque. If you compare the two dyno sheets you will see we picked up almost 100 lb ft. I can't stress enough this new cylinder head tech is amazing.
https://cimg1.ibsrv.net/gimg/www.off...1c93761bd3.jpg
https://cimg2.ibsrv.net/gimg/www.off...f0ad626d8f.jpg

BBYSTWY 03-21-2023 07:29 AM
That's impressive! What's the rest of the combo if you don't mind sharing?

Brad Christy 03-21-2023 07:35 AM
Originally Posted by BBYSTWY (Post 4862554)
That's impressive! What's the rest of the combo if you don't mind sharing?
:food-smiley-007:

Dragracer_Art 03-21-2023 07:46 AM
Originally Posted by ICDEDPPL (Post 4862517)
Custom pistons were 6 months out not that long ago.
If you hurt one, might be waiting a while.

What about CR? N/A or blown?
I always ordered a box of 10 just for this reason alone. Always ran a custom slug that was built to the finished bore size I had.

snapmorgan 03-21-2023 08:09 AM
New 548 builds, AK Racing heads - Page 3 - Offshoreonly.com

These were done on stock Gen 6 502 blocks. 699hp, 642tq

KWright 03-21-2023 08:36 AM
Originally Posted by BBYSTWY (Post 4862554)
That's impressive! What's the rest of the combo if you don't mind sharing?
These are built off the 525 efi platform. We use a Island racing modified 525 throttle body, Hogan sheetmetal intake, and all the 525 electronics. Dustin Whipple turned the computer. There is more details in my 42 poker run rerig thread in the fountain section. To be honest building high hp na engines is very expensive. I have always been a fan of na. If you want big numbers on a reasonable budget definitely go with whipples.


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