turbo2256

I have a shop here in westland that does my work. I am very fussy I usally only work on a few boats and cars a year for people that dont want there s#$t scratched.

audacity

CJ, never said that raising was the answer...i've even seen people add x-boxes to just end up taking them off.... as far as TB mods....i designed and developed a TB for the 502mag efi....lots of work and big $$$$....plenum work...done that too....sometimes the returns are VERY diminishing but when combined yield impressive #'s....i'll tell ya this about that....LOL....runners and cam timing symmetry played a big role...1.5 deg put us back over 80 hp where i wanted it! it really F'ed with the computer

all in all....and all the development work i've done (with someone elses money!LOL).....efi mods are not worth the $$$ spent....my thoughts are you pruchased an efi engine for reliability??? have you changed your game plan????

LL...i like what yo said!

JimV

There are big gains available in the GM castings the question is how much do you want to spend? The intake port responds well with a with a 2.300 intake valve and porting, I have seen airflow numbers as good as merlin heads. (The left port is down slightly on airflow because of design). Its trickey to get the numbers on the exhaust port because of the short turn radius (or lack of) but the airflow numbers still could be had. You will also need to change the exhaust valve to a better profile. No big benifets from bowl porting here. This is no B.S. the stock big block exhaust port (220cfm) flows less air than a good small block chevy head(235cfm). With porting it can be increased to 250 to 270cfm. Also there needs to be some chamber work to help exhaust flow which will lower compression ratio. Now that the heads are working you need to look at the intake manifold. Back in 1992 I bought a EFI system from a company in Arizonia for a triple engine boat. They guaranteed their system made the most power or my money back. Their intake manifold looks like the merc intake. After two weeks on the dyno with a turd for a motor we modified a Dart intake for the injectors. We made 80 hp more and called it a day. I sold the manifold at a swap meet for $175.00. I couldn't sleep for two weeks thinking I ripped the guy off. So much for money back guarantees. What I learned is that the manifold works on a 454, with cylinder heads that ports dont work for marine, operating range up to 5200 rpm with lots of torque at 3500.

diveboy

Hey all,

Thanks for all the good advice and opinions. I agree, I don't want to take any of the dependablity away from my motors. I'm just in the process of gathering some info. to help make some future decisions. As always, the best place to start is right here on OSO.

Thanks!

Tinkerer

Jim V. did my heads 6 years ago on my SCARAB and three years ago I had them freshened up and untill two weeks ago the engines haven't been apart ---0 problems--- The failure I had two weeks ago was caused by a failed roller rocker arm that broke an exhaust rocker arm stud. And as far as the heads being good only for top end that is all bunk. This thing used to be able to beat just about any boat off the line and that is with top end props. That is before I raised the X 2 inches. And I am talking a 9000 lb boat.