aero-offshore

SBC 383
whipple charger
merc thunder bolt iv and merc dist
holley 1050 dominator
over transon exhaust
never runs over 150 degrees water temp

does anybody elses go back to nomal idle if you shut it off then start it right away? mine does so i doubt its heat related.

blue thunder

I never tried aero but that is a good fact. I'll check it out this weekend.

BT

jhnrckr

I have the same problem and it is probably a hotter intake manifold heating up your air/fuel and causing it to atomize better, just like the exhuast crossover was designed for. My heads do not have the crossover, are any of you guys running with a crossover?

blue thunder

No crossover here. I run the edelbrock rpm performer intakes. No splash pan under the intake to keep hot oil off the underside in the valley area either, so I am sure it gets hot under the intake runners. But why would the a/f mix atomize better when hot?

jhnrckr

My guess is the fuel vaporizes bettter with higher temperatures. The exhaust crossover was designed to smooth out the idle so it just stands to reason that without the crossover we are going to have some issues with idle. What temp t-stat are your running? Try pulling out your t-stat for a few runs and see if that helps, if it does we have located your problem.

jhnrckr

By the way
SBC 350
Dart Iron Eagle Heads , 64cc, 180cc intake runner, 2.02/1.60 valves 9.7 CR
Crane Blazer rockers
custom hydraulic cam 218 226
Edelbrock performer intake no exhaust crossover with a oil baffle under it.
holley vac sec 750
HEI distributor
GLM exhaust manifolds 4" thru hulls.
The first incarnation of this motor made just over 400 hp , after a certain unpleasantness I had to machine the heads and ended up with higher cr and stepped up the cam a few degrees so I am guessing I am right around 415-420 hp, no dyno sheet after the rebuild. After a hard run my RPMs jump up from 700 in gear to around 900, I just live with it.

JUSTONCE

Don't think its heat related, cause It never did this before I found my timing problem(not advancing) so it used to run alot hotter. My h20 temp sits at 170-180 is that o.k. for a boat motor or too high?
454 .030 over
eagle rotating assmbly.
extreme marine cam
Harland Sharp rockers
B.G. carb.
Gill dry offshore manifolds & risers
merc 420hp heads & intake

jhnrckr

I run around 140-160 degrees with a 140 degree t-stat, what temp t-stat are you running? I don't think 180 degree H2O temp is bad for a motor but it will beat your oil up a lot quicker.

Formula29

1990 454 thunder bolt ignition, Yes, mine will stick at about 2000 when backing off the gas, if I shut it off, and start it up again it returns to normal. stock quadrojet. I am surprised this if such a common problem.

JUSTONCE

not sure what temp stat.
If I shut it off and start it right back up it still idles up. Maybe if I wait a few min. before restart. I'm gonna work on it tonight so I'll let you all know what I come up with.