This Will NEVER happen if your engine is in any kind of decent condition. Y=
es. Joe Mendillo recommended opening up the oil drain back ports. I don't t=
hink that there's a race engine builder of any brand of engine. That doesn=
't do that. But those engine are being operated well over 6000 RPM's all th=
e time. Those ports are a rough casting. The Olds engines that I've built.=
I cleaned up the drain port. Why. A habit from all the high RPM engines t=
hat I've built. Did I need too. NO. It's that you can't get an old dog from=
doing his old tricks. Bob Dunahugh ________________________________=
From: Bob Dunahugh Sent: Wednesday, January 30,=
2019 10:48 AM To: gmclist Subject: RE: Tid Bit. Gettin=
g to the top of the mountain. And not over load the engine or transmission.=
I've never had my 403 at the wide open throttle position except for p=
assing. And that's on 2 lane roads only. I shift down to a lower gear ratio=
. I'll run the RPMs up to just under 5000 if needed. So that I don't go to=
wide open. My half throttle, and seldom 3/4 at most rule. Is to keep the c=
ombustion chamber pressures/temps lower, exhaust valve temps lower, bearing=
loads down, and thus my over all engine temps lowered in the prosses. The=
next benefit is that my trans temp/load is reduced. The trans that's in th=
e GMC we drive now. Was in the burned GMC. I rebuilt that trans myself in 2=
003. Plus that trans never is on the road without a 17000, to 24000 lbs GVW=
. I've never had any engine problems except for the water pump shaft that t=
wisted off a year ago. I don't know of any GMC that pulls the loads that ou=
rs's does. That 3:70 FD has a lot to do with it. And I do it with the hea=
viest coach. Then the smallest engine. Something to think about the next t=
ime that you don't want to run the RPM's up. Bob Dunahugh ___________=
_____________________ From: Bob Dunahugh Sent: Sunday, January 27, 2019=
11:26 AM To: gmclist Subject: Tid Bit. Getting to the =
top of the mountain. And not over load the engine or transmission. Th=
ink of it this way. You have a 10 speed bike. You shift to a lower ratio. S=
o that it takes less effort for you. The bikes engine. To get down the roa=
d. Or up that hill. Thus you. The bikes engine will run cooler. And not be=
so tired at the top of the hill. The 3:70 FD is an outstanding improvement=
to any GMC. Towing or not. Mileage goes up because your running a higher i=
ntake vacuum. Less load on pistons/bearings. And the water pump is gettin=
g more water to the radiator. The same situation for the transmission. Runs=
cooler with less load. More fluid to the trans cooler. If your running a p=
ower drive chain in the transmission. The trans will not get the less load=
/heat reductions that the 3:70 FD offers. And finally as to transmission lo=
ading on steep climbs. NEVER use more then half throttle. NEVER. And except=
the speed you get. There is a very old thought that running an e=
ngine at higher RPM's is hard on your engine. That idea died in the mid 5=
0's. When compression ratio's went up. Piston technology made great strides=
. Aluminum pistons were replacing the heavy cast iron ones of the day. En=
gine lubrication system were greatly improved. Pulling a heavy load like ar=
e GMC's at low RPM's. Puts more load on the engine pistons, and bearings. =
Reduce the load/heat on your engine, and trans. Don't be overly concerned=
about running the RPM's to the 4000, to 4500 point. I've been in the mou=
ntains with a GVW of 17,000 lbs. That's the weight on one and a half GMC's.=
Using a perfectly stock 403. No headers, no 3 inch exhaust, and no extras =
engine venting. Bob Dunahugh
es. Joe Mendillo recommended opening up the oil drain back ports. I don't t=
hink that there's a race engine builder of any brand of engine. That doesn=
't do that. But those engine are being operated well over 6000 RPM's all th=
e time. Those ports are a rough casting. The Olds engines that I've built.=
I cleaned up the drain port. Why. A habit from all the high RPM engines t=
hat I've built. Did I need too. NO. It's that you can't get an old dog from=
doing his old tricks. Bob Dunahugh ________________________________=
From: Bob Dunahugh Sent: Wednesday, January 30,=
2019 10:48 AM To: gmclist Subject: RE: Tid Bit. Gettin=
g to the top of the mountain. And not over load the engine or transmission.=
I've never had my 403 at the wide open throttle position except for p=
assing. And that's on 2 lane roads only. I shift down to a lower gear ratio=
. I'll run the RPMs up to just under 5000 if needed. So that I don't go to=
wide open. My half throttle, and seldom 3/4 at most rule. Is to keep the c=
ombustion chamber pressures/temps lower, exhaust valve temps lower, bearing=
loads down, and thus my over all engine temps lowered in the prosses. The=
next benefit is that my trans temp/load is reduced. The trans that's in th=
e GMC we drive now. Was in the burned GMC. I rebuilt that trans myself in 2=
003. Plus that trans never is on the road without a 17000, to 24000 lbs GVW=
. I've never had any engine problems except for the water pump shaft that t=
wisted off a year ago. I don't know of any GMC that pulls the loads that ou=
rs's does. That 3:70 FD has a lot to do with it. And I do it with the hea=
viest coach. Then the smallest engine. Something to think about the next t=
ime that you don't want to run the RPM's up. Bob Dunahugh ___________=
_____________________ From: Bob Dunahugh Sent: Sunday, January 27, 2019=
11:26 AM To: gmclist Subject: Tid Bit. Getting to the =
top of the mountain. And not over load the engine or transmission. Th=
ink of it this way. You have a 10 speed bike. You shift to a lower ratio. S=
o that it takes less effort for you. The bikes engine. To get down the roa=
d. Or up that hill. Thus you. The bikes engine will run cooler. And not be=
so tired at the top of the hill. The 3:70 FD is an outstanding improvement=
to any GMC. Towing or not. Mileage goes up because your running a higher i=
ntake vacuum. Less load on pistons/bearings. And the water pump is gettin=
g more water to the radiator. The same situation for the transmission. Runs=
cooler with less load. More fluid to the trans cooler. If your running a p=
ower drive chain in the transmission. The trans will not get the less load=
/heat reductions that the 3:70 FD offers. And finally as to transmission lo=
ading on steep climbs. NEVER use more then half throttle. NEVER. And except=
the speed you get. There is a very old thought that running an e=
ngine at higher RPM's is hard on your engine. That idea died in the mid 5=
0's. When compression ratio's went up. Piston technology made great strides=
. Aluminum pistons were replacing the heavy cast iron ones of the day. En=
gine lubrication system were greatly improved. Pulling a heavy load like ar=
e GMC's at low RPM's. Puts more load on the engine pistons, and bearings. =
Reduce the load/heat on your engine, and trans. Don't be overly concerned=
about running the RPM's to the 4000, to 4500 point. I've been in the mou=
ntains with a GVW of 17,000 lbs. That's the weight on one and a half GMC's.=
Using a perfectly stock 403. No headers, no 3 inch exhaust, and no extras =
engine venting. Bob Dunahugh
