fatheadjames
New member
If you had both at your disposal and both being in the same condition which would you choose to build with a turbo and why?
240 or 300 for turbo build
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The 300 will give you a much wider power band with more low end torque.
The 240 can make the same peak power but at a much higher rpm.
It depends on what you want this engine to do.
If it’s going into a heavy vehicle like a truck you will be happier with the 300.
The 240 can make the same peak power but at a much higher rpm.
It depends on what you want this engine to do.
If it’s going into a heavy vehicle like a truck you will be happier with the 300.
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fatheadjames
New member
It’s just going to be a cruiser. It’s going in a 50 f1. I just wanted to do something different since the 302 that’s in it has a knock and needs to come out. I have what I thought was a 300 but upon further investigation I believe is actually a 1971 240 going off the tag and block numbers. A buddy has a 90s f150 with 300 he said I can have but knows nothing about it.
fatheadjames
New member
It’s a 50 f1 that currently has 302/c4 with an 8.8 with 3.55 gears. No specific power goals in mind. Just want to have fun and surprise people with something different. After seeing multiple people mentioning the 240 will rev higher that might be the better option since I’ll be reusing the c4 for now.
If you can get the 1990s 300 for free grab it because there are parts off of it you may want to use like the intake and exhaust manifolds.
We have had two cases where the turbocharged 240s bent connecting rods under heavy boost but you probably are not going to run it that hard.
There are aftermarket "H" beam chromoly connecting rods for the Chevy 292 six that can be made to work in the 240 six.
Secondly the only catalog pistons available for the 1969 and later 240s are cast replacement pistons which are not recommended for forced induction application.
You would need custom forged pistons from Autotec/Racetec.
The 300 can use the inexpensive Hypereutectic Sealed Power H519P pistons with stock 300 connecting rods if you are going to run low boost if this is a budget build?
The 240 and 300 blocks are basically the same and parts interchange so you can use a 300 crank in the 240 block if the 240 block is in better condition that the 300 block
Is this a low budget build?
We have had two cases where the turbocharged 240s bent connecting rods under heavy boost but you probably are not going to run it that hard.
There are aftermarket "H" beam chromoly connecting rods for the Chevy 292 six that can be made to work in the 240 six.
Secondly the only catalog pistons available for the 1969 and later 240s are cast replacement pistons which are not recommended for forced induction application.
You would need custom forged pistons from Autotec/Racetec.
The 300 can use the inexpensive Hypereutectic Sealed Power H519P pistons with stock 300 connecting rods if you are going to run low boost if this is a budget build?
The 240 and 300 blocks are basically the same and parts interchange so you can use a 300 crank in the 240 block if the 240 block is in better condition that the 300 block
Is this a low budget build?
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fatheadjames
New member
Yeah I planned on getting the 300 regardless to use those parts you mentioned at minimum.
What are you calling heavy boost?
What are you calling heavy boost?
Anything over 12 psi.
Most end up running 15 to 20 psi where the torque and hp is doubled or greater than the naturally aspirated engine.
Are you looking at using the stock EFI intake manifold with an aftermarket system?
fatheadjames
New member
Yes that was my plan. Stock lower efi intake and possibly make a new upper plenum to move the tb to point forward. Run ls coils and add crank and cam sensors to run full sequential with aftermarket ecu. Leaning towards a maxxecu at the moment.
The 1996 Ford 4.9 harmonic balancer has a space on the back for a trigger wheel.
1996 Ford 4.9L F150 F250 F350 Pickup Harmonic Balancer Crankshaft Pulley | eBay
FORD F350 PICKUP 96 6-300 (4.9L). FORD F250 PICKUP 96 6-300 (4.9L). FORD F150 PICKUP 96 6-300 (4.9L). Note : fits 1996 YEAR MODEL ONLY.
www.ebay.com
The RPM range that you want to run the engine at along with the head port flow and cam profile determine the size of the turbocharger so you will eventually have to decide on some things.
The cylinder head is the first consideration as it sets the upper end of the rpm range.
A turbocharged 300 never has to run over 5500 rpm to make big power numbers.
Add another 1000 to 1500 rpm for a 240 six but now you need a solid lifter cam and stiffer valve springs.
The 240 can make comparable power in a rpm range similar to the 300 six by running at a higher boost level.
Of coarse you can design the engine to operate at far less rpm if you just want a lot of torque without high horsepower.
Were you planning on doing port work with larger valves or using the Promaxx CNC ported head or neither?
fatheadjames
New member
I hadn't made it that far yet but yes I was going to weigh out the cost of getting my head worked vs getting a new promaxx setup. I know every little bit helps with these older motors. Cant just slap a cam and turbo on them like the ls stuff Ive played with.
To answer your original question,
First: Since it is going into a 1950 truck I would prefer the wider power band and higher low rpm torque of the 300 especially with an automatic trans where you are giving up some torque to the rear wheels.
Second: The larger displacement makes spooling the turbocharger easier and boost will come in earlier.
Third: There are two aftermarket connecting rods that fit the 300 six if you choose to build a very strong bottom end.
You should pull the head on the 1971 engine and see which six it is.
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fatheadjames
New member
What other rods are available besides the molnar?
Small journal BBC rods, 6.385" long for a 2.100 crank journal.
The BBC rod is a little bit longer than the stock rod which improves the rod angle and reduces piston side loading.
Compstar CSB6385DS3B4AH
Callies Performance CSB6385DS3B4AH Callies Compstar Connecting Rods | Summit Racing
Free Shipping - Callies Compstar Connecting Rods with qualifying orders of $109. Shop Connecting Rods at Summit Racing.
Here is a picture of the Compstar rod with the Autotec piston for the 300 six
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fatheadjames
New member
You still use a stock replacement position for a 300 with the bbc rods or do you have to go custom?
Custom, the BBC rods are longer than a stock 300 rod, so using a stock replacement 300 piston would put it above the deck
What jgavac said since that is his rod and piston showing in the above photo.
Additionally the Compstar rod uses a larger .990" pin.
The Compstar rod is a little bit longer than the stock rod which improves the rod angle and reduces piston side loading.
Even if you use the Molnar 300 six stock length connecting rods, there aren't any forged pistons available and you would need a custom piston anyway.
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