Head Hunter (turbo build)

Jakx13

New member
I got a full 300 with an oil problem for $100. It's carbed! I tore it down and in the process of rebuilding it(Everything looks good but the bearings).

I'm looking at getting Offenhauser duel plane intake, custom built exhaust manifold for a HX35W, and an Howerds cam(1200-4800, off road)

Is the turbo to small?, Or to big?
 
You obviously are looking for low rpm power.
If it is the HX35W with a 54mm compressor inducer, then the turbo will work.

What style exhaust manifold are you looking at making?
 
A standard log type with a twin scroll set up. It should help the turbo spool up faster too. My fear is the turbo is not rated for the power it will put down with 7/8 lbs of boost.
 
It's a twin scroll log type manifold. It should help spool up the turbo quicker than open scroll. Yes the turbo is a second gen cummins turbo(twin scroll). My issue is it's making too much power for the turbo with less the 10lbs of boost.
 
My hx35 makes positive pressure under 2000 rpm when there's enough load present on the stock 4.9 efi engine, you'll like it.
 
Jakx13":18babews said:
My issue is it's making too much power for the turbo with less the 10lbs of boost.

You are correct that the compressor map gets narrow at low pressure ratios and there would be concern about running the turbo into the choke zone.
However the stock 300 head combined with a cam profile for low rpm torque will not flow enough past 4500 rpm to let that happen.

Concerning cam profile.
When using a log style exhaust manifold there is a lot of exhaust back pressure.
When the engine is operating at low rpm the intake port velocity is low and the pressure in the cylinder at the end of the exhaust stroke causes intake port reversion when the intake valve opens resulting in a delay in the start of the intake cycle.

In this case it is better if the time that the intake and exhaust valves are open at the same time is reduced.
This is less of a problem with a turbo engine being used to make boost and power at high rpm where the port velocities are higher.
I had a set of intake port injectors with the plastic tips melted due to intake port reversion on a big cam turbo engine.

If you are looking for early turbo spooling and low rpm boost may I suggest using a cam with less overlap between the exhaust valve closing and the intake valve opening.

The Howard cam you are looking at (#280026-08) has a tight 108 degree LSA which is good for low end torque in a N/A engine where there is exhaust system scavenging that can take advantage of the overlap period.

Here is the Howard turbo cam for low rpm boost. It has a 114 degree LSA and 18 degrees less overlap than the first cam.

What RPM power range are you looking for?

[image]https://www.dropbox.com/s/m7muan0xurh5cbq/Howard%20turbo%20cam.jpg?raw=1[/image]
 
Thanks. Do you want to send me the part info for that cam? I haven't seen anything for it. I know that long tube turbo manifolds make higher RPM power then log type.

This Friday I'm going to be buying some mineral spirit to cleelan the block and parts. Then I'll check the block for truenes. And go from there.

With that said I'll need new piston rings what gap should I be running for the stock compression rate? I'm going to be asking lots of questions, just a heads up.
 
The part number is on the cam sheet I posted.
It is a custom grind. They may need most of the info on the cam sheet just to be sure you get the correct cam.
You may also be able to order the cam through Summit using the same info.

What RPM range do you want boost?
Will this be used with a manual transmission?

Have you considered using the HD exhaust manifold and save yourself a lot of work making a log manifold?
https://www.ebay.com/itm/300-4-9-Ford-H ... 3389!US!-1
 
That HD manifold won't work it's a open scroll set up. I'd like to keep the twin scroll that the HX35W has.

I don't know an transmission yet but I did come with a flywheel. I may just get it resurfaced, and get a M5OD-R2 trans after all the bell housing is the same as a 302 Windsor

RPM's are low to mid, no more then 5k red line. Idle to maby 3k for max boost will be nice. What ever I put it in is going to be lifted with big tires to go rock stopin.
 
Jakx13":279pvlk4 said:
That HD manifold won't work it's a open scroll set up. I'd like to keep the twin scroll that the HX35W has.
I understand. You will be feeding cylinders 1,2,3 to one side of the scroll and 4,5,6 to the other side.

I suspect there will be enough cylinder wear to need new oversized pistons.
It is recommended to use Hypereutectic cast pistons which are stronger than the standard cast pistons.

The compression ratio should be close to 8:1

Are you going to use an intercooler?
 
Yes, water to air aftercooler. I've had good luck with them on my little cus 7.3 IDI. There's no extra turbo lag on his truck, and charge temp of 40-50F.

I'm going to try for the stock ratio if possible. 9.4:1
 
Jakx13":w8tzxg5p said:
Yes, water to air aftercooler. I've had good luck with them on my little cus 7.3 IDI. There's no extra turbo lag on his truck, and charge temp of 40-50F.

I'm going to try for the stock ratio if possible. 9.4:1

I think you meant 8.4:1 which would be fine with an aftercooler.

The Hypereutectic "D" dish pistons have around a 22cc dish which would put the compression ratio right at 8.4 if you leave them .025" in the bore at TDC.
That assumes a 76cc combustion chamber in the head and a .030" over piston.
 
Ok, I must have read something wrong. I swore it was 9.4:1 but hay it's all good.

So is there anything else I'll need to do for boost? I have plans for studs, open the ring gap, offy intake, Howerds cam.

I also have a 450cfm carb for now. I do plan on going EFI later. Using the stock cam as shifter stick. Probably get a first gen exploder to drop it in.
 
The fuel pressure will need to be boost regulated so that the fuel pressure increases 1 psi for every 1 psi of pressure going into the carb.
That also means the fuel pump needs to supply the total fuel pressure.
If the carb needs 6 psi of base fuel pressure and the boost pressure can go as high as 10 psi then the fuel pump needs to supply at least 16 psi.

In order to supply enough fuel to the main circuit in the carb, the power valve fuel passage may need to be drilled slightly larger.

As manifold pressure increases, ignition timing should be retarded.
You can start with 1 degree of retard for every 1 psi of manifold pressure.
With good cooling from the water to air aftercooler you could go less retard.
 
You may want to consider using efi manifolds with with 2" up pipes to a twin scroll t3 flange for the turbo, that will isolate the first 3 from the last 3 cylinders and will give the desired effects of twin scroll. You may have to run a wastegate on each up pipe. Weld the wastegate in the hx35 shut, its too small to hold small boost numbers on a 300" motor.
 
Sorry for not posting anything in a while. I've been working for the last 8 days strate. So parts I need to get still are: bearings for main, rod, and cam; camshaft, pistons, intake manifold and a new turbo.
So I was planning on the HX35W but it caps out at 330hp. With the duel plane intake, cam, p&p, and exhaust manifold all the computer dynos pit it at like 450hp. I normally will take 100hp of to stay safe with real world number.
So far I've just torn down, cleaned, and painted.
 
Jakx13":2tjoi6c3 said:
So I was planning on the HX35W but it caps out at 330hp. With the duel plane intake, cam, p&p, and exhaust manifold all the computer dynos pit it at like 450hp.

You originally wanted power from idle to 3000 rpm and 8 lbs of boost.
The engine wouldn't be making much over 300 hp even at 4500 rpm.
 
Your right but with the M5OD, NP203, and 4.10 gearing I need a turbo that won't be over powered for highway driving to off road destinations. Yes 7lbs ant to much out of the 35, but I'd rather be safe.
I've also been talking to Comp Turbo about there Oil-less twin scroll turbos. And I've had good luck with there 360 bb turbos in the past for good and quick spool up.
The Comp turbo is the same "size" with less weight and is safe to use all the way up to 500hp. So the spooling should be the same if not a bit faster. I'm also thinking that all of the V-Dynos are saying 1.43in diameter, I'll run 1.5in diameter 3 peace manifold.
 
Since the M5OD has a .80 overdrive, would you ever see over 3000 rpm on the highway?
Would you ever drive over 70 mph?

The reason for asking is the following.
A turbocharger compressor at 8 lbs of boost is operating at it's most narrow section of the compressor map.

You can have full boost from 1500 to 3000 rpm with a small compressor or 2500 to 5000 rpm with a larger compressor, but you cannot span 1500 to 5000 rpm with a single compressor.

If you run the smaller compressor too far out it will choke.
If you try to run the larger compressor at too low of an rpm it will go into surge.

A 50 to 52mm compressor inducer is the correct size for boost starting at 1500 rpm on a 300 six.
 
High way speeds are 80 in Idaho. So yes the HX35W has a diameter 54mm, Wal a CT3X-5858 is a 58mm. Yes not ideal, but the 35 has a turbine wheel weight of 140g, as the CT3 is sitting at 120g. With the weight diffrice making some speed up. Lastly the CT3 is ball betting as the 35 is no(can't think of the type)
 
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