Normally Aspirate a Turbo Engine

[Riggy]

Hi Guys,

I am looking at buying a 77 3.0l 930/52 short motor. I was considering making a 2.8SS but possibly go slightly bigger to a 3.2 instead.

Anyone had experience with changing a turbo motor to a NA? Do I need new cylinder heads, cam housings?

I know I need new Ps and Cs, and camshafts. I will likely add ITBs and EFI with EMS.

I've been going through Wayne's book - How to rebuild and modify engines, and Bruce's Peformance handbook. I'll admit that I'm getting a little confused

Cheers
Paul

[stownsen914]

Sounds like a fun project! In addition to pistons and cams, you’ll probably to either port the heads or swap them. Turbo ports are quite small like 32mm, which would limit performance on a NA motor. For pistons, there are some off the shelf 3.0L options, need to confirm if the wrist pin is the same for them to fit your motor.

Scott

[jpnovak]

98x66mm. 3.0SS.

You don't have to port the heads. But you will want to so they will support enough airflow to match the cams and rpm range appropriate for the case.

Also, A 3.0 turbo might be more valuable if you sell and buy a different donor.

[dannobee]

I know a lot of people poo-poo the turbo heads, but they really don't flow THAT bad. Here's a comparison from my flow bench a couple of months ago. Same box stock brand new TRW valve in each head and bone stock seat angles.

Lift 32mm 39mm
.100 63 69
.150 92 99
.200 124 135
.250 153 168
.300 175 192
.350 190 203
.400 198 213
.450 202 225
.500 205 241

The flow doesn't change much after that. Like with any head, at some point you can take the valve completely out and it won't flow much more air. "Massaging" the seat angles will get the low lift numbers up a few cfm. TRW valves aren't the best, but they're plentiful, reasonably priced, and at least have a radius above the cut angle.

[Riggy]

Thanks for the responses guys, and thanks for that great info Dannobee.

I'm thinking 100mm pistons 10.5 compression. Plenty of good fuel here in Oz, but may still go twin plug. New conrods etc for high rpm. DC60 cams as it's a street car.

Can't wait to get stuck into it. My car is a 69 911T updated to an SC many years ago. I'm currently pulling it apart to return it to long hood but adding flares so it will be an RSR interpretation.

[faapgar]

I sent you a PM.Fred

[MBEngineering]

HI Riggy

I have a 3.0Lt (was a) Turbo engine , now a 2.8Lt on Carb's,



it is running ;

66mm crank (T)
lightened flywheel
GT3 oil pump and inter-gear
DC62 cams
JE 95mm single plug wedged piston with cutouts for valves
Carrera 3 heads
SSI heat exchangers
tall PMO manifolds
40 IDA 3C carb's

on Std comp' it is only on 203.2 BHP and 172.9 Ft/Lb torque, both of which run out at 7,000 RPM, lost 12.9 HP in drag from the print out off the R/R

it is due for a up grade to Twin plug and a Higher C.R., dist and pistons

[faapgar]

The pistons you have are probably Ok.When you do this swap you need to use a Pauter or Carillo rod that is a few mm longer to make the compression correct.Stock rods are too short.Use a 132mm rod and the rod to stroke ratio is 2 to 1.Then it will sing and midrange torque is increased as well.66 X 98 bore is over 300 hp in twinplug with 46 Webers on pump gas.Ciao Fred

[Riggy]

Thanks Mike and Fred for the info. I've been off grid for 2 days delivering parts to Melbourne and then picking up new parts and driving home. 8.5 hours each way! Yes I'm a bit tired.

Mike, what compression are you running now?

Fred, That's great info on the rods. 300hp is very adequate for my light car, and plenty of fun.

[faapgar]

Three millimeters in rod length is about 60 hp.I offered Riggy a complete short block with longer Pauter rods for $15,000 shipped that is new.But just a little more than his budget allows for a 77 3.0 Turbo case.I am always glad to help as I have built about 20 of this style from 2.8- 3.1/2.8 -3.0 is the best as the case does not have to be modified.10-15 hp difference from 98-100 mm bore and way more cost with thinner cylinders to lessen life of motor.Ciao Fred

[Riggy]

Hi Fred, What compression are you getting with 132mm rods?

[MBEngineering]

HI Paul

The engine is still running in a 2.7RS at the moment, untill the original engine is sorted to go back in.

when it gets a re-build it will go up to around 10.5:1

[Riggy]

So to clarify

Option 1. Buy 3.0 Turbo short motor. Don't open case. Sell old Ps n Cs. Add new 10.5 98mm Ps n Cs. Port and twin plug heads. New cams, DC60

Option 2. Buy 3.0 Turbo short motor. Open case and replace crank with 66mm. Do necessary case work. Buy 132mm Carillo rods. Keep the original 6.5 c/r Ps n Cs. Should have about 10.5 c/r. Port and twin plug heads. New cams.

I like the idea of not opening the case but I also like the shory stroke option 😀😀

[MBEngineering]

HI Paul

"Option 2. Buy 3.0 Turbo short motor. Open case and replace crank with 66mm. Do necessary case work. Buy 132mm Carillo rods. Keep the original 6.5 c/r Ps n Cs. Should have about 10.5 c/r. Port and twin plug heads. New cams."

you will still need to change the PISTONS to get the C.R. up to 10.5:1, also if you use the T crank, you will need the T rods or custom rods to fit, or a counter weight crank will take a better set of rods.

IF you just get the engine and swap out the TOP end, you might as well just use a SC engine, with the 9 bolt crank and early 9 bolt flywheel