North American Turbocoupe Organization



Question on compression
dwaynem3 Offline
Junior Member
#1
I've finally had my engine rebuilt,the shop said I should have some where between 350/400 hp The question I have is, with a new engine with this hp what would a guess on compression be? I did a compression test 4x it's 140psi across the 4 cyls I thought it should be higher . Any help or comment would help thanks
dwaynem3
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Jeff K Offline
Administrator
#2
Your stock electronics will not support that much HP. You will need an aftermarket PCM or an EEC tuner, etc. High compression and high boost dont go together well, unless running 100+ octane race gas. Did you use dished pistons? Forged, I hope? We need ALL the specs on the rebuild to help you.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Pete D Offline
Administrator
#3
How many miles (breakin) on the engine before you did the compression test.

Like Jeff said, we need to know exactly what internal and external parts are being used. Being able to support 350-400 HP and actually making it are two distinctly different things.
Pete Dunham


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Robert Camp Offline
Posting Freak
#4
As far as the compression test, if built for turbo usage the CR should be around the range 8.0 to 8.5 to 1. So your compression numbers look okay. Don't confuse the normally aspirated high compression engine with a turbo engine. Higher base compression will net a higher compression test value.

As mentioned, with stock electronics (EEC, VAM) and fueling (fuel pump, injectors) you will not get to those numbers. Stock cam is not going to help either as you'll just have to blow on it harder.
Robert Camp
'86 Medium Regatta Blue TC, 5-speed, original owner.
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Sluggo Offline
Posting Freak
#5
There's no reason for it to be higher than that unless it's a race gas only engine. An 8:1 stock block with a stock cam will show about 140 cranking. You can raise static and close the intake valve later and get the same results. Where's your cam card data?
Doug  
88 TC / T5,4.56,Log,SC60,NPR,2277,MegaSquirt
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dwaynem3 Offline
Junior Member
#6
Sorry it took so long to post only in town on the wkends
this is what I can give right now
Comp cams:FORD 2000-2300 OHC 4CYL. 1971-1990 PART#:70-127-5
MOTOR STATE DIST.
GRIND#: F23 268H-110
SPC INSTR 1:
SPC INSTR 2:
INTAKE EXHAUST
VALVE ADJUSTMENT HYD HYD
GROSS VALVE LIFT .440 .440
CAM LOBE LIFT .2640 .2640
ADV [email protected] VALVE LIFT 272 272
VALVE TIMING @ .050 OPEN CLOSE
INTAKE 4BTDC 42ABDC
EXHAUST 42BBDB 4ATDC
THESE SPECS ARE FOR CAM [email protected] INTAKE CENTER LINE EXHAUST CENTER LINE @ 110.O
DURATION @ .050 INTAKE 226 EXHAUST 226
I also have flow charts from intake and exhaust porting that was done I will post it with piston type next but basically it went from
intake range 1179.14 to 1271.53
exhaust range 985.01 to 1052.83
thanks for the replies,
dwaynem3
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