Problems with my new engine
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Joined: Dec 2006
Posts: 53
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From: Zagreb, Croatia
Car: C4 Corvette
Engine: l-98
Transmission: 700r4
Problems with my new engine
I've recently built a new engine after my old one blew up.
Here is link to more details:
http://forums.corvetteforum.com/c4-t...e-project.html
In short here are engine specs
- 2bolt block, overbored 0.020"
- stock crank
- SCAT forged rods 5.7"
- SRP forged pistons, flat-top
- #113 heads, ported, 2.02/1.60 valves
- ported superram
- #24 FMS injectors
- Hooker LT headers
- CC XR288HR cam, 288/294 adv., 236/242 @.050", .55"/.57" lift, 110 LSA
I'm having my tune done by Mick (mseven). Engine fired right up with
his first tune but it was running rough and very rich.
From datalogs, we have noticed that vacuum is low (70+ kPa). So I tried to find if there are any vacuum leaks or other mechanical problems. I did find some issues, but I sorted them out and I still have the same problems.
Problems are next:
When I start the engine it runs stable but very rich. WBO2 is showing high 11 to low 12AFR and considering the size of the cam
and overlap, I think that it's even more rich than that.
As the engine is heating up the problems start. Engine wants to stall and sometimes it stalls if I don't blip a throttle.
Idle starts to go up and down all the time.
IAC ccounts are allways going down. From the moment when I start the engine IAC counts are slowly going down, until
they finally reach zero. If I adjust the throttle screw I can get them to raise, but again, as the engine is running IAC starts to drop.
Map signal is acting very similar. As I start the engine, it's stable at lower 70's but as the problems with stalling start, MAP starts
to jump all over the place. I guess that it's normal that it jumps to 90 because engine almost stalls.
All the time there is way too much fuel as I can see it smoke and it really burns the eyes.
As for vacuums, I have plugged everything except MAP, fuel regulator and PCV hoses.
I have tried to plug the TB with engine running and listen for any vacuum leaks but I can't hear anything.
Any inputs and ideas are welcome!
Here is link to more details:
http://forums.corvetteforum.com/c4-t...e-project.html
In short here are engine specs
- 2bolt block, overbored 0.020"
- stock crank
- SCAT forged rods 5.7"
- SRP forged pistons, flat-top
- #113 heads, ported, 2.02/1.60 valves
- ported superram
- #24 FMS injectors
- Hooker LT headers
- CC XR288HR cam, 288/294 adv., 236/242 @.050", .55"/.57" lift, 110 LSA
I'm having my tune done by Mick (mseven). Engine fired right up with
his first tune but it was running rough and very rich.
From datalogs, we have noticed that vacuum is low (70+ kPa). So I tried to find if there are any vacuum leaks or other mechanical problems. I did find some issues, but I sorted them out and I still have the same problems.
Problems are next:
When I start the engine it runs stable but very rich. WBO2 is showing high 11 to low 12AFR and considering the size of the cam
and overlap, I think that it's even more rich than that.
As the engine is heating up the problems start. Engine wants to stall and sometimes it stalls if I don't blip a throttle.
Idle starts to go up and down all the time.
IAC ccounts are allways going down. From the moment when I start the engine IAC counts are slowly going down, until
they finally reach zero. If I adjust the throttle screw I can get them to raise, but again, as the engine is running IAC starts to drop.
Map signal is acting very similar. As I start the engine, it's stable at lower 70's but as the problems with stalling start, MAP starts
to jump all over the place. I guess that it's normal that it jumps to 90 because engine almost stalls.
All the time there is way too much fuel as I can see it smoke and it really burns the eyes.
As for vacuums, I have plugged everything except MAP, fuel regulator and PCV hoses.
I have tried to plug the TB with engine running and listen for any vacuum leaks but I can't hear anything.
Any inputs and ideas are welcome!
On Probation
Joined: Oct 2008
Posts: 6,319
Likes: 19
From: Northern Utah
Car: seeking '90.5-'92 'bird hardtop
Engine: several
Transmission: none
Axle/Gears: none
Re: Problems with my new engine
Too much cam for good vacuum, even on a 383. Let alone a 355. Oh, you typed 20 over, so you have a 353.
Try a cam with 224/230-112, it'll be correctly matched to the intake manifold, and will build WAY more vacuum.
Try a cam with 224/230-112, it'll be correctly matched to the intake manifold, and will build WAY more vacuum.
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