LT1 or Project Green

[Guest FordMotherFocus]

LT1 or keep pouring money into my car.? Someone on this board has a clever sig. "Speed costs money, how fast do you want to go?" Im down to pulling my motor to see whats wrong with it. I have to pull it no matter what so I have lots of choices and hard decision! This is what I have:

Engine Specs:

74 camaro 350 c.i. short block rebuild

Including 9.5 flat top pistons

Crower solid roller camshaft .567 lift 288 dur

Crane gold 1.65 roller rockers

Crower solid roller lifters

Trick flow pushrods

DartII heads 2.05/1.60,springs rated to .700 lift

Port matched to intake

Brodix HV1 pro bracket intake ported with heads

Fluid damper SFI balancer

Stock water pump with 160 degree thermo

MSD 6al ignition box

stock disty

Holley Street Avenger 770

Summit oil pan and melling pump

Billet valve covers / Edelbrock pro-flo

Accell 8.8 mm wires/ plugs

Sanderson QP1000 Headers

 

Desktop dyno software rates this combo between 464 and 513 horsepower

 

www.compmachine.com cant figure out whats wrong with the engine in the car. I dynoed at 203 hp. Thats less than a stock 350! I am tired of pouring money into this engine. I done waht to put more in it and have it a be a bad motor. I would love to have a slower but very reliable, daily drivable 350Z. I would be happier with a screaming high reving not very daily drivable 350Z. What should I do?

[Pop N Wood]

Looks like a Grumpyvette question.

 

I guess my limited experience question is who did the porting?

[Sumo]

The way i see it is you have three options.

1) Buy LT-1 and make sure you can handle the electronic harness and install of necessary sensors and stuff.

2) Have www.compmachine.com build you a nice 300h.p. smooth idling daily driver "built" motor.

3) Buy a crate engine depending on the horsepower you want and just transfer most of the other stuff like intake, exhaust manifolds, carb, to the new engine.

 

then whatever you do just sell the other engine to make up for the difference.

 

By the way this may sound like a dumb question but did you check if the throttle cable is hooked up properly? I helped out a buddy of mine who was having the same problems on his El Camino and Pontoon boat and found out that the cable would not pull on the carb all the way. We discovered this by accident when he floored the pedal and i told him that i can still open up the carb a little bit. Once the slack was taken care of we got full power back. Just a little slack took a lot so have it checked. I hope it helps.

[jt1]

That combo should be an absolute screamer in a Z, or any car. I'd like to see a little more compression with that cam, intake and heads, but you have a far greater issue than that. First, check the compression. I would guess you should have about 160 psi with no more than 10 psi variation between cylinders. If that's not ok, you have internal issues like bent valves, broken rings, or piston probs. If the comp's good, find TDC and make sure the mark on the damper is right and it's getting the timing it should. Maybe a keyway got cut wrong, or maybe the key is sheared. Maybe the pointer on your timing cover is wrong. If ok, check your cam centerline. It may be off a tooth, or just installed wrong. Pull a plug and watch it fire while turning the motor over. A msd should give a strong blue-white spark. A weak, red, or orange spark means ignition trouble. Check the fuel pressure, should be 5-6 psi while wide open. check for full throttle and the secondaries opening all the way. This bit me hard once.

 

You've got the makings of a super engine there. I wouldn't ditch it, just try to find what's wrong. My bet is some bent valves from really buzzing it some time, cam timing off, or the dampers moved. Don't give up.

 

John

[Guest zfan]

Kevin,

 

It is not compression remember we got 160 to 165 lbs in cylinders. I really do not remember if you have a flat tappet cam or roller type?

 

Could be cam issues but I personally think it is ignition related. that HEI could be shot or the coil. It did not run worth a crap when we took it out for a spin.

 

You do need to keep the rpm's up when driving around it really loads up when you let it go into overdrive at 30 mph. Around town I would keep it in 3rd(drive) when under 40 mph.

 

The other thing it could be is a bad vacuum leak.

We ran out of time the other night but if you would like I can set up a time when my gear head buddies and me can put our heads together and see if we can find the problem. Just call me if you are interested and I will call a couple of friends.

 

That car should scream so DO NOT GIVE UP YET!!

By the way did you call Mickey at Compitition Machine?

 

Mike Worth

972-422-0858/home

214-758-6926/work

[pparaska]

I agree - find out what's wrong with the one you have. The parts list spells a fairly powerful small block to me.

 

Jt1 gave a great checklist of the three things to make sure are right: compression pressure, correct vavle timing, a good spark at the right time, and fuel. Make sure it's not too rich or lean at WOT.

 

I have a buddy that had a GT500 Shelby Mustang with the 428CJ. We always thought it was powerful. After a few too many speeding tickets, he sold it to his dad that lived several states away to make the judge happy. His dad took it to a Shelby specialist in Florida that found that he was missing a 1/2 inch of throttle linkage opening at WOT with the pedal to the floor. I never got a ride in it after that, but that must have made some difference!

[Guest FordMotherFocus]

I did talk to Mickey. He lashed it. Set the carb some more and tried to adjust the timing. The timing is still jumping around real bad. He said that is all he can do without pulling the motor. He thinks the cams could be dialed in wrong or the timing chain could have skipped a tooth. I am going to buy a new distributor and if that solves nothing pull the motor.

[pparaska]

(I don't know your capabilities or knowledge in this area, so I hope it doesn't sound like I'm talking down to you. I'm just trying to help and provide some advice, below. Sorry if you know all this stuff. I'm also anxious to hear any more diagnosis theories and methods so I can learn too.)

 

O.k. Compression is good (but a bit low - I'd want to see more like 180-220 psi of cranking pressure for a hot motor).

 

First would be to make sure the fuel mixture is not excessively rich or lean. A tailpipe exhaust gas analyzer or O2 sensor (preferably wide band) at a performance shop should be able to help here. I've heard that lead substitute addtives can allow spark plug reading like in the days of leaded fuel.

 

If the timing is jumping around, I'd check the advance weights and springs for sticking, etc., wiggle the shaft to check for excessive play, and possibly just swap in a known good distributor from a buddy, instead of buying one. After this, run the engine through it's rpm band while watching the timing. If this checks out and you have plenty of spark, you can feel confident that you have good ignition throughout the rpm range.

 

Now to getting air/fuel into the combustion chambers. Instead of pulling the motor, yank the accessories off the front of the motor, the water pump and timing cover, and degree in the cam, while redoing the TDC mark with a piston stop. This will show you if the timing jumped and you'll be able to assess the timing chain/gears wear and slackness. I'd also check the lift on each valve to see if any are wiped. Also, do a close inspection of the valvetrain to determine if the valves are sticking or if there's any interference in the valvetrain. If all that check out, you can be assured that the valve events are happening as they are supposed to.

 

Now you should have confidence that you have good mixture, compression, good ignition throughout the rpm band, and that the engine is breathing correctly.

 

After that, you know everything you need to be able to find what's wrong.

 

There's a ton of stuff that can be done to diagnose the motor before resorting to pulling it. Some of it obviously must be done with the motor either in the car or on a dyno. Dyno time isn't cheap, but it's easier and more lucrative for the shop.

 

Hope that helps.