I guess this past winter when i was trying to install roller rockers on my new engine(350 400hp) and wipped out the cam. Being as how this engine only had 160miles i was really pissed. So i took it back to local shop tabercorvetteparts.com and was told that another 1500 to redo this. I just wanted my car to actually run, so i had them order a Jasper Engine 350 / 300HP 2625$ installed. Had to give my old engine as core so i lost all the good stuff i had in that one(refer to my old posts).

Well Anyway i get this car back today, and still my 90iroc 350 seems 10000 times more powerful.

74 with/300hp jasper rebuild, edelbrock performer intake holley 600 street avenger,stock dist with pertronix ignition drop in, Hooker super comp headers back to flowmaster 40 series. 4.56 Rear out of a 67.B&M 2500 stall.This combination will NOT break the back tires loose from a dead stop.

My question is, what am i missing? could this be the 400 turbo trans?

I have a 90 iroc with 245hp and a 02 WS6 with 345HP and Both of these feel a million times faster and more responsive.......The iroc without power braking with smoke the rear tires off.

 

You need to stop throwing money at it and get it on a rolling road/dyno.

Not only will this give you an idea of the bhp but also how well the box is delivering it.

 

stop throwing money away, and buy a quality engine. jasper is not quality. they are basic replacement engines. buy a gmpp zz4.

 

Jasper ??? You need to hire an agent to act in your interest.

 

Most importantly, who ever has been guiding you, you need to fire them. The motor you had the wiped lube in, why wasn't it fixed? It would have been cheaper and you would have been back on the road in about the same time as you thought you were going to be with the new Jasper unit. Seriously, you mechanic is a thief. This car will never be fun to have as long as you have people taking advantage of you. Do you really know whether or not you have a new engine in the car, or did they paint up and old tired unit and pulled the wool over your eye's

Find another mechanic and have them check the motor out. Start with compression checks and them move onto the timing, form there check the jetting in the carb, I'm sure its off since this motor has a lot less HP then the one the mechanic stole.

I wish you well, and hope you get the enjoy your vette after this is cleared up.

Riggs.

 

The 300HP would be gross HP so you might be seeing 225 net and probably under 200 rear wheel.

 

What's the difference between gross, net and rear wheels?

I normally just quote flywheel and at the wheels, not familiar with gross and net?

 

Even 200hp at the rear wheels should break the tires loose with 4:56 gears. Maybe it's a cam or ignition issue?

 

Gross is at the flywheel with no engine driven accessories and 'optimized' timing, exhaust and intake systems. This is how HP was rated here until the early 70s and is still used for crate engines. Net is as-installed in the car at the flywheel with all production accessories and systems.

 

Ah so basically you mean with or without ancillaries.

 

As long as the Jasper engine has oil pressure and isn't smoking it will do OK. Problem is that we really don't know what it has for compression etc. Even if they put flat tops in it they are most likely rebuilder type ones that have a shorter height to accomodate deck milling. They often end up .060" or more down in the hole and with a normal rebuilder .040-.050" head gasket you can end up with less than 8.0 compression. Any idea what it has for a cam?

Looking at their site I see a *Class 1* with mild cam upgrade...then a *Performance Engine* with a hyd roller cam...and then a *Class II* with better machining etc. Which do you have?

The compression test will give us an idea of what it has in it..but hopefully you have a spec sheet of some sort. It's never going to be a monster, but 4.56's ought to wake it up for a little bit. Problem is that those gears really want something that can rev 6500+ rpm and this engine ain't got it.

JIM
JIM

 

The new Jasper engine is Class II 300HP.

This shop specializes in only corvettes so i thought they would be the best choice to go to. They even advertise on this fourm.

This is the specs on my old engine.

edelbrock performer rpm cam
gmpp vortec heads
edelbrock performer rpm air gap
holley 600 street avenger carb
Summit rocker arms
converted heads to screw in studs
hooker super comp long tube header going back to pair of flow master 40 series
B&M 2600 stall
rebuild 400 turbo
4.56 gears

cam specs are
Basic Operating RPM Range 1,500-6,500
Intake Duration at 050 inch Lift 234
Exhaust Duration at 050 inch Lift 244
Duration at 050 inch Lift 234 int./244 exh.
Advertised Intake Duration 308
Advertised Exhaust Duration 318
Advertised Duration 308 int./318 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.488 in.


Cylinder Head Style Assembled
Cylinder Head Material Cast iron
Cylinder Head Finish Natural
Combustion Chamber Volume (cc) 64
CNC-Machined Combustion Chamber No
Intake Runner Volume (cc) 170cc

Now i know i shouldnt have got on it before i hit 500 miles but i did at 160miles and it wouldnt break the back tires loose. I was told this was becuase i ran out of money at the end of the build (over 6k for this one), and used stamped non roller stamped rocker arms. So i ordered a set of Scorpion 1.5 full roller rocker arms. I didnt want to take it back for another month so i wanted to try to install them myself.

I read every article on here i could find and watch many videos on youtube. I redid this four or five times making sure it was perfect before i even hoooked the coil back up. But their was a ticking sound that wouldnt stop. I then tried to set rocker arms with engine running and number 6 intake wouldnt stop clicking.

I then turned it off and had it towed of to shop. I was told no warranty because it was a performance application. So i asked what it would take for something with a warranty even a stock replacement. I was presented with this jasper rebuild which was the only option i felt i had left.

Now i am at a lose. I cannot do anything to this engine without voiding the warranty. The tach does not work (cable broke) but when i got her upto 90mph which i am assuming is about 55 it acted like it was running out of gas.

i have a 74 corvette that i owe over 26k on and it still doesnt run.....Gotta love life.

Side note the intake is a professional products cyclone intake not edelbrock performer as i origionally thought.

 

I don't want to sound extremely harsh but you can't complain that life sucks when you decided to mod an engine that wasn't even run-in because it wouldn't light up the rear tires.

Had you shown some patients and waited for the rings to seat properly you might not have felt the need to fit the 1.5 rockers.



Having said that, unless you're being selective with the truth, the shop you're using are very very suspect.

So let me see if I've understood you properly:-

You spent a fortune with this company having an engine built.

You were too impatient to run it in, then complained to them that it lacked power.

Instead of suggesting that you run it in properly they blamed it on standard rockers

You then DIY fitted 1.5 rockers to this engine and wiped the cam.

The same shop that suggested your lack of power was the standard rockers, then offered to take your old, high spec, engine, which probably just needed a new cam in PX for a lower spec production line replacement

Is that correct?



So here's my thoughts.

When you say it wont light up the tires, do you mean from idle, because trying to smoke the tyres from idle with a high stall converter is very hard, the shop should have explained this.

When you complained to the shop about the performance they should have suggested you at least waited until 500-1000 miles before making any assessment of the engine.

Even after that, lighting up the rear tires is a product of torque not peak BHP. The idea that your lack of torque is due to cheap rockers is ridiculous, high ratio rockers are equivalent to fitting a 'faster' cam which moves the power band and torque curve higher up the RPM range, not what you want for lighting the tires up.

If you've explained everything to us accurately, I would never use this company again and maybe get an independent engineers report on the whole story.

When you initially complained about lack of power they should have suggested you ran the car in properly. If after that it wasn't right, they should have done some proper diagnostics, not suggested it was because you didn't spend enough money with them. Then when you wiped the cam, they should have offered a compromise cheap fix as a show of good faith after they made the ridiculous suggestion of the rockers in the first place.

 

No expert but my understanding was that in the sixties GM rated using SAE Gross horsepower ratings on a test stand with no restrictive exhausts, no power devices on the motor, no drive shaft, rear end losses, etc.

In the 70's at some point they shifted to SAE net horsepower ratings which included all of those things.

The third and probably most accurate way is to put the car on a Dyno, tighten it down then run it with the rear wheels driving the Dyno rear wheel rollers to measure the amount of horsepower actually reaching the rear wheels.

If your car was rated at sae gross the most estimates I hear is a loss of 20-30% of that hp through exhaust, driveshaft, gear box, differential and bearings losses to deliver to the rear wheels. There are always mechanical losses when you transfer power is my understanding. A 300 hp sae gross rating would then be something like 225 hp at the rear wheels or expected to be.

Different eras and different measures. It is better to have sae gross 400 hp than 300 hp is all I know!

Lance

 

Ok well first off i am going by advise i have recieved from people off this forum.

IE http://forums.corvetteforum.com/c3-t...ne-issues.html one of my first threads where i was told
and
So i figured that i was told wrong for the break in procedure. I just wanted my car to actually run and be able to drive it. I was not to impatient with it. It probably took me well over a month to put that first 160miles on that engine. To basically insinuate that i am telling half truths is absurd. All i was asking for was some advise that i would be able to tell the mechanic at the dealership when i took it there in a few months.

They took the old engine for the core charge of the new Jasper Rebuild 300hp 350.

Yes from idle. They told me it is how corvettes are designed to hookup and that is why it would not. I have owned an 84/86/97/98 and everyone would light the tires from a stop.

I was told Jasper engines are broke in when installed and i could drive it like i was always going to.

Not higher lift just full roller rocker and not stamped steel.

They offered to fix it for $1500 which is cheaper then the replacement engine i had them purchase. But i was tired of the run around and was told by local parts store that jasper engines had a terrific 3yr 100k warranty. That is the only reason i went with the jasper engine.

 

I cant believe you gave them your old engine as a core. I would have went down to the boneyard and picked up a non running enigne for $50 and gave them that.

 

You definitely have a learning curve ahead of you. That cam is an AWFUL choice for the heads you have.

With the heads you have, and a proper cam, you should have easily been able to "break the back tires loose", especially with your 4.56 gears.

As to your "running out of steam at 90 mph", those gears coupled with a non-overdrive transmission, you'll be doing a little over 5000 rpm at 90... yeah, your motor is pretty much at the end of what it will do.

You need to read some books on engine theory, and try to understand how everything all comes together. Your car sounds like a mish-mash of parts that people who "heard something somewhere about performance" put together.

Good luck... I understand your frustration.

 

Jason I'm not trying to depress you and beat you down, just trying to get across that IMO either you've had some very bad communication with your local shop or they're ripping you off.

I don't have much experience with high stall converters but those I've driven are crap if you just mash the throttle from idle, this isn't how they're designed to work, the shop should have explained this to you.

I'm sorry you've had such bad luck but going back to the engine performance, what's the pull away like if you build the revs on the brakes as you're supposed to with a high stall converter?

 

I hate to see anyone be taken advantage of, You really need to find a near by mechanic to take care of your auto repairs and upgrades. The dealership is so very expensive and you're rolling the dice with what mechanic is going to work on you ride, some care but most don't, about your car being fixed right, the way you want it, and to do it right the first time. Are there any smaller reputable garages in your area that some can point you in the direction of? With the amount of money you have in your ride at this point, I hope you get to enjoy it soon.

Riggs.

 

With respect to my own car when I bought it last fall I had no clue who worked on old cars and did a good job so I went to a local Hardies Sat. Night show of cars and sat and talked with other Vette owners locally until I found who worked on their cars. It was a local garage privately owned and run by a man who raced, has two big block race cars for different types of racing, has a couple desk guys who race, one an oval track guy and the other runs a rail on drag strips, and a couple mechanics, one especially who is terrific with these cars and their systems. They recommended this garage and the first thing I had done there one of the other Vette owners without even telling me went over and looked at the work the mechanic was doing to my car while they were in the process over a several day period. I did the same and over the last six months with all the heavy things I had done we were both there several times watching and consulting with the mechanic and the desk guys. It is the perfect place for me. They have pulled and placed engines and now I've recommended someone who asked here who is using them and if he's happy he may do the same perhaps. This shop does not advertise...but the word of mouth seems to be working well. None of it is cheap but it is work well done and not done if not needed. Your engine saga would never have happened with this shop, ever.

The fellow ahead of me is right...you need to do nothing more until you find a shop like this imho.

Lance