I just wanted to post up and see what people thought on my LT1 build, pretty unhappy about the Dyno results but I don't believe its too its full potential yet. So last Feb I bought a 96Z with a blown motor ripped it out and built a new one, its a stock block .40 over with speedpro pistons, stock rods, eagle crank, factory windage tray, high volume pump, clevite rods, mains and cam bearings. Bottom end was put together by my dad who used to build race motors so everything was spec'd and plastigaged. He also completely balanced it and polished the rods until oil just slid right off of them. For the heads he decided to port exhaust himself based on the pacesetter paper gaskets which he actually got pretty close to opening them up the acutal size of the hole on the gasket and yes he did make sure they aligned well with the header tubes. after porting he evened them out with the sanding rolls and then scotch brited each one until glass smooth, he got pretty deep into the ports too. For the intake mostly the same except for not as quite big and he made a template on the heads of the ported intake holes and matched it over to the intake itself. The heads were also milled down giving me close to 12:1. The cam is a CC306 with scorpion rockers 1.6 ratio, ls7 lifters and stock pushrods. Valve train geo was checked also. Im also running pacesetter longtubes. The car still has stock Injectors, throttle body, coil, opti. It has a 3500 stall through a 4l60 and and a stock 10 bolt. After getting the timing curve and fuel tables tuned in during the tune it put down 320RWHP but with the converter NOT locked up. We were having issues getting it locked up and running out of time so I opted to take it home and bring it back. Got the converter to lock up now, not quite sure what the issue was on the dyno but 320 seems a little weak to me even without lockup. Now im trying to figure out why. Even with the stock TB am I really missing the 20 or so RWHP it "should" have? Is there anything else Im missing thats got me that low? Another thing that has me thinking is iv'e been driving the car for 2 days now and every time I let out of the throttle when Ive had it pinned i can hear the trans squeal. Maybe it could be slipping, and that's why the numbers are down? Just feel like I'm doing something wrong and figured I'd ask. Sorry for the whole long drug out story just trying to give you guys a realistic idea of what I'm actually working with. All ideas are greatly appreciated

Thanks
Ben

 

What size is your engine that would help also all of your power is in the heads/cam/intake and did your dad have the heads flowed before they were installed, I believe that's where your combo is falling short? You basically have a fresh stock engine with a cam, but I would still expect it to put 340-350 to the rear wheels. Get in contact with pcm4less.com or Madtuner.com and give them all of your cars specs and get a mail order tune as a starting point.
But I'll just warn you up front since you're relatively new hear, get your flamesuit ready some of the folks here will give you the business.

 

What rpm did it peak at?

Sounds like you did the all too typical
"I am going to trust the guy who hasn't learned anything in decades"
and got a result inline with that level of knowledge.

Using gaskets as the guide to port a head is decades outdated thinking and based on your result he might have ruined the heads rather than improved them. If the bowl on back is worked enough to dictate the port open up to the gasket that is one thing but working from the gasket end and reaching "pretty deep into the ports" is the wrong way to go. Besides you generally want the exhaust port to be smaller than the header for a lip to hinder reversion.

Did you get the under $200 eagle crank? Those are a LOT weaker than stock. The HV oilpump is another expression of ignorance and will wear out the oilpump drive. Which speedpros? likely heavier than stock with a step backwards ring package as the stock Mahle's are not cheap or easy to improve on.


Don't get fixated on the locked vs. unlocked, it is not that big a deal and isn't what cost you the 30% or more HP this is missing vs. if you had actually good heads/cam on an untouched stock shortblock.

I sincerely hope you find something you overlooked and find 40rwhp instantly, but too much time seeing too many "old school" hack jobs on LT1s suggests you spent a lot of time and effort to get a HP number EASILY achieved on a stock motor with a very mild cam and no head work atall.

The TB isn't the problem and I don't believe the injectors are the problem yet either unless failing.

 

Most "old school" guys know better than to use a high volume oil pump in the SBC.

The stock TB can make over 600 fwhp.


Did you log your dyno pulls with a scan tool? And log the air/fuel?
You could have severe knock retard issues, or your fueling way off. Knock retard will make a lot more difference than the fueling. May just be tuning issues.

 

That is a good point, did the old school guys program it for mid to upper 30s timing not understanding the pcm adds additional and that the LT1 needs less timing than older head designs. Could easily put one into low octane retard.

 

Could just be false retard due to noise. Valve train, over torqued knock sensor, etc.
And, "port matching" the exhaust is wrong. Not likely to cost over 20 hp, however.

A high volume oil pump along with a windage tray makes me hope he doesn't go out and try to find out how fast it will run top end.

 

A real good investment for many here would be Reher & Morrison Racing Engine's book on engine building. Even better, if they still have it, would be attending their engine building school. They are located in Arlington, TX. Great guys.

 

My point on the "port matching" thing was not that the exhaust misshandling would cause a 20hp loss but rather than someone with such an inclination is so clueless as to be unlikely to actually be any good and the whole handling of the heads is likely bad and I would sooner be inclined to consider the heads ruined than "ported".

 

Don't try to figure anything out until you can get it to a track and see what happens.

 

That is a good idea but still I wouldn't get my hopes up on a 70s style build.

 

The ports were done correctly, my dad ported them under guidance from a Local engine builder here in Raleigh who has plenty of experience with Lt1's from the 90's. He even approved and thought they would flow "pretty damn good" same with the intake. The pistons were the speedpro forged and the eagle crank was also forged. This car was not tuned by "old school guys" it was tuned by Mayhem here in Raleigh, who is regarded as one of, if not the best in the area. They also thought the number should've been higher. With that said, me and my dad were just trying to have fun and build a fun little street car, I KNOW that the stuff he was doing wasn't gonna help a whole hell of alot, I KNOW that if I would've sent my heads to Lloyd Elliot I would've had a much better head, I KNOW some of the stuff he was suggesting we do like the High volume pump and **** like that may not the best, but ever since he sold his drag car in 98' he hasn't played with any high performance vehicles until.. well.. now and I don't think I've seen him as excited and involved as he was in this build...really ever. So this whole thing wasn't really about the 3.5hp im losing there, the 4.75 im loosing over there it was just about something we could do together SO NOW WITH ALLLL THAT SAID the transmission lost 3rd and 4th an hour ago and I believe that to be my problem. Slipping on the dyno maybe?

 

Maybe it was slipping on the dyno and is making better power than expected, that would be lucky in one respect.

Seek out a tranny builder very carefully there are a lot of shops who can take your money but not make it last as well as stock much less actually improve it. You don't need any real hardparts upgrades, the stock 4-pinion planetary is just fine, as is the bone stock input shaft etc. What you need is a thoughtful rebuild with careful attention paid to clearances and setting up the shift kit right for quick but not hard shifts.

What rpm did the car peak at? Valvesprings are a really easy place to make a mistake and have power tank early.

 

Good old 3-4 clutch pack.

 

It has comp 918 springs and is peaking around 6200 RPM. How would I get BETTER numbers on the dyno if it was slipping? or are you being facetious?

 

never race a dyno!!! if it was a load bearing dyno the hp number could be dead on or way off, ive seen as much as a 20% difference from an improperly setup mustang dyno to a 224x dynojet.......I was on a local load bearing land and sea dyno that said my 3250lb 138mph trap car made 465rwhp unlocked through the 4l60e, my new shops Dynojet read it at 578rwhp.........my point being don't get hung up on dyno numbers..........and get yourself a scan tool, whats the AFR at WOT and the spark advance at WOT? like ed said it may just be a garbage tune

 

6200 on a cc306 seems low, what are the springs installed at height wise? got a pic of your dyno graph?

 

Im not sure what he set the height on the springs to. The machine shop washed, milled and cleaned up and installed the springs, and new Ferrea 8000 series valves in the heads for me.

 

I'd get the transmission fixed first and remove that variable.
Get the car running and driving well, enjoy it for a while and then maybe look at upgrading the heads. The throttle body needs nothing more than a $30 airfoil at your power level. With LTx heads, the shape of the port is really everything. Just "opening up and smoothing" the intake and exhaust ports is often a great way to kill the inherent efficiency of these heads. Old-school backyard porting methods will kill velocity. I've seen M6 cars dyno 365+ with the CC306 and stock untouched heads that have never been off the car. So you may not be all that far off for what is essentially a stock-headed 306-cammed setup with a slipping tranny.

Mayhem tuned my car and is competent with LT1 stuff so there shouldn't be much worry in the tune.

Just out of curiosity, have you calculated your static CR? What do your pistons weigh? What exhaust setup are you running?

I've seen your threads over on HPJ, you're fast learning how trying these cars can be at times.

 

id look into it just in case, ferrea doesn't make 8000 you prob mean the 6000 which is a perfectly fine choice for what you are doing, the 918 springs install at 125lb on the seat iirc with a 1.800 install height which is where they should be on yours if the pockets haven't been fudged with, that should be plenty to control the cc306 long as they didn't cut your spring pockets deeper then you lost seat pressure and that could be your issue they coil bind at 1.100 leave yourself .050 for safety that gives you .650 to work with, you have .576 so you can shim them .050 if needed to drop the install height down to around 1.770, that should give you around 137~ at the seat (with the 373lb spring rate) which is MORE than enough to control what you've got there........

plus yea fix the trans and hit a different dyno and see what happens

 

Stock injectors? I would use at least 32# with the 306. I have le2 heads and the 306 and I'm using FAST 36#