How do you like the AI 219's? Are they the HCR or just standard?

 

they're just the standards. puts down good power for a n/a ls1.
plan is to have them milled some, when tsp does the stroker.
gonna try and run 11.5/1 cr.

 

Just an update and a good baseline for the coming improvements. My butt-o-meter and tuning logs showed me my car was nose-diving at around 5,600 RPM. There was a huge area-wide Metro Cruise in Grand Rapids this weekend with over 30,000 cars and 150,000 people. Today I attended a subgroup of that at a Berger Chevrolet car show. There was a dyno there and for $40 I thought it would be a great time to get a baseline and see if Tony can hook me up with stuff to bring things back in line.

My old LS1 with LTs, duals, FAST, NW 102, StreetSweeper HT 228/232 .612/.600 111 made 433/409 with the peak HP occurring around 6,400. I warned some people that I knew there that it was going to dive around 5,600. The car ran and sounded great on the dyno but the numbers tell the tale. Just as I felt it my torque "curve" was fat and flat as a 10 year old eating lard ***** and although I made slightly less peak torque (It was in a parking lot on a hot day too) it came on earlier and stayed . . . . until at 5,500 everything absolutely nose dived. It made 405/404. If the trajectory had continued like it did before I'd be around 470. Now it's just the waiting game and after install try to find a local dyno to get a comparison pull.

 

Jerry....Bump the rev limiter past 5600......LOL

Sorry....it was right there.

Were you logging this run?? It would have liked to see what timing and the A/F ratio did at that point it noses over (and after).

Want to say valve float but its almost to abrupt for that although it could be if alot of the springs are toast.

I'm confident replacing all we are you wont be dealing with that situation again but it would be nice to figure out what happened to the current combo although spending time and money to do that seems silly looking forward.

-Tony

PS.....If you do hit another dyno make sure you log timing and fueling so we can see if there is anything funky going on with the basics. If they both look acceptable I would think your springs are shot.

 

That is not the heads being a restriction. That's an issue with the valvetrain. As Tony said, the springs may be toast, but it falls off a cliff. Float typically doesn't look that bad.

I would data log it on the dyno next time and maybe try replacing the valvesprings with some BTR Platinums. You may have 450-470 in the current build...

 

Something is amiss with the setup and I do not think the heads are to blame.

 

Hmmm. I think it's safe to say your ls1#'s & this new run were on different dynos? The first thing I noticed, besides the nose dive, is the tq# for a 383. Looking closer, & comparing to my graph, our tq curves are similar up to about 3500. Right after your tq curve begins to flatten, mine is just getting going. The nose dive after 5500 is also very odd. You noted the fuel tables are falling off. If I had to guess I would think it might be a fueling issue.

 

I was kicking myself after the pull. I have HPT Pro permanently installed and didn't think to have the guy push the record button. Stupid. I do have an AFR gauge on the dash and the operator said it was a little lean up top (13.1) but that wouldn't explain the sudden drop off. My timing (I know it can be mitigated by knock etc.) was a pretty conservative 23 degrees, once again may be a factor but I don't think it would cause a dive.

I agree the valve train looks like the culprit. The springs are Lunati duals with well under 10,000 miles but they combined with a fairly high lift and possibly aggressive ramp cam was giving me float/bounce. It's good to know though as when I sell the heads I can give the new guy a heads up to change them.

At Tony's suggestion I have some Terra Yella rockers on the way that I will put on when my heads get here. With Tony's assembled heads and spec'd cam along with some thicker walled pushrods it should eliminate any problem in the valve train. I'll tape a note on my windshield to "Push the damn button" next time I get on the dyno.

 

Just for some comparison fun here's one of an old pull I found of my 346 showing pre-FAST and after FAST. It's basically the same parts I have now sans the stroke and cam.



and here's a street log from a couple of weeks ago.

 

So, I like to play devil's advocate a lot. I do this with my job as a solutions architect and it helps a lot to find holes in our bids so we can make weaknesses into potential strengths.

I would get the valvetrain issue fixed now and get a good baseline. I'm not saying stepping up to the 220s is a bad idea, but you have no idea what you'll be getting for all the coin spent. It could be 10HP. It could be 40HP. You don't know. And it sounds like you went to the 220s because you thought the heads were a restriction. But what if it could be something as simple as wrong length pushrods? That's a huge difference between $100 and $3k+ spend on the new topend. And in the end, you may gain the 50+HP missing with just an adjustment in your current top end. And then what? Would it still be worth it to drop all the money for another 10-20HP? And that's an answer I can't answer for you...

 

Fair enough and I kind of agree with you except on the point of rod length. I measured 16 push rod lengths and they are not even all the same length as that is just one of the problems with the heads I have now. There are other issues with them and the depth of the valve seats are just one of several. For all of the other money I've thrown at this engine in good parts the 243 heads were definitely a weak spot and arguably one of the most important.

I needed new heads and may have been able to pick up some better than I have now used or new ones for less but I've dealt with enough questionable stuff to want to do it right once.

 

Who ported the 243s?

Remember, ported 243s have hit 600rwhp with a FAST. So they can certainly do whatever you want in the right hands.

 

A local place about 4 years ago. They had never done 243s before and botched the job. Then last year I accidentally marred the head trying to get it onto the engine when I tried to put it over the ARP studs and under the brake booster. I had them touchup-mill them to clean it up and they put a little wavy part I could feel with my nail. I was anxious to get it running after a year down and it leaks a tiny bit of coolant externally by the back part of the head now. They only have 2.02 intake and stock exhaust valves on also. I was going to replace the heads on the build but as always it went way over budget and I ran out of money. I've gone with quality parts on everything I replaced. The heads are the last major piece. I'd like to find some more money under a rock somewhere so I can get an ATI balancer while I have it apart.

 

and what cubic inch was that setup?

 

Same as just about every other cathedral port that hits 600. 440. In fact, show me any cathedral port that does more than 600 on a dynojet with a FAST intake. I'll wait. You really need to move to an LS7 head to break through that 600 limit.

I'm not going to get into a pissing contest over this. The heads he has are fucked, obviously. He needs new heads. But there are a lot of issues. So he's not going to be able to do a back-to-back comparison (which is what a lot of people want).

 

I have seen and been involved with countless dyno sessions both engine and chassis and I can tell you that his current combo without the hiccup at 5600 would have likely carried to 430-440 RWHP. Look at the part of the curve that isn't effected.....most telling is the torque curve which clearly peaks in the low 4000's and is clearly rolling over past 5000 till the "anomaly" occurs at 5600 or so. Had this engine carried cleanly it would have been all over regarding peak power by 6000 or so and that makes sense based on the duration/valve events with the narrow LSA helping to close the intake valve early (which helps build that early torque peak but hurts higher RPM carry).....and the fact a 383 will tap out the airflow quicker and sooner than a 346 due to the additional air it moves at the same RPM.

All of this also backs what I discussed earlier in this thread which is the fact peak power is dictated by airflow, not cubic inch, which only increases torque and changes the shape of the power curve a bit (bringing it in sooner with more low/midrange TQ/HP). My 430 - 440 guess is also in line with what his previous 346 combo made with the same parts that dictate how much air the engine can move (heads, induction, exhaust etc.,) so that makes logical sense as well. Also....and this is a good tidbit for you guys to file away....most of these LS engines that we are discussing (street/strip 7000 or so RPM etc.) make their peak power 1500-1800 past peak torque which in this case would be right around 6000 RPM.

This engine would have never made 470 RWHP....its almost impossible to do that with a small engine only making around 400 ft/lbs and a larger displacement engine would roll over sooner losing its RPM multiplication factor in the process (HP = TQ X RPM / 5252)

Anything the new combo does exceeding 440/400 looks to be a guaranteed winner in my book....assuming the 5600+ gremlin doesn't exist any longer!

I just took the time to plot the theoretical torque curve had it not had the issue and if you look at it I think most would agree at 6000 RPM it would have likely made 370-375 RWTQ at best keeping in mind the larger engine would have started rolling over faster with more RPM. Even if I use 375 RWTQ, that puts the power at 6K at 428 RWHP so my 430 - 440 "air dyno" numbers seem very realistic and 440 might have been a stretch.

Hope this helps....

-Tony

 

Dumb question here, but I thought heads were more affected by bore than stroke. Would 235's do better by virtue of feeding the hungrier air pump?

 

Bore hasnt changed.....its 3.900 in both applications!

-Tony

 

right. That's my question. I would have thought that with the same bore the 220's would be perfect for both. Instead it looks like the 235's might do more better since they move more air? Or would the bore restrict it anyway?

 

235's get handicapped with the smaller bore and larger valves.

Plus the 220's are perfectly sized for a 383 application that will spend almost 99% of it operation cruising the street....especially in a heavy car that the owner is interested in strong low/midrange power, not just punching a big peak.

Its the right tool for the job in this application without a doubt

-Tony