Correct me if I'm wrong but I believe jimlab has a 396ci LT1 using AFR 215cc heads and makes 700hp NA and it was built by Mark Mantalvo (sp?)

So with these exotic heads you really don't need to exceed 7000 rpm? Just a decent roller cam and more than 383 ci?

I'm sure these heads are very thermally efficient so can you run high static CR,13:1, with 94 octane on the street?

Sorry, just trying to see what these heads can really do for a NA street engine.

 

Sure is alot of good info here, for us rookies(me). I come on here every day and learn something new. This is great.

 

Last I heard Jim made 647hp at ~7k. He was looking forward to a bit more tuning though, so there may be more left in that thing. 50 more horses might be a stretch though.

That was my thoughts on the thing. You would like to make the power before 7k and you can do that going this direction. Mine peaked at 6600 rpm and ~650 hp. We picked up a few horses the next day but that's not to out of the ordinary with a good heat cycling of the rings.
Not bad for a 6600 rpm 383. The consensus is out that we could get another 10-15 hp out of it, but I'm happy to leave that in there.
I'm also running a static compression of 12.3:1 as per Chuck's instructions with this cam choice.

-Mindgame

 

I think 13:1 is too much. Unless you have alot of cam and your dynamic compression ratio is low.

They can really do around 700hp if the right combo is put together, and that's in the 6,800 neighborhood.

Jason Short has looked at this, the problem is the funds and if his heads are not going to get him where he wants to go.

Bret

 

Definatly alot of good info here. I especially agree with Mindgame when he mentioned that some people go overboard with bottom end stuff. Put the money into the heads, cam, valvetrain as long as you have a *decent* bottom end. Obviously forged parts at this level, but for NA (and even some power adder), billet stuff is a little overkill.

My top end was considerably more than my bottom end. I chose to put my money into the heads, etc...

On Jimlab's motor (hopefully he will chime in here and correct me if I have mentioned anything wrong about his project)....In talking with Mark, Jim wanted to keep his motor within a couple boundaries. First, it has a pretty small cam. It would be pretty easy to see over 700hp from his 215RR motor. A larger cam would help with that. Also, I think the largest gain on Jim's motor would probably be in the intake manifold. I know that he was limited on intake manifold choices due to parameters within his engine bay (hood)....since this motor is after all going into an RX7 Mark and Jim decided on going with a Hogan, which performs well for the constraints he was facing, but not as good as a single plane would. Either way, for the driveability Jims motor will have, 650hp is VERY respectable.

I too have been thinking very hard over the last year of doing a 15 degree top end on my motor, but for the sake of learning wanted to see what I could get out of my 23* AFRs and LT4 intake. I am in the process of finishing up a few small changes/tuning to the motor now, and should be on the track withn 3 weeks hopefully. After that, a single plane manifold will be going on the car this spring.

I will probably start on either a 15 degree top end or the AFR 215RR's this summer or early fall....700hp with a 7000 redline will be my goal, although I dont know how close I can get to that mark without additional revs.

I am glad to see people trying to raise the level of NA LTx motors.
jason

 

Jason,

That's what I was trying to do on this buildup. I wanted to try and make as much HP between 3k and 7k. I'm sure I went over board on the Billet rods, but was going to spray it aswell. I guess I rather be safer than sorry.

I'm not sure I made the right choise on heads and cam but sure they will do well. Someone on hear told me my combo was similar to yours. AFR 210's which flow
Intake/Exhaust
.200--153.4/103.5
.300--209.1/157.9
.400--254.6/195.7
.450--269.6
.500--281.5/221.6
.550--291.8/227.6
.600--299.3/231.7
.650--306.0/233.6
.700--310.5/235.9
My cam specs are 250/256@.050 and the lift is 644/614 112ls solid roller, and the Commpression is 12.5.1. I was hoping to make around 500rwhp. Sometimes I wonder how much more the 215rr's would have given me, but I'll never know. This car will see the track/street and that's it. Only gets driven a couple of times a week. I guess if you go with the 215's I'll keep track of your progress. My car is all most done so I'll see what she does soon, and post my results.

 

The specs you give are pretty close. I belive he made 490rwhp untuned and he's going to do that. You should be close to your goal when all is said and done.

Good Luck

Bret

 

PNYKILR, your heads are flowing more than mine....looks like around 2-4% better depending on what region of lift. With that cam (and compression)you should be in the 480-500rw range pretty easily.

Actually I have not dynoed my car yet, but I calculate it to be in the 475-480rw range now. It has never been dyno tuned, so I am anxious to get that finished up in the next 3 weeks. It will be nice to see what actually is going on with my car on paper so I can figure out where optimal shift points are. I also might advance or retard my cam based on what the dyno graphs show. Either way, a little more tuning and tweaking with this setup before the single plane intake goes on.

Right now I am about 95% sure that the 215RR will be the basis of my new top end. To date, I believe Mark and Jim are the only people that have used these.....both of which are in the 650hp range with tame cams and non-single plane intake manifolds. However, they both are reving over 7000rpms. I really dont have any desire to drop $2k on a FAST engine managment setup, so it sounds like there are some similar boundaries/goals that a few of us are trying to work within/twoards.

Either way, if I do the 215RRs it will have a single plane intake manifold with a power peak ~6600rpms or so. Most likely I will change the cam to something that only has mabye 3-5 degrees more of duration, but with .030" or more lift.....who knows, mabye I will just reuse my current cam first. I will talk to Cam motions about the power/torque difference between the two before I make a final decision.

I am going to spray eventually since I want to go considerably faster, but I dont know when. I may just keep focusing my money into really trying to go somewhere NA. (~10.4s@134-135 would be kinda the goal). It would be neat to see a true street car do that.

Jason

 

I agree.

Power peaked at 6,600 rpm (just before the ignition-related dip) and recovered to 637 hp out at 7,400 rpm afterward, so there's an interesting area still to be seen between those two points (including the actual power peak) that the FAST eDist should clear up. We still don't know what's in there, and I wouldn't be horribly surprised to see 660-665 horsepower when all is said and done, but I would be very surprised to see 700.

 

I agree, but I did go "overboard" on my bottom end for a reason, and didn't compromise my top end in the process.

I had a Cola 3.875" crankshaft and a set of H-beams, but sold them and had Crower make me a 37 lb. billet crankshaft (also 3.875") and a set of Maxi-Light rods because it was one place where I could shave a lot of weight and help the engine rev more quickly. 505 grams is pretty damn light for a 6.0" steel rod.

My goal was to keep package weight (and size) to an absolute minimum (which are a couple reasons why I chose not to use a supercharger) to avoid upsetting the balance and handling of what started (and should remain) a very light weight (~2,700 lb.) and nearly 50/50 balanced car.

Was any of that necessary for ~650 NA horsepower? Of course not. But they were the strongest and lightest parts I could easily source, and I had the money to spend.

I don't know that my top end was considerably more expensive than my bottom end, but the Hogan's intake didn't help.

I think I put enough into the top end. We wanted a set of raw 215cc castings so that we could remove just what we had to and keep port velocity relatively high while trying to get some really nice flow numbers, and we accomplished that. Again, the Ti valves weren't necessary, but for an engine that'll occasionally turn 7,500-7,600 rpm, it won't hurt, and it'll save a little wear and tear on the valvesprings, possibly.

Had to run on pump gas, and had to be fairly streetable. Not "daily driver" streetable, but nothing that required a trailer, either.

And the package had to fit under the stock hood with adequate clearance, and the bulk of the weight had to sit behind the centerline of the front wheels. But other than that...

Me too...

Although at this point, with the complete elimination of the Opti-spark (FAST eDist) and a FAST SEFI-8LO, the only thing that keeps me from buying an aluminum Bow-Tie block was that we've already sunk so much money into the LT1-specific 215cc RR heads and block machining. I could sell my heads and start over with a "traditional" set of 215cc heads (I'd probably have to scrap the Hogan's intake and Crower rockers and start over again if I wanted to use anything else) but I think Mark would probably have me tracked down and shot in the street like a dog. He wants to see this engine finally finished as badly as I do.

 

Thanks Jim....you were an exception to my line about not neccessarily needing the bling bling bottom end Of course my motor runs 50-60% of the money yours does!

And Jim....you can always sell me your heads

Jason