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That's what I think this engine was/is......an over achiever and a build that just worked a little better than one might have imagined it might simply looking over the specs.
With nothing exotic here this 402 generated 662 HP and 585 Ft/Lbs on an engine dyno....just the right selection of parts that netted some very strong results (on two different engine dynos btw).
If you guys want all the backstory, there is an older much longer thread that you can click on the link below to access, but I wanted to consolidate just the dyno results here and the parts and specs that made it all happen.
So this is basically your bread and butter 402 CID combo.....as most of you already know that is an LS2 block with a 4" stroker crank installed in it
Engine was fitted with aftermarket flat top pistons and a -3 cc effective dish volume (created by the valve reliefs).
Heads were Mamo Motorsports 235 cc cathedral heads that were fitted with 2.100 hollow stem intake valves and 1.600 solid stem exhaust valves.
These heads were designed specifically with medium sized stroker engines in mind (perhaps 400 ish CID is really the sweet spot for them) but they have worked well on 6.0 builds up to LS3 stokers (416's) with very good results.
When the porting was all wrapped up we milled the heads to 66 cc netting us exactly an 11.75 to 1 static compression ratio factoring in the .036 optimized quench distance we set with the correct thickness head gaskets.
I felt with the custom cam I had settled on (that had 18 degrees of overlap) in this size engine, we would bleed off enough cylinder pressure to successfully run 93 pump and still be able to get some decent ignition timing in there.
The engine seemed to run the best with 26.5 degrees which is right in the ballpark I typically find most if my LS builds seem to like (26 - 28 degrees at peak power in gasoline engines at least).
I should also mention Josh also spent a few bucks more for the "CNC plus" version of my heads. This is what most guys on the Net have dubbed "Mamofied", a nickname Pat G. started 20 years ago that stuck immediately. If your an old timer on this board you know who Pat G. is.
Basically after all the CNC work is complete I hand finish the chambers, bowls and short turns completely optimizing all the critical areas of flow where almost every CNC program will leave steps and ridges and sharp edges etc. that disrupts and reduces flow.
This hand finishing work increases both intake and exhaust CFM across the entire curve, increases the air speed and reduce the chance of detonation with no sharp edges or hotspots at all in the combustion chamber (helps with a touch more ignition timing potential as well).
Looks like so when its finished....
Camshaft....we went with something fairly aggressive but not over the top. As I mentioned previously 18 degrees of overlap. It had 243 degrees on the intake side and 249 degrees on the exhaust with a 114 LSA that I ground 3 degrees in to help with the weight of Josh's TBSS.
If this was going in a Vette or a 4th gen FBody (a light application) I would have only run 1 degrees of advance to help it make a little more HP up top but the torque curve this engine made was perfect for the heavier hotrod it's being installed in.
I wont get into specific lobes but with a 1.8 rocker we had .675 lift on the intake side and .671 on the exhaust. And these lobes are not super aggressive by the way. With a premium spring the ramp rates will provide alot of life before needing to be replaced.
Speaking of springs I ran a Manley Nextek set up tight for good spring pressure on the seat (so no valve bounce on the closing side of the cam) but modest over the nose pressure for more parts longevity in mind.
Rockers....Most of you that have followed my builds the last two decades know I run YT Ultralites on ALL my HR builds. They are an optimally designed rocker arm with an HR valvetrain specifically in mind.
Unlike stock rockers they don't sideload and wear out your valve stems and guides due to the fact they have a much more narrow wipe pattern and are rolling (not scrubbing) across the valve tip.
Besides tripling the expected service life of the heads you will make more power with more net lift compared to an OEM rocker. In this case with a 1.8 ratio that benefit was amplified even more with the higher lift and slightly faster valve acceleration the 1.8 ratio provides.
Also, these YT rockers were special upgraded versions only available through Mamo Motorsports that come with MUCH stouter 10mm hardware which I have to drill and tap the heads for on the CNC to accept the much larger 10mm fasteners.
This reduces any flexing of the rocker arms putting more action into the valve. If your rockers and stands are flexing a bit the valve isn't opening as much.
Naturally this also adds more reliability and its much more confidence inspiring to actually put some real torque to your rocker gear (42 Ft/lbs versus the OEM 22). I run the 10mm stuff in everything now.....its well worth the couple of hundred additional it costs.
I have always questioned why the factory went with borderline 8mm fasteners in all the LS valvetrains.....IMO it didnt leave alot of room for growth but Im sure it cost less and was lighter so the bean counters at GM gave it the nod
Induction....another bonus of this build was the height we had to work with allowing us to run a ported LSXRT. It is my favorite cathedral intake but sadly it only fits in trucks or custom applications that have the room.
While not very sexy with the cover on, take it off and your looking at a cross ram with radiused trumpets way high up feeding the intake ports with a straight shot of air and an optimized runner length and taper for most street strip applications
Properly ported the LSXRT performs amazing but they need help with the grinder to realize their max potential. Make no mistake about the fact this intake is part of the magic that helped the "Over Achiever" 402 put up the numbers it did.
Here is a good shot showing just how wicked this manifold is with the breadbox top removed!
Throttle body....Naturally we went with a larger 103 mm Nick Williams TB that Josh also gave me the green light to hand finish as well which adds a bit more CFM to the mix with the very smooth and optimized bore housing shape when Im finished
This additional porting and finishing work gives the 103 even more throttle response which is worth the modest increase in cost all by itself and once again we are optimizing every part being installed here....all the nickels and dimes add up
Lifters.....Johnson short travels got the nod once again. Most of my optimized builds you will see these are the lifters I usually spec out to the guys willing to spend the time in measuring all the cylinders to optimize the preload in every lifter
This nets you more performance and a much quieter valvetrain as well. Its the closest you will get to an SR lifter in performance and you have zero after install maintenance (no valve lash adjustments from time to time).
Its worth the time you invest up front setting it all up and measuring every cylinder because that's it....if you get it right you set it and forget it. This is easily facilitated with custom length Manton pushrods and I have trained quite a few of you guys out there on just how to do this.
One of my current LS7 customers is working on a "How to" and hopefully creating a video as well. If this happens I will share it with the community in it's own thread.
OK.....so this draft has taken me alot longer than I thought it would (shocker!).....so quickly filling in a few more of the blanks we have an ATI lightweight dampner with an aluminum shell and a steel hub (10% U/D).....a ported Melling high volume oil pump and a Cloyes single roller timing chain should also get a mention here.
Headers and exhaust....I honestly don't know so I will let Josh chime in here and fill you guys in on that. Im fairly certain the engine was tested on the dyno with 1.875 primary pipes but will let Josh confirm that.
Once again.....not an exotic engine build here by any stretch of the imagination but alot of extras were included in the form of additional porting and better more optimized parts etc......the T's were crossed and the I's were dotted and all of this paid off well to help an already solid package perform even better.
Did this build cost more than your average build.....sure it did. Better parts and additional porting always does but the end results make you quickly forget about the money spent and not having any regrets about your build is also priceless. Not everyone can say the same
Hope some of you benefit from reading this....if your interested in building something similar please fell free to reach out to me so we can discuss it in more detail
Josh congrats once again on sticking with it and finally getting to the finish line. Im looking forward to hearing about how this combo runs in your truck
Cheers,
Tony
PS....Excuse any typo's and misspelling....I need to get back to work here at the shop....will proof read tomorrow!!
402 cubic inches
11.75 compression
Plastic intake manifold
662 hp at 6650
585 ft lbs at 4800
Very well done once again Tony. Quite the combo here that should be easy on parts. Impressive to say the least.
Tony what do the 235s flow in general after you have worked them over? Say at .600 lift? Great numbers here and very good tq which I know that is where the cathederals can shine (1.45 tq per cubic inch).
Nice combo! There's been more than once when I wish I had an old truck so I could try things without any concern of space. I am so constrained by the form of my car! Case in point.... I still have a single 3.5" exhaust with your LS7 package! LOL!
Great write up Tony, I'm definitely extremely happy with the results once again! When we originally talked I think you told me to expect in the ballpark of 625-630hp as you typically see more with the larger bore 416ci engines.
The headers used were indeed 1.875" American Racing Headers, built for the TBSS, the same headers I will most likely be using in the chassis. Before the engine was taken off the Dyno they did experiment with my old set of 1.750" Stainless Works headers, more to come on that once I talk to Scott the owner and tuner at SD Concept Engineering about the graphs since I wasn't there this time.
Anyways here are some better images of the graphs and my little over achiever. As you can tell from the data she was pretty happy with the tune, I believe it was 12.8:1 commanded AFR and 26.5* of timing like mentioned. And as you can see in the first picture, 3" piping into mufflers as well.
I can't wait to see how the internet will tell you how you could have done it better.
The average power of that thing must be ridiculous.
More cam, more compression, LS3 style heads or small bore LS7 heads, FAST LSXhr intake. Believe me I have heard it all by now but let's not forget a TBSS curb weight is 4550lbs for RWD with no weight reduction, all that 7000+rpm stuff will be a turd down low IMO. I'm very happy with the engine and how well it runs especially for where we wanted it to make the power.
More cam, more compression, LS3 style heads or small bore LS7 heads, FAST LSXhr intake. Believe me I have heard it all by now but let's not forget a TBSS curb weight is 4550lbs for RWD with no weight reduction, all that 7000+rpm stuff will be a turd down low IMO. I'm very happy with the engine and how well it runs especially for where we wanted it to make the power.
**** all of the internet experts, especially the ones who don't even have a vehicle or even know how to work on one.
If you are happy with it, that's all that matters.
Tony, this engine with a carb, would it peak with a higher HP number? Just curious.
Assuming we are talking about a carb with a single plane intake it would have peaked say 400 RPM later (and made a larger peak power figure) but you would have brutalized the bottom and middle of the curve seeing losses in the 40 - 50 ft/lb range down low and in the middle. For this type of application that would have been a really bad choice and the full weight truck would have felt 1000 lbs heavier cruising around town.
This ported LSXRT is simply the perfect intake for this application and the HP it made was still impressive while being outstanding across the bottom and middle as well. Look at the dyno info again.....it's making 500 ft/lbs or better from the bottom of the run to the top.
Part throttle and tip in with the longer straighter runners will be excellent on this thing and this type of power and torque curve will make the truck feel 500 lbs LIGHTER
Double06 had inquired about the MMS 235 flow figures. Basically these heads are almost at their peak flow by .600 lift and that's a good thing. On the intake side they flow low/mid 330's at that lift point only picking up another 5 or so CFM when they peak at .650 - .670 (about 340 CFM there). This is by design and it allows you to take the most advantage of all the air they offer at a lift that's easy to achieve in most of your typical cam designs and having the engine dwell there at max airflow and velocity for a longer period of time will increase the cylinder fill (bumping the engine's BMEP and volumetric efficiency). Exhaust is the same situation btw......at .600 they flow 255 - 260 picking up only another 5 CFM or so by .650 lift (and a few more at .700 but the bulk of the airflow is all in by .600 lift)
Guys....appreciate those of you that have taken the time to comment and post etc. I thought it was a story worth telling that certainly a reasonable percentage of you would appreciate.
Unfortunately or fortunately....LOL, running this business consumes my life now and I don't have the time to post as much as I used to so Im alot more selective about it when I do.
Tony, that's what I suspected. In my mind I was comparing this engine to a stroked 351 Windsor my neighbor had built with carb. He had a slightly higher peak and it was going into a fox body drag car car.
Well done, Tony, well done. Once again, you prove that talent, developed by diligence and discernment, and sweating all the details properly pays off BIG. This is sort of the inverse of tolerance stacking in engineering (a negative thing), you're getting all the little variances to add up in the same direction...positively! I would say amazing but your excellence has become the expectation by those willing to plunk down the coin and us old timers know it. I hope before I die one of your top ends can grace my ride. Few as good and none better, keep doing your thing!
01-24-2022, 05:19 AM
402 CID "Over-Achiever" 93 octane pump gas build 
