Let's remove the added head shim from the SH PT21A0-XBG.21 Nitro racing engine shim removal test

Here we remove the added head shim from the SH PT21A0-XBG and test.

[@cbh148]

Just saw you returned to making vids here about 10 months after this one was made. I bought one of these SH PT21A0-XBG engines and finally got around to running it over the last month (did the idle break-in back in the spring then kept it in the nice plastic box that it comes packaged in to await its day in the buggy). I installed the extra head shim from the beginning. I'm at the 1 gallon mark and it's been great! Noticeably more pep than the 2 Trackstar .21 engines I've been swapping back and forth between for the last 3 years (replacing piston/sleeves on them as they're cheap but seem to lose pinch quickly, though that could be user error). Granted, most engines all behave well at the 1 gallon mark so this could be somewhat of a honeymoon phase, but it this one has had excellent manners and idles like a champ, hasn't been finicky on the tune. I'm running it with an old JP-1 (low end focused) pipe with a JP-3 manifold (don't know if the manifolds were different between the Jammin' JP-1, 2, 3, etc, but this one's hard anodized whereas my JP-1 pipe is polished). I'm enjoying this engine so much that I'm tempted to go ahead and purchase a replacement piston/sleeve/rod for when that time comes. Thanks for the recommendation!

[@NitroTalkwithTodd]

I noticed the same thing with the Trackstars. I went though 5 in three years. I still think they were a great value though. An excellent carb, I've ran carbs from Trackstars on a few engines. The SH pinch starts much lower, and seems to last considerably longer. I bought my 21AO's around two years ago, 3+ gallons on each and they both are still a pleasure to run. Thanks for watching!

[@ElDiabl0187]

That thing was really fast very impressed, awesome power

[@glenhenning9261]

That's one wicked buggy! It would give my 1/8 serpent on road a run for the money and that's sayin' something! On roads are belt driven 2 speeds.

[@stevejackson3564]

What I heard was a better & more take-off on low end. I didn't hear the short lag before you took shim out. I know your trying to make the decision when to make the move on remove or not remove. Thanks for video. I enjoyed your experiment on head shims.

[@NitroTalkwithTodd]

That seems to be the consensus. Although I'll admit that it didn't really stand out to me at the time. I took both of my 21AO's out to test some other engines. While a lot of the hassle I have had since removing them was clutch related, i do miss the ease with which I ran those for almost two years.

[@needmoreboost6369]

It’s definitely given it some more zap! I think you will find good gains de shimming most rtr engines as they are often pretty conservative with comp for less sensitive tuning requirements and longevity, shim to suit the nitro content being used is best and typically more nitro needs more shim’s otherwise you’ll find it eating plugs and difficulty with temperature control even with more fuel or at very least a shorter life than the gains are worth, I’ve found in some cases no gasket beneficial in order to get required comp ratio without machining the button

[@bowi73]

i agree sound and looks the same , i would go back ,like you sad less compression is better for the engine . here in holland the law changed we can only buy 16% nitro i used to use 20/25 % nitro , i haven'd changed the shims good power but you can see the difference and have lean them bit more on 16%

[@jayp9299]

That thing rocks

[@bevinsracing]

I have 2 of these sh engines associated buggy and truggy great power and reliable

[@keithbates695]

So this engine has no problem pushing a truggy. I am definitely thinking about putting this engine in my HB truggy. What you think

[@cbh148]

Just bought my first one. As of last night, I've completed 6 tanks of idling on my break-in chassis. I put the extra head shim in first. I used the heat gun to get the crankcase up to 210~250°F, then put the engine heater on the head to help it hot. Instructions said the carb settings were already set for break-in, but mine wouldn't fire up until I leaned the LSN way down. I never changed the idle gap, and I think the instructions showed 1-1.5mm, but that might've been just for break-in. Curious to know what idle gap you've been using on yours since 1-1.5mm is quite a lot more than the 0.45-0.55mm that JQ recommends for OS engines.

[@needmoreboost6369]

I’d have to say it looks like the sh engines have come a long way in performance and quality with newer models,I guess they are a bit like Kia cars they were garbage but are getting pretty good now

[@Bullwinkle39]

I built a nitrostar 25 from a parts box without head shims, it's becoming a really strong and snappy engine

[@Bullwinkle39]

Might have had 1 shim, I forget now

[@JakeHughes-oo7gy]

I gotta try this on my dynamite engine.

[@rc-ops]

Great video. Thanks for sharing your test

[@samsonight2721]

It seemed to me with the shim removed the low end was more aggressive allot snappier low end take off

[@mcnitro874]

awesome Todd love your videos brother

[@islandrc-duke1972]

great information and great runs,cool motor

[@favulus1]

Quick question Todd. I just converted my mp9 rtr from pullstart to back plate. On my starter box i cant set the back pegs because of the mud guards so i removed them being the mudguards. I noticed on your starter box you don't have the pegs on it at all. Did you do that because of the mud guards or you just decided to run the starter box without the pegs?

[@NitroTalkwithTodd]

I went pegless years ago, for the simple reason of wanting to use one box to start all my buggies. 90% of the starting I do is hyper 7 buggies, so I put a couple little pieces of tape on the box so that I can line up the edge of the chassis with them and quickly start hyper 7s. And with practice I've gotten a lot better at lining other vehicles up over the wheel by sight. Thanks for watching!

[@jdportwerks6795]

Rookie mistake! But it’s happen to all of us at one point! Especially the older we get🙂

[@johnbravo7542]

I caught it

[@SLC_nitro]

Glad ur back! I asked everyone about shiming my os 21tm mainly because it was hitting near 300 during beak in. I try not to tune with temp gun but I didn't want a 350$ paper weight. What's your thoughts? Runs good now after about 3 qt. ( started not temping it)

[@NitroTalkwithTodd]

Adding a head shim can't damage anything, and a reduction in compression can decrease temps. It's worth a try. Have you measured head clearance with stock shims?

[@SLC_nitro]

@NitroTalkwithTodd I haven't. I think the stock shim is .2 . It's also one piece button and head

[@CrivRex]

Could I upgrade my tmaxx 3.3 to this SH .21? Is there much difference?

[@evanmeneilley3228]

And also when you remove a shim you should go higher nitro percentage as you said but didn’t run it

[@colescott1773]

Did you have a problem with the flywheel not wanting to fit properly on the collet the motor came with?

[@ramonguzman6366]

I love the speed on that RC, can you give me the link ,to where i can buy that pipe an heather ,thanks

[@NitroTalkwithTodd]

I've had others ask where they can get the 2035 pipe. Sadly, I haven't seen one for sale in some time. What i do recommend, if it's this engine that you are looking for a pipe for, is the dynamite 053. They are readily available, and this engine loves them.

[@joeloalexis9030]

Is that lake park? I used to go there all the time cool to see it’s still open!!

[@NitroTalkwithTodd]

Still the best $2 you can spend

[@johnnyjackson4490]

Seems to be a little bit more snappy on the bottom.

[@daveshank1921]

What track is this? It wouldn't happen to be Lake Park in Tampa?

[@NitroTalkwithTodd]

The one and only

[@dondagy9109]

Sounds like it came up a little to me

[@johnmadden9754]

Are these engines powerful enough for a truggy?

[@NitroTalkwithTodd]

"powerful enough" is pretty subjective. I have never ran one in truggy, but from the feel of it in buggy compared with other engines that I have, I think it would satisfy me.

[@lipoz-n-nitroz4012]

Without having a feel of the throttle, engine seemed to rev up faster. Messing with shims is something that's not discussed much and most of our education on it comes from the local race scene. I wouldn't recommend people start removing shims without fully understanding what happens when you remove/add shims and what your goal is. Tell you what, that would make for a good video!! Get ready for the keyboard warriors though.

[@NitroTalkwithTodd]

Maybe you didn't stay to the end, and I certainly can understand that with my videos. The reasons not to do this talk is at the end, not the beginning. Hopefully I'll get into video editing at some point and I can fix the video. I appreciate the input.

[@johnmacdonald6833]

What pipe is on it

[@NitroTalkwithTodd]

Associated 2058. My current go-to

[@samsonight2721]

With an engine with 5 gallons on it I just leave it the way had it

[@olivierplayer1633]

you will have more compression without shim

[@Nitro_rc_life]

It sounded better with three 4mm stack

[@Nitro_rc_life]

The****

[@evanmeneilley3228]

Now imagine with a good pipe. Throw that ae pipe away bro. Get the reds 1 piece

[@coryament]

if it isn't broke don't fix it