NOT Your Grandpa’s Big Block! | GM 8.1 Heads Explained | Engine Rehab Episode 8 

We have had two 8.1s and another still in the family. Love every minute with them.

Not sure how I'm just now discovering this content. I've been waiting to see the "all in one" flow chart. Hope to see more 8.1 related content. Thank you Josh's Engine Rehab!

Amazing video thank you for shedding light on such a awesome and looked over power plant.

I’m more of a ford guy, but love to learn stuff, so that’s why I watch your channel. It is amazing to me there isn’t that much aftermarket for these. Especially cylinder heads, these engines seem like they have way better architecture then the old school bbc. Just by looking at the intake runners, no long-short runners, dumb design imo. They corrected that, way easier to tune I’d imagine. With the old school it’s seen you’d have to make compromises, unless you have a sfi system.

Excellent, factual data. Thanks man, good stuff!

Cant wait to assemble my 8.8 with your ported 8.8 heads!

I used to own an 02 GMC 2500HD with the 8.1 and Allison package; great logging truck! Would own another,but you absolutely want the Allison behind them if you're working with them.

Awesome video man. Love it!! I have been a bit afraid to advise running heavy springs in the past cause people use the little stock studs with raylar 8mm nuts. I afraid they going to break off. Thank you for schooling us!

Incredible amount of information thanks for making this video

I own a avalanche 2500 8.1 and I love it. It hauls all my tools and equipment.

Im so happy rayar supports the platform, but I can’t wait for some competition to improve the breed.

I just subscribed, I like the fast editing that keeps the video on topic and efficient. I am sold on this 8.1 swap for my boat. I have a 350 SBC in it now. I think the 8.1 swap with a self learning EFI will bring my boat into the millennia

Thanks for sharing!👊😎

Fantastic info bud!

My uncle has an 8.1L in his Avalanche. I've been talking about how these engines are slept on for 10 years now. I'd love an aluminum block with a 427 rotating assembly with the Raylar heads and intake and 8.1 CPU. Oddly enough, the 427, 454, and 8.1 all have the same bore

I just finished watching Lawrence Tolman on his 8.1 swap yesterday until I saw his videos I forgot all about the 8.1 engine. The first one I saw was on dirt every day in an Avalanche 2500. I’ve always loved big block engines whether it’s Ford GM or Chrysler or even Pontiac. you rarely hear about them anymore. I love the information you’re sharing and well appreciated. If I could I would love to swap one into a 87-91 Chevy caprice classic 4L80 and a 4.10 gear ⚙️ true trac differential. Something mild redline at 5100-5300. I like your idea of running cast iron manifolds and couldn’t agree more with that.

subscribed because 8.1 and damn good info.

Great information. Thanks

Thanks for doing this video

I have an 02 2500hd chevy crew cab 6.0l ,4l80 ,4.10 4x4 and pulled the 6.0 out and swapped in an 8.1 out of an 03 avalanche and love it .

Great video very informative. The problem is the cast pistons in these motors. Stock there are great motor, the upper ring is so close to the valve relief that any excessive heat or pressure over stock seems to persuade the rings to knock off a piece of the piston.

My 8.1 swapped SquareBody crew cab is just about ready to drive. It's been around the parking lot. Still fabricating the exhaust to plug in the O2 sensors to.

Subbed because not another stinking LSx/LTx RU-vid Church ! Keep those outcasts and misfits engines on the spotlight ! You're doing the hotrod community a service. 👌😊👍

Sub’d! I’ve had 2 8.1s and my 04 Suburban 8.1 is running strong but I’d love to build a “modern” 8.8, basically take advantage of the PSI improvements , quality parts selection and some porting and it sounds like you’ve done exactly that! I imagine 500ish HP with a flat torque curve to tow stuff with, stock reliability and make the big burb boogie. Look forward to seeing more 8.8 content!

I love this platform! I plan on using it in a 70 Chevelle with a 4l80

I hope you are right about aftermarket parts but they only made them for 10 years in less common applications. It’s the reason why there isn’t much out there now. I do agree this engine will continue to be more desired and valuable.

1:53 "Well into the four digit horsepower numbers and broke into the 9's I believe". I checked it out and LT's Ugly Truck makes 817whp, lives in the 11's and ran a 10.9 before he rebuilt the 8.1L. 👍

I do wish someone would do this exact video with the 80s and 90s big block 454, I know there's aftermarket but not everyone has 5g to get a set, and 70s oval and square ports you can give it up around my area there no where to be found, I know peanut ports suck but knowing the flow data and springs measurements would be nice when putting something together from a pile of parts

Thinks the first time you drive your burban and press on the gas it’s gonna bring a smile to your face. May be a mere smirk, but a smile to say the least, lol. Look forward to more info on these. Kinda sucks gm didn’t use aluminum for the cylinder heads to cut down on weight. Guess they were more worried about reliability, I’d guess.

I’ve only had 1 LS7 break on me, out of 4 I’ve had I think. After that I beat the hell out of it and never missed a beat

Just saw the I Do Cars teardown video on one of these and I must say, you're right it's functionally just a high-displacement Iron Block LS. Excited to see what the future holds with these powerplants in street performance

How the hell LS are so expensive when you can STILL go to the junkyard and pull a 5.3 for 750 is beyond me. You can get really lucky and find an aluminum 6.2 still, for the exact same price, bc the crusher yard doesn't give a fuck.

What a bunch of junk send it all to me 😁 Good video . You plan to play with the valve job and bowl anymore on the psi exhaust ? Low lift flow is always in the seat/valve Area. Now i have to go out in the shop and do some 8.1 to 8.8 exhaust comparing Going to work good with my little .538/.542 lift cam

This is a rad video!!! I dropped a 8.1 in my 84 c10. I love it so far but when it hits 194° a squeak comes almost sounds like a belt But its not 😅. Any guess what it could be lol. Im hoping something simple not a rebuid lol

How is the exhaust port spacing on the 8.1 compared to a 5.3 or 6.0 ls? Im curious if i could buy a 6.0 turbo manifold...cut the flange off and weld a 8.1 flange on? Guess ima get some exhaust manifold gaskets and compare.

The PAC 1219X springs were a direct drop in for the stock 8.8 beehives on my heads... and work great with my XM296HR cam. Check out my latest videos of it running. Just need to find an engine dyno here in Atlanta to get some numbers.

😎😎😎

The Raylar heads are the Rolex on the table.

Time to go cruise marketplace..

I just want to keep my stop engine 8.1 working as a work engine . What. Should I do to keep it running correct.

I went back to good old chevy 350

In the natural gas industry. Those PSI engines were not very popular with Al Gore. A great engine, but not clean burning enough for the government. Sadly most of them got scrapped, or on someone’s last day at their job, ended up in a shade tree project. A decent catalyst helped with the emissions but those were really costly.

You can move two Head bolts and bolt a conventional Head on the gen 7block

The first 5.3 I bought for my truck 15 years ago was $420 with a lifetime warranty. You can't touch them for that anymore

If I watch all these videos do I get an AA degree in automotive engineering? You are a great teacher although you were a little light on sarcasm today. Enjoyed the “baby” comment.

It would be nice if someone could make an affordable dome piston. Wiseco has a 4032 flat top for $650-700 the cheapest I found. I called around a little bit for some custom pistons and everyone wanted 1,500 dollars.

My eagle230 eliminator (boat) has the. 8.1 in it, thing is a beast…..i believe in the marine industry its called a mag 496

I notice the 8.8 has more rotation of the valves,they should have a steep short side by guess.

Josh I was wondering where you're located I would like to have you do some work on an 8.1 long block

Can u point me the way to a set of 8.8 heads please. I found a 8.8 on ebay but i not sure I can get it to fit my c10 cause of the oil pan. Will a 8.1 oil pan fit the 8.8 also will the 8.1 harness fit the 8.8.

Are the valve angles the same on the PSI 8.8 heads?

Can you put a link on where I can get these 8.8 cylinder heads?

The 8.8 are now being used in propane bobtail trucks

What is the stock valve length on the 8.8 head

What are the flow numbers for a stock 8.8l head? Is it similar to the 8.1? Also can you provide a serial number for a gasoline PSI 8.8l engine so i could call and get pricing? Thanks for all the info you've already provided!

Is there a link to where I can a set of your 8.1L heads???

I have two of these PSI 8.8's and one is being built for my boat to replace the existing 8.1. I'd love to know how much camshaft I can get away with... using a marine (wet) exhaust system. Reversion is a major concern and right now I have a Merc 496HO cam to use. Would love to try the Comp XM296HR in this 8.8 but the 75 degrees of overlap worries me. What is the best marine cam to use in an otherwise stock 8.8 ? Im running the forged 10:1 flat tops and a fresh set of the PSI iron heads.

Where can someone go to get a set of your heads?

I still buy 5.3s for 220.

What version of raylar head did you use in this demonstration?

Aluminum RSX heads from Chevy.

Flow is definitely one of the main things too look at but I don't like the combustion chamber design of that 8.8 head it has no quench pad like the 8.1 head. Id be curious to see a Dyno comparison of 8.1 vs 8.8 because of that.

Do the GM or Raylar heads have the reversion tendency older GM heads have on the exhaust side? What ever happened to the Dart 8100 stuff?

i have a built 8.8 gen 7 big block 547cid. i have 3 8.1L and also have a PSI built 8.8L thats in my 02 chevy 3/4 ton

I like the psi heads myself other than the 8 extra pounds each over 8.1 head 😖

Can I just buy some 8.8 heads ready to drop in from you? Or send some raylar heads direct to you for your corrections? lol. This is above my abilities and I doubt any machinists in my area would know anything about any of these heads except to just toss some stuff at them.

I feel like the L83s are getting cheap though, they just need a stronger aftermarket for swaps

Are the cheaper aluminum heads on ebay (under $2000) even close to the raylar?

anyone know how to contact this guy to do work?

I have a 8.1 in my C3 Corvette has a Dart intake and carburetor. The Dart intake was custom ported and the dual plane was shaved down. It runs really well I have aftermarket race tech pistons rods custom cam roller rockers etc

Id rather spend my money on a Duramax that'll get Tripple mpg and doesn't require race gas

The days of noobs buying an LS for $100. Blowing them up weekly and getting a new one while telling old school SBC/BBC people they are idiots for spending money building 50 year old motos is coming to an end.

that 8.8 psi head, I think I know who the person is, who engineered them for PSI, I'd have to call him to confirm that. But I do remember seeing a set of those castings in pre cubed form in his facility where he did production and R&D for another notably large company back in the late 2000s, 2008-2010 I think IIRC. So whoever is claiming to have designed that head is probably full of shit. All of the design cues in the casting, the layout etc, all classic design stuff that guy did. I also know for a fact he did contract with PSI on development " not sure specifically which products". Soo maybe these aren't the final version and maybe other engineers worked on them after, but I am fairly confident in who probably had a significant hand in that 8.8 design. To throw you a bone , the guy who designed those $7000 heads you salvaged, I can't say for certain same guy, but likely ;), the original RHS heads 11* valve angle,were actually designed by ET performance in Walled lake Michigan and manufactured under contract for RHS by ET cylinder head prior to their bankruptcy in the mid 2000's. You'd be surprised how many after market cylinder heads got developed at that company.

you dont put an LS swap in a vehicle. an LS swap is not a thing, its a verb. a verb is an action. its something you do thats why its called a swap. 🤦🏻‍♂️ get it straight lol.

I'm a Ford guy through and through have been since the 80s n LOVE the new coyote. BUT I LOVE THE gm 8.1 and since the day it came out I have been confused how it hasn't been a hobby breaking star . Even bone stock it's a monster torquer 🎉

Good information......... BUT THE CONSTANT INTERRUPTION IS EXTREMELY IRRITATING, LIKE EVERY 6TH WORD THE VIDEO STOPS , HAD TO SHUT YOU OFF

Ive had a chance to drive my 8.1 swapped SquareBody Crew cab. And its fun to drive now. Got a lot of finishing touches left to do still