484 4.1 or 109 3.8 for Street Car

[DJackson1357]

A few years back the engine in my dad's 87 GN wiped a lobe and we're just now getting back to putting it back together. Due to some other issues, the block we had in there (85 20 bolt block actually) is junk. To replace it I have either a 484 4.1 block or a N/A 109 block. Both are standard bore and the 4.1 does NOT have any cracks on the deck surface. The rest of the combo will be:

- Champion Ported Irons
- 206 Roller
- TE-44
- Dutt Neck Intercooler
- PTC 2800 Stall Converter
- Meth Injection

Even though it's a bit overkill, either engine will receive a girdle, head studs and the rods already have ARP bolts. Boost will be limited to less than 20 psi.

For this application I'm really leaning towards the 4.1 for the additional torque and quicker spool. I know the 109 will be stronger, but I don't believe I'm really going to be stressing the 4.1. In searching through the archives it looks like a few people have had issues with cracking the cylinder walls (and some with cracked lifter valleys I think). Can anyone chime in on this? I've also been able to find people running 120+ traps with 484 blocks and cracked decks.

Any thoughts?

 

[DaRonne Edwards]

I would say the 4.1. More cubes+more air flow=More horsepower

 

[Nick Micale]

My personal experience with the 4.1 engines is that I have built a few for my self and my customers, and love them.

All have been awesome performers on the street, and killer at the track. I have one production 4.1 on the stand being assembled for a high 9 sec build, and 2 working in the machine shop, and planning under way for the fourth 4.1!

In our desert conditions, I have run a 4.1 9.80/135 MPH at 18 psi with a 70mm turbo. The street cars I have built with 4.1 engines have noticeably more low end than a 3.8, and I have yet to have seen a damaged block?

I built one 4.1 with 0.060" over pistons and no cylinder wall problems with this low 11 sec. build.

Here are my opinions on your build as you have listed:

1. Don't waste your $$$ on a girdle, invest it in a forged crank.

2. If you are going to use alky injection, be SURE you have ample fuel supply which normally requires some upgrades to the fuel system

3. Chamfer the head bolt holes on the deck to prevent cracks.

 

[Jerryl]

My personal experience with the 4.1 engines is that I have built a few for my self and my customers, and love them. . . . . . .

Nick,
Great feedback from an experienced builder.

Probably covered 1000 times but . . . . based on your experience;
How would a 4.1 production block compare in performance to a stroked 109?

 

[DaRonne Edwards]

So if you use a forged crank there is no need for a girdle? Why is this?

 

[fuzzyGN]

The girdle is there to keep the crank from flexing. If you use an aftermarket crank, the crank keeps itself from twisting and flexing. This is what I did and have zero regrets. The 4.1L will always be superior than even a stroked 3.8 because it is more cubes and more importantly the bore is bigger. The bigger bore unshrouds the valves and lets the engine breathe easier. More torque and less boost is needed to make the same HP. Add a little more compression and it will be a beast.

 

[Nick Micale]

Eric and I have communicated a lot over many years about engine builds, and we both favor the 4.1, and he nailed the answers for the crank and bore advantage.

On most all 4.1 builds we install 2 center steel caps for added block strength. The weak point in the 4.1 and 3.8 block is the main web between the cam bearing and main bearing saddle. Even with a girdle, we have seen many blocks give up in that area.

With caps and a forged crank, bottom end strength and reliability is greatly increased. When you consider the forged crank weighs almost twice than a cast crank, it becomes obvious it is a much better, stronger piece.

Most all the 4.1 builds I have done in recent years are using a 3.625" stroke crank which yields about 272 cu. in.

Combine the added displacement with the larger bore for much better breathing, and it then provides awesome low end torque, and will pull with crazy HP to 7ooo HP and beyond with the proper supporting parts.

One thing is when you go with a 4.1 build, be sure you figure good tires in your budget, because you will be ripping them off in short order!

 

[DJackson1357]

My personal experience with the 4.1 engines is that I have built a few for my self and my customers, and love them.

All have been awesome performers on the street, and killer at the track. I have one production 4.1 on the stand being assembled for a high 9 sec build, and 2 working in the machine shop, and planning under way for the fourth 4.1!

In our desert conditions, I have run a 4.1 9.80/135 MPH at 18 psi with a 70mm turbo. The street cars I have built with 4.1 engines have noticeably more low end than a 3.8, and I have yet to have seen a damaged block?

I built one 4.1 with 0.060" over pistons and no cylinder wall problems with this low 11 sec. build.

Here are my opinions on your build as you have listed:

1. Don't waste your $$$ on a girdle, invest it in a forged crank.

2. If you are going to use alky injection, be SURE you have ample fuel supply which normally requires some upgrades to the fuel system

3. Chamfer the head bolt holes on the deck to prevent cracks.

Thanks for the hands on experience. I think it was Lee Thompson who mentioned he'd cracked a few blocks, but I hadn't heard of anyone else with the issue. Figured I'd ask anyway.

I've already got the girdle on order, so I'll go ahead and use it anyway. Might look into a steel crank for good measure too. Is there an affordable unit currently out there?

For the fuel system the car currently has a hotwired Walbro 340 and 42.5 lb injectors. I'm not sure if it would be worth it to upgrade the injectors at this point as I'll be sticking with the TE-44 for the time being.

How far do you typically take the head bolt holes down? I've heard go 2 threads, but want to check before removing any material.

Which blocks have you typically ran in the past? From the pictures I've seen the 484 block seems to have the least material in the deck, but (minus cracks) most people that have ran them don't mention any issues.

Before the 3.8 wiped a lobe I'd swapped in a 10" PTC 2800 stall converter. Does anyone think this would be too much with the small cam / turbo and the extra cubes? I've still got a re-stalled D5 that went to about 2600 floating around I could put back in. I'm assuming keep the PTC, especially in case we upgrade to slightly larger turbo in the next couple years.

Overall I'm really looking forward to this build. The car hasn't ran in 2 years, so my dad and I are both ready to get it going and drive the crap out of it.

 

[forcefed3.8's]

The PTC will be fine, way better than a restalled D5. That little 44 will be working hard with a 4.1, heads, and cam. Spool fast, but might not be too happy over 22psi. A larger turbo will need more injector, and a better 9.5" converter. 10 sec power will drive over a 10" converter.

 

[HouseofSpeed]

Much of the discussion about the necessity of a girdle avoids the obvious...block design. Most manufacturers have gone to a skirted block...meaning that the caps and mains do not sit lower than the pan rails. Growing up in a machine shop and then teaching the craft years later has given me the opportunity to see about every thing under the sun...and see all that stuff fail at some point. A girdle on a skirted block is pointless...if the casting is that weak there is nothing that bolting that girdle on will do to save it. Even sillier is to run a girdle across the caps on a non-skirted block (ala a Ford Windsor engine) which was really popular in the mid to late 90s as guys were trying to keep the cranks in and the blocks from splitting through the cam journals and main saddles on stock 5.0 roller blocks. All the girdle will do on one of those is keep the caps together when it shites the crank through the pan...LOL. I have built a ton of Buicks and really like the 4.1 base...makes sense plain and simple...as outlined by Nick and others. Get a GOOD crank and put the center caps in it...let it eat. The only weak spot I have seen on these has been core shift in the cam journals...even minute amounts will eat cams in blocks that have been built one too many times....believe it or not, that iron moves around a bunch through thousands of heat cycles and tons of cylinder pressure. Finally....get a machinist that knows Buicks....not LS1s or FEs...not EFI LT1s or L98s....but LC2s, they can baffle the hell out of someone that has no experience with them.