[UBZ]

I have just acquired a F10a to put in the project LJ .
From what I have been told, it is from a 1979-82 SC100 Coupe ( Cervo SS40 GTX)


the engine is mounted east /west , and apart from some obvious differences related to mounting is the same block / setup as a SJ410 4wd.

however the rumour mill says that the SC100 f10a makes 50-52hp compared to the 46hp of the SJ410 . apparently they have had factory head work etc done to achieve this .

the main differences I see are different intake /exhaust manifolds and an F8a style side draft Mikuni Carb .

Does anyone have any more information in regard to these engines ?

Photos

Intake Manifold Side - Notice the oil filler is on the sump as the engine it laid over alot more in the car. Intake manifold angle downward as well.


Exhaust Side - Nice looking log manifold


Tappet Cover - No hole for oil cap


Remote oil Filter - can be removed and oil filter mount in normal 4wd location


Mikuni Side Draft Carb from front - very similar to the F8A Carb - Not what i would expect to see on a F10A


Carb from Rear - Notice the vacuum advance port for the Distributor beside where the carb bolts to the manifold - Other main difference i can see is that the return fuel line to the tank comes from the bottom of the carb (by the plunger arm) instead of from the fuel pump (only has inlet / outlet to carb and no tank return)

[sideways]

FWIW the JDM SJ40 is also rated at 52ps. I'd guess there's no actual difference and it's just a different way of rating things?

[UBZ]

sideways wrote:

FWIW the JDM SJ40 is also rated at 52ps. I'd guess there's no actual difference and it's just a different way of rating things?

Yeah every different specification you look at says something different .

So I have decided to Find out once and for all .

A few hours later . It looks lie the engine was partilly rebuilt - new bearing shells / seals top end work . But the head has never been off.

I cant see any differences in the Block

Head - Looks like a one piece head - need to clean it some more to be sure


Only markings I could find on the head


Crankshaft


Piston - Oil rings are well stuck ! explains the carbon buildup on the valves and in the exhaust


I have another standard F10A out of a 83 SJ410 that I an going to strip today so i can get some comparison measurements / pictures and clear up this rumor of larger valves etc once and for all.

[sideways]

To save you the trouble of pulling the other engine apart, check out my post here.

viewtopic.php?f=5&t=44601&p=799731#p799731

Thanks for posting the pics, it's cool to see that stuff.

[303zuke]

The references I have show the Fronte SC100 was released in 1978, alongside the LJ80. Makes you wonder why, if the F10A was available, they didn't fit that to the LJ80 first up.


Anyway, there a few small differences between the Fronte F10A and Sierra F10A. The may be year of manufacture issues, or design evolutions. In any case, the dimensions are the same, with most internal parts, gaskets and seals being the same part numbers.




However, there is a difference with the head. It is not some "Factory head work", it is a stock LJ80 F8A head (P/N 11110-73001). This has the typical LJ features like the round fuel pump and diagonal bolt pattern for the timing belt housing. The valves are the same size (and P/Ns) on the F8A and F10A. Fitting the LJ80 head does give a higher compression ratio, due to slightly smaller combustion chambers. Fronte is 9.0:1, Sierra is 8.8:1. There is no trickery with the cam, it is a stock standard LJ80 cam.

[Highway-Star]

So many subtle variations. Most awesome thread in ages!

Oh the remote oil filter sounds interesting. Mines less convenient to change since I put a power steering pump next to it

[Rhinoman]

I looked into this years ago and in the UK they were both rated at 45bhp. On my 410 I ran a 1 1/2" SU carb with the manifold opened out and that made a good difference. It cam off a very quick engine that had been reworked by Janspeed. Someone on here had a twin carb manifold for the 410, I don't know if they ever fitted it. The F10D engine is rumoured to use the same block.

[UBZ]

Awesome Info 303zuke

I had come to the same conclusion that it was an F8A head after measuring it, but nice to know it was done from factory and its not some horey kiwi mechanics work

What has become obvious is the build quality on the earlier engines is better . The SC100 engine (#1000667) has little Suzuki "S" emblems embossed all over it , along with "Made in Japan" . These are on the head , manifolds ,covers etc . The casting work is smother and more refined . And ancillary attachments of better build quality.
Whereas the later SJ410 Engine (#6601678) is virtually devoid of Suzuki branding.
I would say at a guess that the early F10A engines were made with the same Tooling / Plant as the original F8A Engines .
And the later engines were build in a new plant / Tooling / Subcontractors?? . And with reduced branding for the overseas markets.

Some Comparisons

Left: Normal F10A Head (800 marking) from a SJ410 - Right F8A Head from SC100
Cam seal housing on the F8A head is interesting as in why Suzuki thought it was originally necessary


Rear Camshaft housing - Left: SC100 - Right: SJ410
Much oil volume from the SC100 and notice the casting quality difference .


Left: SC100 Mikuni Fuel Pump - Right: SJ410 No Name Pump
No tank return on the SC100 Pump - so the Carb is receiving full pump pressure?


Timing Covers Top: F8A Style from SC100 - Bottom: Normal F10A from SJ410


Water Pumps Left: F8A Pump from SC100 (Has a Fixed Stud) Right: Normal F10A Pump (has a raised mount bottom right)


Crank Pulleys Left: Normal F10A from SJ410 - Right: SC100 Pulley (lighter and bigger)


Intake manifolds - Top: SC100 - Bottom SJ410
The internal airways are virtually identical . The Difference is only in the water jacket which is much larger on the SC100 . Maybe to account fro the hotter more constricted engine bay?


SC100 Remote oil filter setup
The 3 holes in the block are threaded and the adapter screws into the block


Compared to a normal F10A oil filter mount .
Anyone know if the if the threaded bit is screwed in like the SC100 or Pressed?


SC100 Block - Exhaust Side
3 untapped mounts, left hand side above oil pressure sensor hole.
Suzuki Emblem , Made in Japan - Center
Block Water drain hole , right hand side next to F10A (F8A blocks have these water drains as well)


Sj410 Block - Exhaust Side
2 tapped mounts ,left hand side above oil pressure sensor hole.
SUZUKI - Center
No Water Drain hole


Top Left: SC100 Mikuni Carb - Bottom Left: LJ81 F8A Mikuni Carb - Right: SJ410 Aisian Carb
SC100 Carb has a different Choke cable setup, Vac advance for Dissy and tank fuel return at bottom , but looks and measures up the same as the LJ81 F8A Carb
Next step is to pull the jets to compare .

[303zuke]

UBZ wrote:

What has become obvious is the build quality on the earlier engines is better . The SC100 engine (#1000667) has little Suzuki "S" emblems embossed all over it , along with "Made in Japan" . These are on the head , manifolds ,covers etc . The casting work is smother and more refined . And ancillary attachments of better build quality.
Whereas the later SJ410 Engine (#6601678) is virtually devoid of Suzuki branding.

What always tickled me with the early Suzukis (LJ50, LJ80, and ST10, ST80 ST90 Carry) was the fact that most BOLTS had the Suzuki S embossed into the head of the bolt to indicate grade. How many manufacturers these days would have their own branded bolts?

Oil Filter stud on the F10A Sierra block also screws in to the block.

[Santos]

This thread rocks, love the remote oil filter guessing that is the new 'want' item of all the enthusiast.
I think the lack of branding came down to a cost thing, most japanese manufacturers work on the 'toyota' lean manufacturing model.

Most vintage suzuki bikes have the S embossed bolts etc, i love the S stamped rubber handgrips and kick stands

[Santos]

Just speculation but several possibilities why LJ's had F8A and not F10A from day one. (making it a LJ100? )

1) 1000cc was the luxury/sporty motor so it was in the Cervo/Sc100 not the LJ80

2) The option i think more likely. Suzuki tend to make the engines for the 4wd's beefier than their hatch equivelants. I noticed when pulling apart G13's that the swift engines have skinny rods and marginally lighter cranks compared to sierra engines. Going by this maybe the 800cc was way of 'strengthening' Smaller bore = thicker cylinder walls

3) Tax bracket/ design rules in certain markets.

[sideways]

Oh giggity.

What's the main jet in the sc carb?

[UBZ]

sideways wrote:

What's the main jet in the sc carb?

The SC100 F10a Carb - 90 Main Jet
LJ81 F8a Carb - 70.5 Main Jet

[jonno_racing]

Question for you guys, I have a bunch of what i think to be f10 carbs I have collected, how would I I'd them as f10 or f8?

[sideways]

LJ80 (and SC100) don't have the fuel cut solenoid and have smaller bolt spacing on the manifold.

[Santos]

jonno_racing wrote:

Question for you guys, I have a bunch of what i think to be f10 carbs I have collected, how would I I'd them as f10 or f8?

wouldn't you just look at stamping of mikuni or aisin?

[jonno_racing]

Not sure, i will grab out my spares and have a look!
i think they all have fuel cut solenoids though

[UBZ]

Interestingly the Main Jet from the SJ410 Asisn Carb is only 80.1
not 100% sure as the jet has been abused and is hard to read .

Anyone else have one they can check?
I am not that schooled up on carbs and what the numbers mean , am I assuming correctly that a larger number means more fuel ? Is the measurement standard across different brands of carbs?

[Rhinoman]

UBZ wrote:

Interestingly the Main Jet from the SJ410 Asisn Carb is only 80.1
not 100% sure as the jet has been abused and is hard to read .

Anyone else have one they can check?
I am not that schooled up on carbs and what the numbers mean , am I assuming correctly that a larger number means more fuel ? Is the measurement standard across different brands of carbs?

A bigger number means more fuel for the same type of jet, the taper into and out of the jet can make a significant difference to the flow rate. There is no real correlation from one carb manufacturer to another.