Vintage Baja FJ40 Build for Desert Racing...

[Suhaib Kiani]

Not sure how to explain exactly how we ended up here but we essentially have an old school FJ40 with a V8 engine and stock suspension. We are looking to prep and tune it for desert racing in Pakistan essentially using stock suspension and basic components i.e. none of the fancy coils / triple bypass stuff which our budget does not allow ....

Looking to get some insights from racers/builders on how exactly it was done back in the day as I understand that there is a long history of CJs (and some FJs) rattling their leaf springs on the Baja trails before the modern trophy trucks too over!

Specific points to ponder on include tire size (31 vs 33s), gear ratios (4.1s vs 5.3s), leaf spring calibration (heavy vs light packs, shackles, bushes), shock tuning (double vs triple), aero dynamics (wings on some vintage cars)..... generally any advice would be helpful at this stage....

Thanks for the interest, hoping to get some responses as its quite difficult to tap into this experience any place else.

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[Suhaib Kiani]

Here is a concise build thread of the Toyota FJ40 on iH8MUD Forum with videos and pics: http://forum.ih8mud.com/40-55-series...lp-needed.html

At this stage, a specific question we are looking into is whether to go for an SOA setup to get more wheel travel and soften up the suspension. At this stage the SUA with stock springs and single shocks are quite stiff though there is still a fair bit of body roll. I was looking to go move the springs over axle with a slightly wider diff, lower gearing (5.3 vs current 4.1) with 35 inch tires (currently 31s) with stiff double shocks (simplish bilsteins without reservoirs) at each end an anti-sway bars front and back.

My worry is that tradiditionally the vintage racers (CJs and FJs) never went with an SOA setup and my worry is that we may end up messing up the handling completely in the worst scenario or alternatively be no better off than with current limited wheel travel.....

[Mark Newhan]

Welcome to RDC... Spring under and spring were done back in the day. As you know they aren't used much except for in limited classes. If you get hold of Deaver Spring here in California they should be able to advise on and build you anything you need. I would suggest a two link in conjunction with the leafs. You can get a very good working vehicle using a 3.0 bypass per wheel and a good set of spring. I would also say the 35" tire would be the best option as the larger tire helps absorb the bumps and rocks.

I couldn't speak to the gearing without knowing what the power plant is producing as well as the transmission. I would say that if the engine would have a hard time pulling a 35" tire then you would most likely want to go with 5.30's if that is your two options.

Good luck!

[retroblazer]

I had a chance to read the build thread and throughly enjoyed it. My first race car was a 1972 FJ-40. First, the biggest improvement you could make in the off road ride quality is to add 12-14 inches to the wheelbase. No other single modification will come close to having the same effect.... Second, it is common to reverse the direction of the front spring shackle and mount it at the back of the spring. There are kits sold in the US to do just this, but I don't recall the name of the company that sells this gear. I'm sure your crafty guys can fab this locally. It is also a good time to look at lengthening the front springs. I ordinarily wouldn't recommend a SOA in front because it raises the center of gravity and is tough to get the truck to handle. The only advantage that I can name for the SOA is that there is less to drag in the sand if the springs are on top of the axle. Only the pumpkin hangs below the axle tube on an SOA with the springs on top. I'm still negative on an SOA up front if you want to go fast.
Deaver does make a great set of leaf springs. They are the best, but it's hard on my wallet to have springs shipped domestically, let alone internationally, so you are best to develop local sources/ salvage yards for your springs. I'd look for some of the rear springs off of the older Land Cruiser wagons. You will have to experimnent with taking the overload and heavy leafs out of the spring packs for best results. On the otherhand, what is forcing you to stay with leafs at all?

[Suhaib Kiani]

Retroblazer & Mark,
Many thanks for your replies and insights. Its really an honor to read that our little project out here was of interest to you guys.
The FJ40 project has been a budget attempt to race against better prepped and more expensive rigs where the choice of the platform was more out of a retro/vintage romance than a competitive decision. Although we’re a bit out of our league in the big local class with our V8 engine pitching us against more modern trucks, we aren’t really up against trophy trucks either… Here is a short video with the competition and the terrain:
On Leaf Springs, I feel that the prime reasons we are sticking to them at this stage are budget and reliability. Over time, if we stick to the car, we will probably move to coilovers at the front with maybe SOA at the back along with a wheelbase stretch of 10-12 inches. At this stage, our only other option was to slide in an OEM Toyota coil suspension which wasn't really all that exciting particularly since it probably would have been less reliable, less adaptable and more expensive than the leaf spring suspension. Hence, since we cannot really afford Deavers, we are working to set-up the leaf springs in a manner that is suitable for desert racing. Some of the challenges are that the truck is fairly light for an FJ40 (around 2800lbs) and with OEM Toyota FJ springs things seem to be oversprung with limited travel. We just did a double shock conversion on a sister rig which solved the body sway and added to high speed stability but made the ride bumpy as hell. Some pics of the set-up here: http://www.ijc.com.pk/forum/viewtopic.php?f=22&p=5063#p5063 . The double shocks are there for now primarily to fight shock fade and to fight body sway, but I am not sure if the shocks are valved appropriately. Would love to hear thoughts on what would be ideal shock choice out here as we could probably have some room left in our budget.
On shackle reversal and longer leafs upfront, we have had several discussions in our team and there is some reluctance on modifications which might change the steering geometry given that the rigs will see a fair bit of road time. The rear leafs on the sister rig have been changed to slightly longer and more flexible 70 series leafs which end up netting some 7-8 inches of travel, a jump from 4-5 inches on stock. On the other rig we are looking into a longer custom pack in the rear hoping to get it upto 10 inches travel and some 6+ inches of wheelbase extention. I guess this is the setup we will be going out with for this season which is our first forray into desert racing and we will mainly look to finish with the right side up
On the gearing, I think we will end up sticking to 31 inch tires for now, but I am interested on how you guys would pick the ideal diff ratio given the 1UZ engine (250 HP@ 5600 rpm and 260 lbs ft of torque @4400 rpm (see graph: http://www.lextreme.com/1uzfe_info.html) and H150 gear box ratios (4.529, 2.464, 1.49, 1, 0.881).
Once again, many thanks for the interest and feedback!
Best Regards.
Suhaib Kiani

[retroblazer]

A couple of things come to mind after watching the video. First, a number of the trucks were longer wheel base pickup trucks, or whatever you might call them. An FJ-45 configuration might be a good alternative to extneding your wheel base. One of the biggest limitations to making the front end of a solid axle 4wd with leaf springs survive is the driveshaft. Getting one to stay on the car for a race can be a huge challenge. I had worked over the past three years with a driveshaft specialist, Jesse at High Angle Drivelines to develop a driveshaft that has almost 11 inches of spline length. So the front wheel travel limit will likely be set by how much bind free travel the driveshaft offers. You will or should dry cycle the suspension. It's pain in the butt to do it with leaf springs, but it must be done. Use the main leaf spring and a spacer to compensate for the rest of the spring pack to check for interference and binding. To set your spring rate, start with the main leaf and the next two in the pack, then add one leaf back at a time, until you have just enough spring rate to support the truck, but not too much. Without shocks on, the truck should still cycle all the way down to the bottom with one or two people bouncing on the end of the car. I use an anti-sway bar on my front end. If you rely on the springs to stop body roll, it will be too stiff.
After the spring packs are set, shocks will be key. The guys at Bilstein Shocks have been very helpful to me. Maybe we can get one of them on here to make a recommendation, but ideally you want to get a shock that is rebuildable and adjustable. One other item that could be helpful is a bumpstop. With limited front travel, a hydraulic bumpstop, will help keep the axle from slamming into the frame upon full compression of the suspension and are relatively affordable.

[randy s]

the things i got from watching that piece are dust and silt, keeping it pinned, and your passion for the sport. combine these things and a few others and you have the recipe for the ultimate goal that's universal..fun. good luck with your build..

[Suhaib Kiani]

the things i got from watching that piece are dust and silt, keeping it pinned, and your passion for the sport. combine these things and a few others and you have the recipe for the ultimate goal that's universal..fun. good luck with your build..

Many Thanks Randy. All the best to you too in your endeavours!

[Suhaib Kiani]

....You will or should dry cycle the suspension. It's pain in the butt to do it with leaf springs, but it must be done. Use the main leaf spring and a spacer to compensate for the rest of the spring pack to check for interference and binding. To set your spring rate, start with the main leaf and the next two in the pack, then add one leaf back at a time, until you have just enough spring rate to support the truck, but not too much. Without shocks on, the truck should still cycle all the way down to the bottom with one or two people bouncing on the end of the car. I use an anti-sway bar on my front end. If you rely on the springs to stop body roll, it will be too stiff.

Thanks again Retroblazer! Its really wonderful to get first hand feedback from you as I understand you still run leafs on your rig. We did sort of play around with the number of leafs and ended up with ridiculously low numbers: 4 leaf packs up front and back (http://www.ijc.com.pk/forum/download/file.php?id=7601 & http://www.ijc.com.pk/forum/download/file.php?id=7600). Not sure if this is ideal but these Toyota leafs are quite wide and thick for a light rig.

On the bumpstops, we put in some spongy rubber bumps (http://www.ijc.com.pk/forum/download/file.php?id=7599) which helped a bit but not sure how long these will last. We have been thinking about getting these Bilstein air bumps http://www.polyperformance.com/shop/...p-p-28434.html and perhaps will order a set of 2inch travel ones.

[retroblazer]

I would recommend using the 4" bumpstops over the 2". The supplier you found, Poly Performance, is well known shop with a great reputation. They should be able to help you with shock selection and valving. Personally, I would recommend a set of 9100's. One on each corner with bumpstops in the front.
The springs may seem light, but the best way to find out is to test and experiment. Ordinarily most people over spring, so try adding one leaf back to the pack that allows full flex. Another consideration on the springs is to change the clamp set-up. Most stock springs have a couple of clamps that pinch the spring pack. Most of our performance springs have a more open clamp system that allow the spring pack to open up at full droop. Rather than pinch the pack, the clamps are like U's with a bolt across the opening of the clamp.