Help installing IROC front bumper on a 930?

[David]

I'm trying to install a TRE front IROC bumper on my '79. First it was too wide, so I cut 1" out of the middle. Now the Setrab PC10-2 oil cooler won't fit behind the bumper with the inch removed and I really need to take another 1/4" out of the bumper.

Anyone go through this and have suggestions?

[RSR Racer]

I do a lot of composite work and have experienced less than ideal fitment on every fiberglass part I have purchased. The quality of these items is never what you would hope for especially at the cost these days.

You are not going to like my suggestion.....Since the oil cooler will not fit in the shortened housing, you should put the section you cut out back in. To narrow the bumper without loosing clearance for the cooler, take out an equal section just past where the lower section of the oil cooler box is flared back into the lower valance. That way, you will cut out a short piece of the straight section between the oil cooler housing and the parking light on each side.

It sounds simple but, be prepared to have to make some radius corrections and some reshaping of the bumper at both cut areas to keep the shape and contour nice and smooth. It will be a bit of work but should give you the results you are looking for.

Lay up the glass pretty thick behind the new cuts when you bond it back together so you can sand and shape the area to smoothly integrate from the center section to each side. When you put the pieces back together both in the center section and on the side pieces, be sure to bevel sand the pieces like with welding. For a stronger joint, you can drill holes on either side of the repair and fill the holes with chopped glass, then a layer of course mat following by some cloth. Best if that initial lay up is done all at once.

It is a good idea to sand off the gel coat on the outside of the joints so you can lay up two layers of tightly woven but thin cloth to maximize the strength of the joint. After you are done, it will look pretty bad! If you use good cloth and are careful to fully saturate the repair, you can shape and sand it smooth again.

Once the general shape is what you want, then sand the part uniformly using 220 grit over the entire surface. Next spray with two coats of a high build two part polyester primer (not regular primer for metal!). You will need a primer guy with a large orifice nozzle for that paint. Sand and apply another coat of primer as necessary to get it to the finish you want. If you sand out some air bubbles, use a little bondo to fill the holes and prime again. Provided there is no raw fiberglass or bondo exposed, sand it to 400 and its ready for paint.

Its a ton of work but it can turn out nicely. I used a similar method as well as making foam molds to create the fit and shape I wanted for my RSR bumper. Started with a crappy quality poorly fitting fiberglass bumper but am pretty happy with the finished look:



Hope that helps,

bob

[BoxsterGT]

Spectacular workmanship Bob.

Where can we see more of this beautiful RSR?

Len

[David]

Thanks Bob, you're the second person who's told me to cut it in thirds rather than in half. I'm pretty good at asking but not so good at listening.

I played with it more last night and I think I can get the oil cooler to fit by juggling around with the fittings a little more. So I'm going to keep going the way I'm going for now. I'll post pics with the progress.

[RSR Racer]

Originally Posted by BoxsterGT

Spectacular workmanship Bob.

Where can we see more of this beautiful RSR?

Len

hmmmm, don't want to hijack Davids thread and can't really post pics here as it is neither turbo'ed or supercharged....my only N/A 911, LOL.

bob

[smurfbus]

I managed to sqeeze a brumos front mount behind tre iroc but it was really tight and had to remove a lot of the front opening material and make room at the bulkhead? sheat behind it. The ends are a bit wide but I'm ok with it.

[Jeff Alton]

Have you reached out to Dave at TRE? I have always found him responsive.... Depsite the variences in all of these cars, the part should not require much massaging to fix...

We have local carbon fibre/FG team to help us when in a similar situation. But if I bought a part needing that much work to fit to an original car, I would send it back.

Cheers

[smurfbus]

I bet they have some front mount specks to go with the bumper if asked. Mine is pretty big.

[David]

Originally Posted by Jeff Alton

Have you reached out to Dave at TRE? I have always found him responsive.... Depsite the variences in all of these cars, the part should not require much massaging to fix...

We have local carbon fibre/FG team to help us when in a similar situation. But if I bought a part needing that much work to fit to an original car, I would send it back.

Cheers

I have. He recommended cutting it in half. I asked him about what oil cooler to use and waiting to hear back.

A friend of mine has an old IROC bumper in storage so I borrowed it this week. It's also a TRE and about 10 years older. It fits exactly the same as the one I just got so must be the same mold. I know early 930's were somewhat custom with hand welded fenders so maybe that has something to do with it which is why I'm curious if anyone else has had this issue.

I think I can make it work with the Setrab PC10-2 cooler I bought by running a 45° fitting at the top where there's more bumper room and a 90° fitting at the bottom where it can run under the sheet metal and clear the tight lower bumper oil cooler area.

Here's how it fit before removing 1" from the middle:

[smurfbus]

My flares seem to be inline but mine is 78 build.

[Jeff Alton]

Originally Posted by David

I have. He recommended cutting it in half. I asked him about what oil cooler to use and waiting to hear back.

A friend of mine has an old IROC bumper in storage so I borrowed it this week. It's also a TRE and about 10 years older. It fits exactly the same as the one I just got so must be the same mold. I know early 930's were somewhat custom with hand welded fenders so maybe that has something to do with it which is why I'm curious if anyone else has had this issue.

I think I can make it work with the Setrab PC10-2 cooler I bought by running a 45° fitting at the top where there's more bumper room and a 90° fitting at the bottom where it can run under the sheet metal and clear the tight lower bumper oil cooler area.

Here's how it fit before removing 1" from the middle:

[

Its odd that the factory bumper parts fit all the cars, yet aftermarket ones fit "some" cars....

At any rate, I would not be pleased with a bumper I had to cut up. The mold is off, end of story.

We use the Setrab 172 coolers behind most bumpers. We have used a couple CSF ones as well. I can look up the exact CSF number as well.

[pkabush]

Tom (Ahh garage time) has a few good videos on fitting glass bumpers. In one vid he sets up the bumper in the hot Calli sun and proceeds to heat it up with a heat gun. Then he wrapped it end to end with a ratchet strap, clamped it with some straight edges to prevent buckling and let it sit for a few hours. The point of the exercise was to bring the ends of the bumper in so it would better match the fenders. It seamed to have worked well. From the first pic posted it looks like this method may have worked. I understand it’s to late as yours is already sectioned but perhaps it would help others in the same predicament.

[slow&rusty]

Neat thread.
My experience is the same as Bob's and what David is going through, every aftermarket fiberglass piece requires cutting, massaging, fiberglassing, tweaking, then more cutting, more massaging, wash, rinse, repeat!

The upside is I quite like fiberglass work and pretty decent at it. I wish I was closer David, I would swing by and give you a hand. Currently I am in bed with the flu and trying to get better, so I can get back into the garage.

Anyway I like the idea of using fittings to make it work, I am running a large oil cooler on one of my cars, and that's exactly what I did to make it fit.

Best of luck and keep us posted.
One of these good days we'll get together.
Yasin

[David]

I changed the lower fitting from a 45 to a 90 (thanks batinc.net for fast delivery!). Now the cut bumper fits with no room to spare. I’ll get it to the fiberglass shop next week to do the messy work. Hopefully these pics from the backside are clear enough to show how tight a fit it is to the cooler and fittings.

Yasin, let me know when you’re well and we’ll road trip up to visit!

[jayhawk]

Dave:

Have you considered the air flow you are going to get through that cooler having it mounted right up against the front bulkhead like that? My guess is not very much. You might consider modifying the from of the tub to allow air to flow through the cooler and out of the bottom of the car. The Pumpkin was like that when I bought her and making that modification was one of the first things I did to her (2008). 30K track miles later and it has to be scorching hot on a short track for my temp gauge to climb even a little bit above "normal"

With all the effort you are putting into making the bumper fit properly, getting the air to flow through the cooler would be worth it IMHO.

[David]

The car came with a front mounted oil cooler which was bolted directly against the front bulkhead with only two holes cut in the C2 bumper for air. I never had oil temp issues while driving in Houston heat and on track days. The cooler was larger than what I have now but the new one will have significantly better air flow from the front and out the back than what I had.

In the last week I’ve thought of buying a smaller oil cooler that would fit into the bumper opening better but I feel the larger cooler I have is the better option if I can make it work.

[pkabush]

I’d definitely try it first before cutting up your 930 tub. Do you also have a fender cooler or will it be just the center. I’d think that center cooler would be fine but I’m in Seattle not Texas.
Your solution with the fittings look good.

[David]

Here’s the oil cooler that was mounted tight against the bulkhead and the new cooler that has about 1/2” clearance to the bulkhead at the closest point:

[David]

More pics of the previous oil cooler mounted against the bulkhead with two small bumper openings for cooling air. I'm curious to know what this oil cooler is if anyone knows.

[David]

And more pics: