Advice on Engine Build Gen 2

[serafins]

Going to be putting together an engine for my Gen 2 this winter.

I have GTSR heads that were ran at Lemans. These are the big port heads with "stock" bowl and runners. Although if you look close you can see where Caldwell ported them and then bead blasted the runners and bowl to make it look untouched. On top will be a Gen 3 intake ported to match by Greg Good. Single blade throttle body will be used. T&D roller rockers 1.7. Compression should be right at 11:1 with a 4.030 diameter, .40 thickness MLS head gasket.

Cam will be custom through JMB. Oiling will be external wet sump with mods to the windage tray to correct the drainback issues. JMB spins to 7k on similar builds. I don't want to go quite that high but I think peak power will have to be north of 63-6400 with how big the head and intake ports are.

Now, the questions that I haven't been able to answer:

is there any advantage to switching to the Gen 3 timing set? I have heard of a few people doing this. I know I have to go Gen 3 if I want an adjustable cam gear. Before I finalize the cam I'd like to get it made for the gen 3 timing setup if necessary.

Is there any reason to use the Gen 2 intake gaskets over the Gen 3 gaskets? The Gen 3 looks like a superior design and otherwise identical.

Is 11:1 going to be too much compression? The cam is going to be fairly large which I know will help bleed off compression down low, and up top detonation isnt as likely to occur. But I have no experience building these engines. I come from the SBF world where an aluminum headed engine can run 11:1 no problem with an identical bore and similar stroke to the viper engine. So I assume it will be ok. But would love to hear from someone with experience. The alternative is to run a stock thickness head gasket which will drop compression to the 10.5:1 range.

 

[99RT10GTS]

On the question of the timing sets, Gen 2 is typically a single bolt, the Gen 3's are a 3 bolt setup. Prefix sells 3 bolt cam wheels, but do not use the Gen 3 cam wheel because the timing marks are in a different location and will not work.

With a proper tune, 11.0 is fine, but I would try up the quality of fuel, maybe mix in some 110 for safety and more power. .

 

[Goggles Pizano]

You machining oiling on the crank and block for cylinder 2 (if I remember correctly) bearing lack of oil?

What ecu are you using?

 

[Dan Cragin]

The GTSR heads cool well and have little core shift, so they can be ported fairly well without the exhaust ports cracking, but they really don't flow that well as the GTSR
was a restricted motor. Changing to Gen 3 heads, Stryker Heads or the Gen 4 conversion will make big power. It just depends on your HP goal. With that Gen 3 intake you
loose a lot of torque. Only advantage is to run the engine over 6500rpm, in which case you need to at least run an external oil pump, or a dry sump. You can get away with
just the external pump.

They don't make aftermarket adjustable timing sets anymore, so yes a Modified Gen 3 timing will work. The cam timing is different so you need to machine it and modify it
so you can degree the cam. Prefix does this. You will want to specify a 3 bolt cam as well. Some cams can be made in billet, which is another good option. You will want a
performance low bleed lifter with a oil through roller if you can get that.

I never ran more than 10.25 to compression on street motors. If you have lots of overlap or a small LSA you can go more. Problem is this motor has no knock control. If you
get some bad gas and run it hard or track it, your will hurt the motor. Trust me I know.

Im sure your engine builder will be doing the normal bottom end upgrades and improving the oiling. Nitrating the crank is common and a SFI balancer is a must.

Hope this helps.

 

[serafins]

The GTSR heads cool well and have little core shift, so they can be ported fairly well without the exhaust ports cracking, but they really don't flow that well as the GTSR
was a restricted motor. Changing to Gen 3 heads, Stryker Heads or the Gen 4 conversion will make big power. It just depends on your HP goal. With that Gen 3 intake you
loose a lot of torque. Only advantage is to run the engine over 6500rpm, in which case you need to at least run an external oil pump, or a dry sump. You can get away with
just the external pump.

They don't make aftermarket adjustable timing sets anymore, so yes a Modified Gen 3 timing will work. The cam timing is different so you need to machine it and modify it
so you can degree the cam. Prefix does this. You will want to specify a 3 bolt cam as well. Some cams can be made in billet, which is another good option. You will want a
performance low bleed lifter with a oil through roller if you can get that.

I never ran more than 10.25 to compression on street motors. If you have lots of overlap or a small LSA you can go more. Problem is this motor has no knock control. If you
get some bad gas and run it hard or track it, your will hurt the motor. Trust me I know.

Im sure your engine builder will be doing the normal bottom end upgrades and improving the oiling. Nitrating the crank is common and a SFI balancer is a must.

Hope this helps.

Thanks Dan. Very helpful. I was hoping you'd chime in as you set this car up for the original owner and it still runs great 25 years later. I'd hate to grenade your handiwork.

I'll be bumping the compression down some then to get it as close to 10.25:1 as I can with 64cc chambers on the heads. SFI balancer is 100% happening as part of the external wet sump kit. Nitrating the crank probably not. Goal is to not pull the short block from the car yet. I'll inspect the bearings next season and see if it needs some help. In that case it will get the full blown ARP stud/line boring treatment.

The goal isn't ultimate HP. It's more so a project to put some old Lemans-run parts back into service again instead of having them just collect dust. I picked the Gen 3 intake because it looked the most like the GTSR individual throttle body box. But if it turns out to be a dog I'll have Greg do the Gen 2 intake and put it back on. I'm not married to anything in the build except the heads.

It will be getting an external wet sump and all the pan/windage tray tricks.

It will be running stock ECU tuned by Prefix if I can get away with it. Their shop is about 10 minutes from my house. Preliminarily they think they'll be able to tune it, but if not that will give me an excuse to go Motec and incorporate a flex fuel setup.

My hope is these heads are hiding a few surprises. These are not the later GTSR heads available through the Mopar catalog. These were the 1st run heads run by Caldwell at Lemans in 1997. The heads were cast in 1996. They wear stock part numbers but they are nowhere near stock. The intake ports are 2.35" by 1.25". I bought them from a guy who was a test driver with Caldwell, and allegedly they were on one of the cars that finished LeMans in 1997 and ran 12th at Daytona in GT1 earlier in the year. The ports look CNC'd and then sandblasted to me. But I can't verify any of that and won't know until I put it together. At the end of the day I'll be happy if it runs good and picks up a few rpm over the stock 5900 cutoff.