Rev capabilities

[Markviiisvt4]

I'm curious as to where people start getting nervous about the bottom end coming apart RPM wise.

[Dave96z34]

Your good lil past 7k but you wont get there with out tunner. With my blower I dont like going past 6500 becuse of eaton couldnt make a blower that is worth a danm.

[Markviiisvt4]

The tuning I'm not so worried about. I've got that covered. I'm new to the 60* engines coming from 3800's, and wasn't real sure just how much the 3.4 bottom end could take. For the project I'm working on right now I was looking for something that could reach a little higher into the RPM range then the 3800, and was told people have pushed this engine to 8k.

[RedZMonte]

Id be more worried about the top end.. valve float.. with a well built head (springs, retainers, Seals w/ Clips, ect) you could get 8000 fine... but you need to do work to the motor other then that, most of the DOHC stop making power and start dropping just before 7K, no reason to rev any higher if the motor is not going to be efficent/make power above 7K.

S

[pocket-rocket]

Id be more worried about the top end.. valve float.. with a well built head (springs, retainers, Seals w/ Clips, ect) you could get 8000 fine... but you need to do work to the motor other then that, most of the DOHC stop making power and start dropping just before 7K, no reason to rev any higher if the motor is not going to be efficent/make power above 7K.

S

I concur. There was a guy with a DOHC in a Fiero that I think ran his out to 8k. He said he had valve float, but I've read later down the road the choppyness on the dyno was from a bad spark plug wire. He also had a custom fabbed intake that moved his power band up a couple k rpms too, which is why he took it up that high. In my 92, I shift (in some gears) at ~7100 rpm and my rev limiter is at 7150. I have yet to get any shavings at an oil change to indicate anything is being worn out any faster than normal from it and I've done it countless times, so it's got to be just fine because it still sounds the same at any rpm that it's always sounded.

[Markviiisvt4]

I'll give you a run down of the project, and a little bit of my back ground.

I have a 93 s10 that tips the scales at about 1500 pounds minus motor and trans. The body has been channeled 4 inches over the chassis to lower the center of gravity, and the rear suspension has been swapped out in favor of a 3 series BMW independent rear set up. I used a bell housing from a 94 s10 with a 2.2 liter (shares the same bolt pattern with most FWD gm's) and mated a TKO 5 speed from a mustang. It will be used as a weekend warrior road racer and occasional drifting duties. The original plan for an engine was a 3800, but I've decided I want something a bit more peaky and rev happy. Enter 3.4 DOHC. For a living I build custom headers, custom intakes and turbo systems for RDP Motorsport so getting the power band where I want it, or the tuning won't be a problem. Some quick number crunching says with an 8 inch intake runner length and independent 42mm Throttle bodies with a set of medium to short headers should push the HP peak close to 7500 rpm or higher. From what I've read no one has really maxed the heads out. I know its not really practical, but in reality I'm just board with the 3800 and am looking for a new pet project to make some s2000 guys scratch their heads. All that hopefulness is for not however if the bottom end won't live up there, hence the question.

[jman093]

Sounds like a fun project!

I don't think rotating assembly is the issue at all as going past 7k is commonplace on stock engines with a tune and even if you wanted to rebuild it stronger, hypereutectic pistons are available on summit and I think the forged 3500 crank works in this engine and some connecting rods from other engines also work in the LQ1. Others here would know better than me about the rods and crank. WOT-TECH also sells lighter lifters which would really help the valvetrain at high rpm. The problem with the engine is there is zero aftermarket parts available. The pistons and lifters are the only two aftermarket pieces I know of for this engine. No exhaust, intake mani, cams, TB, etc, so yeah, you'll be fabbing all your own parts (and make some for us too while you're at it!).

[Markviiisvt4]

Every thing I make will be one off unless there's enough interest to recoupe the r n d costs. Then I don't have a problem selling things like header flanges intake parts and other things.

[RedZMonte]

I would suspect you can get simmilar results with a large single TB and not having the headache of doing individual TB's... custom upper intake manifold and '96 LQ1 lower would make good results i think.. Springs, Retianers, Light weight lifters and a nice valve job would be just peachy on the top end.. Ofcourse anytime you can lower the rotatinoal mass your going to not only rev faster but safer... Knife edge, Micro pollish and ballance crank would be a good idea if your going to make a HIGH reving motor...

Would love to see the build, Post pics of progress if the project is a go

S

[Markviiisvt4]

I agree that one large TB and some tuned intake runners would likely give me the same results on a dyno sheet, but the throttle response benefit from the ITB's is well worth the effort. Not only that but can you imagine what this thing will sound like at 8k

[Markviiisvt4]

I'm working on getting another engine stand rounded up, and as soon as that happens I'll start with some pics.

[pocket-rocket]

I think the forged 3500 crank works in this engine and some connecting rods from other engines

For stock stroke, you can go with the old school 327 SBC rods, but you have to have the big end machined narrower. Otherwise they fit fine (same small end journal size, as well as big end and rod length from what I've read). As for the 3500, it's got larger rod journals, so you either need different rods, or have the rod journals turned down to fit. I think the stroke is different as well.

[Markviiisvt4]

didnt there used to be a chart that listed the specs on all the 60* engines?

[bszopi]

didnt there used to be a chart that listed the specs on all the 60* engines?

http://bszopi.net/drupal/

Use that for now, until we get all the old content moved over to the new system. Use the left hand menu to select the engine you want, as the content part of the site gets screwed up with the Specifications for some reason (has to do with the HTML tables used in the pages).

[timg]

Sounds like a fun build. Good luck. I'm not sure what your goals are, but NA, you will likely struggle to break 300 whp even with headers and an custom intake. Since you do turbo kit fabrication, have you considered a GT35R or GT40R? This motor loves boost.

If you ever do need to rebuild the motor, a few of us have had custom pistons and rods made. Mine were from CP and Pauter. Modified SBC rods will also work.

Tim