Hi guys,
I am trying to decide on which motor would be better to start with. The goal is to make it a turbo motor that could reliable spin to 8,000+rpm.
Some thoughts are:
If it will be a L98 variant
destroked 400 machined for oversized studs on heads
4-bolt splayed caps, maybe with a girdle.
lightened, race balanced chamfered and knife-edged crank
lightweight rods, and pistons, with total seal rings
I'd like to make it a hydraulic roller cam and lifter assemby;
Can it take this kind of abuse or will it have to be a solid assembly?
AFR heads ported w/ inconel valves
shaft mounted rockers and dual valve springs.
Speedway corvettes headers and turbo is undecided.
Can this combination or a similar one acheive these goals?
Would a LT1 type block be a better choice?
Any help or suggestions are welcome.
Thanks,
Mike

 

if you are starting from scratch, and you are serious.. go with a little M block and add your internals. this block will give you a thicker deck, can be machined to about anything you would want around 427 or so CI's, has a stronger web for less deflection and would be a better suited starting point for the high end internals you are throwing in it. if not, the LTx block would be the better choice of the two you put out to be decided on. they are stouter thent he L98 block. and can be made to run with a rear mount distributor and have relatively good heads available and a solid intake manifold setup. just my opinion though.. ultimately, you have to make the choice.. do you have a budget or is this a no expense spared dream build?

Chris

 

Thank you Chris,
Well I plan on taking my time with this build so I guess it would be all the best parts and research that I can put into it and making everything synch together correctly. What I would ultimately like is a nascar style engine that will be turbocharged. I read that a typical nascar motor can spin to 9-9500RPM and produce 750 horsepower but they have solid lifter etc, correct?. I understand that these motors are approx 358 ci and are custom everything including the block, but does it sound feesable to build a similar motor but with a hydraulic roller assembly? Is the Lt1 or Lt4's intake manifold or miniram capable of making decent power up to these rpm? Or will a single plain manifold with a accufab or equivelent throttle body be necassary? Thanks Again Chris for your expertise.

 

building a 9000rpm on sbc is ain't easy and ultimately very expensive. For most or all street cars I think it is not practical to want to even thinking about doing it.

You will be shocks what the costs to build a nascar motor 358ci and 750hp and on top of that they rebuild the motor after the runs.
The last time I check titainium connecting rod cost $2800 a set. Just a thought.

 

you may be better off seeing if you can find a "used" nascar setup from somewhere.

 

Thank you Bruce and Brian for the thought,
Bruce I am a little apprehensive about using something like titanium in it. Do you think that they would be overkill? Yeah I have seen some nascar stuff on ebay but its not exactly what I'm looking for. A friend of mine has a destroked 400 with a 350 crank (377ci)It is a solid cam and lifter assembly. It is also carburated and has a tremec t-5 tranny. I have personally seen this car rev to 8,000-8,500 on the street and track with no problems for close to two years now. However,there is nothing really exotic about this motor except that the whole rotating assembly has been race balanced, and the crank was knife edged if my memory serves my correct. What connecting rods and pistons would you think are up to this task? If you guys were to build a motor like this what parts would you put in it? What kind of machining would you recommend also? This isn't my first build but it will be the most expensive and meticulous.
Thanks again,
Michael

 

Running 8000 to 8500 the motor is not going to last long because of the piston speed.

Once you get past about 6000 longivity goes out the window, not because of it coming apart, but wear on the pistons and rings, at least this is what i have read and been told.

I can tell you that i have i BBC that will turn up past 7500 (7200 chip) and i have never got more than 10,000 miles out of a motor. ymmv

 

A friend of mine used to run a 377 destroker with a glide behind it in his 68 camaro. His shift point was 10,500 but the motor was designed and built for it. It was in fact a nascar motor that was rejected by a team for only making around the 700hp mark. With 300 ish nos shot it ran many low 9 passes but eventually beat itself to death. From the abuse I seen the motor take I would say a 377 using a dart or motown block might be what you are looking for.

 

sonic,

you hit a trade off.. to spin revs like that you need light weight pistons.. to run a turbo, you need strong pistons with meat up top to handle the elevated cylinder pressures boost create. also if you plan on running high revs and boost.. a customized oiling system will be a huge benefit.. by using a drysump system and having oil sprayed on the back of the pistons to help cool them down.. but this causes added weight on the rotating mass which will play havoc on connecting rods... it can be done.. but why? horsepower is a function of RPM... and in a naturally aspirated engine.. you need to turn higher revs to produce similar horsepower as a larger engine can at lower rpm from its ability to pump more air per revolution. if you plan on using a turbocharger.. you are eliminating the need to spin ultra high revs so i think that the wisest option here is to rethink your strategy. high revs will require a very unfriendly turbo camshaft grind.. you will end up robbing peter to pay paul throughout the build making compromises that are otherwise unnecessary to achieve the same power level and maintain a much safer engine combination. start with a power goal, and then map the easiest most cost effective way to hit that goal. building a solid motor is key for either route you choose.. but I would aim for revs in the 6500 range and with great flowing heads and a matched turbo system, you will be amazed at the level of power that can be harnessed with the Gen II platform.

Chris

 

Well....we have a car here and it has a 2-main 400 block with 350 internals, just forged stuff. Well, it has years running with just a general overhaul every year or two. It has a powerglide and leaves the line at 7800 with shift point at 8600 with no problem. Carburated no power adders with a best of 9.71.
So i think with very good internals it will hold up.

But...going forced induction is another story.

 

From everything I've read to get big power from a given number of cubic inches, you need to either go high revs with an NA motor or lower revs with a boosted motor.

What is this for. Street or track?

 

you would be much happier with a low rev boosted combination. I prefer turbos but they must be fabbed for the c4.

the really high rev stuff run super stiff springs that get hot and won't live on the street.

a realible blower or turbo combination will make lots more torque too.

the used nascar stuff is available, and a mildly built sb2 is a killer setup.

lpe did one in a c4 and made a nice streetable 600 hp and drove the car to 219 or so. I saw this car go through the carlisle auction and was drooling.

I currently make about 520 rwhp in a stroker ZR-1, it turns up to 7500 and is built to take it!! but it wasn't cheap and NOT what I recommend unless you have deep pockets.

I bought the car DONE from LPE, the receipt was 36k!!! thank goodness the whole car didn't cost me much more than that.

 

LT1

 

It will be used mainly for the track with occasional street-cruise use. It will be trailered to the track as well.