0Road-Race Vette

I am in the middle of redoing my 68 vert for this year. It is a 427/390 car, and retains it's original motor.
I have decided not to restore it back to original.

My question is this:

Is there a proven dynoed combination( not just guestimating) that I can get about 550-600HP out of this 427 motor and still keep it running on pump gas?

I am hoping that one of you has done one of these 427's and has had it on the dyno.

I know of all the aftermarket heads, roller cams, etc... out there.

I am looking for advice on SPECIFIC combinations of parts (heads, cams etc) and what RESULTS they yielded on the dyno.

My only limitations are pump gas, and I want to clear a stock height L88 hood so I assume I would be limited to a performer RPM intake (in order to run a 3" element air cleaner.

I am not interested in a stroker motor. Also will the bottom end of this 427 (crank and rods) hold up to 550HP for street driving purposes? (I am not planning on racing the car. I will just drive it and get on it once in a while)

Any help will be appreciated.

midyearvette

the original bottom end will be fine as long as if you have 3/8" rod bolts, you go to arp fasteners, your two bolt block will handle 600 horse. pick a combination that will produce 500 lbs torque at around 3500 rpm and a red line of 6000-6200 with oval alum. heads....a lot of manufacturers make cam and head kits to help you achieve what you want, with dynoed info........if you are planning on more than 6500 rpm then go to a rod with 7/16 bolts. and a kit with large square port heads...you should not exceed 10.5 -1 compression on pump gas with aluminum heads.cast iron..9.5 to 10 to 1

3JsVette

Take a look at this article from Corvette Fever on a 427/425 motor. http://www.corvettefever.com/techart...ild/index.html

If your looking for 550+ horsepower you may want to go crate motor or have a motor built.

Did you decide on the build for this car yet? Are you going to build something that can be reversed back to stock if the next owner is looking for that? If that's the case just put that 427/390 motor on the side. There will always be a market for it whether it goes with the car or not. I know I didn't answer your original question but I think by the time you're done building this 427 their won't be enough original parts left for it to have been worth your trouble. You said you don't want to build a stroker but if you're going to take up all that room in the engine compartment you might as well make the most of it. No substitute for cubic inches especially on pump gas.

The bottom line is no matter what you decide Stan I'm sure this will be another outstanding dispaly of you and your shop's talent. Good luck with the build. I can't wait to see it unfold.

TheSkunkWorks

Perfectly plausible. Not a guru, but I'm currently working towards a conservative ~550 HP (SAE) 427 pump gas build up myself, tho a solid roller, 4-bolt w/studs and H-beams, which will be spending a day on the dyno before installation. If you keep the revs down, assuming sound building practices, you'll be fine with main studs and upgraded rod bolts.

FWIW, I would think twice about not running the full L88 CAI, and keep on rethinking until you decide to do so. Such an engine isn't going to be happy breathing in hot, under hood air; besides, it will make more power with CAI. This is a bigger priority IMHO than having a huge filter.


TSW

gkull

Are you going to use a solid or Hyd roller?

I drive around with 434 ci and 11.8 compression on pump gas

roscobbc

I know you don't want a 'stroker' engine, but it would not cost any more to build. The advantage is that you can be a little bit more 'adventurous' in terms of specification without loss of drivability. I replaced the L36 in my manual '68 with a 'stroker' 489 with 10.5 c/r, Brodix Race Rite oval port heads, Air Gap dual plane RPM inlet, Proform 950 DP carb and a 236/240 hydraulic flat tappet cam. This dyno'd at 528 hp @ 5900 rpm and 565 ft/lbs torque @ 3850 rpm. Other than having a power band that starts at 1100 rpm this is a streetable as the stock L36 unit. I did need to use an L88 hood, stock drop-down air filter housing, and 2" element.

0Road-Race Vette

Thanks guys.

gkull, I am not opposed to using a solid roller .

I also understand that with aluminum heads, and enough valve overlap I can get away with a bit more compression and still run on pump gas.

So I want to see what others have done and what results it yielded.


Originaly I was looking at a Scott Shafiroff 434 SB for this car, but after talking to them, for the almost $11k for their pump gas motor they told me I would have to retard the timing to run on 93 octane and therefore lose some HP, and them it seemed a bit expensive.

JCG500PLUS

Look into some of the BIG inch GM crate engines,you get the best of both worlds.

midyearvette

sure road race could build his vintage for about half the money as his original post was if it was feasible which it is......however i would not hesitate to go zz 454 and baggie the original mill if it is in the budget...

TheSkunkWorks

One thing that will catch you out on the 427 is what I consider to be a lack of off-the-shelf piston selection, which means custom slugs if you don't wish to greatly compromise your build (read, "$$$"). No big deal if you'd rather spec out your own anyway, as I prefer.

IMHO, if you're not going to rev past ~6300, stay with an HR cam w/ high-flow oval port heads. That said, I'm going with a solid roller w/ rectangle ports; limiter set at 7200. (No crate engine for me.) It will be a while, as I've got a few more expensive items to acquire, but I'll post up results when it's done (hopefully this summer).

Grumpy 427

I had just a motor a while back. it made 550 HP and 513 tq on the dyno. We started with a 2 bolt main block, GM cross drilled steel crank,3/8 rods with ARP bolts. Pistons were TRW forged slugs,11.20-1 compression with a set of Edelbrock RPM Performer OVAL port heads. the cam was a hydraulic roller .585/.585 with .245/.255 @ .050 on a 112 LSA. I wanted to run nitrous so thats why the 112 LSA. I ran a Holley strip dominator intake and 850 dbl pump carb. The motor made a ton of vaccum and would idle very nicely.

0Road-Race Vette

Those are some pretty good numbers. Could the motor run on pump gas with 11.2-1 compression ?

midyearvette

the zz 454 will match those numbers..check out last months super chevy.........lower compression and more streetable roller and a waranty and it's all new!!

Derrick Reynolds

Caveat: I used to do a lot of work on my, and other people's, engines and I have rebuilt several on my own. However, this was all a few decades ago and at no time have I ever claimed to be an expert, or even particularly knowledgable about the selection of internal engine parts. In other words, I know how to take them apart, and I know how to put them together, beyond that it all gets a little fuzzy....

Well, he didn't specify why he didn't want a stroker, but won't it cost more to build a stroker because he would be replacing the drive shaft and bearings, whereas he was planning to use the existing underneath? Also, my recollection is that strokers are great for increased torque and a widened band of high torque, but doesn't the longer stroke reduce the advisable maximum rpm of the motor?

TheSkunkWorks

Don't sell yourself short. In this day of chasing max HP/TQ figures without regard to the bigger picture, a lot of would be experts don't understand as much, tho we're actually talking about changing the crankshaft together with longer rods (which any engine builder worth their salt would install in a stroker at even more expense). Also, you've touched on a couple of reasons why I recently aborted a 496 in favor of another 427 myself. Having excessive torque early in the power band might have made AA/FC style burnouts a breeze, but putting power down on corner exit and pulling to higher revs on top end are far higher priorities of mine.



edit - btw, a big block doesn't necessarily have to have 11:1 to make over 500 hp.

0Road-Race Vette

I guess, ultimately I would like to hit 550HP with my 427, retaining the stock crank and rods, and not break the bank.(by that I mean keeping it in the 6-7k range.)

That should be possible right?

If not, then I need to just look at crate motors because the cost will be very close to one, and I can just save my 427.


I have gotten different estimates on this and it seems that most people are quoting me prices that are somewhat similar to crate motors.


Being a body man and not a mechanic, I guess what I dont understand is why the cost is so similar when on one hand you can get a new bottom end and on the other you are using your own.


I certainly am not a skimper on parts but I just want the reasons behind it.

gkull

the more hp per ci increases the cost, longevity, and how street friendly it is.

All crate motors have a built in profit margin. so they skimp on anything they can.

To make 550 hp out of 427 - 468 ci you are going to need heads that flow just over 300 cfm and a roller cam with 242 - 246 I @ .050 duration

of course headers and free flowing dual exhaust and an intake that can flow up to near 6500 rpm

midyearvette

great question...back in the day we could buy an alu head complete less intake l88 from rodenfels chevrolet in columbus ohio for 850.00!!...it would cost that much to find one in a bone yard or a strip out short block and build one yourself back then. plus you have to add profit for the engine builder, crate engines have changed all that......if 6-7 k is your budget, save the old mill for posterity and go zz 454 or bigger, all you have to change is the flywheel and EVERYTHING is brand spanking new with a warranty!!......

TheSkunkWorks

Good heads and quality roller valvetrain components don't come cheap for the BB, so it's tough for a custom build to compete with crate engine houses, cost wise. However, as such "bargain" engines won't likely have all the good stuff in them, so make sure and do your homework if you choose to go that route. Also, be on the lookout for combinations which stress peak power above all else, as it could well have nasty manners with which you don't want to live.

Given my experience with "outsourced" engines, if I had to choose between the two, I'd rather build "less motor" with better components and do my own blueprinting and assembly "in house" than buy off the rack simply for the sake of the power per dollar ratio. I could probably crack this nut for a good bit less than I'll have wrapped up in my build by the time all is said and done, but IMHO value doesn't always come with the lower price tag. That's my take, FWIW...

0Road-Race Vette

As far as the GM crate motors are concerned, they dont seem to perform as well as advertised. Every one I have seen on a dyno, makes considerably less power than advertised.

So I am a little hesitant to go that route again.

It seems the only way you will get real HP is by dynoing the motor, not listening to fantacy figures.

That is why I was asking for actual data, should I choose to build the 427.

I would hate to buy certain parts and have them not perform to expectations.