Duke901

Well, my 438 is coming along and just want to have other people opinion on it. Here are the specs of the car

1985 iroc, 700r4 2800 stall, 3:42 gear

454 block 60 over
427 crank
7/16 rods
arias dome top pistons 11.5
comp EX284H 574-578 lift 240-246 duration
781 heads, 2.19 intake and 1.88 exhaust
comp rockers,push rods,lifters,guide plates,retainers,seals,springs
RPM air gap intake
Edelbrock 750 #1411

RB83L69

Looks like a pretty mild 427 build to me, with too much money in some of the parts, that won't do any good....

Why not a 454?

Why such a small, low-perf street carb?

What rockers? what valves? what valve springs?

Why stock heads, a stock crank, some kind of rods with better hardware, and mega$$$$$$$$ pistons?

Should run hard, just seems like you left alot on the table, and aren't being economically efficient.

If I was building a motor like that, I'd put money into a better crank and heads, a long time before I'd pony up that kind of wheelbarrows full of $$$ for pistons that won't do much for the total package.

Which incidentally, I am (454); but not for one of these cars.

firebirdjones

Sounds like you are building a good one. Any reason you are going with those factory heads? Just something you had laying around I guess? Thats alot of compression for a cast iron head unless you plan on running some good gas.
Alot of people like those edelbrock carbs, and I am sure they work fine, I am more of a fan of holley carbs myself, an HP would work nice on that combo.
What are you going to do for a rearend? I don't think a 7.5 10 bolt will last long behind a motor like that, and you could probably get away with some more gear also, 427's like rpm It's all a matter of what you want to do with the car and how much money you have to spend. Pretty cool putting a big block in a 3rd gen though, big block chevys are my favorite to tinker with. Goodluck,,,,,,,Larry.

firebirdjones

Sorry RB83L69, Looks like you posted here while I was still typing. I agree with you on your points, why not a 454? I am a fan of cubes too, I was figuring he had this stuff laying around or something, of course if it is all store bought I would have went right for the cubes. You bring up another good point on the rods, I assume they are stock. Are they rods with the larger 7/16 bolts or the smaller 3/8 rods. Aftermarket rods are the way to go if you have the money. I have had good luck with the factory 7/16 rods after they have been resized and ARP hardware installed, as long as the machine work is good.
With the smaller cube big block you could probably use a looser converter too with that cam, if you are going for all out quarter mile and 60 foot times. Larry.

Duke901

Well, I bought the shortblock already built for $1000 The rods are the 7/16. I got the heads done really cheap, so thats why I went with those, but the heads have all comp hardware, the valves have been enlarged to the 2.19 and 1.88. Not to sure who made the valves. The bottom end has ARP bolts. I went with the 2800 TCI converter because it was cheap. The crank has been turned 20. With all this I really haven't spent that much money. down the line I want to get better heads but for know I think it should move the car pretty well. What do you think this might run?
Thanks Mike

greezemonkey

iTrader: (14)

Duke-

sounds like a good combo so far..

454 block..ready for a 4.00 stroke down the road good till .100 over on the street and few bores in between

781 heads are large port ovals..would be my first choice for strockers especially ones with the 2.19`s (rare) if they are originals

from what I recall true 427 cranks were 5140 steel (tuff)

7/16 rods ...why say any more?, dimples are more than enough.

11.5 dome aries...Mmmm Gas will be expensive, even premium with octane booster won`t do on hot days hope you have a bigger cam in mind or a local race pump and deep pockets...10.5 is doable on the pump though


Duke....The Cam

it`s a flat tappet, and it pushes the limit of the chevrolet lifters to the limit..mostly to destruction. I tried several XE grinds in my first big block, all of which failed in the bay or shortly there after. Go with a magnum for comp or a pro street design..really I wont stick a flat tappet cam in a big block that I own ever again...say goodbye short block after it eats a few lobes! and then say hello to a new charge for another short block + a roller cam set up then.
Good luck if you go with the XE line...diffintely remove the inner springs from your heads if u want any chance of that cam working out.....OHhh and pray if your religious

Comp valve train....(cept for XE)

Air Gap...


Eldey Carb..... Holley based or Demon



It sounds like it going to be one stout car, cam might be a bit small ....try getting around the 620-630 lift range . also don`t forget your american express


All views are opinions are not endoresed or expressed by all of the viewers of this thread




[edit] remove the inner springs for the cam break in period...re-install them after the initial break in [/edit]

IHI

iTrader: (1)

Mis matched components that will easily put you into the mid to high 12's.

You really need at least a 4000 stall with that cam, it's gonna be very doggie down low-you may not notice it until you install a real convertor with the right stall speed then you'll feel what I'm talking about. Throw the edelbrock away once you get ready to go fast-then install a Holley 750-850HP series carb, heck even a standard 750DP is gonna get you ALOT more power, just not mpg freindly.

Also a bunch of compression for that duration, would've been alot street friendly'r with about 10:1. 781 heads are great for a build like this (low budget), but I've seen a few flow sheets from 781 heads takin to the hilt and they still dont flow sheeot, so the heads are killing you at this point. Ask my buddy with his new 496, big compression, huge solid roller, and a $1500 set of 781 cast heads how it feels to get spotted by pump gas firebird with mufflers (he ran 7.28 I ran 7.02 this weekend)

With all the big blocks being built by my buddies using those heads, none are faster than me cubes vary from 454-496, closest is within .4, now strap a nice set of aftermarkets on.....then it may get interesting finally getting beat by pig block equipped cars.

Will make a nice street car though even though you'll be running race gas to keep from swiss cheesing pistons.

AlkyIROC

Nothing wrong with 781 castings. I still have a bunch of them around here. A couple are still bone stock waiting for some work to be done to them. The 2.19/1.88 never came stock in those castings but it doesn't take much to have them installed. A bit of port work and the heads are really good to use. I was using them for a few years and ran easily into the 11's but after dropping a couple of valves and destroying a couple of heads, I switched to Merlin oval port iron heads. I used those for at least 2 years and over the winter, I got a good deal on some Canfield rectangular port aluminum heads. If for some reason you can't find 781 heads, 049's are just as good. No street car needs rectangular port heads. The most popular factory iron casting for those is 990.

Depending on exactly what you want to do with the car, I also have to say there's a mismatch of parts. It will still run well but has more potential if different parts are used.

Motor City Mike

The stock 7/16" bolt rods served me well in my 800 hp supercharged engine for many years without any problems, despite bouncing off the rev limiter several times (7k chip) and going through periods of detonation which eventually took out a piston. They were well prepped with ARP bolts though. I have since upgraded to a set of Eagle H-beams with L19 bolts, since I really felt I was pushing my luck.

Duke901

Yes, this build is very low budget. I do plan on getting better parts down the line, right know I just want to get the car moving with what I can.

The heads have the full comp package, Do you think those springs will be all right?

I wouldn't have minded going with lower compression but thats how the motor was put together before I bought it.

SSC

As long as the springs came with the comp kit for that cam you will be fine. I have a 272 or 274 kit in my 427 yea it's been a long time even for a car I havent driven more then a mile, freaking body shop 2-1/2 years??. I want my malibu back!! Anyway the springs in that kit were rated well above the lift on the cam so you should be allright.