drspencer

I have a '71 350 convert that will need a rebuild or crate sometime in the future. I'd like to get some more HP, but want to keep it stock looking under the hood.

I don't race, I use pump gas, and I don't care for the loppy idle that a radical cam gives. Having said all that, how would you build this motor?

Thanks

Peterbuilt

For starters check out the 'Sticky' by Barry K (at the top) and re-curve the distributor so that your timing is all in at 2,800 to 3,000 RPM. A $10.00 ACCEL kit will give you a lot more get up and go and your distributor will be all set for the next motor. PG.

Roadster71

I dropped in a zz4 crate engine in my 71 and never looked back. Painted it chevy orange and all the bolt on's from the orig engine fit right up no problem. With the exception of alum heads it looks like it belongs there.
The orig #'s matching engine is in the garage and will go with the car if I ever sell.

drspencer

Wouldn't I have to use their intake if I went this route?

Roadster71

Yes you would. There is no problem with hood clearance and the stock Q-jet will work just fine.

MotorHead

Put a 3.75 in. stroke crank in there. Makes it a 383 and no one can tell from the outside. Get a pair of iron double hump heads with 2.02 valves, a bigger cam, up the compression to 10:1 and you will have a 400HP / 450 TQ motor that no one will know it's not the original 350ci.

Then tell them you've never been to the drag strip and you will only bet 100 bucks that's how it started for me

BKbroiler

This is a good approach if you want significantly more HP with stock appearance. You also need to bore the cylinders .030 for 383 cu inches. Motorhead is optimistic with 400HP using double hump heads and stock exh. manifolds. I would guess you could add 100HP going this route - that is with a fairly mild cam. I assume you're starting with 200HP.

drspencer

I'm starting with a stock 350/270HP. I don't want it to idle any rougher than it does now, so I imagine that limits my choice of cams.

Would I be better off storing thr original motor and tinkering with a crate motor?

Thanks

jackson

Given that, you may be better off with a crate. And with that lopey idle comment, it'd better be the mildest crate such as a plain old Goodwrench p/n 10067353 as it's nearly a clone of L48 ... and there's nothing wrong w/ x353 if that's what suits YOU as it's a real good value ... But ... BUT...

If you simply rebuild stock 71 350/270 aka L48 ... and replace THREE key things that no one can see ... it'll make noticably more power.
(1) First rebuild replacing L48 dish pistons with small dome Sealed Power p/n H618CP pistons ... and
(2) use thin Felpro p/n 1094 head gaskets ... pistons & gaskets will raise compression about 1-1/4 whole numbers greater than OE rating ... then
(3) Also, replace L48 cam with a slightly larger one such as Summit p/n K1102.

Other than specific pistons, gaskets & cam ... proceed as typical overhaul. It'll still run easy on pump gas but'll make about 40-45 more horsepower than stock L48. And it'll idle almost like stock ... Almost. The H618CP pistons & 1094 gaskets (more compression) ALONE are probably worth 25-30 hp. No one can see those pistons or gaskets or cam.

FYI, if for some reason your L48 idles rough now but you suspect it's entirely stock L48 ... then something's amiss ... because properly tuned & running stock L48 w/ L48 cam is rather smooooth.

-edit- first thing, definately tweek the distributor/ BarryK per Pete's suggestion.

BKbroiler

The 270HP was a gross number, starting in 72 the HP figures were net and the L48 became 200, I think. So that is the number you need to compare to today's standards. That's why I said 300 would be a big increase for you.
Re the crate motors - they will all look different than your original. If you were to convert yours to a 383 and put a Comp XE262 cam in it, it would idle like a stocker. I know because that's the combination in my car.

drspencer

Excuse my ignorance, but can't I just bolt up my stock intake & exhaust to the crate motor of my choice?

Thanks

Brass Pass

You might find some ideas at Brzezinski Racing Products. They do a lot of go fast work on stock intake manifolds, exhaust manifolds and heads. The owner (I believe his name is Randy) is very knowledgable and may have some ideas for you.

I bought some 2.5 inch Ram Horn exhaust manifolds that had CNC work done from them. Parts can be pricey, but they have always been honest and do American quality work which they stand behind. I will buy from them again in the future.

Here is a link:

http://www.castheads.com/

BKbroiler

The exhaust manifolds will bolt up to the majority of crate motor heads. The intake will bolt up to non-Vortec or Fast Burn type heads which alot of crate motors have, particularly the GM crate motors. Others might use aluminum heads with logos on the front which would be noticeable to an informed observer.
Overall, a crate motor is your quickest and easiest solution even if you sacrifice some of the original look, in my opinion.

427Hotrod

Go straight for a 406" motor. Port some 2.5" exhaust manifolds, same with the intake (or grind all the names off a Performer intake and paint it orange). The added cubes will allow for more cam to be smooth. Spread LSA on cam out to smooth it and have LOTS of fun while looking stock!


JIM

Rmorgan&11

another thing to look at is a Hyd. Roller Cam & Valve train setup ? You can run a pretty stout cam and still have a smooth Idle...without cam break in headaches

scott2173

i also have a 71 350/270
ive asked the same question about stock look more power
ive asked about useing the double hump heads and was told that the acessorys are different and you cant bolt up the a/c ?

63mako

You need 1969 or 1970 heads. Casting number ending with 186, 187, 041, 414. These flow decent in stock form but you can port them big time. These can be hogged out to flow big numbers. Combine this with a healthy hydraulic retro roller, Flat top or small dome pistons, 2 1/2 " ramhorns with 2 1/2" pipes into free flowing mufflers and a decent intake painted orange. Easy 400 HP. Looks bone stock. Add a 3.75 stroke crank and bump the torque up a lot.

MotorHead

There is one OEM 400 block that has the same number of freeze plugs as a 350 block. You cannot tell the difference, use an internally balanced crank. Real sleeper here, can have a little fun at the track racing guys that think it's a 350

Alex66

Thats exactly what I did

Sigforty

You replied to a 9 year old thread.