I am now the proud owner of an 85 Jimmy!! Anyway I have a basically stock 305 that was "freshened up " about 20,000 miles ago.

This last weekend we put an Edelbrok performer manifold, platinum plugs and basically gave it a good tune-up.

What I want is 300 HP. What do I need to do? What do you feel the best upgrades for this engine are?

I am going to be getting headers and an exaughst in the next couple of weeks, that should help it breathe a bit better.

Thanks! I can't wait to have a mean rock crawling, mud slinging machine!

Get some 202/160 heads that will wake it up.....headers go with 1 1/2 in tubes from flange to collector. What you'll need to do rocks is "Torque" not HP but they do come together in upgrades. You might wanna put a RV cam in your motor with maybe even a set of 1.6 rockers to give you better "low end". Just a few ideas before it gets really $$$$.....start saving for a 383 buildup.....

Pull the 305 and replace with a 350 to start........


:flipoff2: :flipoff2: :flipoff2:


I could be very wrong on this as I try to steer clear of 305's, but I don't think it will take 2.02 and 1.60" valves. If I'm not mistaken the bore is too small and you will have contact. Most 305's I know of have 1.84/1.50 valves. You are also going to lose a lot of torque with the larger valves.

I am assuming the truck is carbureted also. Your biggest gain would probably come from a cam swap. The bumpstick makes a HUGE difference in performance. You can look in to something like a Comp Cams Xtreme Energy 250H should work well. I would suggest calling them and making sure first though. They have a 1-800 # for that.

Getting almost 1HP per cube out of a 305 should be a interesting exercise, but it can be done. You might also seriously look around at finding a nice 350 or 400 to swap in. There is no replacement for displacement.

Good Luck

The complete Performer package (cam, intake, heads) will net you about 310HP with a 350. Probably good for ~250-265HP with a 305 I'd guess. Will set ya back about $1,500 though & that's 3/4 of the way to a 300HP crate engine from GM.

TEX

!THERE IS NO REPLACEMENT FOR MORE DISPLACMENT!

But if you insist on keeping the 305 I would start with the whole upper end i.e. send the heads and intake to your local machine shop and let them go to town with them, press in hardened seats, put 2.5/1.60s or even 2.08/1.60s in them, then let them completely port and polish the heads and intake as much as possible! After that get a larger carb (750 double pumper or 800 q-jet would be my choice) and by that point with all your other goodies you should have a runnin 305 HAHAHA! But really just invest in a big block, and if its too big, make a 426 strocker small block. And show us big block guys how its done.

I have to agree with the other guys.Get rid of the 305 and slap in atleast a 350.I have a 305 in my blazer.It does alright with the 4 speed and 4:10s but it needs more!!!I jump in my '77 crewcab with the 454 bored out and cammed and 4 speed and it is a different world!!!With a 350 or 400 you can even keep the Edlebrock intake.:usa:

First off congrats on the new ride.

Just stick with the 305 as is, they really aren't all that bad when backed up with a manual trans.
The Autos on the other hand, suck the power right out of 'em.

The 305's do not breath very-well because the bore is so small and shrouds the valves. Also, with the 305's smaller bore it will not allow for larger valves to be installed (pretty dawg-awn sure larger valves can not be installed- but could be wrong). So, it's really a up-hill battle to get any "real" power out of those mills. They can be built, but in my mind - it's a wast of time and money.

Build a good solid 350.
My grand mother could tell you how to build a 300 H/P 350, it's a walk in the park.

Chevy's Rule!! I am so happy with my Jimmy. I sold my Toyota Tacoma to get it and man I love this thing and I love working on it. Even my wife likes it enough to let me put money into it. I want to thank you guys for all the help you have given me. I am going to start looking for a 350. I am going to put an exaughst and bump up the voltage on my HEI and then leave it there. I don't want to waste any more $$ unless it is on stuff that I can swing to my 350. I am going to run this 305 into the ground it still has a lot of life left in it. Which is good while I am still in school.

So my next questions are:

1- Should I find and old truck with a poor 350 buy it and build it?

or

2- Should I just get a crate engine?

and

3- For all of you who are going to reccomend a crate engine where are the better places to buy them?

The Chevy Forum is awesome.

Oh and I was out at the Good Year Extreme comp here in Cedar City this morning. It was great. Wish I could have stayed longer. . .

~AM

If you know about the internals of engines and feel confident in your abilitys than build one.If not get a crate engine.GM sells brand new 350s for very good prices.Even have awesome warranty.You can get a basic 350 from GM for around $1500.Throw a cam in it and go.Blazin:rasta:

Here's what I'd do:

Get a 87 up 350 4-bolt main with factory roller cam, rebuild the short block with a balanced 383 stroker kit from powerhouse or speed-o-motive, throw in a hydraulic roller from the manufacturer of choice. cam specs: 225@.050 / .490 lift, 112-114 lobe centers. Get a assembled set of World Products S/R heads, full roller rockers (not roller tip only). Add a billet electronic distributor, 7-quart oil pan, hi-vol pump and pickup from Summit and headers and go.

If you ever think your spray the engine with nitrous or spin faster than 5000-5500 rpm, then spend the extra $1500 on a forged crank, rods and pistons. You'll love the power this combo will make.

Otherwise get a crate engine...

I would not go to the bigger vavles in a 305 they will end up hurting the torque and only helping on the top end where the motor usually doesn't run at anyway.

if you want to just make the 305 work i'd put on headers, dual plane intake manifold, rv cam, and take the heads off and have about 0.010 cut off.

what i would really do is kick that freaking 305 to the curb or back into that 1978 oldsmobile cutlass supreme that it came out of and get a 350.
350 is the best because it doesn't have overheating problems like the 400. and because it is the single most popular engine. which means cheaper rebuilds and more products available.

350engine, 202 valves, flat top pistons, head work done by a head shop with a flow bench, balance, and of course double pump. you'll have a hard hiting engine. bring your cam card to the head builder so that he will know how to port it.
remember that horspower is in the heads do not try to save money on them. and also the cam and porting have to be a matching set.
aluminum heads make more horspower of course, but you must in crease your comprestion to get that power out of them. a friend of mine runns 11:5 to 1 with alum heads.

Originally posted by hawaii500_1999

350engine, 202 valves, flat top pistons, head work done by a head shop with a flow bench, balance, and of course double pump.

Why would you spend the $ putting 202's in a motor that's going in something heavy like a blazer. :confused: The 194's are much better for building torque. If he's going to do a buildup on a budget the L31 vortecs are the way to go. If you wanted HP then the way you suggested is fine, but in a heavy truck like the Blazer, you would be crazy to pay for port/polishing, etc on a torque motor.

Small blocks suck

You now you want that 502HP ramjet 502 crate motor! But yet again if you insist on a small block build a 426 stroker out of an old 400 4-bolt block. Find some vortech heads, which are a dime a dozen, and let a machine shop put it all together. But remember, small blocks suck. BBC FORE LIFE! It’s all about inches baby inches.

Why would you spend the $ putting 202's in a motor that's going in something heavy like a blazer. The 194's are much better for building torque. If he's going to do a buildup on a budget the L31 vortecs are the way to go. If you wanted HP then the way you suggested is fine, but in a heavy truck like the Blazer, you would be crazy to pay for port/polishing, etc on a torque motor.
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i'm not saying to get the heads hoged out to 300cc intake runners or anything like that but there is almost always a way to get more power from a profetional port job. that's why i said for him to bring his cam card with him. and as for the 202's i haven't ever noticed a low end drop when i change from the 194's. it's usually valve over lap and too big of intake runners, or single plane manifolds that i have noticed a vacumn drop.
but i am the first to say that i am not an expert. i am just trying to share my experiences.
i do under stand that with a smaller intake volume the velocity of the intake charge is faster resulting in more low end power.
i still think that 202's are better for all around power.:p

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Small blocks suck

You now you want that 502HP ramjet 502 crate motor! But yet again if you insist on a small block build a 426 stroker out of an old 400 4-bolt block. Find some vortech heads, which are a dime a dozen, and let a machine shop put it all together. But remember, small blocks suck. BBC FORE LIFE! It’s all about inches baby inches.
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LOL
big blocks rule!!:flipoff2: