jonny_z9

Hey guys, this is my first post. I have a 91 rs that i got with a 3.1. last year i did the v8 swap and put in a 305 because i already had it. But now I have some money to build a real motor. I have a 2 bolt main 350, and a set of 186 camel hump heads. I found an engine kit that looks pretty nice, here's the link http://www.northernautoparts.com/part/ek-ek1900 so with my 64cc heads and the flat top pistons in the kit, using .041 felpro head gaskets estimated about 10.89:1 CR, Sound about right? And also i'm having the heads machined and new springs to support a bigger cam, thinking of something like a .488" lift. And one of my biggest qestions, what octane fuel should i run with 10.9:1 compression?

92RS_Ttop

iTrader: (3)

I've used Northern Auto Parts for all of my engine builds. Great prices and great customer service! 10.9:1 compression is going to be hard to avoid detonation on iron heads. You'll need at least 91 octane fuel, and will probably need to dial back the timing advance a bit. You could go with a .043" head gasket to drop your CR a bit without losing much power. Also, it's hard to know what your compression ratio will be without knowing the depth of the pistons at TDC. The link you posted is for pre-1980 blocks. What is the casting number on your block?

There's also better heads out there than the camel humps these days, even without going aftermarket. Vortec heads will give you the same chamber volume and will flow better. You'll need a Vortec-specific intake and I believe you'll still need to have them machined for the lift you want. At the moment, I can't remember the max lift specs on them without machining, so I may be wrong on that part. Vortec heads can be had pretty cheaply at junkyards, I got a set for around $80 at my local U-Pull. If you're getting them machined for more lift, might as well go the extra bit and get them machined for larger valves as well.

jonny_z9

The block is a later model, i think 91. Its a 1 piece rear main and tbi style heads were on it. I cant get the casting number at the moment. And I agree with vortec heads, i've done quite a bit of research on them. But my dad offered me these 186 heads for free so they work a little better with my budget. I have searched in my area (iowa) and the vortec heads are pretty pricy around here, then I'd still need to pay for machining and get ann intake. So for now i think i'm just going to run the old double humps. I'll probably upgrade down the road

jonny_z9

The highest octane pump gas in my area is only 91, I will run that for sure atleast, i just am not sure if I need to mix it with some race fuel to raise the octane rating (I probably will anyways on nights I mess around a little or go to the track) But i just want to be sure I won't melt the pistons or anything running only 91 octane. And thanks for the response btw

92RS_Ttop

iTrader: (3)

If your using a 91 block, that kit you linked in your first post won't work. It's for a pre-1980 block which is a 2 pice rear main seal block. 1 piece blocks didn't appear till 1987.

As for the heads, the machining costs will be the same for either the camel humps or the Vortecs. Only difference is the cost of the heads themselves. While I certainly understand the concept of "these heads are free, those aren't" as I've done it myself there is something to be said for only paying for something once as well. Plus you'll have the added cost of 2 intake manifolds as they are different from one set of heads to the other. Unless you're getting a manifold to go with the camels.

sofakingdom

iTrader: (1)

That has those cheeeep hypereutectic flat-top pistons; they'll be .045" or more "doen in the hole" at TDC. Your ACTUAL AS-BUILT compression ratio will be about 9.3:1. No need to get all wound up about "premium" gas, you won't be needing it, and all it will do for you, is slow you down and decrease your mileage.

Double-humps are fine, as long as you don't have to put money into em. For DECADES that was all we had, and we did just fine. Given the basic nature of that bottom-end kit, they're entirely "enough", even if not "state of the art". In this day and time, as long as you can avoid spending money on em, run em and enjoy em. If they DO require spending money, put your money into better cores. (Vortec)

Only thing in that kit that's "pre-1980", is the rear main seal and pan gasket. If the block is from 80-ish to 85, you'll need a different pan gasket; and if it's 86-up, the different seal as well.

People who quote that lift spec usually are referring to the ancient Stone Age generic copy of copied copies of generically copied generic copies of generic cam copies like the Summit one. Given that the difference between that old crap and the best flat-tappet cam you can buy today is less than ONE TANK OF GAS, seems kinds stoooopid and pointless to cripple your project that way. Get a better cam.

Then of course, make sure you have an appropriate carb and ignition system on it. I'd suggest a Holley 6210 and a DUI.

jonny_z9

Yes I'm aware I would need to buy a late model pan gasket abd rear main seal. Since that would be extra I may just get vortec heads and use a late model kit. I suppose I'll call some junkyards and price heads. What trucks came with the desired vortec heads? I dont remember the good casting numbers. Should I just asks for 96-98 silverado cylinder heads?

jonny_z9

If those pistons aren't all they're cracked up to be, should I exclude the pistons from the kit and run my stock 8.5:1 compressiin pistons. What cr would that put me at? I'd love to put the car at 350hp or more but don't have a large budget. Just looking for the most bang for my buck here

sofakingdom

iTrader: (1)

Doesn't make sense. There's no logical connection between Vortec heads and either getting the cheeeeep kit and replacing the parts that won't fit, or getting the right kit but might cost a bit more. Heads are not a factor in the choice of the "kit" or vice-versa.

96-2000 trucks have Vortec heads. Casting #s are 906 or 062.

If you decide to go that route, walk physically up to the counter (NOT call em on the phone) and tell em you're looking for heads for your 97 Silvy. DO NOT utter the word "Vortec". DO NOT even PRETEND you know the casting #s. Instead, you are a carpenter / landscaper / whatever that just needs to fix your broken truck and you just need to get the same ones. You are a regular guy trying to fix his work truck, NOT a hot-rodder playing with his toy. When they bring you a set of heads, look em over, of course; if they're NOT the right ones, tell em they won't do, but DO NOT mention the casting #s!!! mumble something about "the intake bolts don't look right, the ones on the truck only have 4 bolts" or some such. The point is, avoid the "hot-rodder cover charge" that you will otherwise get hit with. You're just a regular guy making his living and trying to fix his broke tools.

Keep in mind, you'll have to buy an intake manifold if you use Vortec heads. By the time you have bought all that heads and intake, you will have spent AHELLUVALOT more than a gasket and a seal.

The stock pistons in a stock TBI motor, if that's what you've got, are about the same compression as the ones in the "kit". The reason to change pistons would be, if the motor is wore out and needs to be rebuilt. In that case, you CAN'T use the stock pistons, because the bores will be .030" larger than the old pistons when you get the block back from the machine shop. OTOH if the motor DOESN'T need a rebuild, that is, if it has no ring ridge or other cylinder wear, and the crank and bearings are all in good shape, then you don't need either the "kit" OR machine work on it; you just need to clean it up and run it. Which will leave about $1000 extra in your pocket. The risk of course is, that if you decide to cut that corner, put it all in there as-is, and you might THEN discover that it's ACTUALLY at the end of its life; rings don't seal, bearings are shot, crank is wore down, whatever, and now you have a smoking, knocking, short-lived POS in your car instead of a new motor. Decision time.

IMO the best bang for the buck, IF YOUR 186s DON'T NEED MONEY SUNK INTO EM, is to run those, and IF YOUR BLOCK DOESN'T NEED MONEY SUNK INTO IT, run it as-is, otherwise use the cheeeeep kit. It'll work fine for what you're doing.

jonny_z9

My 186's are not assembled and will need to be machined. And I checked everything on my block with a micrometer and I can use std everything. Less than .010 ring ridge so I am going to hone it and use std pistons.

jonny_z9

I found a circle track 350 "602" crate engine for sale locally, it was ran out of oil. But has vortec heads and intake on it. Its all stock and still sealed from GM. He's asking 400$. I think this sounds like a good deal, anybody disagree? I could probably sell the 8qt oil pan and block (if the mains were not spun too bad) and re coop some of my money

92RS_Ttop

iTrader: (3)

I'd go for it. Vortec heads and an intake will run you close to $400, and probably more than that. Especially if you need to get the heads machined.