305 heads on a 350 need help!

i recently bought a 1990 chevy camaro with a 305 h.o. motor in it that had a blown head gasket. in my garage i had a 1973 chevy 350 that needed rings and bearings. so i take apart the 350 and redo the rings and bearings (main and rod) hone out the cylinders and start putting it back together. when i get to the heads i decided to use the heads off the 305 to make higher compression. the 350 heads are the 78cc chambers and the 305 heads are 58cc ones. since the pistons were flat tops with valve grooves in both motors i think it should work fine. the 78cc heads were good for around 8.5:1 compression and best i can figure the 58cc ones will get me up around 10.75:1. i used the 350 head gaskets and put the motor back together. only problem i ran into was when bolting on the intake manifold i noticed that chevrolet had decided to change the angle of the middle 2 bolts on both sides of the intake, but everything else seamed to line up fine. so i ground out the slots for the bolts a bit on the manifold so i could get the bolts thru at the proper angle. everything seamed to torque up fine. then i installed new plugs, wires, and a hei ditributor. the carb. is a 4 barrel holley 600. i set the timing and started the motor and it runs terribly (i did put in the highest rating gas i can get at the pump because of the new higher compression). it acts like its badly out of time. i played with the distibutor several times and even made sure that i wasn't 180' out on the stroke. it vibrates terribly, overheats very fast, and backfires periodically when starting it. i was so determined it was timing i pulled the oil pan and timing cover back off to check to see if i had the timing chain off a tooth or something but everything was normal. i tried a new distributor and tested all my plug wires to make sure they are firing. i've done all i know how to do to fix the problem anyone ever ran into this before? could an intake gasket leak possibly be the problem. oh i also used the harmonic balancer off the 305 since it was in better shape than the one that was on the 350 but it slid on the 350 crank with no problem. they are both the same size and have the same bolt holes and everything. i sure appreciate any help given, thanks in advance.

the head gaskets for the 350" (from 1973) are a Fel-Pro #7733PT2.
this 350" gasket covers most ALL SBC from mid-'60s to like '74.

the 305"heads from the 1990 Camaro should use a different part number:
Fel-Pro#8510PT
(used in 305s from like '89-93)

your overheating might be the fact that your gasket might be blocking some water passages through the heads.
I'd get a gasket for each, and overlay them to be sure.

if this is not a problem, spray some carb cleaner around your intake to insure there is not a massive vacuum leak, as this would affect idle, and temperature.

did you do an initial cold lash on the valves, to get them close prior to firing?

hope this helps,
chris

...sorry,
the 305c.i.
pt#8510PT heads covered 1977-93.

Shure thos 5.0 liters will give you more squeeze but they an't gona flow shit compared to 350 heads, i would have put your money in the 5.7 heads and get some real flow. :2cents: :thumbsup:

i had the guy at orielly's overlay the 2 headgaskets and he said that all the water jacket holes were in both gaskets that just the bore was slightly different. i did run all the rocker arms down close before firing it up. tightened them till u could barely spin the rods by hand when the lifter is bottomed out, but made sure not to over tighten them. the massive vacumn leak is a possiblity though. will the holley mount on an older edelbrock performer intake without an adapter?
i just went and pulled off the intake and it didn't look like the intake gasket had any areas with blowby, but when i drained the oil out of the pan it had a strong gas odor and seamed alot thinner than the 15/50 weight i had put in it. what has me worried is the vibration. it is acting like a 350 that has a 400 SB flywheel on it with the big counterweight. if you set a glass of water on the hood when it was running it would sloshed it everywhere. i can't figure out where the vibration is coming from. i took my time putting the motor together and double checked everything so i'm pretty sure everything internally is working right. this thing has me dazed and confused.
Stewart

ok i went out and checked out where the carb mounted to the intake, and it looks like i need an adapter. there was one small part of the holley carb that didn't seal up with the intake. (the runner going to the 3/8 vacumn line on the back left of the carb if in front of the car facing the motor) could all this trouble be caused by a vacumn leak though? i mean i've had vacumn leaks with cracked vac. hoses and whatnot and never had one run like this. damn motor starting to get on my nerves. may just tow the car to the local highschool and let the kids whack it with a bat for dollar a pop.

You still might have something incompatible there. The 305 to 350 interchange is a "not exactly" case by what you're saying. The over thin oil with the gas is an over rich condition. To check for a vacuum leak, I start with putting my hand over the airhorn of the carb. If the idle smooths out, you have a vacuum leak. You can pin point it with carb cleaner as previously suggested. Also make sure that the distributor isn't a tooth off location.

Bob

ok heres whats up now. i got the car running. i had some problems with the electric fan and the fuel pump relays, but i bypassed a few sensors and they kick on and work fine now. the only problem i am having now is a few ticking lifters (easy fix) and a deep knocking sound coming from the passenger side of the motor. i set the timing at about 4 deg. and it jumps up higher when the vacumn advance kicks in. could the knocking be from the timing ( since i have no clue what it should be on this higher compression motor). could it be from the gas maybe? i know u have to run higher octane gas for higher compression motors. i put in the premium 93 octane at the pump. thanks for all the help so far everyone.

is it a pinging type of knock or a metal on metal type of sound?

there is the light clicking of the loose lifter then a deeper sound that seams to come from deeper in the motor. best way i can describe it is a knock as if someone was tapping a broomstick on a concrete flood.Stewart

The knocking sound is not good. Try pulling off one plug wire at a time on that bank to isolate the noise to a particular cylinder. It will lessen when the cylinder doesn't have the combustion load on it. I'd guess that you have either a rod or main bearing problem.

Or you can use a short stick as a "listening post". Big wood dowels or a piece of broom stick about 2 feet long is good for this. With the engine running, place the stick as close to the noise as possible, against the base of the cylinder head should do it. Put your ear to the stick, you'd be amazed at what you'll hear. A piece of heater hose might work, but not as well.

Bob

thanks for the advice bob. i plan on checking it with a broomstick soon as i get my son to school. last night a friend stopped by and i let him listen to the knock. he said it sounds like i have a lifter going "flat"..... i have never had any problems with a lifter so i can't say if it sounds like one or not. has anyone had a problem with a flat lifter and if so does it cause a knocking sound? the knocking doesn't start at all until the motor warms up to roughly 175` and you can't hear it at all at idle. have to rev it up to 2500 or 3k before ya can hear it. i know i definatly have some lifters clicking but i just havn't adjusted the rockers yet (hate to spend the time doing that if i'm just gonna have to yank the motor again....). so what do you guys think?

I would go ahead and ajdust the rockers. You got nothin' to lose and you might find out which lifter is possibly collapsed. In the event where one is too tight, you could do damage to the cam if you don't do it ASAP. What follows will work with hydraulic lifters only.

Pop both valve covers, don't bother warming up the engine up right now. Just let it run, start on either bank. Back off the rocker nut until you hear it clack. Tighten it to the "zero" point, where the noise goes away. Go 1/4 turn, let the motor settle out. Then go another 1/4 turn, again wait for it to settle, or smooth out. The book says anywhere from a total of 3/4 to 1 full turn, but for the first go around a total 1/2 turn should get you in the ball park. I use 1/2 a turn total with used motors most of the time, 3/4 with new ones.

You can fine tune it after the motor is sorted out, but this should tell you if you have a bad lifter. I won't be around over the long weekend, so good luck and I'll check back monday or tuesday.

Bob

Shure thos 5.0 liters will give you more squeeze but they an't gona flow shit compared to 350 heads,

This comment should be repeated. IMHO you have a seriously mismatched combination here. All detonation and no flow.
The 305 hears have smaller valves than even the 'small' valve (1.94 intake) 350 heads. They simply will not fill the cylinders effectively.

Also the reduction in chamber size will produce a HUGE increase in compression. So not only will you lose power, but you will need premium with octane booster to do it.

Put the 350 heads back on. They will be much better.

ok i pulled my valve covers and was gonna get the rockers all adjusted to stop the clicking so i could hear the knocking better. what i found is not good. very little if any oil is squirting out of my rocker arm holes. what are all the known causes of this? i got to looking at the oil pressure and it starts out fine (15 at idle and 28-30 when revved)then as the engine heats up it drops dramtically. is 3-4 lbs. at idle and if ya rev it up to 3500-4k it jumps up to 15 lbs. or so. i talked with some friends and they are all saying oil pump is bad but i didn't think there was a whole lot that could go wrong with an oil pump other than being jammed up by something. i am useing 20/50 oil so it should be good and thick which should help pressure i figured. i have hear that a cam bearing could be out and cause it not to oil the top of the block but the knocking is still coming from the lower end once it warms up. i checked my push rods to make sure they weren't clogged and they were fine. could the lifters all be clogged? basically i just need to know if i need to focus on the oil pump or the cam bearings or if there is something else i need to check that i don't know about. is there any way to test the oil pump while the engines in the car? the car is running much better besides the oiling issue. i drove it today and it has plenty of power and the vibration stopped after i checked and filled the transmission (not sure why that would cause a vibration....). then the oil pressure started dropping so i parked it quickly. any advice would be greatly appreciated. Stewart

Did you put in a new oil pump when you put this thing together?

Pumps wear out, in that the clearances between the two pump gears and the housing gets too big.
When this happens you get low pressure as you describe.
If the pump is new, the pick up tube may be leaking or the pressure relief valve is stuck open.

BTW the low pressure might have wiped your bearings. If you drop the pan to change the pump, take off a couple of bearing caps and have a quick look at the bearings for signs of damage.

Good idea to park it for now. You should have good oil pressure at idle, I'd like to see 30-40 lbs myself. My big block had 60 at cruising speed with straight 50 weight oil.

Did you change the cam bearings? The oil holes have to line up with the corresponding holes in the block. Since you have a knock already, as someone else suggested, drop the pan and look at some of the main bearings. If you could isolate the knock to a particular cylinder, pop off the rod caps on that journal.

I think that your oil pump is the root of all your problems. The pickup tube might be loose at the pump casting. I never play with used oil pumps, they are cheap enough for a name brand one. I like to use a high volume one as opposed to a high pressure one. If the tube feels loose (yours may have fallen off) I stake it in place with a sharp punch. Pull the pump cover and look for metal shavings or heat discoloration, in any event, chuck that oil pump.

I hate to say it, but you're probably better off pulling the engine and putting it on an engine stand. Do you know how to use Plastigage for checking bearing clearances? Most good parts stores carry them and they do come with instructions, or you can ask here. Also take off your oil filter and hold it in a bench vise, cut the can off towards the base with a hacksaw. Look at the element closely, take it apart if you have to. If you see any appreciable amount of metal (more than a speck or 2), I would take the entire engine apart for a good inspection followed by a professional hot tanking.

Bob

please keep us posted stewertbc
i'm dying hear how this all plays out

there is the possibility that your oil pump pickup is either coming off or developing a leak - or getting plugged up even. possibly your spin on adapter has a malfunctioning bypass valve & your filter is clogged? the only other thing i'd think would be a bearing going bad (rod bearing would not only explain the lower end knock, but also the oil pressure loss as well). best to be safe than sorry - yank the motor, pull the oil pan, check your bearing clearances. i know it's a pain in the butt, but - better to buy a new pan gasket & spend a few hours pulling the motor than to throw a rod & have to buy a new motor altogether. get yourself a plastigauge & check your clearances. there's really not a lot to go wrong in your oil pump, but - i trust you DID replace it when you did the bottom end, right? (i mean, come on, you're going to do all that & not put in a new oil pump? that would be like buying a new car but putting in your old oil filter or spark plugs only worse! the oil pump is the life pump of your engine)