JLM

Okay hello there. These forums rock, and I don't even own a camaro, but my S10 is about half of one. Here's my dilemna. My 305 is gutless. I built the engine because I had it laying around.

Stock block, Stock 85? 305 T/A heads. fresh edelbrock 650 carb.

I used cast flat top pistons and a cam w/ the following specs: int lift .281, exh .296 lift, int dur 278, exh dur 288. I also used 1.5 roller rockers.

fel pro stock head gaskets.

timing is set about 15-20 btdc at idle

Soooooooo... Why the hell is my compression only 125 psi?!?! Is it the wrong cam causing the problem? My previous STOCK 305 would run circles around this thing. I would doubt I even have 200 hp. It's got a manual tranny so a slipping isn't an issue in this case. the clutch bites hard.

Please, HELP! Thank in advance!

Lo-tec

It's slow because you posted this on the third-gen forum...

...if you posted on an S10 forum, it might get quicker!!



welcome to the boards

sofakingdom

iTrader: (1)

Looks an awful lot like the legendary 204°/214° "RV" cam. Don't be expecting much difference, if any, from stock; especially if it used to be the L69 motor.

Possibly the cam is retarded one tooth. (Timing chain not aligned properly)

Irockz

iTrader: (1)

Yes,that is indeed the Mellings MTC1 or one of it's varients.As Sofa said,not much of a cam,but it shouldn't equate to a totally gutless engine.Having had 2 V8 S10s,even the meekest engine should feel pretty strong in that small of a package.I'm with Sofa,you have lined up the wrong set of marks on the timing gears,got it a tooth or so off,or the valves are adjusted too tight.
PS:a Comp XE252 would be a great little cam for what you are doing,would be head and shoulders better than your current stick.

JLM

Cool thanks I'll let you know what I come up with. I still don't understand the crappy compression, can I find out if the cam is off by removing the valve cover instead of the timing cover? Vaccuum is steady however idle flucuates a bit. BTW I've adjusted the valves twice by using the TDC method, not by running the engine.

SSC

The MTC-1 is a great 305 cam and should do real well under 5k especially in an S10.

Back the valves off 1/2 turn and see what you get or just some $18 oil deflectors and see what a hot lash adjustment will do. It sounds like you ran the valves too tight and that will cause lower then normal cyl pressure and crappy performance as well.

JLM

Thanks a lot for all of the help. Also when I adjust the valves both #1 cylinder valves are closed like they should be, which would steer me away from being a tooth off, but if it is off by one tooth that would explain everything. However I know the marks were lined up properly at assembly. And it IS the mtc-1 mellings cam. I can't believe you knew that.

JLM

Allright an update: retested some stuff,

compression: 115psi
vaccuum: 15-16
ign timing: 30 btdc at idle to run well at all
trouble with emissions
crappy idle below 900rpm

I think that cam is off

JLM

YEA! it was 180* off! Jeez what a headache. Beware of the gear timing marks! apparently they changed them at some point, but I think the truth is I used the chilton manual and in the Firebird book they have incorrect captions on the photos, displaying the timing marks 180 off from where they should be. I'm surprised this thing even ran allright with no backfire. So now it's all set and I was only able to drive it around the block but the roads are all icey here so I'll have to get on it tomorrow, but it never ran so smooth at 750 rpm. I'll recheck my vaccuum and compression tomorrow and re-post. Hell yea. Chilton sucks again!

Fast355

iTrader: (2)

AHA, you got tricked. The timing marks are lined up for #6 TDC when they are opposed from each other. They are both straight up when aligned for #1.

I ran a Federal Mogul CS1014R in my TBI 305 for a while. It pulled down 20-22 in/hg of vacuum @ 650 PRM with the TBI setup running things.

sofakingdom

iTrader: (1)

Your cam is one tooth off.

Re-check the cam timing.

There's no such thing as "180°" off. #1 TDC occurs TWICE during one engine cycle; once at firing, and once at the end of the exhaust stroke and beginning of the intake stroke. "Dot to dot" on the chain is the latter instance of #1 TDC, both dots at 12:00 is #1 firing. Either will work for lining up the cam to the crank, although it's MUCH easier to see and get right at "dot to dot".

Your cam is one tooth retarded from where it should be; which puts the cam about 12° retarded or so, from where it's supposed to be.

Guest

He may have fixed it when he went in there, at least it sounds like it.

JLM

Well ****. the compression is still low, vaccuum is at 16 psi...smooth idle though. timing at 8 btdc. this is getting annoying

JLM

Well.....my compression is still low. I put a significant amount of oil in the cylinder and it raised the compression to 140ish. The amount of oil could have raised the compression, or my piston rings never sat in. The rings were gapped correctly, installed staggered correctly, and the piston came to the top of the deck. The rings were installed correct side up. The engine burns no oil.
I'm at a loss here, and the I am sure the valves are sealing completely. The heads are 62cc from a 77? 305, they ARE NOT from the T/A like I thought originally. I checked the casting numbers.
In regards to the smoother idle, it is probably because of the 8* timing instead of the 30 sum that it was set at.
Any advice before this thing gets torn down?