General advice

[Aaron jackson 87]

Hello, just looking for some advice on my new engine... it is a 1987 blazer originally a 305tbi now converted to 350 carb. Over the last few months i have built the 350 to replace the 305. Its a 1995 block running stock pistons, rods and crank. Edelbrock preformer intake, edelbrock 1403 500cfm carb, sum1102 cam and lifters, home ported 193 heads, intake/ exhaust, and combustion chamber, gasket matched, stock valves, lapped and stock valve springs. Heads were not milled. Running 8 degress advanced. Now thats out of the way... i have a few questions to reach its potential. Engine broke in well, has aprox 4 hours run time and maybe 100 miles. I have the 305 exhaust manifolds hooked up to it, are they hurting flow possibly? Would putting the 350 manifolds on it change anything? Still has the y pipe and cat. Also there is a breif hesitation when pushing gas pedal but clears up with depressing pedal further, what do i do to find out if i need different jetting? Is the 500cfm carb too small? Just looking for any advice on ANYTHING to get the most out of it. I built this motor in my driveway and had little machine work done to it and am fairly suprised it runs as well as it does. Any advice questions or comments?

 

[thearborbarber]

305/350 manifolds are one in the same. They aren't hurting you but there is some power on the table that headers would free up.

 

[Aaron jackson 87]

305/350 manifolds are one in the same. They aren't hurting you but there is some power on the table that headers would free up.

Ok, headers were a thought at one point, however i read on another post that headers wouldnt really benifit on a sub 300hp engine, i have no idea what the hp would be after the rebuild, though i doubt im in that range. It has the stock 2.25 exhaust pipe, that i am planning to convert to true dual to hopefully get it to breathe better with the "upgraded" cam and heads, would headers be worth it on an engine running less than 5200rpm? I also hurd somewhere that 305 manifolds are an 1/8 inch smaller on the inner diameter of the tubing than a 350 manifold, does that have any truth to it? Thank you

 

[Stinky]

The standard carb on a 350 is a 600. Check the Ebrock website...but I bet they recommend the 500 for 305's and small CID motors. A single 2.25 exhaust...your manifolds don't matter. What kind of converter do you have? Is it an aftermarket...it should be. I'm not sure if they are the same as yours, but I've heard that the TBI and Vortec exhaust manifolds are the best, you may or may not have those. Do a search on Rockauto.com and see how the PNs compare...you could always put on Ram's Horns. You need the ones that come out and then have a turn in them, not like these. https://www.summitracing.com/parts/big-11704flt/overview/

I have a '90 Sub...the exhaust is a stock 3". But, the cat is a low-flow cat. The wye is a bit bigger than on my '86 (1/8").

The 1st thing that I'd do is get rid of the 2.25 exhaust and get a high-flow cat.

 

[Blazooki]

Letting an engine breath and flow exhaust better works on any engine. Ram Horns wont fit on Vortec motor. I found that out the hard way cause that was my original plan. They don't bolt up to Vortec heads and if they did the down tube is into the motor mount, even if you could find the curved ones. If you want headers find a set of shorties like these: https://www.summitracing.com/parts/pte-h8036 . You dont need to go 3 inch tube unless your staying single exhaust. If you dont live in a state that requires a cat, then loose it. If you have a visual inspection then get a high flow cat or gut the stock one. If you go dual exhaust then 2.25 will be fine.

 

[Bent77]

1) Standard carb on a 350 is a 750 CFM, and yes, its a huge difference.

2) Is +8° you cam timing or distributor? Not sure where you live, carburated I ran that much or more as my initial timing.

3) Factory manifolds will work fine as long as the rest of the exhaust system flows well. Is it a single exhaust? If so, maybe consider stepping up the pipe size and using an after market muffler and cat.

Factory torque converter is fine

 

[Aaron jackson 87]

1) Standard carb on a 350 is a 750 CFM, and yes, its a huge difference.

2) Is +8° you cam timing or distributor? Not sure where you live, carburated I ran that much or more as my initial timing.

3) Factory manifolds will work fine as long as the rest of the exhaust system flows well. Is it a single exhaust? If so, maybe consider stepping up the pipe size and using an after market muffler and cat.

Factory torque converter is fine

Cam was installed dot to dot, so that would be 8 degress through dst. Checked my timing this afternoon after it had a hard time starting and giving a nice pop from the carb, some how it was at 0° when i checked thia time, wlmust have slipped when i was tightening the hold down bolt. I re adjusted and locked it down at 8° at 800~ rpm. Seems to start better and has more pep than it did, also the hesitation i felt from the carb seemed to go away 90%. I never have known how to calculate what my timing should be set to, is using timing degree tape or a dial timing light the only way to find my total advance? Info i have found has been relatively vague. With my setup what would be a good inital timing to set at, or is 8° generally good setting? Thanks for all advice!

 

[Aaron jackson 87]

Cam was installed dot to dot, so that would be 8 degress through dst. Checked my timing this afternoon after it had a hard time starting and giving a nice pop from the carb, some how it was at 0° when i checked thia time, wlmust have slipped when i was tightening the hold down bolt. I re adjusted and locked it down at 8° at 800~ rpm. Seems to start better and has more pep than it did, also the hesitation i felt from the carb seemed to go away 90%. I never have known how to calculate what my timing should be set to, is using timing degree tape or a dial timing light the only way to find my total advance? Info i have found has been relatively vague. With my setup what would be a good inital timing to set at, or is 8° generally good setting? Thanks for all advice!

Just to add... it is a single exhaust with a catty, and i live in grand junction... aprox 4700 elevation, if it matters

 

[Bent77]

Just to add... it is a single exhaust with a catty, and i live in grand junction... aprox 4700 elevation, if it matters

Yeah all that matters. We will Presume the exhaust is clear and functional. Add 4* to your initial, and use better gas.

 

[Bent77]

If it pings, pull it back to 8*
I used to run 14* base on 91 without issue

 

[Aaron jackson 87]

Yeah all that matters. We will Presume the exhaust is clear and functional. Add 4* to your initial, and use better gas.

Ok, just to be clear, you are sugesting add 4° to the 8 that im already running for 12° initial timing? Dont mean to sound dumb... i bought the blazer in September of last year with a full tank of gas and a blown engine for 1500, the wife loved it . just did the break in at the end of December, and have about a quarter tank of original gas left, maybe ill check the timing again with fresh gas and see if anything changes.

 

[Bent77]

Ok, just to be clear, you are sugesting add 4° to the 8 that im already running for 12° initial timing? Dont mean to sound dumb... i bought the blazer in September of last year with a full tank of gas and a blown engine for 1500, the wife loved it . just did the break in at the end of December, and have about a quarter tank of original gas left, maybe ill check the timing again with fresh gas and see if anything changes.

Run some good gas through it first. 5 month old gas is no good for sure. If it needs a little extra try then

My rule of thumb for timing is 2* +2* for each 1000' elevation. That would give you 12, plus 2 to grow on makes 14*!

 

[Aaron jackson 87]

Run some good gas through it first. 5 month old gas is no good for sure. If it needs a little extra try then

My rule of thumb for timing is 2* +2* for each 1000' elevation. That would give you 12, plus 2 to grow on makes 14*!

Good to know about elevation formula, never knew... ill get some gas and try a little more advance. By "ping" do you mean missfire? I never did understand that term lol

 

[Bent77]

The ping is a knock, caused by detonation in the engine. Often associated with a hard load, excess timing, or crap gas. Sounds like a chevy 6.2 diesel does, only intermittently.

I would not be concerned about the timing until you know the gas is good.
On fresh gas, it might run just fine and not need tweaking as well

 

[Aaron jackson 87]

The ping is a knock, caused by detonation in the engine. Often associated with a hard load, excess timing, or crap gas. Sounds like a chevy 6.2 diesel does, only intermittently.

I would not be concerned about the timing until you know the gas is good.
On fresh gas, it might run just fine and not need tweaking as well

Great, thank you, your advice is greatly appreciated! Decided to join this forum because im always tinkering with these old blazers, ive owned 3 of them since my 19th birthday, my first a 74 soft top Cheyenne edition, paid 1500 for it, dang near perfect condition, too bad my 19 year old self diddnt take care of things..dang it mom... blew 3 motors in it, 2 of witch i built myself, being the reason the failed... lost it due to a repossession on the loan to buy it. Beat myself up every day over it. I have an 89 tbi thats been my dd for the last 3 years. Traded a pos motorhome for it from a guy who rolled it off a small cliff, fixed it up and i freakin love it. Have the 87 now and hope to have many many years ahead to fix it. Glad to be around guys who love them as much as me... not everyone wants the fancy toyota, witch are great no doubt, but im sorry toyota, chevy was towin airplanes around in the 80s long before that kinda thing was "cool."not too impressed... gotta love the chevys!

 

[Bent77]

Yep lots of info on this forum, welcome aboard! Wander about!


Several guys in your neighborhood as well for parts and such

 

[scpaul]

If after you try the adjustments that you have been given and if you still have the hesitation, you might try playing with the accelerator pump. With all of the mods that you have done, I'd bet that the larger carb would help in several places. Pull some your plugs and read them. There should be a page on here somewhere that shows pictures and what to do when you read the plugs. The elevation may be part of it. The carb manufacturers used to set the carbs for a std. elevation at the factory, sorry, but I don't remember the elevation. I don't think that it was as high as 4700 ft. though. There is ALOT of good info on this site.

Good luck, Paul

 

[Aaron jackson 87]

If after you try the adjustments that you have been given and if you still have the hesitation, you might try playing with the accelerator pump. With all of the mods that you have done, I'd bet that the larger carb would help in several places. Pull some your plugs and read them. There should be a page on here somewhere that shows pictures and what to do when you read the plugs. The elevation may be part of it. The carb manufacturers used to set the carbs for a std. elevation at the factory, sorry, but I don't remember the elevation. I don't think that it was as high as 4700 ft. though. There is ALOT of good info on this site.

Good luck, Paul

Will do! Gonna do some diggin'

 

[Aaron jackson 87]

Hello again, here is where im at.
I got fresh gas today and hooked up the timing light to check things out, locked in at 8°, i loosend the bolt and advanced to 10° which raised my idle from 800 to 1000, a little more than o want to run so i adjusted it back to 800, re checked timing, and it went back down to 8°. Its been a while and im not sure if that is normal, any thoughts?

 

[kgblazerfive]

idle screw changes idle. The idle will increase when you add timing. Use the idle screw to lower it.
Get a bigger carb.
I run mine about 10-12 advanced. My 454 likes alot more then that.