RE: hot rodding a 4.3L
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RE: hot rodding a 4.3L - 9/15/2006 7:10:48 PM
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swartlkk
Posts: 14528
Joined: 5/1/2005
From: Waterloo, NY
Status: offline
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Ok, so they acheived the 0.07 longer stroke, from 3.48 to 3.55, by offset grinding the crank. Yeah, 0.07 is the max you can get by doing this. Once you get the journal to the same diameter as a 350, you can do pretty much anything with the pistons and rods for cheap. The only difference between the rods in a 350 vs the rods in a 4.3L is the crank journal diameter (see below).
350 v8 crankshaft rod journal diameter = 2.0986-2.0998in
262 v6 crankshaft rod journal diameter = 2.2487-2.2497in
Here's an illustration I drew up quick of what we are talking about for those wondering:
With this, you need to get longer rods and possibly change the pin location (depending on the rods) for the wrist pin that connects the rod to the piston. Also, you'll need to specify 350 v8 rods and bearings.
And while higher ratio rockers do add lift, they do not add duration or affect the overlap. Overlap and duration being HUGE for any forced induction application. Just increasing the lift alone will give decent gains on a stock or slightly modified motor, but if you aspire to do anything bigger/better, spend the money up front for a larger aftermarket cam because you'll save money in the long run.
Blazer SS, thank you for the clarification. Please understand that this was not something that I enjoy doing, but it is necessary to keep the information listed on this forum accurate.
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RE: hot rodding a 4.3L - 9/15/2006 10:18:07 PM
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Blazer SS
Posts: 32
Joined: 6/16/2005
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No problem. Hence the word forum. Thanks for the diagram.
Another word of advice. If you plan on having your heads done ( porting, bigger valves, springs ) LEAVE THE INTAKE VALVE SIZE ALONE!!!! ( VORTEC) Work on the exhaust side, YES. but do not increase the valve size on the intake side. You will hurt more than help the flow of the heads. I found this out the hard way ( wallet ). I went with 2.02 intake and 1.6 exhaust, what happened is that I shrouded the intake valve by making it bigger! You would think that all that you had to do was deshroud the intake valves, Wrong! Once that was done , my whole chamber size was changed and it was a domino effect from there! Compression was off, pistons had to be changed, Port both sides but only change the exhaust valve size.
Exhaust evac, very important to forced induction engines, we also need a wide LSA for great performance. again forced air only!! Normally aspirated go with more valve overlap.
Get a valve spring job! Check your seat pressure, closed and open, factory springs are notorious for unequal seat pressures, Replace the factory rockers! If only to replace them with the same specs, again notorious for being off . Go with a good aftermarket set, if they say 1.5, 1.6 they usually are. The factory rockers could be as low as 1.4. Meaning your valves are not opening as fully as they should.
Why I say get roller tips? If your Blazer is a 98 and below and you have non adjustable rocker studs you can replace them in less than a hour! If you have adjustable studs go with full roller rockers. I can't remember the years that came with rollers (trunions) but I think it is 2000 and above? Just having all of the valves open and close as they should will greatly improve on your performance.
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RE: hot rodding a 4.3L - 9/19/2006 1:56:48 PM
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Hanr3
Wheels & Tire Moderator
Posts: 3482
Joined: 5/11/2005
Status: offline
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Thanks for the clarification.
That makes alot more sense now.
I have a '93 4.3L V6 and a bare V6 block (unknown origin) both sitting in my garage. For some reason I think the bare block is aluminum. I'll have to check it out tonight.
Sorry, the point is I am going to be rebuilding one of them. I was serious when I said I like the V6 engine. Gobs of power from it. Plus its about 100 pounds lighter then a V8. Eventually this rebuilt engine will go into a off-road toy. I want it light as possible.
_____________________________
"Some people spend an entire lifetime wondering if they made a difference.
The Marines don't have that problem."
-President Ronald Reagan
'87 S10-Blazer - SOLD
'93 S10-Blazer 4x4x4 - Sons DD, engine swap is done.
'00 S10-Blazer 4x4x4 - My
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RE: hot rodding a 4.3L - 9/19/2006 8:58:43 PM
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Blazer SS
Posts: 32
Joined: 6/16/2005
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Try a Edlebrock set, Intake, cam, and rockers, Higher comp pistons will release the beast. Have fun with it!
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RE: hot rodding a 4.3L - 9/19/2006 10:18:01 PM
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Hanr3
Wheels & Tire Moderator
Posts: 3482
Joined: 5/11/2005
Status: offline
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I have been looking at the various cam kits out there. I want to keep it TBI. I'll have to check out the Edelbrock stuf. Been looking at the Crane cams lately. I like thier truck avenger series.
_____________________________
"Some people spend an entire lifetime wondering if they made a difference.
The Marines don't have that problem."
-President Ronald Reagan
'87 S10-Blazer - SOLD
'93 S10-Blazer 4x4x4 - Sons DD, engine swap is done.
'00 S10-Blazer 4x4x4 - My
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RE: hot rodding a 4.3L - 9/30/2008 7:31:44 AM
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Big Blaze
Posts: 6
Joined: 3/11/2008
Status: offline
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Just remember that on those stroker cranks that they are offset ground, so it is taking away from the strength of the factory crank. For forced induction it would probably be best to stay with the stock crank.
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RE: hot rodding a 4.3L - 9/30/2008 8:31:00 AM
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Duntov
Posts: 210
Joined: 2/29/2008
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I considered installing a 350 engine in my ''''91 Blazer but after I did some research, I chose not to start a project of that magnatude and build a strong "bolt in" 4.3L instead. I ned two engines, a brbuildable 4.3L ( w/o balance shaft) to build while keepinmg the original 1991 engine in the Blazer to drive while building the other. I have collected about $600 worth of internal engine parts for the new engine while they are still avaliable. Many parts for the 4.3L also fit a 350 V8 engine, no availability issue there. It will take me about a week to switch engines and have the new engine running strong enough.
Optional 350 V8 installation:
Assuming a well rebuilt 350 engine will cost $1700, including the core.
A new radiator for a V8.....$300.
An auxillary transmission oil cooler will be needed...$200.
(possible transmission rebuild...$1800)
A 350 V8 oil pan for a 4WD Blazer...$500..
A special off-set oil filter adapter for 4WD...$50.
Kiss your 4WD engine oil cooler goodby.
Headers and exhaust system for a V8...$700.
A Power-Trax No Slip differential...$500.
(Or a 8.5 rear axle assembly...$1000)
Total: From $3950 to $6550. plus labor cost if any.
And you can forget about passing a emissions test.
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You better think it over about "dropping in" a V8. If I was going to go to that much trouble, a Chevrolet Rat Motor 427 or 454 V8 would be my choice.
< Message edited by Duntov -- 9/30/2008 8:43:58 AM >
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Competely original. My Blazer even has 1991 air in the spare.
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