Considering another engine swap in the spring... still not sure which one yet

[MuddiGGEr25]

Ok so i was cruising around in the 6.2l v20 1988 suburban, thinking how it gets 13-18mpg with 4.10 Gears, and although i love getting 15+mpg on the highway without even having OD, and thats actually kinda important right now with no job. it got me thinking... would the N/A 6.2l with a rebuilt IP slightly turned up, maybe even advanced the pump timing, be able to haul a 7,500-10,500lb RV at 55MPH and still maintain the fuel economy?  The PO claimed to tow a 6,000lbs trailer with WD hitch with this burb up from california loaded with thier stuff for moving and 3 kids, and claimed 16MPG, the only issue was slowing on the biggest hills, thats about 14,000lbs gross, and i can honestly say that i towed cliffy 7,000lbs all the way home the day we bought this rig (7000+lbs) at 55mph except for the really really steep hills, we only got around 9-11 MPG averaged across the 180 mile one way trip, but we were using diesel that had been sitting since 2010.

the RV and the burb both have 4.10 gear ratios, the RV is much taller, and heavier than the burb by itself, the original 400sbc was rated for 305FT-lbs at 2000RPM and the 6.2L was at 240-ft-lbs for the first version and 285ft-lbs for the 1985 version so mine is somewhere around 285 ft-lbs for 1988.

So with minor adjustments i would think that i could gain the 20-30 torque difference, and save significantly in fuel on camping trips.

I am running electric fuel pump so no issue there... both have the TH400 3spd so no issue there, i would have to swap the filler necks possibly and maybe swap the dash cluster in the v20, maybe not even bother and use the glow plug and FIW lights for other indicator lights, i can always wire up a couple dummy lights in the RV for that.

I would not expect to tow the Suburban behind the RV obviously but maybe a saturn or geo (2000-2300lbs)


Is there anything else i am missing?  I have the 400sbc A/C compressor still, and the 6.2L has dual A/C so i would want the suburban to keep the A/C so i think i would need a 454 A/C compressor, but its not important if the RV has cab A/C because it has a roof A/C and in inverter and will be getting a CS130 alternator upgrade (around 140A).


Am i missing anything critical?



specs here
http://matveynator.ru/f/9efda83135c6d53e16e47aab9a0122c4.pdf

[Stewart G Griffin]

How often will you tow?

[Irish_Alley]

what engine you plan on swapping with? me personally wouldnt think just a simple motor swap would give you that much of a benefit vs getting a trans with OD

[MuddiGGEr25]

what engine you plan on swapping with? me personally wouldnt think just a simple motor swap would give you that much of a benefit vs getting a trans with OD

My thoughts are to put the 400+HP 454 into the V20 blue suburban mainly because 1. its a factory 3/4 and already has all the towing options including cooler, 56" springs, looks nicer, and the 6.2L is gutless if i actually want to race, but otherwise a good strong puller.

Then place the 6.2L into the G30 1-ton RV we have, i know for a sure fact the 400ci+TH400+4.10 gears will get 13-14MPG consistently at 55-60MPH, once the emissions was removed and timing adjusted. and the worst i ever got towing in the old RV with the 400 was 11 and that was with a 7,000lbs travel trailer on the back.

i was assuming that since i put the 454 in and even at 50MPH im barely pulling off 6.9MPG in the RV, i might as well switch back to less fuel hungry engine if we want to make any trips next year. (most trips we have mapped out are in the 900-1600 mile range ONE way.)

The RV chassis is really not designed to tow more than 3500lbs because of the frame extensions, so a small car (geo , saturn, toyota, etc) would be the most being towed 4 down around 2,000lbs

How often will you tow?

The 3/4 suburban would be asked to tow quite often, as in atleast towing cliffy to mud events once the 42's are installed in the spring, and my wife wants to play in the mud too but not in the big truck because she is afraid of flipping over, so i figure 400hp at her disposal, and i can go play in the big truck, plus i would be able to tow whatever i can think of with a built 454/TH400/4.10 ratio

I know i will lose MPG considerably in the blue suburban if i do this swap, and im sure i could either put in a monster transmission 700r4 built for the tq or change the axle ratios to lower the RPMs, either way would be fine and probably the same cost unless i find a deal. but the main objective is to get the RV back into the 10+mpg range like it had from the factory with the 400SBC