Is there any difference between a big block originally put in a P30 chassis and one that was in a 1 ton panel truck chassis? Specifically, 1986 Barth Regal 25' vs one pulled out of a mid 70s 1 ton panel truck, rebuilt, and put in the Barth. Somewhere in the dark recesses of my brain, I recall that the big blocks built for motor homes had a different cam for more torque. Therefore the big block out of the mid 70s panel truck wouldn't unless it had been part of the rebuild. Any other differences like heads, headers, carbs, etc.? Thanks

Jim

True 86-89 had a few changes. Post 86 chassis had tank mounted fuel pumps to help with vaper lock problems. Exhaust manifolds changed from cast iron to stainless. Dual air pumps. Depending on year of engine it may not have hardened valves. Changed in the 70,s for unleaded gas. As for cam I would think a truck or rv would be close. 70's intake most likely will not have EGR valve. If it runs good, has good compression, and good oil pressure I wouldn't be concerned. Most of us are not putting more than a few thousand miles a year on them.

The 454 was used from about 1965 to about 2000. The early blocks were all the same until 1990. All of the trucks and motorhomes were carbureted, with the cars and pickups fuel injected in the 80's. These were referred to as Mark IV engines.

After 90 they were all fuel injected. They came out with the Gen V block which had no provision for mechanical fuel pump, four bolt mains and started using a one piece rear main seal. 96-2000 were the Gen VI Vortec series, they had different oil cooler plumbing, roller camshaft setups, 4 bolt mains and multiport fuel injection.

I believe all the 454 blocks/cranks from 1965 to 1990 were the same. Pistons varied, as did valves, compression, and hp. 69 to 72 engines had the highest compression, up to 10 to 1. After about 74 they were all the same, about 8 to 1.

When I looked at camshafts the OEM cams were all the same after 74. In the 90's the FI engines had different cams and manifolds.

Back in the first gas crisis there were a bunch of so called RV cams the cam shaft companies offered (i.e. Iskenderian) that claimed better mileage, torque, etc. To my knowledge none of them did much better than OEM.

When I replaced my 454 HO cam I used the cam from the 502 HT engine. It has less lift and duration than the OEM HO engine but more than the EPA street versions.

From what I can tell, in the 1985-1990 timeframe, GM used the engine code W to indicate 454 with the quadrajet. Engine code N was for TBI. The quadrajet we have on the P chassis Barth rigs of this era was 17085212, and from what I have gathered, this number was also used on the largest 4 door pickup trucks of the same era, with the 454. I would tend to think that with the same carb, the cam is going to be the same. I would also think that the TBI engine has a different cam.

One thing to think about, when comparing to a 1970s cam, a high torque RV cam from the factory might be comparable to a "normal" cam of the '70s. The differences are the changes in context due to emissions concerns, etc. The W engine I think is rated at 230HP, what was that panel track engine rated at?

Heads might be different with different combustion chamber volumes, to give different compression ratios. Probably both use the smaller "oval port" intake passages.

Matt

While my '89 24' SOB had a 350, the PO had gotten info on the 454. The GM literature indeed listed the RV option at 230 HP. Sorry, I can't remember the torque specs. BTW, the PO had considered replacing the 350 with the 454, but it would've meant upgrades to the front suspension, diffy, and maybe the tranny. He had wanted to pull a toad, but discarded the idea due to costs.