cam question

two89w · 02-02-04, 04:12 AM

If I was to put a 351windsor cam into my 289/302 with adjusted firing order,timing etc would the performance be any different if I was to put in the same spec cam with 302 timing?

Steve Toner · 02-02-04, 10:56 AM

Firing order makes no difference in performance. I posted something a while back showing that the 351 firing order is really just a mirror image of the 302 firing order - I'll see if I can dig it up...

Steve Toner · 02-02-04, 11:07 AM

Here is the link to the previous discussion on firing order. [img]/ubbthreads/images/graemlins/cool.gif[/img]

Keith · 02-02-04, 12:01 PM

I don't believe a 351W cam will fit in 289/302 as the 351w cam is made from a larger diameter cam blank. The 351w cam will fit into a 5.0 block but not a 289/302. The 5.0 and the 302 are not the same block as they have different cam bearing bore size and a different deck height among other things.
A 289/302 block could be modified to accept a 351w cam, however, as most cam grinds for the 351w are availlable in the smaller base size for a 289/302 there is no good reason to do it.
Keith

Steve Toner · 02-02-04, 01:51 PM

Keith,

I'm confused. Summit sells the same cam bearings for 211 through 351W engines. I'm not a 351W expert by any means, but this appears to contradict what you said.

The firing order is different between the 351W and the 289, but there are certainly cams available for the 289 that come with the 351 firing order - my engine has one (and this was my engine builder's choice, not mine - as I've said, I don't think there is any significant difference).

Kevin M · 02-02-04, 02:11 PM

The 1985 to 95 5.0 block has higher lifter bosses because of the switch to a roller cam. These engines normally use a cam with a larger base circle. This is not the same as the bearing size, which is the same on all 302 and 351W engines. The base circle size is only an issue with hydraulic roller cams using factory type lifters. Crane makes a special retrofit hydraulic roller lifter that allows you to run a 5.0 (Large Base Circle) cam in an early block. The only other change that this requires is different length pushrods.

As a side note, you can change the firing order on these motors without a problem as long as you are not using the early factory Speed Density injection system.

Kevin

40 Bud · 02-02-04, 07:33 PM

I was told some time back that the advantage to the 351 windsor firing order was not needing a cross over exhaust.

Steve Toner · 02-03-04, 12:01 AM

[ QUOTE ]
I was told some time back that the advantage to the 351 windsor firing order was not needing a cross over exhaust.

[/ QUOTE ]

You were lied to [img]/ubbthreads/images/graemlins/shocked.gif[/img] To eliminate the crossover, you'd need to alternate firing between the left & right side of the block. Cylinders 1-4 are on one side of the engine, while 5-8 are on the other side.

289 order: 1-5-4-2-6-3-7-8
4 & 2 are on the same side, as are 7 & 8.

351 order: 1-3-7-2-6-5-4-8
1 & 3 are on the same side, as are 6 & 5.

**Chris K** · 02-03-04, 02:06 AM

The revised firing order was/is intended to keep any two cylinders from firnig on the same crank journal. In the case of the 289/302 1-5 cylinder firing vs. the 351w firing of 1-3, thus relieving stress to the common crank journal.
Hope this helps

Adam C. · 02-03-04, 09:12 AM

Then what about cylinders 4 and 8?

**Chris K** · 02-03-04, 02:05 PM

Adam, you make a good point, perhaps I mis-spoke and after doing a little research I find that the later firing order it seems is geared toward a re-distribution of load overall on the crank/journals. I was always under the impression that the 1-5 firing was the load problem, but as you say "what about the 4-8 firing?" perhaps the rear is not as affected as the front. I would go on to say that the earlier 7-8 crossfiring is also eliminated, but again what about the later 6-5 ( I dont think the crossfire issue was the reason for the change).

Kalun D · 02-15-04, 04:17 AM

The only thing I can think of that it might affect is the headers, and then only minimally. It depends how the firing order affects the crossover and sometimes the headers are built to effect a circular firing pattern to swirl the exhaust in the collectors. I can't imagine it losing more than 5 HP or so even if both crossover and swirl were wrong.

jimbo · 02-17-04, 10:46 PM

So, since I haven't bought a camshaft for my engine yet, which will have crossover headers in the traditional pattern, and since I am looking for a flat-tappet cam, should I look for a cam with the revised firing order or doesn't it matter much? My engine is a 68 302.