engine & head combo

347 Views 3 Replies 4 Participants Last post by Z_dust, Oct 12, 2004

gunlaker4

Discussion Starter · Oct 11, 2004

I have two L28 motors and am going to spend most of my current funds on a fiberglass 280YZ body with a roadster deck lid and suspension upgrades; run for a season and save up money for next phase, motor. My final goal on this car aims towards SCCA Solo and a weekend road car with a power to weight ratio to take down any American made lead sleds, ie '70's GTOs, Trans Am's. For now, I am planning on swapping the p79 head for a n47 on a f54 block with flat top pistons for the increased compersion at no extra cost. I am planning on an exhaust header and running the SU carbs and intake (stock '71, retuned for new combo). 110,000 miles on short block. Hope to use for another 20k, then build either a 250hp L28 for over 20mpg, or 300+hp small block for under 10mpg.

F54 block with N47 head
Stock cam and this combo, 175hp?
Will a cam be necassary to utilize the increased compression?
New cam and combo, 200hp?
Will the exhaust ports on the n47 eliminate benifits of increased compression?
I port 2-stroke snowmobile heads and see 'how to's' on other posts for these heads. Simple exhaust port clean up & polish to flow compression?
SU carbs and intake able to utilize the benifits of increased compression?

Save

Status: Not open for further replies.

1 - 4 of 4 Posts

steves280

· #2 · Oct 12, 2004

Stock cam and this combo, 175hp?

Doubtful, all you've done is raise the compression, expect maybe 140-150.

Will a cam be necassary to utilize the increased compression?

Yes, it will probably ping without careful tuning.

New cam and combo, 200hp?

Doubtful, unless it's a REALLY hot cam with port work to the head etc.

Will the exhaust ports on the n47 eliminate benifits of increased compression?

?? They are the same as the P79.

I port 2-stroke snowmobile heads and see 'how to's' on other posts for these heads. Simple exhaust port clean up & polish to flow compression?

"flow compression"?

SU carbs and intake able to utilize the benifits of increased compression?

Yes.

See less See more

Save

wangsman

· #3 · Oct 12, 2004

Gas milage is more of a weight and rpm and tuning issue not engine size.

My V8 car get over 20 in the highway! And that is with a big cam. I drove it 50 miles round trip to the drag races, ran it 5 times, and drove home and used a 1/4 tank.

The new corvette gets 28 mpg on the highway even with 400 hp!

Use a 350 cid, 260 cam, T5 trans, 3.54 gear, tuned holley or Q-jet carb, and you can get 25+ mpg on the highway and make 375 hp with 180cc AFR heads.

Save

Z_dust

· #4 · Oct 12, 2004

Hey gunlaker4 I have had the flat piston F54/N47 combo on my 77z for about 7 months now. I can tell you that I feel a difference mostly above 3K RPM. The car pulls really good to around 5500rpm. I have never have any detonation problems with it and I run factory cam with FI.

I guess its OK but I need more HP, that's why I'm going turbo

Save

1 - 4 of 4 Posts

Status: Not open for further replies.

Top Contributors this Month